A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF … · 2018. 1. 8. · characteristics of pervious concrete for pavement use lim emiko (b.eng (hons), m.eng, national university of

CHARACTERISTICS OF PERVIOUS CONCRETE

FOR PAVEMENT USE

LIM EMIKO

(B.Eng (Hons), M.Eng, National University of Singapore)

A THESIS SUBMITTED

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

DEPARTMENT OF CIVIL AND ENVIRONMENTAL

ENGINEERING

NATIONAL UNIVERSITY OF SINGAPORE

2016

i

DECLARATION

I hereby declare that the thesis is my original work and it has been written by

me in its entirety. I have duly acknowledged all the sources of information

which have been used in the thesis.

This thesis has also not been submitted for any degree in any university

previously.

30th June 2016

ii

ACKNOWLEDGEMENTS

I would like to express my utmost appreciation and gratitude to my

supervisors, Professor Tan Kiang Hwee and Professor Fwa Tien Fang for their

invaluable guidance, tutelage, help and encouragement throughout the

research. I also extend my heartfelt gratitude to Professor S.P. Lim from the

Mechanical Engineering/Applied Mechanics Group for his tutelage and help.

I would extend my heartfelt appreciation to Professor Zhang Min

Hong, Assistant Professor Raymond Ong, members of my Ph.D. committee

and Professor David Chua for their insightful and helpful recommendations in

improving my research. My sincere thanks also go to Professor Chew Chye

Heng from the Mechanical Engineering Group for the specialised knowledge

he provided.

Thanks are also accorded to Wei Leng, Mr Foo, Mr Goh, Mr Farouk

and Teresa of the Transportation Engineering Laboratory; Stanley, Mr Koh,

Mr Ang, Mr Ow, Mr Kamsan, Mr Ishak and Mr Choo of the Structural

Laboratory and Mr Cheng, Priscilla and Amy of the Mechanical Engineering

Laboratory for their kind assistance and full support in the course of this

research. Thanks are also addressed to my colleagues and friends, Dr Zhang

Lei, Dr Ju Fenghua, Dr Yang Jiasheng, Maggie, Fu Rao, Yin Lu, Yujie, and

Akshay for their kind help and friendship.

Finally, I am especially grateful to my parents for their infinite care,

encouragements and support. This work is dedicated to my parents.

iii

Table of Contents

ACKNOWLEDGEMENTS ............................................................................... ii

SUMMARY ...................................................................................................... vi

LIST OF TABLES ......................................................................................... viii

LIST OF FIGURES ........................................................................................... x

CHAPTER 1 INTRODUCTION ..................................................................... 15

1.1 General ................................................................................................... 15

1.1.1 Advantages and limitations ............................................................. 16

1.1.2 Applications ..................................................................................... 16

1.2 Significance of current study ................................................................. 19

1.3 Objectives and scope of research ........................................................... 20

1.3.1 Physical and mechanical properties ................................................. 20

1.3.2 Clogging characteristics .................................................................. 21

1.3.3 Sound absorption characteristics ..................................................... 21

1.4 Structure of thesis ................................................................................... 22

CHAPTER 2 LITERATURE REVIEW .......................................................... 23

2.1 Physical and mechanical properties of pervious concrete ...................... 23

2.1.1 Effect of mixture proportion ............................................................ 23

2.1.1.1 Compressive strength ............................................................... 25

2.1.1.2 Flexural Strength ...................................................................... 26

2.1.1.3 Porosity .................................................................................... 26

2.1.1.4 Permeability ............................................................................. 27

2.1.2 Use of supplementary materials in pervious concrete mixes .......... 27

2.1.3 Fiber reinforcement for pervious concrete ...................................... 29

2.2 Clogging characteristics of pervious concrete ....................................... 31

2.2.1 Effect of clogging materials ............................................................ 32

2.2.2 Service life of pervious concrete pavements with clogging ............ 34

2.3 Sound absorption properties of pervious concrete ................................. 35

2.3.1 Acoustic properties of pervious concrete pavements ...................... 36

2.4 Target performances ............................................................................... 37

2.5 Summary ................................................................................................ 38

iv

CHAPTER 3 PHYSICAL AND MECHANICAL PROPERTIES OF

PERVIOUS CONCRETE ................................................................................ 49

3.1 Test programme...................................................................................... 49

3.1.1 Materials .......................................................................................... 51

3.1.2 Test specimens ................................................................................. 52

3.1.3 Test methodology ............................................................................ 52

3.1.4 Workability ...................................................................................... 54

3.2 Test results and discussion ..................................................................... 55

3.2.1 Unreinforced pervious concrete....................................................... 55

3.2.2 Steel fiber reinforced pervious concrete .......................................... 57

3.3 Summary ................................................................................................ 60

CHAPTER 4 CLOGGING CHARACTERISTICS OF PERVIOUS

CONCRETE .................................................................................................... 85

4.1 Evaluation of clogging characteristics and porosity .............................. 85

4.1.1 Measurement of permeability coefficient ........................................ 86

4.1.2 Clogging procedure ......................................................................... 86

4.1.3 Clogging materials ........................................................................... 87

4.1.4 Measurement of porosity ................................................................. 88

4.2 Pavement mixtures ................................................................................. 89

4.2.1 Pervious Concrete Mixtures ............................................................ 89

4.2.2 Porous Asphalt Mixtures ................................................................. 89

4.3 Test results and discussion ..................................................................... 90

4.3.1 Effect of different clogging materials .............................................. 90

4.3.2 Comparison of permeability ............................................................ 91

4.3.3 Comparison of clogging behaviour ................................................. 92

4.3.4 Effect of steel fibers on clogging behaviour .................................... 96

4.4 Evaluation of clogging potential of porous materials ............................ 97

4.4.1 Analysis of permeability reduction due to clogging ........................ 99

4.5 Summary .............................................................................................. 100

CHAPTER 5 SOUND ABSORPTION CAPACITY OF PERVIOUS

CONCRETE .................................................................................................. 120

5.1 Experimental Program.......................................................................... 121

v

5.1.1 Pavement materials ........................................................................ 121

5.1.2 Test specimens and conditioning ................................................... 122

5.1.3. Acoustic absorption measurement ........................................... 123

5.2 Test results and discussion ................................................................... 125

5.2.1 Effect of different road materials (Test Series A) ......................... 125

5.2.2 Effect of porosity (Test Series B) .................................................. 127

5.2.3 Effect of thickness (Test Series C) ................................................ 128

5.2.4 Effect of clogging (Test Series D) ................................................. 129

5.3 Sound pressure level dB(A) ................................................................. 131

5.4 Summary .............................................................................................. 134

CHAPTER 6 CONCLUSION........................................................................ 179

6.1 Review of work done ........................................................................... 179

6.2 Summary of main findings ................................................................... 179

6.2.1 Physical and mechanical properties of pervious concrete ............. 179

6.2.2 Clogging characteristics of pervious concrete ............................... 180

6.2.3 Sound absorption capacity of pervious concrete ........................... 180

6.3 Recommendations for further research ................................................ 181

LIST OF PUBLICATIONS ........................................................................... 183

REFERENCES .............................................................................................. 185

ANNEX A: Residual Normality Analysis ..................................................... 211

ANNEX B: Statistical analysis using T-Test: Two samples assuming ...............

unequal variances for selected mixes ............................................................. 220

vi

SUMMARY

Pervious concrete may be used in road pavements to prevent flash

flooding and provide wet-weather skid resistance due to its porous nature.

Besides adequate strength, it must possess good clogging and sound

absorption characteristics. This study investigated the use of steel fibers in

enhancing the flexural strength of pervious concrete without compromising its

permeability and porosity. To meet these requirements, the target strength of

the pervious concrete was 3.5 MPa and the permeability and porosity were 10

mm/s and 20% or higher respectively.

To achieve a highly permeable and porous pavement with reasonable

compressive and flexural strengths, the CA/C ratio should be in the region of

4.25, water-cement ratio of around 0.3 and cement in the range of 360 kg/m3

to 400 kg/m3. However without the use of steel fibers, target performances

would be difficult to achieve.

Results showed that fiber inclusion up to 2.25% by volume met the

target performances and a minimum dosage of 1.5% was recommended for

practical mix design.

At porosities ranging from 10% to 25%, pervious concrete provided

better clogging characteristics than porous asphalt. Adding steel fibers did not

affect the performance. Pervious concrete was found to possess better

clogging resistance than porous asphalt mixtures having the same level of

porosity.

The sound absorption capacity of pervious concrete was compared to

those of normal, steel fiber-reinforced concrete, lean concrete, porous asphalt,

vii

open-graded asphalt and dense asphalt. Pervious concrete with or without steel

fiber was found to achieve a significant overall sound pressure reduction of

more than 4.5 dB(A) when compared to normal weight concrete and dense

graded asphalt mixes.

When fully clogged, pervious concrete and porous asphalt had

comparable overall sound pressure levels. Comparing the before and after

effects of clogging, the sound absorption capacities of pervious concrete and

porous asphalt were not compromised and a minor increase of about 1 dB(A)

was noted.

In summary, this research has (a) provided a new pervious concrete

mix design that meets the target performances of having reasonable flexural

strength, permeability and porosity for pavement use, (b) recommended

porosity level for good drainage performance with satisfactory clogging

resistance and (c) evaluated and compared expected sound absorption

properties of the recommended pervious concrete mix design with other

existing road materials.

viii

LIST OF TABLES

Table 2.1 Typical ranges of material proportions in pervious concrete .......... 39

Table 2.2 Pervious concrete target requirements ............................................. 40

Table 3.1 Types of tests and various test samples ........................................... 61

Table 3.2(a) Mix proportion design (Part 1) .................................................... 62

Table 3.2 (b) Mix proportion design (Part II) .................................................. 62

Table 3.3 (a) Gradation of small and large coarse aggregates ......................... 63

Table 3.4 Properties of steel fibers .................................................................. 63

Table 3.5: Physical and mechanical properties of pervious concrete .............. 64

Table 3.5: Physical and mechanical properties of pervious concrete (cont’d) 65

Table 3.6 Summary of test results.................................................................... 66

Table 3.6 Summary of test results (Cont’d) ..................................................... 67

Table 3.7 Recommended steel fiber dosages ................................................... 67

Table 4.1 Mixture design of pervious concrete ............................................. 103

Table 4.2 Aggregate gradations and mix composition of porous asphalt mix

........................................................................................................................ 104

designs............................................................................................................ 104

Table 4.3 Porosity and permeability coefficient of pervious concrete and .... 105

porous asphalt specimens ............................................................................... 105

Table 4.4 Rates of increase of permeability coefficient with porosity for ..... 106

porous asphalt and pervious concrete mixtures ............................................. 106

Table 4.5 Measured porosity of steel fiber pervious concrete specimens ..... 107

Table 5.1 Sound Absorption Test Program.................................................... 136

Table 5.1 Sound Absorption Test Program (Cont’d) ..................................... 137

Table 5.2 Gradation analysis for coarse and fine aggregates ......................... 138

Table 5.3 Mix proportions of concrete samples............................................. 139

Table 5.4 Aggregate gradation and mix composition of asphalt mix designs

........................................................................................................................ 140

Table 5.5 Measured sound absorption coefficients for Series A with different ..

material types ................................................................................................. 141

ix

Table 5.6 Porosity of specimens for Series B on materials type ................... 145

Table 5.7 Peak sound absorption coefficient for pervious concrete and porous .

asphalt specimens for Series B test with different porosities ........................ 145

Table 5.8 Measured sound absorption coefficients for Series C with different...

thicknesses of pavement layer ....................................................................... 146

Table 5.9 Target porosity and measured porosity of the samples for Series D ...

with different degrees of clogging ................................................................. 149

Table 5.10 Measured sound absorption coefficients for Series D with different

degrees of clogging ........................................................................................ 150

Table 5.11 Peak α values for different porosity and the frequency that they 155

occur at for clogging series D ........................................................................ 155

Table 5.12 1/3 octave frequency sound pressures for all test specimens (Series

........................................................................................................................ 156

A, B, C and D) ............................................................................................... 156

Table 5.13 Overall sound pressures for all specimens (Series A, B, C and D)

........................................................................................................................ 159

x

LIST OF FIGURES

Figure 2.1 Effect of cement content ................................................................. 44

Figure 2.2 Effect of coarse aggregate content ................................................. 45

Figure 2.3 Effect of water-cement ratio ........................................................... 46

Figure 2.4 Effect of fiber dosage ..................................................................... 47

Figure 2.5 Compressive strength (MPa) versus porosity (%) .......................... 48

Figure 2.6 Flexural strength (MPa) versus permeability (mm/s) ..................... 48

Figure 3.1 Steel 3D-S, 3D-L, 4D and 5D hook-end fibers (Dramix) .............. 68

Figure 3.2 Test samples ................................................................................... 68

Figure.3.3 Constant-head permeability test set-up .......................................... 69

Figure 3.4 Volume measure with fresh pervious concrete for density test ...... 69

Figure 3.5 Ball test for workability of pervious concrete (Sonebi and Bassuoni,

2013) ................................................................................................................ 70

Figure 3.6 Slump test ....................................................................................... 70

Figure 3.7: Physical and mechanical properties of pervious concrete ............. 71

Figure 3.8 Effect of coarse aggregate size in unreinforced pervious concrete 75

Figure 3.9 Effect of water-cement ratio in unreinforced pervious concrete .... 76

Figure 3.10 Effect of cement content in unreinforced pervious concrete ........ 77

Figure 3.11 Compressive strength of fiber reinforced pervious concrete ........ 78

Figure 3.12 Flexural strength results of fiber reinforced pervious concrete .... 79

Figure 3.13 Permeability results of fiber reinforced pervious concrete ........... 80

Figure 3.14 Porosity results of fiber reinforced pervious concrete .................. 81

Figure 3.15 Effect of fiber length in fiber reinforced pervious concrete ......... 82

Figure 3.16 Flexural strength versus permeability of test mixes ..................... 83

Figure 3.17 Compressive strength versus porosity of test mixes..................... 83

Figure 3.18 Relationship between flexural strength and porosity of pervious 84

concrete ............................................................................................................ 84

Figure 3.19 Relationship between flexural strength and permeability of ............

pervious concrete ............................................................................................. 84

Figure 4.1 Gradations of common clogging materials on Singapore roads ... 108

xi

Figure 4.2 Permeability versus clogging stages of pervious concrete and .... 109

porous asphalt at 20% porosity. ..................................................................... 109

Figure 4.3 Relationship between porosity and permeability coefficient ....... 110

Figure 4.4 Effect of clogging cycle on permeability coefficients .................. 111

Figure 4.5 Comparison of permeability deterioration curves of porous asphalt..

and pervious concrete mixtures ..................................................................... 112

Figure 4.6 Pervious concrete and porous asphalt mixes of different porosities ..

after clogging effect ....................................................................................... 113

Figure 4.7 Clogged fiber reinforced pervious concrete specimen ................. 114

Figure 4.8 Clogging characteristics of steel fiber reinforced pervious concrete .

specimens ....................................................................................................... 114

Figure 4.9 Average soil retained for pervious concrete and porous asphalt ........

samples with different porosities ................................................................... 115

Figure 4.10 Permeability deterioration factor (αc) ......................................... 116

Figure 4.11 Permeability deterioration factor (αc) for pervious concrete and .....

porous asphalt specimens ............................................................................... 117

Figure 4.12 Permeability deterioration factor (αc) for unreinforced pervious .....

concrete and fiber reinforced pervious concrete specimens .......................... 119

Figure 5.1 Sample holder for acoustic absorption tests ................................. 160

Figure 5.2 Pervious concrete samples – (a) 0% clogged; (b) 25% clogged; .......

(c) 50% clogged; (d) 75% clogged; (e) 100% clogged .................................. 161

Figure 5.3 Porous asphalt samples – (a) 0% clogged; (b) 25% clogged; ............

(c) 50% clogged; (d) 75% clogged; (e) 100% clogged .................................. 162

Figure 5.4 (a) Impedance tube setup for frequencies 100 -500 Hz;.....................

(b) Impedance tube setup for frequencies 600 - 2000 Hz .............................. 163

Figure 5.5 Low and high frequency sound waves ......................................... 164

Figure 5.6 Sound absorption coefficient values for eight road materials ...... 164

Figure 5.7 Sound absorption coefficient values for (a) pervious concrete (b) .....

porous asphalt at varying porosities in Test Series B .................................... 165

Figure 5.8 Comparison of sound absorption coefficient values for pervious ......

concrete and porous asphalt at individual target porosities in Test .....................

Series B .......................................................................................................... 166

xii

Figure 5.9 Sample thicknesses ....................................................................... 168

Figure 5.10 Sound absorption coefficient values for pervious concrete and .......

porous asphalt at different thicknesses in Test Series C ................................ 169

Figure 5.11 Comparison of pervious concrete and porous asphalt by thickness .

in Test Series C .............................................................................................. 170

Figure 5.12 Sound absorption coefficient values for pervious concrete and . 172

porous asphalt at varying clogging percentages in Test Series D .................. 172

Figure 5.13 (a) Sound pressure levels dB(A) at 1/3 octave frequencies and (b) .

overall sound pressure levels dB(A) for different road materials in Test Series

A ..................................................................................................................... 173

Figure 5.14 Sound pressure levels dB(A) at 1/3 octave frequencies for (a) ........

pervious concrete (b) porous asphalt and (c) overall sound pressure levels

dB(A) for pervious concrete (PC) and porous asphalt (PA) of varying porosity

........................................................................................................................ 174

Figure 5.15 (a) Sound pressure levels dB(A) at 1/3 octave frequencies and (b) .

overall sound pressure levels dB(A) for pervious concrete (PC) and porous

asphalt (PA) of varying thickness in Test Series C ........................................ 176

Figure 5.16 Sound pressure levels dB(A) at 1/3 octave frequencies for (a) ........

pervious concrete (b) porous asphalt and (c) overall sound pressure levels

dB(A) for pervious concrete (PC) and porous asphalt (PA) of varying clogging

percentage in Test Series D ............................................................................ 177

xiii

LIST OF SYMBOLS

A cross-sectional area;

Aair mass of dry specimen in air, (g);

B mass of specimen immersed in water (g);

D density (unit weight) of concrete (kg/m3);

df fibre diameter (m);

dp mean particle diameter (m);

g acceleration due to gravity (m/s2),

H constant water head (mm);

i hydraulic gradient;

k permeability coefficient (mm/s);

k0 initial permeability coefficient (mm/s);

L thickness (mm);

mc mass of clogging material retained in specimen (kg);

Mc mass of the container filled with concrete (kg);

Mm mass of the container (kg);

np porosity (%);

n experimental coefficient;

N total number of centre frequencies;

PA(t) instantaneous A-weighted SPL (Pa);

pref reference sound pressure level (SPL) = (20 x 10-6

Pa);

Q amount of water collected (mm3);

sv volumetric specific surface area of permeable medium (m-1

);

T specified time interval (sec);

xiv

t test duration(sec);

V volume (m3);

Vc clogging material retained (m3),

Vm volume of the container (m3);

Vr total void ratio (%);

VT volume of specimen (m3);

W1 weight of sample immersed in water (kg);

W2 weight of sample in air (kg);

WA % binder (asphalt);

Wagg weight of aggregate (g);

Wbit weight of bitumen (g);

WA’ A-weighted sound power level (PWL);

Wref reference sound power level (PWL) = (10-12

watts);

α sound absorption coefficient (empirical constant);

αc permeability deterioration rate (empirical constant);

ηw viscosity of water (kg/m.s);

λ shape factor function of tortuosity of medium;

ρc density of clogging material (kg/m3);

ρw density of water (kg/m3);

σ specific deposit of clogging material.

15

CHAPTER 1 INTRODUCTION

1.1 General

Urbanization is increasing with the growth in world population. As

cities expand, the drainage networks in many cities are unable to handle the

higher runoff due to the increased built up areas. As such, flooding has

become a common occurrence. A good alternative is to use pervious concrete

as road pavement material to supplement the passive storm water management

system.

Pervious concrete is described typically as a near zero-slump, open

graded material consisting of Portland cement, coarse aggregates with little or

no fine aggregates, admixtures and water (ACI Committee Report 522, 2010).

The use of pervious concrete in pavements and housing dated back to the 18th

century in Europe as it was cheaper compared to conventional concrete due to

the lesser amount of cement used during its construction (Chopra et al., 2007).

In the 1990s and early 2000s, pervious concrete was used as a wearing course

on high‐speed roads in Europe and Japan. Pervious concrete also served as a

noise reducer and safety measure. The interconnected void network in

pervious concrete reduces noise and removes water from the vehicle wheel

path thus improving skid resistance and effectively improving road safety.

(Environmental protection agency, 2008; ISU-FHWA-ACPA, 2006 and

Kagata et al., 2004).

The connected pores in pervious concrete range from 2 mm to 8 mm in

size and allow water to pass through easily. The void content could range from

15% to 35% and typical compressive and flexural strengths are between 2.8 to

16

28 MPa and 0.6 to 4.8 MPa respectively. Pervious concrete is weaker in

strength as compared to normal weight concrete but provides better drainage.

The drainage rate of pervious concrete pavement varies with aggregate size

and density of the mixture and is typically between 1.4 mm/s to 12.2 mm/s.

1.1.1 Advantages and limitations

Pervious concrete is increasingly used in the United States because of

its various environmental benefits such as controlling storm water runoff,

restoring groundwater supplies and reducing water and soil pollution (Youngs,

2005; Tennis et al., 2004 and Kajio, 1998). Further advantages of a pervious

concrete pavement are its ability to decrease the effect of heat-island as

surface temperature is lowered due to increased evaporation of water;

increased skid resistance and surface friction; reduction in tire noise as it

absorbs the noise and dissipates it within the pavement. It can be considered a

green and recyclable building material (Kevern et al., 2009; Haselbach et al.,

2006; Ferguson, 2005; US EPA, 1999 and Bean et al., 2007).

Some disadvantages of pervious concrete include its inability to handle

heavy traffic loadings due to its low compressive and flexural strengths. Also

the drainage function of pervious concrete may be lost due to clogging over

time and this requires effective and timely cleaning. Such timely maintenance

and cleaning of the pervious concrete may be costly. (Kevern et al., 2009;

Haselbach et al., 2006; US EPA, 1999 and Balades et al., 1995).

1.1.2 Applications

Pervious concrete has been used in a wide range of applications not

only in parking lots, road shoulders, minor pavements, base course for streets,

17

roads, driveways and airports, surface course for parks and tennis courts; but

also for greenhouse floors to keep the floor free of standing water; thermal

insulation applications; walls and floors where better acoustic characteristics

are desired; bridge embankments, structures and seawalls, drains as well as

sewage treatment plant sludge beds (ACI Committee report 522, 2010).

(a) Surface course - Pervious concrete is used as a surface course for

parking lots and minor road strips to a large extent in the U.S. Many parking

lots in Florida consist of a pervious concrete surface course, which is useful as

Florida frequently encounters heavy storms that cause a quick accumulation of

large amounts of stormwater. The use of pervious concrete reduces runoff

volume; designers prefer the stormwater to be retained on-site to recharge the

groundwater system and the cost effectiveness of using pervious concrete over

conventional pavements is greatly enhanced with the elimination of storm

sewers (ACI Committee report, 2010).

(b) Parking lots - Pervious concrete has also been used in parking lots

in the central Florida area as early as the 1970s (Medico, 1975). The

Environmental Protection Agency (EPA) has adopted a policy that

recommends the use of pervious pavements as part of their Best Management

Practices (BMPs) as a way for communities to mitigate the problem of

stormwater runoff. Pervious concrete parking lots have also been selected as

an integral solution to the problem of hot pavements in the Cool Communities

Program. The air temperature over pervious parking lots is generally cooler

than asphalt. Pervious concrete parking lots also reduce snow and ice build-up

and are considered a non-pollutant to the environment. Schaefer et al., (2008)

reported that pervious concrete has been used as a construction vehicle

18

parking area test section in Sioux City, Iowa; visitor parking area at North

Liberty, Iowa and handicapped parking area at the Iowa Great Lakes Maritime

Museum. The design thickness for pervious concrete pavements is 125 mm to

300 mm for normal concrete parking lots.

(c) Base and subbase - Pervious concrete for roadways is usually used

as a drainable base or sub-base material, and as a roadway surface or friction

course. Although good drainage characteristics are derived, strength

requirements may vary depending on the location of the material in the

pavement section. The design thickness for pervious concrete roadway

pavements is between 150 mm to 300 mm. Maynard (1970) noted that bonded

overlays as thin as 50 mm have been used.

A pervious concrete base drains water that would normally accumulate

beneath a pavement. This type of construction helps to reduce pumping of

subgrade materials that could lead to the failure of the pavement. The States of

California, Illinois, Oklahoma and Wisconsin in U.S have standard

specifications for constructing drainable bases and edge drains using pervious

concrete (Mathis, 1990). Pervious concrete in these applications is usually of

lower compressive strengths at around 7 MPa or less and is used together with

a nonwoven geotextile fabric.

(d) Other applications - Pervious concrete shoulders have been used in

France to reduce pumping beneath concrete pavements. Air-entraining

admixtures are used to increase resistance to freezing and thawing. Porosities

of about 15 to 25 % have been found to nearly eliminate the risk due to

freezing unless the concrete is allowed to become saturated with water.

19

Compressive strengths are often less than 14 MPa at 28 days (ACI Committee

Report 522, 2010).

1.2 Significance of current study

Due to the wet-tropical climate and rapidly increasing built-up areas,

many urban cities like Singapore are subjected to flash floodings during heavy

downpour. The use of pervious concrete pavements (Chan et al., 2012) would

effectively drain away rainwater as well as provide a temporary storage for

flood water during high tides.

The major requirements for pervious concrete to be used in major road

pavements are adequate flexural strength, porosity and permeability. However

because permeability and porosity decrease with increasing flexural strength,

the challenge in pervious concrete mix proportioning is in achieving a balance

between an acceptable permeability and flexural strength. The inclusion of

fibers in pervious concrete is an effective step in preventing the expansion of

micro-cracks and to increase the flexural strength of pervious concrete (Seung

et al., 2012).

The first part of this research will therefore investigate the use of steel

fibers having different hooked-end configurations and in varying dosages in

pervious concrete, with a focus on flexural and compressive strengths,

porosity and permeability. Target satisfactory performances are: a flexural

strength exceeding 3.5 MPa, porosity more than 20% and permeability above

10 mm/s. The target strength follows the minimum requirement for rigid

pavement according to AASHTO (1993).

20

The second part of the study will focus on the clogging characteristics

of pervious concrete. Because of the large pore sizes, clogging of pervious

concrete due to dust and debris when in service would be a major concern.

The permeability and clogging characteristics of pervious concrete mixtures

were also compared with porous asphalt mixes.

The third part of the study will evaluate the sound absorption capacity

of pervious concrete. Pervious concrete has been noted to produce a quieter

environment; however, little study has been done in this respect. A

comparison with other road pavements materials, that is, normal weight

concrete, lean concrete; dense asphalt, open-graded and porous asphalt was

carried out.

1.3 Objectives and scope of research

The main objective of this research is to investigate the use of pervious

concrete for road pavements with focus on flexural strength, porosity and

permeability. Steel fiber reinforced pervious concrete would be explored. The

second objective is to evaluate the clogging performance and the third

objective to assess the sound absorption capacity of pervious concrete. The

scope of work is as follows.

1.3.1 Physical and mechanical properties

The effect of mix proportion and steel fibers on the compressive and

flexural strengths and porosity and permeability of pervious concrete was

studied. Test parameters included the coarse aggregate size, cement content,

21

water-cement ratio, type and dosage of steel fibers. The steel fibers had

hooked ends of different configurations.

1.3.2 Clogging characteristics

The effect of clogging on the permeability of pervious concrete was

investigated and compared to porous asphalt. Four types of clogging materials

were first analysed; they were residual soil, fine to medium sand, fine to

coarse sand and medium to coarse sand. The type of sand most detrimental to

the clogging of pervious concrete and porous asphalt was used for further

tests. The experimental programme considered four target porosity levels

which covered the likely range that a porous pavement material would

undergo through its entire useful service life. Empirical equations relating the

permeability and porosity were established. The effect of clogging on steel

fiber reinforced pervious concrete was also examined.

1.3.3 Sound absorption characteristics

The sound absorption characteristics of pervious concrete was

investigated and compared with other pavement materials including normal

weight concrete; lean concrete; porous asphalt, open-graded and dense asphalt

mixtures. Test parameters included porosity, thickness and clogging

percentage.

22

1.4 Structure of thesis

The thesis contains six chapters.

Chapter 1 gives an introduction on the use of pervious concrete in road

pavements. The research significance, objectives and scope of work are

highlighted.

Chapter 2 provides a review of the physical and mechanical

properties, the clogging and the sound absorption characteristics of pervious

concrete. Test methods for the various properties are also summarized.

Chapter 3 describes the test programme carried out on the physical

and mechanical properties of pervious concrete with and without steel fibers.

The materials, mix proportion, mixture preparation and test methods are

detailed. Test results are discussed and mixture proportions are recommended.

Chapter 4 presents the test programme and results on the clogging

characteristics of pervious concrete and porous asphalt with porosities ranging

from 10% to 25%. The effect of steel fiber inclusion on clogging is also

presented.

Chapter 5 discusses the test programme and results on the sound

characteristics of pervious concrete. Comparison with porous asphalt mixtures

is made.

Chapter 6 summarizes the work carried out and draws conclusions

and offers recommendations for future research.

23

CHAPTER 2 LITERATURE REVIEW

This chapter reviews previous works on the mechanical and physical

properties, clogging as well as sound absorption characteristics of pervious

concrete. The use of fibers in pervious concrete and test methods for clogging

are also described.

2.1 Physical and mechanical properties of pervious concrete

2.1.1 Effect of mixture proportion

The study on compressive strength, flexural strength, porosity and

permeability is of significance as they have been found to be influenced by the

mixture proportions, that is, cement content, coarse aggregate content and

water-cement ratio. When the cement content is increased, there will be an

increase in compressive and flexural strengths; however porosity and

permeability will be compromised. When the coarse aggregate content is

increased, the changes in compressive strength, flexural strength, porosity and

permeability are not as significant as other factors like the cement content and

water-cementitious ratio of the mixture proportion (ACI committee report 522,

2010).

The water-cementitious material (w/cm) ratio is an important

consideration to obtain the desired strength and void structure in pervious

concrete. A high w/cm ratio reduces the adhesion of the paste to aggregates

and causes the paste to flow and fill the voids even when lightly compacted. A

low w/cm ratio prevents good mixing and tends to cause balling in the mixer,

leading to an uneven distribution of cement paste, and therefore reducing the

ultimate strength and durability of concrete. Conventional w/cm ratio versus

24

compressive strength relation for normal concrete does not apply to pervious

concrete (ACI committee report 522, 2010).

Compared to conventional concretes with similar quantities of

cementitious materials, pervious concrete has lower compressive, flexural, and

bond strengths (Joung and Grasley, 2008; Crouch et al., 2007; Schaefer et al.,

2006; Fortes and Merighi, 2006; Kagata et al., 2004; Taniguchi and Yoshida,

2004; Zouaghi et al., 2000; Ghafoori et al., 1995; Malhorta, 1976).

The strength, porosity and permeability of pervious concrete depend on

the mixture design. Table 2.1 shows the typical ranges of material proportions

in pervious concrete according to the National Ready Mixed Concrete

Association (NRMCA, 2011) and the American Concrete Institute (ACI

Committee 522, 2010). Typical cement content is between 267 to 415 kg/m3,

coarse aggregate content ranges from 1190 to 1480 kg/m3 and water-cement

ratio from 0.27 to 0.36.

The strength and drainage properties of pervious concrete are primarily

determined by paste strength, aggregate type and volume of interconnected

voids (Crouch et al., 2007; Olek et al., 2003; Ghafoori et al., 1995 and Suzuki

et al., 1994).

Figures 2.1 to 2.3 show the effect of cement content, coarse aggregate

content and water-cement ratio, respectively, on the compressive strength,

flexural strength, porosity and permeability of pervious concrete.

Cement and coarse aggregate contents in the range of 200 – 500 kg/m3

and 1400 – 1800 kg/m3, respectively, resulted in compressive strength from 5 -

25

38 MPa; flexural strength from 0.5 - 4.8 MPa; porosity from 13 - 33% and

permeability from 1 - 32 mm/s. Increase in cement and coarse aggregate

contents typically results in an increase in the compressive and flexural

strengths, but a reduction in the permeability and porosity of pervious concrete

is not so distinct as indicated by Figures 2.1 and 2.2.

From Figure 2.3, it can be noted that a water-cement ratio ranging from

0.25 - 0.51 can result in compressive strength from 5 - 38 MPa; flexural

strength from 0.5 - 4.8 MPa; porosity from 2 - 33% and permeability from

0.25 - 31 mm/s. An increase in water-cement ratio resulted in a reduction in

compressive strength as well as permeability. The optimum water-cement ratio

ranges from 0.25 – 0.35 for a reasonable compressive strength, flexural

strength, porosity and permeability (Hesami et al.,2014; Bhutta et al., 2012;

Deo et al., 2011; Kevern et al., 2011; Huang et al., 2010; Neithalath et

al.,2010; Sumanasooriya et al., 2010 and Haselbach et al., 2006).

Figure 2.4 shows the effect of fiber dosage using polypropylene and

steel fibers. Fiber dosage ranging from 0.16% – 1%, results in compressive

strength from 7.5 – 22.5 MPa; flexural strength from 0.7 – 2.6 MPa; porosity

from 22 – 27.2% and permeability from 2.5 - 14 mm/s (Rehder et al., 2014;

Kevern et al., 2014; Hesami et al.,2014; Xiang et al., 2011 and Huang et al.,

2010).

2.1.1.1 Compressive strength

Research works by Sumanasooriya et al. (2012); Deo and Neithalath,

(2011); Neithalath et al. (2010); Sumanasooriya and Neithalath (2005) and

Bhutta et al. (2011) indicated that a reduction in the porosity of the pervious

26

concrete mixture would result in an increase in the compressive strength. This

result is supported by Agar-Ozbek et al. (2013) and Crouch et al. (2007) who

both noted that increasing the coarse aggregate content would result in a

decreasing amount of cement paste to fill up the pores and thus higher pore

contents in the pervious concrete matrix. As less cement paste is available for

aggregate bonding, the compressive strength would be lowered. Generally, a

10% increase in porosity approximately halves the compressive strength of

pervious concrete irrespective of the paste content and compaction procedure.

2.1.1.2 Flexural Strength

Nissoux et al. (1993) and Brite/Euram Report (1994) noted that a

flexural strength of about 3 MPa has been observed for a pervious concrete

proportioned using 6 to 10 mm aggregates and having 25% porosity. Bin

(2011) and Tennis et al. (2006) were both able to obtain flexural strength of

between 1.0 to 3.8 MPa.

2.1.1.3 Porosity

Porosity is highly dependent on several factors, that is, aggregate

gradation, cementitious material content, water-to-cementitious material ratio

and compactive effort (ACI Committee Report, 2010). Mulligan (2005) noted

that pervious concrete could achieve compressive strengths of approximately

17 MPa but with a reduction in porosity. This is supported by Schaefer et al.

(2008) who reported that the seven-day compressive strength decreased

linearly as porosity increased.

27

2.1.1.4 Permeability

The permeability of a material depends on the size and connectivity of

voids within its structure. It can be measured using the falling-head or the

constant-head permeameter method. In the falling head method, a fixed

amount of water is allowed to flow through the sample and the time taken for

all the water to flow through the sample is recorded. In the constant-head

permeameter method (Joung and Grasley, 2008; Delatte et al., 2007; Fortes

and Merighi, 2006; Olek et al., 2003), the sides of the pervious concrete

sample are sealed, a head (height) of water is maintained above the top end of

the sample and the volume of water that exits the lower end of the cylinder is

collected for a specified amount of time. The volume and the time taken are

measured, from which the permeability coefficient is determined.

Montes and Haselbach (2006) noted that the coefficient of

permeability of pervious concrete can range from 2 mm/s to 12 mm/s. It is

directly related to porosity and the pore sizes. Meininger (1988) has shown

that a minimum porosity of approximately 15% is required to achieve

significant permeability. For a porosity of 20% to 25% the coefficient of

permeability was reported to be approximately 10 mm/s (Brite/Euram Report,

1994).

2.1.2 Use of supplementary materials in pervious concrete mixes

Jing and Jiang (2003) reported that due to the presence of voids in

pervious concrete, it was difficult to obtain high strength by using common

material mix proportion. They found that the use of polymer superplasticer

and silica fume could enhance the strength of pervious concrete greatly. But it

28

was challenging to ensure good water permeability due to the polymer filling

up the pore spaces. They obtained a high compressive strength of about 50

MPa and a flexural strength 6 MPa but permeability was reduced to as low as

2.9 mm/s.

A study of pervious concrete incorporating lightweight aggregates was

performed by Kim and Lee (2010). They reported that samples with

lightweight aggregates had lower compressive strength compared to normal

weight aggregate samples.

Xiang et al. (2011) did a study on pervious concrete mixtures made

with latex and noted that these mixes exhibited lower porosity and

permeability but higher compressive and abrasion resistance than those

without latex. Results obtained from laboratory mixtures showed a low

permeability of 1.8 mm/s to 2 mm/s and compressive strength of 22 MPa to 30

MPa while field test mixtures gave a very low permeability of 0.2 mm/s but a

high compressive strength of 50 MPa.

Bhutta et al. (2011) evaluated high performance pervious concrete

(HPPC) properties using a thickening water-soluble cellulose based polymer

powder. The observed porosities were in the range of 18% - 23%, compressive

strength between 16 - 25 MPa, flexural strength between 3.5 – 4.8 MPa and

permeability between 2 –17 mm/s. They were able to obtain a high

compressive strength of 25 MPa and flexural strength of 4.8 MPa; however,

permeability was compromised and was around 2 mm/s.

It was concluded that the addition of polymer to pervious concrete

mixture would decrease the permeability but significantly increase the

29

compressive and flexural strengths. This is because of the strong bond

between the cement paste and aggregate resulting from the use of the polymer.

The use of recycled aggregates in pervious concrete was studied by

Sata et al. (2013). They reported that pervious concrete containing crushed

structural concrete materials and crushed clay brick gave lower compressive

strengths than those containing natural aggregates. A moderate compressive

strength of 13.6 MPa, low splitting tensile strength of 1.8 MPa but a high

permeability of 17.1 mm/s were recorded.

Last, the use of municipal solid waste incinerator bottom ash

(MSWIBA) in pervious concrete was investigated by Kuo et al. (2013). They

noted that there was no significant difference in compressive strength, porosity

and permeability between pervious concrete made with MSWIBA and those

made with natural aggregates. When MSWIBA was used in pervious concrete,

a low compressive strength but high permeability in the range of 4.8 – 12.7

MPa and 6 – 41 mm/s respectively were obtained.

From the above review, it can be noted that compressive strength and

flexural strength can be enhanced by using appropriate supplementary

materials but permeability and porosity would be compromised.

2.1.3 Fiber reinforcement for pervious concrete

Fibers can be made of synthetic and organic materials such as

polypropylene and cellulose; as well as steel. Joung (2008) noted that the use

of fibers has limited effect on the compressive strength of normal concrete but

a significant effect on the flexural strength of normal concrete. With sufficient

30

flexural strength and good permeability and porosity, fiber reinforced pervious

concrete can be used for pavements. Joung (2008) also concluded that

traditional straight fiber reinforcement such as polypropylene and cellulose

fibers will provide only minimal improvement in the flexural strength of

pervious concrete. Similarly, Kevern et al. (2014), Rehder et al. (2014), Xiang

et al. (2011), Schaefer and Kevern (2011) and Huang et al. (2010) found that

the use of polypropylene and cellulose fibers were unable to provide

satisfactory flexural strengths suitable for urban road usage.

Schaefer and Kevern (2011) noted that the addition of cellulose fibres

had limited effect on the initial workability of pervious concrete. Xiang et al.

(2011) tested pervious concrete with polypropylene fibers and obtained a

compressive strength of approximately 16 MPa and permeability of 3.4 mm/s,

which however do not satisfy the required performance for urban road usage.

Kevern et al. (2014) also studied polypropylene fibers at dosage rates of

0.16%, 0.33% and 0.49% per volume of concrete. They concluded that the

compressive and flexural strengths were also not significantly improved but

permeability decreased with the addition of cellulose fibers.

Hesami et al. (2014) did a study using steel fibers at a dosage rate of

0.5%. They reported a permeability ranging from 0.9 mm/s to 2.1 mm/s and a

flexural strength of about 2.7 MPa. They noted that the use of steel fibers

provided promising flexural strength and permeability.

In summary, polypropylene and cellulose fiber reinforced pervious

concrete did not give any strength enhancement, while steel fiber reinforced

31

pervious concrete appeared to be promising in meeting the target performance

for road use and need to be further studied.

2.2 Clogging characteristics of pervious concrete

The influx of stormwater containing suspended solid matter such as

dirt, fine sand and debris can lead to a gradual reduction in the drainage

capacity or permeability of pervious concrete when used as a surface course in

pavements or parking lots. The most common equipment used to study the

clogging characteristics of pavement material is the constant head or falling

head permeameter as mentioned in Section 2.1.1.4. Instead of using the

constant head permeameter to test for permeability, an adjustable wooden

flume machine to estimate the permeability of the specimen after clogging was

used by Haselbach et al. (2006).

The constant-head clogging method used in this study was referenced

from Tan et al. (2001), Mata, (2008), Joung et al. (2008) and Deo et al. (2009).

This clogging method was said to entail good repeatability of results. The

constant-head clogging test procedure involved the addition of clogging

material into the water which is then flushed through the specimen. The

permeability of the test specimen is measured after clogging and then

compared to a terminal permeability of 1 mm/s as recommended by Fwa et al.

(2002), Tan et al. (2000) and Fwa et al. (1998). If the terminal permeability is

not reached, the clogging cycles are continued until the permeability is smaller

than 1mm/s indicating that further addition of clogging material would cause a

negligible reduction in the permeability.

32

2.2.1 Effect of clogging materials

Runoff carrying with it a large amount of suspended particles is known

to be the main source that causes clogging of pore spaces in porous pavements

during their life time (Nielsen, 2007; Siriwardene et al. 2007 and Yong et al.

2008). Siriwardene et al. (2007) reported that clogging may also occur due to

the inorganic and organic particles from traffic activities and localized

vegetation or dust that is often found on roadways.

According to Cooley (1999), sand particles and solid materials are

pushed into the pores of the permeable pavement by the weight of the passing

vehicles which may also crush them into finer sizes. These sand and solid

particles can be brought into the pores by flowing water from a storm event. It

is possible that the vehicle weight may push materials into the pavement at the

front part of the tire, and the back part of the tire may create a suction to

remove some of the solids. Under certain conditions and depending on the

type and size of solids, once in the pores, the clogging materials may become

embedded and accumulate to cause clogging of the pores. When a significant

percentage of the pores in the permeable pavement are clogged, the

permeability of the pavement is reduced and water begins to pool on the

pavement surface. This will defeat the purpose of having a permeable

pavement.

Kayhanian et al. (2012) assessed the clogging of pervious pavements

in parking lots and reported that an important factor causing a reduction in

pavement permeability is the mass of fine particles less than 38 µm. The

presence of larger pore sizes due to large aggregates in the material resulted in

33

the easy entry of the clogging material through the pore structure, while

smaller pore sizes due to small aggregates inhibited the entry of the clogging

material into the pore structure. This was supported by works by Hasselbach et

al. (2006) and Taniguchi and Yoshida (2004) who reported that using smaller

aggregate sizes created smaller void spaces which was conducive to collecting

clogging material, which in turn gradually clogged the pores and rendered the

porous pavement impermeable.

Bean et al. (2007) investigated the influence of different clogging

materials such as sand sediments, fine grained sediments and a combination of

these materials on their deposition and subsequent reduction in the

permeability rates of pervious concrete pavements laid on either sandy soil,

silty soil or silty-sand soil. It was found that sand sediments were the most

detrimental clogging material. This finding was further supported by Deo et al.

(2010) who used fine sand of less than 0.84 mm in size and coarse sand

ranging from 0.84 mm to 1.80 mm in size to test for the permeability reduction

in pervious concretes due to clogging. When coarser sand was used as the

clogging material, the reduction in permeability was not substantial as the

coarse sand was larger than the pore size and thus unable to clog the pores of

the pervious concrete matrix.

Both Siriwardene et al. (2007) and Yong et al. (2008) concluded that

sand particles less than 6 μm in size was detrimental to pervious concrete.

Siriwardene et al. (2007) investigated the physical clogging of permeable

pavements and found that the main factor in the development of clogging was

the migration of particles less than 6 μm in diameter. Yong et al. (2008) also

used particles less than 6 μm present in the simulated stormwater to clog the

34

pavements. The accumulation of the particles less than 6 μm in diameter over

the 17.5 weeks resulted in significant clogging of the permeable pavement

when the flood storms were simulated.

In summary, from research done by Bean et al. (2007), Siriwardene et

al. (2007), Yong et al. (2008), Deo et al. (2010) and Kayhanian et al. (2012),

common sand sizes used in clogging tests are in the range of 6 μm to 1.80 mm.

2.2.2 Service life of pervious concrete pavements with clogging

A pervious concrete pavement upon opening to traffic may experience

an initial reduction in permeability as reported by Abbot and Comino-Mateos

(2006) who stated that clogging could occur within the first two years of

pavement construction and that pervious concrete pavement would experience

a reduction in permeability of up to 10% of its initial value in 2-3 years.

However, the pervious concrete pavement still retained its functionality in

years to come as Wingerter and Paine (1989) reported from a field

investigation conducted in Florida on pervious concrete pavements that

pervious concrete pavements showed small amounts of clogging after

approximately 13 years of service. Wanielista et al. (2007) also indicated that

pervious concrete pavement in Florida and other southeast United States

locations that were installed 10 to 15 years ago with no maintenance

requirements, were still operating in a satisfactory manner with insignificant

amounts of clogging.

35

2.3 Sound absorption properties of pervious concrete

Traffic noise reduction has become important especially to the

residential environment. To mitigate traffic noise, porous pavement materials

that can absorb sound waves over wide frequency ranges should be examined

(Mun, 2010).

An effective way to lower noise is to reduce noise generation at the

source. Pervious concrete is considered a quiet pavement (Rasmussen et al.

2008) as it produces noise level between 96 to 98 decibels dB(A) when tested

under normal traffic speed according to AASHTO TP76 Standard Method of

Test Measurement of Tire/Pavement Noise Using the On-Board Sound

Intensity (OBSI) Method (AASHTO 2010). For traditional concrete, the noise

level ranged from 100 to 110 dB(A) (National CP Tech Center, 2011).

When studying road noise due to vehicles travelling at normal traffic

speeds, most tires and road combinations show peaks within the range of 630 -

2000 Hz. This is particularly the case for car tires, but in many cases also for

truck tires (Sandberg, 2003). Most highway noise falls into a narrower

frequency range of 800 - 1200 Hz (Neithalath et al., 2005).

Wang and Lu (1999) and Voronina (1999) stated that in a rigid-framed

porous material, the pore walls are non-deforming, and thus acoustic

absorption occur primarily due to viscous losses and thermo-elastic damping

as the sound propagates through a large number of air cavities. Due to their

interconnected pores, pervious concrete and porous asphalt result in reduction

in tire-generated noise in two ways (Berhard, 2002). First, tire-pavement noise

generation is altered by a reduction in air pumping that occurs when air is

36

drawn into and pumped out of the gaps between tread blocks in the tires. This

allows air to escape through the pavement. Second, the reflection and

scattering of acoustic waves in the pores result in absorption and dissipation of

sound through internal friction (Neithalath et al., 2005).

In general, noise absorption characteristics are measured using the

impedance tube (Luong et al., 2014; Gonzalez et al., 2013; Izevbekhai, 2011;

Ahammed and Tighe, 2011; Kim and Lee, 2010; Seddeq, 2009; Park et

al.,2005; Tiwari et al., 2004 and Neithalath et al., 2005). For traffic noise, the

A-filter is used, which generally concentrates on the frequencies between 1000

and 4000 Hz; which are the frequencies for which human has the greatest

sensitivity as well as values in the 1/3 octave band. Values in which the A-

filter are used are referred to as “A-weighted decibels” or dB (A) (EUPAVE,

2015). Factors that affect the sound absorption capacity of a porous material

would be its porosity; tortuosity and thickness (Seddeq, 2009).

2.3.1 Acoustic properties of pervious concrete pavements

To measure sound pressure levels, a phonometer or the on-board sound

intensity method can be used. The phonometer is a device to measure the

sound intensity directly and this test method is different from the on-board

sound intensity (OBSI) test method which employs microphones attached to

the vehicle wheels.

From the sound level reading at a site test using a phonometer done by

Agostinacchio and Cuomo (2006), pervious concrete, normal concrete and

asphalt pavement each had a reading of 76.02 dB(A); 81.02 dB(A) and 79.90

dB(A) respectively. Based on sound absorption performance, pervious

37

concrete behaved better than conventional pavement materials such as normal

weight concrete and dense graded asphalt. When clogged, Izevbekhai (2011)

reported that the sound absorption capacity of pervious concrete pavements

was reduced.

For pervious concrete, the typical sound absorption coefficient (α)

ranges from 0.2 to 0.98 (Kim and Lee, 2010 and Park et al., (2005)), and from

0.1 to 0.90 for porous asphalt (Luong et al., 2014; Losa and Leandri, 2012;

Mun, 2010 and Meiarashi et al., 1995).

2.4 Target performances

Table 2.2 tabulates the target performances for pervious concrete.

Referring to AASHTO (1993) and FHWA (2011), a minimum flexural

strength of 3.5 MPa would be needed for pervious concrete pavement.

To be comparable to porous asphalt pavement in most countries in

Europe, USA and Asia, a minimum porosity of 20% is required for pervious

concrete (Belgian Road Research Center, 2000). As for the required

permeability, it is noted that for countries with temperate or drier climate,

permeability higher than 0.09 mm/s would be needed. However, due to South

East Asia’s tropical climate and the increasingly high intensity rainfall in

recent times, a permeability of more than 1.16 mm/s is necessary. Based on

the Brite/Euram Report (Brite-Euram Project, 1994) as well as to ensure

sufficient drainage in major pavements, a target permeability of more than 10

mm/s was therefore selected for this research.

38

Figures 2.5 and 2.6 show the target performance in terms of

compressive strength, flexural strength, porosity and permeability of pervious

concrete to be used in urban pavements, versus those of pervious concrete

investigated by various investigators. The latter include conventional as well

as fiber reinforced pervious concrete.

2.5 Summary

In this chapter, research works on pervious concrete, covering mixture

proportioning, compressive strength, flexural strength, porosity and

permeability, use of fiber reinforcement, clogging and sound absorption

characteristics were reviewed.

From the literature review on both pervious concrete and porous

asphalt mixes, satisfactory performance for pervious concrete for use in urban

pavements were set as having a flexural strength exceeding 3.5 MPa, porosity

more than 20% and permeability above 10 mm/s so as to ensure good

drainage.

For the study of clogging characteristics, common sand sizes used for

clogging tests range from less than 6 μm to 1.80 mm. The impedance tube

serves as the most appropriate sound absorption measurement method in the

laboratory and is widely used and adopted in this research. Porous pavement

materials provide higher sound absorption capacity over a wide frequency

range, thus aiding in tire/road noise reduction.

39

Table 2.1 Typical ranges of material proportions in pervious concrete

NRMCA

(2011)

ACI Committee 522

(2010)

Cementitious materials (kg /m3) 267 - 326 270 - 415

Aggregate (kg /m3) 1190 - 1480 1190 - 1480

w/cm (by mass) 0.27 – 0.36 0.27 – 0.34

Aggregate: cement ratio (by

mass) - 4 - 4.5

40

Table 2.2 Pervious concrete target requirements

Pervious

Concrete

Properties

Requirements Reference Remarks Target

Performance

Flexural

Strength

Normal Concrete

Pavement

3.5 MPa –

8.27 MPa

Normal Concrete

Pavement

AASHTO Guide

for design of

pavement

structures, 1993.

Specification

Pervious Concrete

Pavement

1.03 MPa

– 3.79

MPa.

0.60 MPa

– 4.80

MPa

Pervious Concrete

Pavement

FHWA, 2011,

Obla, 2007 and

Tennis et al.,

2004.

Various pervious

concrete

literature review:

Meininger 1988;

Xiang et al.,

2011; Huang et

al., 2010 and

Bhutta et al.,

2012.

General

property

Typical

laboratory

samples results

More than

3.5 MPa.

Porosity Pervious Concrete

Pavement

15 - 35%

13.0 -

32.6 %

Pervious Concrete

Pavement

ACI 522R-10

Report on

pervious

concrete

recommendation

Various pervious

concrete

literature review:

Meininger 1988;

Deo et al., 2011;

Neithalath et al.,

2010;

Sumanasooriya

et al., 2010;

Haselbach et al.,

2006; Huang et

al., 2010;

Kevern et al.,

2011 and Bhutta

et al., 2012.

General

property

Typical

laboratory

samples results

More than

20%.

41

Table 2.2 Pervious concrete target requirements (Cont’d)

Pervious

Concrete

Properties


Performance

Porosity

Asphalt porous

pavement

Europe

European

porous asphalt

mixes: at least

20% porosity.

United

Kingdom:

20% porosity

and 27.2 %.

Spain: 15 - 22

%.

Belgium: 19 –

25 %.

Switzerland:

14.6 - 21.1 %.

Netherlands:

minimum 20%

porosity.

Italy:

minimum 18 -

22 %.

Asphalt porous

pavement

Europe

Kandhal and

Mallick, 1998

Nicholls,

1998; Daines,

1986.

Ruiz et al.,

1990.

Van

Heystraeten

and Moraux,

1990.

Isenring et al.

1990.

Van der Zwan

et al., 1990.

Huber, 2000.

Specification

Specification

Specification

Specification

Specification

Specification

Specification

More than

20%.

Asia

Australia:

Porosity >

20% and 18 -

23 %.

Singapore: 20

- 26%.

Malaysia:

Porosity >

18%.

South Korea:

Porosity > 20

%.

South Africa:

5 - 6.5 %

Asia

Alderson, A,

1996, Leach

and Limb,

1986.

Land

Transport

Authority,

Guwe et al.,

2002.

JKR, 2008.

Hamzah et al.,

2004.

Liebenberg et

al., 2004.

Specification

Specification

Specification

Specification

Specification

42


Pervious

Concrete

Properties


Performance

Permeability

Pervious Concrete

Pavement

Singapore:

0.04 mm/s –

0.3 mm/s

1.35 mm/s –

12.2 mm/s

1.3 mm/s –

31 mm/s

10 mm/s for

a porosity of

20 – 25%

Pervious Concrete

Pavement

Chan et al.,

2012.

FHWA, 2011,

Obla, 2007 and

Tennis et al.,

2004.

Various

pervious

concrete

literature

review:

Meininger

1988;

Haselbach

et.al.,2006;

Mahboub et

al., 2009;

Xiang et al.,

2011; Huang

et al., 2010 and

Bhutta et al.,

2012.

Brite/Euram

Report , 1994.

Rainfall

intensity

General

Property

Typical

laboratory

samples

results

Typical

laboratory

samples

results

More than

10 mm/s.

.

Asphalt porous

pavement

USA

Georgia:

0.45 mm/s –

0.92 mm/s.

Arizona:

0.09 mm/s –

0.54 mm/s.

North

Carolina:

Permeability

> 1.16 mm/s.

Mississippi:

Permeability

> 0.35 mm/s.

Asphalt porous

pavement

USA

Santha, 1997.

Hossain et al.,

1992.

Putman and

Kline, 2012.

Putman and

Kline, 2012.

Specification

Specification

Specification

Specification

43


Pervious

Concrete

Properties


Performance

Permeability

Europe

European

porous

asphalt mix >

1.2 mm/s.

United

Kingdom:

5.43 mm/s –

7.79 mm/s

(laboratory

test); 11.3

mm/s to 50.9

mm/s (actual

road test).

Switzerland:

0.76 mm/s –

3.48 mm/s.

Europe

Watson et

al., 1998.

Daines,

1986.

Isenring et

al. 1990.

Specification

Laboratory

results and

actual road

tests

Specification

More than

10 mm/s. Asia

Singapore: 5–

8 mm/s.

Malaysia:

Permeability

> 1.16 mm/s.

South Korea:

Permeability

> 1 mm/s.

Asia

Guwe et

al., 2002.

Mallick,

2000 and

Hamzah et

al., 2010.

Hamzah et

al., 2004.

Typical

laboratory

samples

results

Specification

Specification

South Africa:

0.01 mm/s –

0.06 mm/s.

Liebenberg

et al., 2004.

Specification

44

Figure 2.1 Effect of cement content

45

Figure 2.2 Effect of coarse aggregate content

46

Figure 2.3 Effect of water-cement ratio

47

Figure 2.4 Effect of fiber dosage

48

Figure 2.5 Compressive strength (MPa) versus porosity (%)

Figure 2.6 Flexural strength (MPa) versus permeability (mm/s)

0

5

10

15

20

25

30

0 10 20 30 40

Com

pre

ssiv

e S

tren

gth

MP

a

Porosity %

Meininger (1988)

Huang et.al (2010)

Huang et.al (2010)

Polypropylene fibers

Deo et.al (2011)

Bhutta et al (2012)

Hesami et al (2014)

Target research area

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 5 10 15 20 25 30 35 40

Fle

xura

l S

tren

gth

MP

a

Permeability mm/s

Meininger (1988)

Huang et.al (2010)

Huang et.al (2010)


Xiang et.al (2011)

Xiang et.al (2011)


Bhutta et al (2012)

Hesami et al (2014)


49

CHAPTER 3 PHYSICAL AND MECHANICAL PROPERTIES OF

PERVIOUS CONCRETE

An extensive test programme was carried out on the physical and

mechanical properties of pervious concrete. Part I of the test program covered

unreinforced pervious concrete with different mix proportions, while Part II

explored steel fiber reinforced pervious concrete. For Part I, the objective was

to achieve a mix design that provides adequate strength in pervious concrete

without compromising on porosity and permeability. The test variables studied

were coarse aggregate to cement ratio, w/c ratio, cement content and coarse

aggregate size. For Part II, the properties of pervious concrete reinforced with

discrete steel fibers were investigated. To satisfy traffic loading requirements

for major road pavements, the steel fiber-reinforced pervious concrete must

have adequate strength and be reasonably permeable to provide good drainage.

Hook-end steel fibers having different end configurations and in dosages from

1% to 2.5% by volume were considered.

3.1 Test programme

The mix proportions for pervious concrete in Part I of this

experimental study took into account existing practices as well as

recommendations from ACI Committee Report 522R-10. An earlier study by

Ang (2005) indicated that a coarse aggregate content of 1560 kg/m3 and water-

cement ratio of 0.3 resulted in a good permeability of 37.3 mm/s and porosity

of 25%.Therefore, the same aggregate content and water-cement were used as

the basis for the present study. Also, as a higher cement content would lower

both the permeability and porosity of pervious concrete, a moderate cement

50

content of 367 kg/m3 was selected. The increased coarse aggregate content of

1560 kg/m3 as compared to the recommended coarse aggregate range of 1190

– 1480 kg/m3 (ACI committee report 522, 2010) would also help to create

larger pores which are conducive in enhancing permeability and increasing

porosity.

Table 3.1 shows the type of tests conducted. They included tests for

compressive strength, flexural strength, porosity and permeability. For each

test three samples were used. The compressive strength test was carried out in

accordance with BS EN 12390-3: 2009 while the flexural strength test

followed ASTM C78-10. The porosity and permeability were determined

using methods employed in previous research works.

Table 3.2 shows the mix proportions of the samples. A total of 62

mixes were studied. Part I of the study consisted of Series R, A, B and C

specimens. Series R represents the reference mix with a w/c ratio of 0.3,

cement content at 367 kg/m3, coarse aggregate content at 1560 kg/m

3 and

water content at 110.1 kg/m3; Series A consisted of mixes with blended coarse

aggregates, that is, the CA/C ratio was kept at 6.45 and w/c ratio at 0.3 while

the ratios of small to large aggregates were varied and denoted by 0 : 1 (a), 1 :

3 (x), 1 : 1 (y), 3 : 1 (z) and 1 : 0 (b). In Series B, the water-cement ratio was

varied with other parameters kept the same as mix R. In Series C, the cement

content was varied.

Part II of the study consisted of the remaining three series, D, E and F,

specimens of which were cast with 3D-S, 4D and 5D discrete steel fibers (as

described in Section 3.1.1) respectively, with dosage varying from 1% to

2.5%. In these fiber-reinforced pervious concrete mixes, the w/c ratio, cement

51

content, coarse aggregate content and water were kept at 0.3, 367 kg/m3, 1560

kg/m3 and 110.1 kg/m

3 respectively.

3.1.1 Materials

ASTM Type I ordinary Portland cement with chemical composition

and physical properties complying with ASTM C 150-12 requirements was

used. Coarse aggregates were natural crushed granite complying with the

grading requirements of ASTM C 33-11a and having a specific gravity of

2.65. Table 3.3 shows the gradation of small and large size coarse aggregates.

The small coarse aggregates complied to Size 89 (9.5 to 1.18 mm) while the

large coarse aggregates complied to Size 67 (19.0 to 4.75 mm). A

conventional superplasticier meeting the requirements of ASTM C494 Type F

and G with a dosage of 1300 ml/ 100 kg of cement was used in Series A. The

conventional superplasticier belongs to the sulfonated naphthalene-

formaldehyde condensates polymer group. A comb polymer superplasticizer

(SP-C) formulated with carboxylated acrylic ester copolymers

(polycarboxylates), containing no added chloride and meeting the

requirements of ASTM C494 Type G superplasticier was used to improve

workability and in turn enhance the bonding between aggregates and cement

in all other series. The dosage of the superplasticier was 800 ml/ 100 kg of

cement.

Figure 3.1 shows the configurations and Table 3.4 tabulates the

properties of the steel fibers. The 3D steel fibers had 1 hook-end; while 4D

and 5D fibers had 1.5 and 2 hook-ends, respectively. The length and diameter

of the steel fibers range from 30 to 65 mm and 0.5 mm to 0.92 mm

52

respectively; the aspect ratio ranges from 60 to 80 and the tensile strength

from 1130 to 2250 MPa.

3.1.2 Test specimens

Figure 3.2 show the various types of test specimens. They were cast

and cured according to ASTM C192/C192M-15. Concrete cubes of 100 mm

side dimensions were used to study the compressive strengths; whilst prisms

measuring 100 mm by 100 mm in cross-section and 400 mm in length, were

used for the flexural tests. The cylindrical samples for porosity and

permeability tests had a diameter of 150 mm and a height of 50 mm. The

moulds were filled with freshly mixed concrete in three layers of

approximately equal volume. Each layer was tamped 25 times. After casting,

the samples were covered with a non-absorptive, non-reactive sheet of tough,

durable impervious plastic for 24 + 8 hours, after which they were demolded

9and cured in a fog room for 1, 7 or 28 days.

3.1.3 Test methodology

The Avery Denison test machine was used to obtain the compressive

and flexural strengths. The compressive strength test was determined

according to BS EN 12390-3: 2009 while the flexural strength test according

to ASTM C78-10.

The porosity of the hardened pervious concrete samples was

determined based on Archimedes principle by taking the difference in weight

between the oven-dry and water saturated submerged samples. It is given by

(Sonebi and Bassuoni, 2013; Bhutta et al., 2012, Lian et al, 2011; Goede, 2009

and Montes et al, 2005):

53

Vr = [ 1 − W2−W1

ρw V ] x 100% (3.1)

where: Vr = total void ratio in %; W1 = weight of sample immersed in water;

W2 = weight of sample in air; ρw = density of water and V = volume of

sample.

The above test method was initially proposed by Montes et al. (2005),

and was later incorporated into ASTM C1754/C1754M – 12; “Standard test

method for density and void content of hardened pervious concrete”.

The NUS constant head permeameter (Singapore Patent number

67286, 2001) was used to determine the permeability of the specimens. As

shown in Figure 3.3, a submersible pump provided a constant inflow of water

into the inlet cylinder such that a constant head of water was maintained at the

desired water head in the inlet cylinder. The flow of water was controlled

using valves. The flow rate of water was determined by measuring the volume

of water collected from the in-flow hose. The permeability samples were

sealed with waterproof thread tape to prevent side-flow of water, thus ensuring

1-D flow only. Plasticine was used to seal off any leakage that would occur in

the setup. During the test, the amount of outflow water was measured and the

permeability coefficient computed from the modified Darcy’s equation (Fwa

et al., 2002, Tan et al., 2000 and Fwa et al., 1998):

v = k . in (3.2)

in which

v = Q

t A (3.3)

i = H

L (3.4)

54

whereby k = permeability coefficient in mm/s; i = hydraulic gradient, n =

experimental coefficient; L = thickness of specimen in mm; Q = amount of

water collected in mm3; t = test duration in seconds; A = cross-sectional area

of the specimen and H = constant water head in mm. For the given test

materials and test conditions, n can be taken as a constant of 0.7 without any

significant error of practical significance (Fwa et al., 2002, Tan et al., 2000

and Fwa et al., 1998).

The ASTM C1688/C1688M – 12 method was used to determine the

density of fresh pervious concrete. The volume measure was first weighed and

recorded to the nearest gram. The freshly mixed pervious concrete was then

put into the container (Figure 3.4) and the cylinder was then weighed again to

the nearest gram. The density was calculated from:

D = (Mc – Mm)/Vm (3.5)

where: D = density (unit weight) of concrete, kg/m3; Mc = mass of the measure

filled with concrete, kg; Mm = mass of the measure, kg; Vm = volume of the

measure, m3.

3.1.4 Workability

Currently, there is no specification on the slump for pervious concrete.

To check for the workabiltiy of pervious concrete, the “Ball test”

recommended by Amde and Rogge (2013) and Goede (2009) was carried out.

The fresh pervious concrete for each mix gave good workability as shown in

Figure 3.5. The incorporation of steel fibers in the pervious concrete mix did

not cause any difference in workability of the fresh concrete. This can also be

55

observed from Figure 3.5. Both pictures (with and without steel fibers) show

good workability using the Ball Test.

The conventional slump test was also conducted as shown in Figure

3.6 to complement the “Ball test”. Zero or near zero slump was obtained for

all the test mixes. The use of steel fibers did not cause a change in the

workability and the slump was zero or near zero for both mixes with and

without steel fibers.

3.2 Test results and discussion

The test results for the physical and mechanical properties of all the

mixes at ages of 1, 7 and 28 days are listed in Table 3.5. The permeability test

results were only for the 28-day test. From the graphs of Series A to F shown

in Figure 3.7, there is an evident trend of compressive and flexural strengths

increasing and porosity decreasing over the period of 28 days. Pertaining to

the compressive strength trend, there was a significant increase in strength

from 1 to 7 days, while the compressive strength increase from 7 to 28 days

was not substantial. The increase in flexural strength was marginal while the

porosity values showed a consistent decline over the 28-days test period.

3.2.1 Unreinforced pervious concrete

Table 3.6 summarizes the 28-day test results for compressive strength,

flexural strength, permeability, porosity and density.

Effect of CA/C ratio. Specimens R1a and R1b both had a CA/C ratio of

4.25, within the ACI 522R-10 recommended range for pervious concrete. The

porosity was above 20%. The compressive and flexural strengths were

56

approximately 12.3 MPa and 2.7 MPa respectively. As shown in Figure 3.8(a),

Mix A1a and A1b with coarse aggregate-to-cement (CA/C) ratio of 6.45 had a

high porosity of about 30%. The large amount of coarse aggregates in the

specimens resulted in large pore gaps and thus higher porosities. However the

corresponding compressive strength was less than 10 MPa. As the pervious

concrete mixes are near zero slumps, mixes with smaller coarse aggregates

performed marginally better than mixes with larger coarse aggregates due to

the regular and more even arrangement of the aggregates in the concrete

matrix.

Mixes with a blend of coarse aggregates, that is, mix A1x, A1y, A1z

with small and large coarse aggregate in proportion of 1 : 3, 1 : 1 and 3 : 1

respectively, had lower permeability and porosity in comparison to mixes with

100% small coarse aggregates and 100% large coarse aggregates, as shown in

Figure 3.8(b).

The combined aggregate grading curves was plotted as shown in

Figure 3.8(c). The three blended gradations for mixes (A1x, A1y, A1z) fall

outside the upper and lower limits of ASTM C33 and thus these aggregate

gradations were not selected for further studies, and therefore only mixes with

(a) small coarse aggregates and (b) large coarse aggregates were examined in

the study.

Effect of w/c ratio. In Series B and as shown in Figure 3.9, the water-

cement ratio was varied from 0.2 to 0.35, although the recommended ACI

522R-10 range is between 0.27 to 0.34. With a water-cement ratio of 0.25, as

in Specimens B1a and B1b, the mix became too dry and brittle despite using a

57

higher dosage of the new range superplasticier (SP-C). As a result, a

comparatively low compressive strength of less than 15 MPa was obtained.

Permeability on the other hand increased to approximately 20 mm/s. The

permeability of the other Series B mixes was also reasonably high, i.e. more

than 20 mm/s, but the strengths were low, being 10 to 14 MPa in compression

and 2 to 3 MPa in flexure.

Effect of cement content. In Series C, the cement content was varied

from 242 kg/m3 to 495 kg/m

3, with water-cement ratio and coarse aggregate

content the same as Mixes R1a and R1b, that is, at 0.3 and 1560 kg/m3

respectively. Both the compressive and flexural strengths increased with

higher cement content regardless of whether small or large coarse aggregates

were used; however, the permeability reduced to as low as 4.25 mm/s as

shown in Figure 3.10. For practical use, the cement content should be around

400 kg/m3 to ensure a minimum flexural strength of 3 MPa and permeability

of more than 10 mm/s.

3.2.2 Steel fiber reinforced pervious concrete

Regardless of the use of small or large coarse aggregates in the mixes,

inclusion of steel fibers resulted in increasing compressive and flexural

strengths without compromising the permeability and porosity as shown in

Figures 3.11 to 3.14 for Series D, E and F mixes. No significant difference in

permeability, porosity, and compressive and flexural strengths were observed

58

between mixes reinforced with short or long 3D steel fibers, as shown in

Figure 3.15.

With increasing number of hooks at the ends of the steel fibers, the

flexural and compressive strengths were found to increase due to further

interlocking between the fibers and the cement paste, up to fiber dosage of

2.25%, as shown in Figures 3.11 and 3.12. However, the difference in flexural

strength were not significantly different among 3D, 4D and 5D steel fibers. A

minimum fiber dosage of 1.5% was needed to achieve the target flexural

strength of 3.5 MPa.

The use of 3D, 4D and 5D hook-end steel fibers showed some

differences in permeability and porosity, as shown in Figures 3.13 and 3.14.

The difference in permeability was more pronounced for the large coarse

aggregate mix as shown in Figure 3.13(b). This could be due to the irregular

settlement of the large coarse aggregates in the pervious concrete matrix

which thus led to a larger variation in permeability. With a higher fiber

content, improvement in permeability and porosity was not expected, due to

the balling effect and the uneven spread of fibers.

Figure 3.16 compares the observed flexural strength and permeability

of mixes with target performance indices. Regardless of the size of coarse

aggregates and fiber type, the permeability in general decreased with

increasing flexural strength. Mixes with smaller coarse aggregates and steel

fibers of multiple hook ends performed better than the others.

The target permeability is 10 mm/s and flexural strength is 3.5 MPa, as

recommended by AASHTO (1993) for road pavements. It is seen that mixes

satisfying the target performance were those using small coarse aggregates

59

with a fiber dosage of at least 1.5% for 3D fibers and 1% for 4D and 5D

fibers. For mixes using large coarse aggregates, the mixes meeting the targets

had between 1.5 and 2.25% of 3D fibers, or between 1 and 1.5% of 4D fibers.

Figure 3.17 shows the results for the compressive strength and

porosity. In general, the compressive strength decreased with increasing

porosity of the mix. The target porosity is 20% and compressive strength is 12

MPa. These were achieved in mixes with small coarse aggregates having 3D

or 4D fibers up to 2.25% or 5D fibers up to 2%. For mixes using large coarse

aggregates, the target compressive strength and porosity were achieved if the

fibre dosage is not more than 1.75%, 1.5% and 1%, respectively, for 3D, 4D

and 5D fibers.

From the above observations, the recommended fiber dosages to

ensure adequate flexural strength and reasonable permeability and porosity for

pavement use are summarized in Table 3.7. In general, a dosage of 1.5%

appeared to be the optimal. The most favourable mix (which has the best

combination of good porosity, permeability and flexural strength) would be

using small aggregates with 2% 5D steel fibers.

Figures 3.18 and 3.19 compare the current test results data with those

of other researchers. The flexural strength decreases with an increase in

porosity as well as permeability. Some of the current test results fall in the

upper right corner of the graphs and these results aid in the improvement of

pervious concrete mix design.

60

3.3 Summary

The first part of the test programme was carried out to investigate the

effect of mix proportion on the mechanical (compressive and flexural) and

physical (porosity and permeability) properties of pervious concrete. To

achieve a highly permeable and porous pavement with reasonable compressive

and flexural strengths, the CA/C ratio should be in the region of 4.25, water-

cement ratio of around 0.3 and cement in the range of 360 kg/m3 to 400 kg/m

3.

However, without the use of steel fibers, the target performances were not

achieved.

The second part of the test programme was conducted to investigate

the mechanical and physical properties of steel fiber-reinforced pervious

concrete for road pavement. It was noted that the steel fibers were effective in

increasing the compressive and flexural strengths of pervious concrete without

compromising on permeability and porosity. A minimum dosage of 1.5% steel

fiber by volume would be required to achieve the target flexural strength of

3.5 MPa, permeability of 10 mm/s and porosity of 20%.

The current study test results that fall in the upper right corner of the

graphs shown in Figure 3.18 and 3.19, aid in the improvement of pervious

concrete mix design done by past researchers: Hesami et al., (2014), Bhutta et

al., (2012), Xiang et al., (2011), Huang et al., (2010) and Meininger (1998).

61

Table 3.1 Types of tests and various test samples

Mechanical

and drainage

Properties

Destructive

test

Age at time

of testing of

concrete

(days)

No. of

specimen

for each

test

Test

method/standard/

references

Compressive

strength Yes 1,7 and 28 3 cubes

BS EN 12390-3:

2009

Flexural

strength Yes 7 and 28 3 prisms ASTM C78-10

Porosity No 1,7 and 28 3 cylinders

(Sonebi and

Bassuoni, 2013,

Bhutta et al.,

2012, Lian et al,

2011 and Goede,

2009)

Permeability No 28 3 cylinders

Modified Darcy’s

equation – (Fwa

et al., 2002, Tan

et al., 2000 and

Fwa et al., 1998)

62

Table 3.2(a) Mix proportion design (Part 1)

Mix Test

Variable

w/c

ratio

Cement

(C)/

[kg/m3]

Water/

[kg/m3]

Coarse

Aggregate

(CA)/

[kg/m3]

CA/C Additives

Part

I

Ra,b Reference

0.3

367 110.1

1560

4.25 SP-C

A1a,b,

x,y,z

CA/C

ratio 242 72.6 6.45

Conventional

SP

B1a,b

w/c ratio

0.2

367

73.4

4.25

SP-C

B2a,b 0.25 91.8

B3a,b 0.33 121.1

B4a,b 0.35 128.5

C1a,b

Cement

Content 0.3

242 72.6 6.45

C2a,b 300 90.0 5.20

C3a,b 400 120.0 3.90

C4a,b 430 129.0 3.63

C5a,b 495 148.5 3.15

* a: denotes small coarse aggregates (9.5mm); b: denotes large coarse aggregates

(19.5 mm) being used in the mix.

- x: denotes blended coarse aggregates with small and large coarse aggregates in

proportion of 1:3.

- y: denotes blended coarse aggregates with small and large coarse aggregates in

proportion of 1:1.

- z: denotes blended coarse aggregates with small and large coarse aggregates in

proportion of 3:1.

Table 3.2 (b) Mix proportion design (Part II)

Mix

Test

Variable

Steel fiber dosage by

volume of concrete (%)

Part

II

D1a,b

3D-S

Fibers

1.0

D2a,b 1.50

D3a,b 1.75

D4a,b 2.0

D5a,b 2.25

D6a,b 2.50

D7a 3D-L

Fibers 2.0

E1a,b

Steel 4D

Fibers

1.0

E2a,b 1.50

E3a,b 1.75

E4a,b 2.0

E5a,b 2.25

E6a,b 2.50

F1a,b

Steel 5D

Fibers

1.0

F2a,b 1.50

F3a,b 1.75

F4a,b 2.0

F5a,b 2.25

F6a,b 2.50

Note = All mixes in Part II had a w/c

ratio: 0.3, cement content: 367kg/m3,

water content: 110.1kg.m3, coarse

aggregate content: 1560 kg/m3, CA/C

ratio: 4.25 and used SP-C

superplasticier.

63

Table 3.3 (a) Gradation of small and large coarse aggregates

Size

(mm)

Large Coarse Aggregate

(% by mass)

Small Coarse Aggregate

(% by mass)

Cumulative

passing

Grading

requirement

Cumulative

passing

Grading

requirement

19.0 95 90 - 100 - -

12.5 - - - -

9.5 38 20 - 55 95 90 - 100

4.75 5 0 - 10 38 20 - 55

2.36 3 0 - 5 18 5 - 30

1.18 - - 5 0 - 10

0.30 - - 3 0 - 5

Pan 0 0 0 0

(b) Gradation of small and large aggregates in graphical form

Table 3.4 Properties of steel fibers

Steel Fibers

Type

Length

(mm)

Diameter

(mm)

Aspect

Ratio

Tensile Strength

(MPa)

3D-S 30 0.50 60 1130

3D-L 60 0.75 80 1100

4D 60 0.92 65 1500

5D 65 0.92 65 2250

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100

Per

cen

tage

Pass

ing (

%)

Sieve Size (mm)

Large Coarse AggregateLarge CA Lower limitLarge CA Upper limitSmall Coarse AggregateSmall CA Lower limitSmall CA Upper limit

64

Table 3.5: Physical and mechanical properties of pervious concrete

Test

Variable

Compressive Strength

MPa

Flexural Strength

MPa Porosity %

Permeability

mm/s

1-day 7-day 28-day 7-day 28-day 1-day 7-day 28-day 28-day

R1a Reference

4.22 10.3 11.9 1.85 2.68 27.0 24.3 22.1 13.8

R1b 5.12 10.7 12.6 2.78 2.75 26.9 24.2 21.6 13

Part

I

A1a

CA/C

ratio

4.24 5.20 8.4 NA NA 38.20 36.70 31.1 37.5

A1b 5.11 5.60 8.6 NA NA 42.10 40.40 35.5 39.8

A1x 4.22 6.10 8.9 NA NA 34.70 32.10 29.2 32.4

A1y 5.01 6.00 8.8 NA NA 35.30 33.60 30.8 34.7

A1z 4.25 6.20 9.1 NA NA 33.60 31.30 27.9 28.1

B1a

w/c ratio

4.22 9.7 11.6 1.41 1.98 32.2 25.8 23.0 23.5

B1b 5.01 10.4 11.7 1.53 1.86 28.0 25.1 22.2 17.1

B2a 4.25 10.3 11.8 2.11 2.54 29.2 25.8 22.6 22.4

B2b 5.08 11.2 12.0 2.09 2.78 27.7 25.1 21.8 14.0

B3a 4.40 10.1 13.1 2.29 2.82 25.6 20.5 18.3 12.1

B3b 5.25 11.0 14.2 2.69 2.88 21.9 19.7 17.4 11.0

B4a 4.62 11.2 13.9 2.69 2.90 20.0 17.7 15.5 11.2

B4b 5.36 11.8 14.3 2.48 2.93 18.8 17.0 14.8 9.7

C1a

Cement

content

2.60 6.0 8.4 1.12 1.58 43.5 34.8 31.1 35.9

C1b 3.01 6.4 8.6 1.39 1.69 44.7 40.1 35.5 37.8

C2a 3.01 7.4 9.7 2.10 2.53 32.3 28.5 25.0 20.8

C2b 3.61 8.0 10.3 2.00 2.66 39.1 35.4 30.8 26.3

C3a 6.42 14.9 20.7 2.57 3.02 18.3 14.7 13.1 7.7

C3b 8.12 17.2 23.2 3.03 3.11 17.8 15.9 14.1 9.5

C4a 8.96 22.0 28.9 3.01 3.23 16.6 14.7 12.9 6.2

C4b 12.53 27.9 35.8 2.80 3.25 9.4 8.5 7.4 4.0

C5a 11.04 25.6 35.6 3.18 3.58 11.8 9.4 8.4 4.8

C5b 14.63 30.9 39.8 3.34 3.52 6.6 5.9 5.2 3.7

Part II

D1a

3D-S Fibers

4.25 10.4 13.7 2.85 3.31 33.3 29.4 25.8 13.4

D1b 5.22 11.6 14.9 2.59 3.32 29.5 26.7 23.2 11.7

D2a 4.84 11.2 15.6 2.48 3.49 34.6 27.7 24.7 12.9

D2b 5.60 11.8 16.0 2.87 3.50 28.0 25.1 22.2 11.4

D3a 5.61 13.8 16.5 2.92 3.52 30.4 26.9 23.6 12.6

D3b 6.83 15.2 17.0 2.66 3.55 26.0 23.6 20.5 10.9

D4a 6.29 14.6 17.5 2.54 3.58 32.1 25.6 22.9 12.3

D4b 7.63 16.1 17.8 2.95 3.60 24.2 21.7 19.2 10.3

D5a 6.36 15.6 18.5 2.99 3.60 27.7 24.5 21.5 11.8

D5b 7.81 17.4 18.9 2.72 3.62 22.9 20.7 18.0 10.1

D6a 6.39 14.8 19.6 2.56 3.61 27.7 22.2 19.8 11.2

D6b 7.88 16.7 20.5 2.98 3.64 21.2 19.0 16.8 9.5

- N.A – results not available.

65

Table 3.5: Physical and mechanical properties of pervious concrete (cont’d)

Test Variable

Compressive Strength

MPa

Flexural

Strength MPa Porosity %

Permeability

mm/s

1-day 7-day 28-day 7-day 28-

day 1-day 7-day 28-day 28-day

Part

II

D7a 3D-L

Fibers 5.29 15.1 17.1 2.97 3.58 14.8 13.1 23.3 11.5

E1a

4D Fibers

4.24 11.8 15.1 2.62 3.33 30.1 27.3 23.7 13.1

E1b 4.19 11.0 15.3 2.49 3.34 29.3 23.4 20.9 10.8

E2a 4.45 12.4 16.7 2.91 3.55 29.0 26.0 23.0 12.3

E2b 4.97 13.1 17.2 2.95 3.55 25.9 22.9 20.1 10.5

E3a 5.48 15.2 17.3 2.73 3.64 28.2 25.5 22.2 12.0

E3b 5.72 15.0 17.8 2.56 3.60 27.0 21.6 19.3 9.4

E4a 5.70 15.8 18.4 3.08 3.76 27.3 24.5 21.7 11.2

E4b 6.41 16.9 18.8 3.05 3.68 24.0 21.2 18.6 8.9

E5a 6.12 17.0 19.3 2.87 3.83 24.1 21.9 19.0 10.9

E5b 6.27 16.5 20.1 2.63 3.71 23.9 19.2 17.1 8.3

E6a 5.94 16.5 20.5 3.21 3.91 22.1 19.8 17.5 10.8

E6b 6.79 17.9 21.1 3.17 3.82 20.4 18.0 15.8 7.2

F1a

5D Fibers

5.05 14.0 17.1 2.67 3.36 29.1 26.3 22.9 13.0

F1b 5.06 13.3 17.5 2.50 3.35 28.8 23.1 20.6 9.7

F2a 5.41 15.0 18.8 3.08 3.75 28.4 25.4 22.5 12.1

F2b 5.57 14.7 18.3 2.99 3.60 25.0 22.1 19.4 8.0

F3a 6.49 18.0 19.1 3.04 3.87 27.3 24.7 21.5 11.6

F3b 6.27 16.5 18.5 2.66 3.76 26.6 21.3 19.0 6.6

F4a 6.82 18.9 20.6 3.58 4.00 26.8 24.1 21.3 11.5

F4b 7.16 18.8 20.2 3.34 3.97 23.7 21.0 18.4 6.1

F5a 7.50 20.8 21.0 3.30 4.06 23.7 21.5 18.7 10.8

F5b 7.11 18.7 20.5 2.95 4.02 22.8 18.3 16.3 5.9

F6a 7.19 20.0 21.3 3.62 4.12 21.4 19.2 17.0 10.7

F6b 7.65 20.1 20.8 3.51 4.08 19.5 17.2 15.1 5.4

66

Table 3.6 Summary of test results

Mix Test

Variable

Compressive

Strength

[MPa]

Flexural

Strength

[MPa]

Permeability

[mm/s]

Porosity

[%]

Density

[kg/m3]

Part

I

R1a Reference

11.9 2.68 13.8 22.1 1890

R1b 12.6 2.75 13 21.6 2002

A1a

CA/C

ratio

8.4 N.A 37.5 31.1 N.A

A1b 8.6 N.A 39.8 35.5 N.A

A1x 8.9 N.A 32.4 29.2 N.A

A1y 8.8 N.A 34.7 30.8 N.A

A1z 9.1 N.A 28.1 27.9 N.A

B1a

w/c ratio

11.6 1.98 23.5 23.0 1710

B1b 11.7 1.86 17.1 22.2 1840

B2a 11.8 2.54 22.4 22.6 1814

B2b 12.0 2.78 14.0 21.8 1956

B3a 13.1 2.82 12.1 18.3 1923

B3b 14.2 2.88 11.0 17.4 2082

B4a 13.9 2.90 11.2 15.5 1978

B4b 14.3 2.93 9.7 14.8 2105

C1a

Cement

Content

8.4 1.58 35.9 31.1 1820

C1b 8.6 1.69 37.8 35.5 1900

C2a 9.7 2.53 20.8 25.0 1855

C2b 10.3 2.66 26.3 30.8 1943

C3a 15.7 3.02 7.7 13.1 2050

C3b 16.2 3.11 9.5 14.1 2040

C4a 20.9 3.23 6.2 12.9 2061

C4b 22.8 3.25 4.0 7.4 2080

C5a 35.6 3.58 4.8 8.4 2175

C5b 39.8 3.52 3.7 5.2 2196

Part

II

D1a

3D-S

Fibers

13.7 3.31 13.4 25.8 1825

D1b 14.9 3.32 11.7 23.2 1963

D2a 15.6 3.49 12.9 24.7 1830

D2b 16.0 3.50 11.4 22.2 1975

D3a 16.5 3.52 12.6 23.6 1855

D3b 17.0 3.55 10.9 20.5 1986

D4a 17.5 3.58 12.3 22.9 1872

D4b 17.8 3.60 10.3 19.2 1990

D5a 18.5 3.60 11.8 21.5 1923

D5b 18.9 3.62 10.1 18.0 2012

D6a 19.6 3.61 11.2 19.8 1951

D6b 20.5 3.64 9.5 16.8 2094

D7a 3D-L

Fibers 17.1 3.58 11.5 23.3 1892

E1a

4D Fibers

15.1 3.33 13.1 23.7 1831

E1b 15.3 3.34 10.8 20.9 1963

E2a 16.7 3.55 12.3 23 1846

E2b 17.2 3.55 10.5 20.1 1991

E3a 17.3 3.64 12.0 22.2 1875

E3b 17.8 3.60 9.4 19.3 2009

E4a 18.4 3.76 11.2 21.7 1905

E4b 18.8 3.68 8.9 18.6 2015

E5a 19.3 3.83 10.9 19.0 1933

E5b 20.1 3.71 8.3 17.1 2027

E6a 20.5 3.91 10.8 17.5 1965

E6b 21.1 3.82 7.2 15.8 2056

67

Table 3.6 Summary of test results (Cont’d)

Mix Test

Variable

Compressive

Strength

[MPa]

Flexural

Strength

[MPa]

Permeability

[mm/s]

Porosity

[%]

Density

[kg/m3]

Part

II

F1a

5D Fibers

17.1 3.36 13.0 22.9 1840

F1b 17.5 3.35 9.7 20.6 1979

F2a 18.8 3.75 12.1 22.5 1854

F2b 18.3 3.60 8.0 19.4 2030

F3a 19.1 3.87 11.6 21.5 1863

F3b 18.5 3.76 6.6 19.0 2051

F4a 20.6 4.00 11.5 21.3 1931

F4b 20.2 3.97 6.1 18.4 2086

F5a 21.0 4.06 10.8 18.7 1986

F5b 20.5 4.02 5.9 16.3 2097

F6a 21.3 4.12 10.7 17.0 2012

F6b 20.8 4.08 5.4 15.1 2103

Table 3.7 Recommended steel fiber dosages

Maximum size of

coarse aggregates

(mm)

3D Fibers 4D Fibers 5D Fibers

9.5 1.5 – 2.25% 1 – 2.25% 1 – 2 %

19.0 1.5 – 1.75% 1 – 1.5% Nil

68

Figure 3.1 Steel 3D-S, 3D-L, 4D and 5D hook-end fibers (Dramix)

(a) Compressive test specimen (b) Permeability test specimen

(c) Flexural test specimen

Figure 3.2 Test samples

5D Fiber (2 hook-end)

3D-S Fiber (1 hook-end)

3D-L Fiber (1 hook-end)

4D Fiber (1.5 hook-end)

69

Figure.3.3 Constant-head permeability test set-up

Figure 3.4 Volume measure with fresh pervious concrete for density test

70

(a) Too little water (b) Appropiate amount of water (c) Too much water

Without steel fiber With steel fiber

(d) Current study

Figure 3.5 Ball test for workability of pervious concrete (Sonebi and Bassuoni,

2013)

(a) Without steel fiber (b) With steel fiber

Figure 3.6 Slump test

71

(a) Series A – blend ratio

(b) Series B – w/c ratio

Figure 3.7: Physical and mechanical properties of pervious concrete

0

5

10

15

20

25

30

35

1-day 7-day 28-day 1-day 7-day 28-day 28-day

Compressive Strength (MPa) Porosity (%) Permeability

(mm/s)

A1a A1b A1x A1y A1z

0

5

10

15

20

25

30

35


Compressive Strength (MPa) Flexural Strength (MPa) Porosity (%) Permeability

(mm/s)

B1a B1b B2a B2b R1a R1b B3a B3b B4a B4b

72

(c) Series C – cement content

(d) Series D – 3D-S fibers

Figure 3.7: Physical and mechanical properties of pervious concrete (cont’d)

0

5

10

15

20

25

30

35

40

45

50



(mm/s)

C1a C1b C2a C2b R1a R1b C3a C3b C4a C4b C5a C5b

0

5

10

15

20

25

30

35

40



(mm/s)

D1a D1b D2a D2b D3a D3b D4a D4b D5a D5b D6a D6b D7a

73

(e) Series E – 4D fibers

(f) Series F – 5D fibers

Figure 3.7: Physical and mechanical properties of pervious concrete (cont’d)

0

5

10

15

20

25

30

35



(mm/s)

E1a E1b E2a E2b E3a E3b E4a E4b E5a E5b E6a E6b

0

5

10

15

20

25

30

35



(mm/s)

F1a F1b F2a F2b F3a F3b F4a F4b F5a F5b F6a F6b

74

* R: denotes the reference mix, a: denotes small coarse aggregates (9.5mm);

b: denotes large coarse aggregates (19.5 mm) being used in the mix.

(a) Effect of size

(b) Effect of blend ratio

0

10

20

30

40

50

60

R1a A1a R1b A1b

Pro

per

ties

Mix

Compressive Strength [MPa] Flexural Strength [MPa]

Permeability [mm/s] Porosity [%]

xx xx

0

10

20

30

40

50

60

A1a A1x A1y A1z A1b

Pro

per

ties

0 : 1 1 : 3 1 : 1 3 : 1

Compressive Strength [MPa]

Permeability [mm/s]

Porosity [%]

1 : 0

Small to

large

aggregate

ratio

75

(c)

Figure 3.8 Effect of coarse aggregate size in unreinforced pervious concrete

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10 100

Per

cen

tage

Pass

ing (

%)

Sieve Size (mm)

Large CA Lower limit

Large CA Upper limit

Small CA Lower limit

Small CA Upper limit

A1x 1:3

A1y 1:1

A1z 3:1

76

(a) Mixes with small coarse aggregates

(b) Mixes with large coarse aggregates

Figure 3.9 Effect of water-cement ratio in unreinforced pervious concrete

0

5

10

15

20

25

30

0.2 0.25 0.3 0.33 0.35

Pro

per

ties

w/c ratio

Compressive Strength (MPa) Flexural Strength (MPa)

Permeability (mm/s) Porosity (%)

0

5

10

15

20

25

30

0.2 0.25 0.3 0.33 0.35

Pro

per

ties

w/c ratio

Compressive Strength (MPa) Flexural Strength (MPa)

Permeability (mm/s) Porosity (%)

77

(a) Mixes with small coarse aggregates

(b) Mixes with large coarse aggregates

Figure 3.10 Effect of cement content in unreinforced pervious concrete

0

10

20

30

40

50

60

242 300 367 400 430 495

Pro

per

ties

Cement Content (kg/m3)

Compressive Strength (MPa) Flexural Strength (MPa)Permeability (mm/s) Porosity (%)

0

10

20

30

40

50

60

242 300 367 400 430 495

Pro

per

ties

Cement Content (kg/m3)

Compressive Strength (MPa) Flexural Strength (MPa)Permeability (mm/s) Porosity (%)

78

(a) Small coarse aggregates

(b) Large coarse aggregates

Figure 3.11 Compressive strength of fiber reinforced pervious concrete

10

12

14

16

18

20

22

24

1 1.5 1.75 2 2.25 2.5

Com

pre

ssiv

e S

tren

gth

(M

Pa)

Volume fraction of steel fiber (%)

5D

4D

3D-S

10

12

14

16

18

20

22

24

1.0 1.5 1.8 2.0 2.3 2.5

Com

pre

ssiv

e S

tren

gth

(M

Pa)

Volume fraction of steel fiber (%)

5D

4D

3D-S

79

(a) Small coarse aggregates

(b) Large coarse aggregates

Figure 3.12 Flexural strength results of fiber reinforced pervious concrete

0

1

2

3

4

5

1 1.5 1.75 2 2.25 2.5

Fle

xura

l S

tren

gth

(M

Pa)

Volume fraction of steel fibers (%)

5D

4D

3D-S

0

1

2

3

4

5

1.0 1.5 1.8 2.0 2.3 2.5

Fle

xura

l S

tren

gth

(M

Pa)


5D

4D

3D-S

80

(a) Using small coarse aggregates

(b) Using large coarse aggregates

Figure 3.13 Permeability results of fiber reinforced pervious concrete

0

2

4

6

8

10

12

14

1.0 1.5 1.8 2.0 2.3 2.5

Per

mea

bil

ity (

mm

/s)


3D-S

4D

5D

0

2

4

6

8

10

12

14

1.0 1.5 1.8 2.0 2.3 2.5

Per

mea

bil

ity (

mm

/s)


3D-S

4D

5D

81

(a) Using small coarse aggregates

(b) Using large coarse aggregates

Figure 3.14 Porosity results of fiber reinforced pervious concrete

10

12

14

16

18

20

22

24

26

28

1.0 1.5 1.8 2.0 2.3 2.5

Poro

sity

(%

)


3D-S

4D

5D

10

12

14

16

18

20

22

24

26

28

1.0 1.5 1.8 2.0 2.3 2.5

Poro

sity

(%

)


3D-S

4D

5D

82

Figure 3.15 Effect of fiber length in fiber reinforced pervious concrete

0

5

10

15

20

25

30

Compressive

Strength (MPa)

Flexural Strength

(MPa)

Porosity (%) Permeability

(mm/s)

3D short 3D Long

83

Figure 3.16 Flexural strength versus permeability of test mixes

Figure 3.17 Compressive strength versus porosity of test mixes

84

Figure 3.18 Relationship between flexural strength and porosity of pervious

concrete

Figure 3.19 Relationship between flexural strength and permeability of

pervious concrete

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 10 20 30 40

Fle

xura

l S

tren

gth

MP

a

Porosity %

Meininger (1988)

Huang et.al (2010)

Huang et.al (2010)


Bhutta et al (2012)

Hesami et al (2014)

Lim et al. (2013a,b)

Present study-Steel

fibers mix

AASHTO

Recommendation


0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 5 10 15 20 25 30 35 40

Fle

xura

l S

tren

gth

MP

a

Permeability mm/s

Meininger (1988)

Huang et.al (2010)

Huang et.al (2010)

Polypropylene fibersXiang et.al (2011)

Xiang et.al (2011)

Polypropylene fibersBhutta et al (2012)

Hesami et al (2014)

Lim et al. (2013a,b)

Present study-Steel

fibers mix

AASHTO

Recommendation


85

CHAPTER 4 CLOGGING CHARACTERISTICS OF PERVIOUS

CONCRETE

The clogging resistance of pervious concrete pavement governs its

functional durability and its service life. In this study, the clogging

characteristics of pervious concrete was investigated using four types of sand

with sizes ranging from less than 75 µm to 1.18 mm, which are most

commonly found on Singapore’s roads. The critical sand size was adopted to

further compare the clogging characteristics of pervious concrete with porous

asphalt.

4.1 Evaluation of clogging characteristics and porosity

While it is important to design a porous pavement with a high level of

porosity and permeability, it is equally important to ensure that the pores are

not easily clogged up so that a sufficiently high level of permeability could be

maintained throughout the service life of the pavement. Thus it is important to

evaluate the initial permeability of a porous pavement material as well as the

reduction in permeability caused by clogging.

In practice, porous asphalt and pervious concrete may be considered.

The laboratory study was therefore carried out to compare the permeability

and clogging characteristics of a pervious concrete mixture with a porous

asphalt mixture with various mixture porosities. The test program considered

four target porosity levels, 10%, 15%, 20% and 25%, which cover the

practical range of porosity. Permeability coefficient (i.e. hydraulic

conductivity) was selected as the drainage parameter to characterize the

drainage capacity of porous materials. The permeability coefficient was

86

determined by a constant head permeameter, and the clogging performance

was determined using a constant-head permeameter. The clogging

characteristics was studied by introducing clogging materials into the porous

materials and measuring the decrease in permeability coefficient of the test

materials at different stages of clogging.

4.1.1 Measurement of permeability coefficient

A constant-head test apparatus was used to measure the coefficient of

permeability as described in Chapter 3 and shown schematically in Figure 3.3.

An upstream inflow reservoir was used to maintain a constant upper water

level, while a downstream outflow weir was used to establish a constant lower

water level. The apparatus consisted of an open-ended vertical cylinder with

an internal diameter of 150 mm to receive a 150 mm diameter specimen. A

submersible pump provides a constant inflow of water into the inlet cylinder.

In the present study, a constant hydraulic head of 41.5 cm was maintained

throughout the test.

4.1.2 Clogging procedure

To establish the clogging permeability deterioration trend, clogging

materials were introduced in ten cycles so that a sufficient number of data

points could be obtained before the test specimen was fully clogged. A series

of trial clogging tests were conducted to determine an appropriate amount of

clogging material to apply at each cycle, and it was found that applying 5.3 g

(i.e. an application amount of 2000 g per square m) per cycle would allow 10

clogging cycles to be conducted before the specimen was rendered fully

clogged and reached terminal clogging state. The adopted clogging procedure

87

is described as follows: 5.3 gram of clogging material in the form of fine-

grained soil was brought into each specimen by means of water that was

repeatedly fed through the 150 mm diameter cylinder of the constant head

permeameter. Permeability coefficient measurements were performed

repeatedly at an interval of three minutes until the change in the measured

permeability value was negligible. To establish the deterioration in

permeability as clogging developed, the permeability of the specimen was

measured after each and every of the ten cycles of the clogging process.

To find out the amount of soil retained in the specimen, the specimen was

weighed before and after each clogging stage. The entire test procedure,

including the clogging process and permeability coefficient measurements,

took 3 to 3.5 hours per specimen.

4.1.3 Clogging materials

The soils deposited from dirty wheels of vehicles, or vehicles carrying

earth or construction materials have been the major sources of clogging

materials on porous pavements. For this study, sand was used as a clogging

material because it is commonly found on urban roads. Residual soil was also

used as it is the common subgrade soil that pavements in Singapore are

constructed upon and spillage of this material has been known to clog the

pores of porous asphalt pavements. Their sizes usually range from less than 75

μm to 1.18 mm. Figure 4.1 shows the gradations of typical residual soils and

construction sands commonly found on Singapore roads and used as clogging

materials in this study. Earlier studies by Fwa et al. (2002), Tan et al. (2000)

and Fwa et al. (1998), found that of the various sizes of these clogging

88

materials, fines smaller than 75 µm had insignificant effect in inducing

clogging as compared to the larger size materials, and that the component with

sizes between 600 µm and 1.18 mm were the most detrimental in creating

clogging in porous materials. Hence, this component of the residual soil was

employed in the clogging procedure in the present study.

4.1.4 Measurement of porosity

The pervious concrete porosity test was determined from equation

(3.1) given in Chapter 3. The porosity test method was initially originally

proposed by Montes et al. (2005), and later incorporated into ASTM

C1754/C1754M – 12: standard test method for density and void content of

hardened pervious concrete.

The asphalt porosity test follows ASTM: D1188 – 07, whereby the

asphalt specimens were wrapped with parafilm and the porosity of the asphalt

specimens determined as follows:

% air void = D− Sm

D x 100 (4.1)

with

D = Wagg+WbitWagg

2.63+

Wbit1.05

(4.2)

Wbit = WA

100−WA x Wagg (4.3)

Sm = A𝑎𝑖𝑟

A𝑎𝑖𝑟−B (g/ml) (4.4)

89

whereby Aair = mass of dry specimen in air, g; B = mass of specimen

immersed in water, g; Wbit = Weight of bitumen, g; Wagg = Weight of

aggregate, g.

4.2 Pavement mixtures

The first part of this research was to study how pervious concrete and

porous asphalt mixtures differ in their permeability and clogging

characteristics. For each of the two mixture types, four sets were prepared to

achieve approximately the following levels of porosity: 10%, 15%, 20% and

25%. The second part was to examine how steel fiber pervious concrete

mixtures with varying fiber dosages perform. The fiber dosage studied were:

1%, 1.5%, 2% and 2.5%.

4.2.1 Pervious Concrete Mixtures

Details of the pervious concrete and steel fibers can be found in

Section 3.2.1. To produce specimens of the target porosity levels as well as

with different steel fiber dosages, specimens were prepared using different

mix proportions as shown in Table 4.1. The water-cement ratio was held

constant at 0.3 and the coarse aggregate content at 1560 kg/m3. Triplicate

samples were produced for each mix design. The mixtures with the “F” in its

designation contained steel fibers.

4.2.2 Porous Asphalt Mixtures

The asphalt mixtures were the porous asphalt mixtures used in

Singapore road construction. Table 4.2 shows the aggregate gradations and

90

mix proportions of three open-graded/porous asphalt paving mix designs for

pavement wearing course: mix PA-13 with porosity (i.e. air void content)

ranging from 8 to 12% approximately, mix PA-16 having porosity from 15%

to 20% approximately, and PA-20 with porosity from around 20% to more

than 25%. Crushed granite stone aggregate, which was the common type of

road making aggregate in Singapore, was used for the mixes. The asphalt

binder was a polymer modified binder of grade PG76-22. The porosity of each

mix could be varied by adjusting the binder content within the allowable range

of 4.5 to 5.5% by weight of total mix.


4.3.1 Effect of different clogging materials

Four types of clogging materials were used to determine the most

detrimental sand size for pervious concrete as well as porous asphalt. A porous

mix (PC20) of 20% porosity was chosen as reference, as this is commonly

adopted in construction.

Figure 4.2 shows the deterioration in permeability of pervious concrete

and porous asphalt over ten cycles of clogging with four different types of

clogging materials. In general, clogging increased with the size of the clogging

material. Medium to coarse sand (600 μm to 1.18 mm) was most detrimental

in causing clogging. This is because this type of sand consists of a large

proportion of relatively large size sand particles, which are less likely to pass

through the pore structure thus causing a blockage.

The amount of residual soil that adhered to pervious concrete was

insignificant. The residual soil was observed to pass through the specimen

91

almost immediately after being added into the inlet cylinder of the constant

head permeameter. Residual soil (less than 75 μm) is therefore least

detrimental in clogging pervious concrete.

4.3.2 Comparison of permeability

Table 4.3 presents the initial porosity and permeability coefficient of

both pervious concrete and porous asphalt specimens. Figure 4.3 shows that

for both pervious concrete and porous asphalt mixtures, the initial

permeability coefficient increases exponentially with the porosity level, as

represented by the following two regression equations:

for pervious concrete: k = 0.949e0.132P

R2 = 0.922 (4.5)

for porous asphalt: k = 0.627e0.126P

R2 = 0.898 (4.6)

where k = permeability coefficient in mm/s, and P = porosity in percent. It is

therefore beneficial to raise the initial porosity as much as practical, without

compromising on the strength of the material.

Table 4.4 shows that the permeability coefficient, k and rate of

permeability, ∆k/ ∆P, increase with porosity. Pervious concrete had a higher

permeability coefficient than porous asphalt with the same porosity; the

difference being larger with higher porosity. The difference in permeability

coefficient increased from 1.3 mm/s at a porosity of 10% to 11.1 mm/s at a

porosity of 25%. The rate of increase of permeability coefficient with porosity

was thus higher for pervious concrete than for porous asphalt. Thus higher

gains in permeability coefficient from increasing mix porosity can be achieved

in pervious concrete compared to porous asphalt.

92

4.3.3 Comparison of clogging behaviour

As described earlier, clogging material was added in ten equal amounts of

5.3g each so that the changes in permeability could be monitored as clogging

developed. Therefore, including the initial permeability value, there were

eleven data points of permeability measurements that defined the permeability

deterioration trend caused by clogging.

Figure 4.4 shows the clogging test results of the pervious concrete and

porous asphalt mixes. For each of the four permeability deterioration curves

(corresponding to four porosity levels), the range of measured permeability

values at each of the ten stages of the clogging process is also indicated. The

variation of the measured permeability coefficient values obtained from three

replicate test specimens is represented by the range bars indicated in Figure

4.4. Pervious concrete always performed better than porous asphalt with the

same initial porosity at each stage of clogging development.

Excluding the pervious concrete with 20% porosity, the higher the porosity

level, the higher was the variation among the measured permeability

coefficient data. This could be because a mixture with a higher porosity would

have more flow channels, and there would be more possible patterns of

clogging development than a mixture with a lower porosity, thus leading to

larger variations in the resulting permeability coefficient values in the

clogging tests of replicate specimens.

The deterioration in permeability of both porous materials can be described

by exponential relation obtained from regression analysis:

93

For pervious concrete with:

10% Porosity: k = 2.453e-0.338N

R2 = 0.996 (4.7)

15% Porosity: k = 13.019e-0.271N

R2 = 0.948 (4.8)

20% Porosity: k = 15.790e-0.304N

R2 = 0.989 (4.9)

25% Porosity: k = 17.117e-0.062N

R2 = 0.952 (4.10)

For porous asphalt with:

10% Porosity: k = 2.127e-0.291N

R2 = 0.992 (4.11)

15% Porosity: k = 4.927e-0.416N

R2 = 0.978 (4.12)

20% Porosity: k = 7.668e-0.290N

R2 = 0.992 (4.13)

25% Porosity: k = 15.272e-0.211N

R2 = 0.992 (4.14)

where k = permeability coefficient in mm/s, and N = number of clogging

cycle. The residuals for equations (4.7) to (4.14) were normally distributed as

the P-value was more than 0.05 using the Anderson-Darling Normality Test as

shown in Annex A.

For porous asphalt mixtures, Figure 4.4(b) shows that the relative

permeability of specimens of the four target porosity levels remained

unchanged throughout the clogging process. Generally, differences in

permeability coefficients of different target porosity levels decreased as the

clogging process progressed. This is also the case for the test results of

pervious concrete specimens shown in Figure 4.4(a).

94

The permeability deterioration curves in Figure 4.4 suggest that, for both

pervious concrete and porous asphalt, there was a significant improvement in

permeability performance when the mixture porosity was increased from 20%

to 25%.

The permeability deterioration curves of pervious concrete and porous

asphalt are compared in Figure 4.5. The difference between the two material

types was smallest (in the order of about 2 mm/s) for a porosity of 10%, and

largest (approximately of the order of 5 mm/s) for a porosity of 25%.

Clogging was reached when the deterioration in permeability began to

level off and there was negligible change in the permeability coefficient

between successive clogging stages. As shown in Figure 4.5, except for

pervious concrete and porous asphalt specimens with an initial porosity of

25%, all specimens with lower initial porosity reached the terminal state

before the 10th

stage of clogging. This finding further reinforces the need to

design for a porosity of more than 20% for porous pavement mixes in practice.

Hypothesis testing using the T-test: Two-samples assuming unequal

variances statistical analysis was conducted for the permeability deterioration

of the eight porous mixtures, namely: PC10, PC15, PC20, P25, PA10, PA15,

PA20 and PA25, for clogging cycles 0 to 10. The result are shown in Annex B

Table B-1. Based on the analysis, most of the results were accepted at the 95%

confidence level as most of their p-values were less than 0.05. The null

hypothesis was rejected in favor of the alternative hypothesis. For values

highlighted in bold, their p-value was greater than 0.05, therefore the results

were not statistically significant at the 95% significance level. The null

hypothesis was not rejected and the results were not statistically different.

95

Figure 4.6 shows the appearance of the pervious concrete and porous

asphalt specimens after clogging tests. Test results suggested that pervious

concrete was superior to the porous asphalt in resistance to clogging. Based on

past studies (Shimeno et al., 2010; Fwa et al., 2002, Tan et al., 2000 and Fwa

et al., 1998 and FCPA, 1990), the factors that affect the clogging behaviors of

a porous material include (i) type of clogging materials, (ii) gradation of

aggregates in the mixture, and (iii) the type of binder. Factor (i) was ruled out

in this study because the same type of clogging material was used for the

clogging tests. As for factor (ii), the use of large size aggregates is known to

improve permeability and clogging resistance, but is unlikely to be a main

reason in the present study even though the coarse aggregate gradation of

pervious concrete varied from those of the porous asphalt mixtures. The most

likely reason was probably due to the properties of the binders used and

Manning roughness coefficient. The Manning roughness coefficient is based

on the empirical Manning formula, estimating the average velocity of a liquid

flowing in a conduit that does not completely enclose the liquid. The Manning

coefficient is dependent on many factors including surface roughness and

sinuosity (FHWA, 2005). Serving as walls for flow channels in the porous

mixture, asphalt and concrete would exhibit different flow resistance. Their

clogging resistance would be affected by their adhesion properties with

clogging materials. In this instance, the Manning roughness coefficients for

asphalt and concrete would be different, thereby contributing to different

resistance to flows.

So far no other research has been done to evaluate how the properties of

the binders affect the clogging behaviour. However it was noted that when

96

exposed to higher temperature, the asphalt becomes more viscous and more

fine particles are attracted to it. Further research is needed to study in detail

the effects of these factors on the different clogging-resistance characteristics

of the two porous materials.

4.3.4 Effect of steel fibers on clogging behaviour

Figure 4.7 shows the appearance of pervious concrete with steel fibers

after they were subjected to clogging tests. The steel fiber dosage is given in

Table 4.1 and the measured porosity of the specimens in Table 4.5. The steel

fiber reinforced pervious concrete had a water-cement ratio of 0.3, cement

content of 367 kg/m3, water content of 110.1 kg/m

3, coarse aggregate content

of 1560 kg/m3 and steel fiber dosage varying from 1% to 2.5%, in the mixture

proportion.

The reduction in coefficient of permeability in steel fiber reinforced

pervious concrete due to the introduction of clogging materials is shown in

Figure 4.8. All mixes have porosity of around 20% (see Table 4.5), that is,

ranging from 23% with 1% fiber, to 17% with 2.5% fiber. The initial

permeability coefficient was around 13 mm/s for Mix F1 (with 1% fiber)

decreasing to 11 mm/s for Mix F2.5 (with 2.5% fiber), compared to about 15

mm/s for the pervious concrete mix PC20/F0 without steel fibers. For

comparison, the results for a porous asphalt mix PA20 with a porosity of 20%

and initial permeability of about 9 mm/s is also shown in Figure 4.8.

The reduction in permeability coefficient was similar for mixes

containing fibers up to about 2%. With higher steel fiber dosage, the reduction

was higher especially in the initial few cycles. The permeability coefficient of

97

previous concrete was higher than that of porous asphalt at all stages,

especially where the steel fiber content was less than 2%, indicating that it is

less susceptible to clogging. After ten cycles of clogging, however, the

permeability coefficient of all samples reduced to below 1 mm/s.

4.4 Evaluation of clogging potential of porous materials

The Kozeny-Carmen equation (Tan et al., 2003) has been used widely

in the modelling of the clogging mechanisms of various media. The equation

is given by:

k0 = (λ ρw g/ηw)[np3/(1- np)

2] (1/ sv

2) (4.15)

where,

k0 : initial permeability of permeable medium (m/s),

λ : shape factor function of tortuosity of medium,

ρw : density of water (kg/m3),

g : acceleration due to gravity (m/s2),

ηw : viscosity of water (kg/m.s),

np : porosity of permeable medium,

sv : volumetric specific surface area of permeable medium

= 6/dp for spherical particles (m-1

)

= 4/df for fibers (m-1

),

dp : mean particle diameter (m), and

df : fiber diameter (m).

The effect of clogging can be considered by introducing a term known

as the specific deposit of the clogging material, σ which is given by

σ = Vc / VT (4.16)

in which

98

Vc = mc / ρc (4.17)

where

VT : volume of specimen (m3),

Vc : clogging material retained within the specimen (m3),

mc : mass of clogging material retained in specimen (kg), and

ρc : density of clogging material (kg/m3).

Based on Kozeny-Carmen equation, Giroud (1996) derived a

theoretical model for the reduction in the permeability of geotextiles due to

soil clogging. Blazejeski and Sadzide (1997) used the Kozeny-Carmen

equation to study the effect of permeability on sand due to clogging. Later on,

Wu and Huang (2000) also modified the Kozeny-Carmen equation to study

the effects of sediment clogging gravel beds.

Tan et al. (2003) earlier formulated a theoretical model to study the

clogging behavior of permeable bases. According to the model, the reduced

permeability caused by clogging can be expressed as a function the initial

permeability k0 as follows:

k = 𝑘0 (1−𝑛)2

𝑛3

(𝑛− ∝𝑐𝜎)3

[1−(𝑛−∝𝑐𝜎)]2 (4.18)

where,

k : permeability of specimen (mm/s),

k0 : initial permeability of specimen (mm/s),

np : porosity of specimen,

σ : specific deposit of clogging material, and

αc : empirical constant.

99

The empirical constant αc is a positive value which is related to the rate

of deterioration of permeability caused by clogging. A higher αc would

indicate a more rapid decrease in permeability for the porous material tested.

In the current study, the experimental empirical constant αc was

determined from Equation (4.18) for pervious concrete and porous asphalt.

4.4.1 Analysis of permeability reduction due to clogging

Figure 4.9 shows the average amount of soil retained with respect to

permeability from three samples for pervious concrete and porous asphalt after

clogging tests.

By rearranging equation (4.18), a non-linear system with c on both

sides of the equation is formed and shown in equation (4.19). By performing

iterative substitution, the c values can be obtained. Figure 4.10 depict the c

factor of the pervious concrete and porous asphalt specimens with target

porosities at 10%, 15%, 20% and 25%.

𝑘

𝑘0

𝑛3

(1−𝑛)2 [1 − (𝑛 −∝𝑐 𝜎)]2 = (𝑛 −∝𝑐 𝜎)3 (4.19)

The properties of pervious concrete mixtures that affect the value of αc

include the initial porosity, the gradation of aggregates and the cement

content; whilst the properties of porous asphalt mixtures that affect the values

of αc are the initial porosity, the gradation of aggregates and the type and

grade of asphalt binder.

100

Figure 4.11 illustrates that pervious concrete had lower permeability

deterioration factor c compared to porous asphalt at all porosity levels. This

implies that pervious concrete has better clogging resistance performance as

compared to porous asphalt.

Figure 4.12 shows pervious concrete reinforced with 2% steel had

comparable permeability deterioration factor c as unreinforced pervious

concrete with an initial porosity of 20%. This indicates that the incorporation

of fibers did not affect the clogging resistance of pervious concrete.

It is of interest to note that when the initial porosity is less than 10% or

more than 24%, the deterioration c factor would be lower. At low porosity, it

is difficult for the clogging materials to find their way into the test specimen,

resulting in a low deterioration rate of permeability. As the initial porosity

increases, more clogging materials could be brought into and trapped within

the specimen to result in clogging, and hence a higher rate of permeability

deterioration. However when the initial porosity of the specimen becomes

sufficiently high, the flow channels in the specimen are wide and the flow

velocity is high enough to carry the clogging materials through the specimen

without causing much clogging.

4.5 Summary

The results of a laboratory clogging study have been reported and

analysed in this chapter. The study compared the permeability and clogging

characteristics of two types of porous pavement materials at four levels of

porosity: 10%, 15%, 20% and 25%. The two porous materials studied were

101

pervious concrete and porous asphalt. Three replicate specimens were

prepared at each target porosity level for each of the two test materials. In the

clogging test of each test specimen, a laboratory clogging procedure was

adopted to introduce a fixed amount of clogging material in ten stages by

means of a constant-head apparatus. This procedure allowed permeability

coefficient to be measured at each stage and thus enabled deterioration in

permeability to be determined as clogging progressed.

For both pervious concrete and porous asphalt mixtures, the

permeability and clogging resistance increased substantially when the mixture

porosity was increased beyond 20%. These findings provide supporting

experimental evidence to the common practice of specifying a porosity of

more than 20% for porous pavement materials. Also, at all four porosity

levels, the pervious concrete specimens gave higher initial permeability than

the porous asphalt specimens. The difference became larger as the porosity

increased.

Comparing the deterioration in permeability of pervious concrete with

porous asphalt specimens, it was found that for the same porosity, pervious

concrete always performed better than porous asphalt throughout the entire

clogging process. Again, the difference between the performances of the two

material types increased with porosity.

Incorporation of steel fibers dosage up to 2% did not affect the

clogging resistance of pervious concrete. The current study is of significance

as a comparison of the permeability and clogging characteristics of pervious

102

concrete and porous asphalt at four levels of porosity: 10%, 15%, 20% and

25% was made.

103

Table 4.1 Mixture design of pervious concrete

Mix w/c

ratio

Cement/

[kg/m3]

Water/

[kg/m3]

Coarse

Aggregate/

[kg/m3]

Target

porosity level

[%]

Steel Fiber

dosage

[%]

PC10

0.3

495 148.5

1560

10

- PC15 400 120.0 15

PC20* 367 110.1 20

PC25 300 90.0 25

F1

367 110.1 20

1.0

F1.5 1.5

F2 2.0

F2.5 2.5

* Reference mix

104

Table 4.2 Aggregate gradations and mix composition of porous asphalt mix

designs

Mix Design Porous Asphalt

PA-13

Porous Asphalt

PA-16

Porous Asphalt

PA-20

Sieve Size (% passing) (% passing) (% passing)

20mm - - 100

16mm - 100 95

13.2mm 100 70 85

9.5mm 85 59 72

4.75mm 45 33 22

2.36mm 30 22 18

1.18mm 25 16 -

600um 20 10 13

300um 13 6 9

150um 10 4 7

75um 4 3 6

Asphalt Binder

Content (% by

Weight of

Total Mix)

4.5 to 5.5

Air void

content (%) 8 to 12 15 to 20 20 to 25 or

more

105

Table 4.3 Porosity and permeability coefficient of pervious concrete and

porous asphalt specimens

Target

Porosity

Porous Asphalt Pervious Concrete

Actual

Specimen

Porosity (%)

Permeability

Coefficient

(mm/s)

Actual Specimen

Porosity (%)

Permeability

Coefficient

(mm/s)

10%

8.82 2.68 9.95 4.70

11.4 2.49 7.30 1.94

10.8 2.26 7.24 1.58

15%

14.0 3.19 16.2 8.79

16.2 3.60 16.2 11.4

16.4 3.45 15.5 9.81

20%

18.5 9.72 21.6 14.6

18.6 8.79 20.7 15.2

21.6 8.64 19.3 14.6

25%

24.6 13.5 24.1 26.2

23.8 11.5 26.3 23.4

26.6 21.1 26.7 25.3

106

Table 4.4 Rates of increase of permeability coefficient with porosity for

porous asphalt and pervious concrete mixtures

Porosity

(%)

Permeability

coefficient, k (mm/s)

∆k/ ∆P

Difference

between k

of Porous

Asphalt

and

Pervious

Concrete

(mm/s)

Porous

Asphalt

Pervious

concrete

Porous

Asphalt

Pervious

concrete

10 2.2 3.6 0.40 0.66 1.3

15 4.2 6.9 0.72 1.28 2.7

20 7.8 13.3 1.36 2.48 5.5

25 14.6 25.7 - - 11.1

107

Table 4.5 Measured porosity of steel fiber pervious concrete specimens

Target

Porosity Mix

5D Steel Fiber

Dosages (%)

Initial

Porosity

(%)

Average Porosity (%)

20%

F1 1

23.9

22.9 23.4

21.4

F1.5 1.5

23.5

22.5 24.1

19.9

F2 2

22.4

21.3 20.5

21.0

F2.5 2.5

18.0

17.2 17.0

17.2

108

Figure 4.1 Gradations of common clogging materials on Singapore roads

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10

Per

cent

Pas

sing (

%)

Particle Size (mm)

Medium-coarse sand

Fine-medium sand

Fine to coarse sand

Residual Soil

109

(a) Pervious Concrete

(b) Porous Asphalt

Figure 4.2 Permeability versus clogging stages of pervious concrete and

porous asphalt at 20% porosity.

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity,

k (

mm

/s)

Clogging Cycle

Residual Soil (Less than 75µm)

Fine to medium sand (150µm to 600µm)

Fine to coarse sand (75µm to 1.18mm)

Medium to coarse sand (600µm to 1.18mm)

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity,

k (

mm

/s)

Clogging Cycle

Residual Soil (Less than 75µm)Fine to medium sand (150µm to 600µm)Fine to coarse sand (75µm to 1.18mm)Medium to coarse sand (600µm to 1.18mm)

110

Figure 4.3 Relationship between porosity and permeability coefficient

Pervious concrete:

y = 0.949e0.132P

R² = 0.922

Porous asphalt:

y = 0.627e0.126P

R² = 0.898

02468

1012141618202224262830

0 5 10 15 20 25 30

Per

mea

bil

ity c

oef

fici

ent,

k (

mm

/s)

Porosity, P (%)

Pervious Concrete

Porous Asphalt

111

(a) Pervious Concrete with Target Porosity P%.

(b) Porous Asphalt with Target Porosity P%.

Figure 4.4 Effect of clogging cycle on permeability coefficients

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity C

oef

fici

ent,

k (

mm

/s)

Clogging Cycle

PC 10% PC 15%

PC 20% PC 25%

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity C

oef

fici

ent,

k (

mm

/s)

Clogging Cycle

PA 10% PA 15%PA 20% PA 25%

112

Figure 4.5 Comparison of permeability deterioration curves of porous asphalt

and pervious concrete mixtures

0123456789

101112131415161718192021222324252627

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity C

oef

fici

ent,

k (

mm

/s)

Clogging Cycle

PA 10% PA 15%PA 20% PA 25%PC 10% PC 15%PC 20% PC 25%

Legend:

PA = Porous Asphalt

PC = Pervious Concrete

Numerical values indicate porosity %

PC 25%

PC 20%

PA 25%

PC 15%

PA 20% PA 15%

PC 10%

PA 10%

113

(i) 10% (ii) 15%

(iii) 20% (iv) 25%


(i) 10% (ii) 15%

(iii) 20% (iv) 25%

(b) Porous Asphalt

Figure 4.6 Pervious concrete and porous asphalt mixes of different porosities

after clogging effect

114

Figure 4.7 Clogged fiber reinforced pervious concrete specimen

Figure 4.8 Clogging characteristics of steel fiber reinforced pervious concrete

specimens

0123456789

10111213141516

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity C

oef

fici

ent,

k (

mm

/s)

Clogging Stage

PC20 F1 F1.5

F2 F2.5 PA20

PC20/F0

F2

F1.5

F1

F2.5

PA20

115

(a) Pervious concrete

(b) Porous Asphalt

Figure 4.9 Average soil retained for pervious concrete and porous asphalt

samples with different porosities

0

2

4

6

8

10

12

14

16

18

20

22

0 500 1000 1500 2000

Per

mea

bil

ity,

k (

mm

/s)

Soil retained (g/m2)

10% 15% 20% 25%

0

2

4

6

8

10

12

14

16

18

0 500 1000 1500 2000

Per

mea

bil

ity,

k (

mm

/s)

Soil retained (g/m2)

10% 15% 20% 25%

116


(b) Porous Asphalt

Figure 4.10 Permeability deterioration factor (αc)

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PC10 PC15 PC20 PC25

0

2

4

6

8

10

12

14

16

18

20

22

24

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PA10 PA15 PA20 PA25

117

(a) 10% porosity

(b) 15% porosity

Figure 4.11 Permeability deterioration factor (αc) for pervious concrete and

porous asphalt specimens

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PC10 PA10

0

1

2

3

4

5

6

7

8

9

10

11

12

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PC15 PA15

118

(c) 20% porosity

(d) 25% porosity

Figure 4.11 Permeability deterioration factor (αc) for pervious concrete and

porous asphalt specimens (Cont’d)

0

2

4

6

8

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PC20 PA20

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

PC25 PA25

119

Figure 4.12 Permeability deterioration factor (αc) for unreinforced pervious

concrete and fiber reinforced pervious concrete specimens

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity d

eter

iora

tion f

acto

r, α

c

Clogging cycle

F2 PC20

120

CHAPTER 5 SOUND ABSORPTION CAPACITY OF PERVIOUS

CONCRETE

Due to the rapid rate of urbanisation throughout the world, road traffic

noise has become a significant public concern as over exposure to noise over

an extended period of time can cause serious health problems such as sleeping

disturbance, hypertension, immunity decline and psychological imbalance.

There are two ways to mitigate road traffic noise: (i) to reduce the volume of

traffic on the roads, (ii) to install sound absorption barriers and (iii) to reduce

tire-pavement noise through selection of pavement wearing course materials.

In this study, the focus is on method (iii) by increasing the sound

absorption capacity of the road pavement. This is a measure that targets the

problem of road traffic noise emission at the source. Pervious concrete

pavement has the capacity to absorb and dissipate sound in view of the voids

in the matrix of its porous structure. However a durability issue to note is that

over time, clogging of the pores in the pervious concrete pavement will reduce

its capacity for sound absorption. Therefore, it is of interests to study the

following issues in evaluating the sound absorption capacity of pervious

concrete:

1. The sound absorption performance of pervious concrete compared to

other common road materials such as normal weight concrete, dense

graded asphalt and porous asphalt mixtures;

2. The effect of the initial porosity of the pavement in relation to the

sound absorption capacity of pervious concrete;

121

3. The effect of the thickness of the pavement on the sound absorption

capacity of pervious concrete; and

4. The effect of clogging on the sound absorption capacity of pervious

concrete.

5.1 Experimental Program

Table 5.1 shows the experimental program for the present study. A

total of 32 mixes grouped into four series “A” to “D” were studied. Series “A”

consisted of specimens with different road materials; Series “B” comprised

pervious concrete and porous asphalt mixes with different porosities; Series

“C” consisted of mixes with different sample thickness and Series “D”

considered specimens subjected to different degrees of clogging. The “degree

of clogging” (% clogged) is defined as percentage of original porosity

retained, that is, % clogged = ( Pclogged / Poriginal ) x 100%.

5.1.1 Pavement materials

Table 5.2 shows the coarse and fine aggregate gradations for pervious

concrete, normal weight concrete and lean concrete. Lean concrete is a

concrete with high water content and low cement content. It is usually used as

the sub-base in pavement construction. For the pervious concrete and normal

weight concrete mixtures, the cement, coarse aggregates and 5D hooked-end

steel fibers were the same as those specified in Section 3.1.1.

The fine aggregates used for the normal weight concrete and lean

concrete mixes were natural sand complying with the requirements of ASTM

C 33-11a and having specific gravity of 2.60. Table 5.3 details all the concrete

122

mix proportions used in this sound absorption study. The 28-day compressive

strength for the normal weight concrete mixture and lean concrete mixture

were 40.1 MPa and 7.8 MPa respectively.

The asphalt mixtures were those used in Singapore road construction.

Table 5.4 shows the aggregate gradations and mix proportions of one dense

graded asphalt mix (W3B) and three open-graded/porous asphalt paving mix

designs (PA-13, PA-16 and PA-20) for pavement wearing course. W3B has

porosity ranging from 3% to 4%, mix PA-13 has porosity ranging from 8% to

12% approximately, mix PA-16 has porosity from 15% to 20% approximately,

and mix PA-20 has porosity from around 20% to more than 25%. Crushed

granite stone aggregate, which was the common type of road making

aggregate in Singapore, was used for the mixes. The asphalt binder was a

polymer modified binder of grade PG76-22. The porosity of each mix could

be varied by adjusting the binder content within the allowable range of each

mix design. Three replicate specimens for each kind of mix (same porosity

and thickness) were compacted and analyzed. The results of the three replicate

tests samples were then averaged to give the results presented in this study.

The bituminous mixtures had been compacted in samples of approximately 6.3

cm in height using a Marshall compactor.

5.1.2 Test specimens and conditioning

The samples in Series A, B and C had a diameter of 100 mm, while

those in Series D had a diameter of 150 mm. The samples in Series A, B and

D were 50 mm thick. For Series C, the test variable is the effect of thickness of

sample layer, therefore three sample thicknesses were explored: 63 mm, 100

123

mm and 200 mm. Figure 5.1 shows schematically the 100 mm diameter and

150 diameter moulds used to hold the specimens during testing. The holes in

the plates are to ensure that the sample mould/holder could be secured tightly

to the impedance tube by screws.

Medium to coarse sand (600 um to 1.18 mm) in size was used as

clogging material in Series D specimens. The clogging procedure was the

same as that described in Chapter 4. The clogged specimens of five different

degrees of clogging can be seen from Figure 5.2 and 5.3.

5.1.3. Acoustic absorption measurement

The acoustic absorption coefficient of a test specimen was measured

using a Bruel & Kjaer (B&K) impedance tube for a frequency range from 100

to 2000 Hz following the BS EN ISO 10534-2 (2001) specification.

Figure 5.4 show the sound absorption test setup with low and high

frequency impedance tubes. Measurements were carried out according to the

standing wave method in which a loudspeaker sets up a sound field in a tube

which was terminated by the sample at the far end. A pure tone signal is

supplied to the loudspeaker and a plane wave is generated in the tube in the

direction of the sample. The wave is partially reflected from the sample and

the interference between the incident and reflected waves gives rise to a

standing wave pattern. By measuring the ratio between the maximum and

minimum sound pressure, the absorption coefficient of the sample for zero

degree incident sound can be calculated. Since the sample was the only

absorbing material, the measured absorption coefficient α is very closely

related to its sound absorbing properties.

124

By means of a clamping device, the sample holder was fastened to one

end of the measuring tube; the other end of which was screwed onto the box

containing the loudspeaker. The probe microphone was supported by a small

gliding carriage. Through an axial hole in the loud speaker, the probe

microphone was then inserted into it.

The sample was laterally coated with a thin film of silicone to eliminate

the air gap between the specimens and the tube. This is because if the sample

is not well insulated inside the impedance tube, the absorption measurements

could be affected by the air that escaped from an open pore on the sides of the

specimen.

Frequencies of 100 Hz to 500 Hz are considered to be in the low frequency

range while 600 Hz to 2000 Hz to be in the high frequency range. For the low

frequencies; 100, 150, 200, 250, 300, 350, 400 and 500 Hz, the impedance

tube was 100 mm in diameter and 1 metre in length. For the high frequencies;

600, 700, 800, 900, 1000, 1250, 1500, 1750 and 2000 Hz, the impedance tube

was 29 mm in diameter and 0.28 metre in length. The averages of three

readings were taken for each frequency.

Figure 5.5 illustrates why the diameter of the impedance tube has to be

smaller for higher frequencies so as to be able to sustain a standing wave in

the tube (Allard, 1993). Take for instance at 1000 Hz, the wavelength is 3 cm

for which the pressure would not be uniform across a diameter of 100 mm.

Therefore to maintain a plane wave across the diameter of the tube, a smaller

diameter of 29 mm is needed. At 2000 Hz, the wavelength is about 1.5 cm for

which the pressure would not be uniform across a diameter of 100 mm.

125

Therefore to maintain a plane wave across the diameter of the tube, a smaller

diameter of 29 mm is still needed.

The frequency range of interest was limited to 100 Hz to 2000 Hz in

this study. A 100 Hz threshold was used as the lowest limit because at lower

frequencies, the acoustic pressure was hard to stabilize. The higher limit of

2000 Hz was used because tire-pavement noise is most prevalent to the human

ear at frequencies of 800 – 1200 Hz. In the case of a material that absorbs

sound waves perfectly, the absorption coefficient, α, would be 1.0, whereas a

material that does not absorb sound at all would have an absorption

coefficient, α, equal to 0 (Neithalath et al., 2006).


5.2.1 Effect of different road materials (Test Series A)

The measured sound absorption coefficient for Test Series A (see

Table 5.1), covering eight road materials, namely: pervious concrete (PC);

steel fiber-reinforced pervious concrete (PF); normal weight concrete (NC),

steel fiber-reinforced normal weight concrete (NF), lean concrete (LC), porous

asphalt (PA), open-graded asphalt (OG) and dense asphalt (NA), are

summarised in Table 5.5 and plotted in Figure 5.6. The following can be

deduced from the test results:

Effect of steel fibers. The sound absorption capacities of both pervious

concrete and normal weight concrete, with and without fibers, did not differ

significantly for the entire frequency range. It thus can be said that the use of

steel fibers do not affect the sound absorption properties of the mixes.

126

Pervious concrete versus normal concrete. Pervious concrete had

better sound absorption capacity compared to normal weight concrete for the

entire frequency range. Notably, the maximum value of sound absorption

coefficients, α, for pervious concrete and normal weight concrete were 0.92

and 0.12 respectively. The lowest sound absorption coefficients for pervious

concrete and normal weight concrete were 0.40 and 0.07 respectively.

Normal weight concrete versus lean concrete. The sound absorption

coefficient curves for normal weight concrete and lean concrete were

comparable as both their porosities were in the range of 3% to 4% and their

surfaces were impermeable.

Pervious concrete versus lean concrete. Pervious concrete also had

better sound absorption capacity compared to lean concrete for the entire

frequency range. In particular, the maximum value of sound absorption

coefficients α for pervious concrete and lean concrete were 0.92 and 0.11

respectively. The lowest sound absorption coefficients for pervious concrete

and normal weight concrete were 0.40 and 0.06 respectively.

Pervious concrete versus porous asphalt. Pervious concrete had

marginally better sound absorption capacity when compared to porous asphalt.

Both their peak sound absorption coefficients occurred at the frequency of 800

Hz but their values differed. The sound absorption coefficient α value for

pervious concrete was highest at 0.92 whereas porous asphalt was at 0.83. The

sound absorption coefficient α value was lowest at 0.40 for pervious concrete

and 0.30 for porous asphalt.

127

Porous asphalt versus open-graded asphalt versus dense asphalt.

Comparing the three types of asphalt mixes, porous asphalt had better sound

absorption capacity than open-graded asphalt which in turn performed better

than dense graded asphalt. The difference in sound absorption capacity for the

three mixes could be attributed to differences in their porosities. Porous, open-

graded and dense asphalt had porosities of 20%, 10% and 3% - 4%

respectively. The peak sound absorption coefficient for porous, open-graded

and dense asphalt mixes were 0.83, 0.67 and 0.18 respectively. The lowest

sound absorption coefficient for porous, open-graded and dense asphalt mixes

were 0.30, 0.22 and 0.12 respectively.

Overall, pervious concrete had the best sound absorption capacity

amongst the eight types of mixes tested. The use of steel fibers had no effect

on the sound absorption capacity of the mix.

5.2.2 Effect of porosity (Test Series B)

Four different porosities ranging from 10% to 25% at intervals of 5%

were considered for the sound absorption tests of pervious concrete and

porous asphalt specimens respectively. Table 5.6 shows the measured porosity

of the test samples and Figures 5.7 and 5.8 show graphically the sound

absorption coefficients of pervious concrete and porous asphalt at various

frequencies. Increasing the porosity slightly increased the frequencies from

500 Hz to 600 Hz at which the maximum sound absorption occurred, for both

pervious concrete and porous asphalt.

Table 5.7 shows the peak sound absorption coefficient for pervious

concrete and porous asphalt. For both pervious concrete and porous asphalt,

128

mix with a porosity of 10% had a lower sound absorption coefficient than the

corresponding mixtures with a porosity of 15%. When the porosity increased

from 15% to 20%, there was no change in the maximum values of the sound

absorption coefficient, but there was a shift in the peaks of frequency from 500

Hz to 600 Hz.

As the porosity was increased from 20% to 25%, the maximum sound

absorption coefficient decreased. This is in line with the findings by Neithalath

et al. (2005) who researched with the porosity ranging from 15% to 35% and

indicated that the results seemed counter-intuitive. It has been experimentally

shown that an increase in pore size reduces the maximum absorption

coefficient (Marolf et al., 2004). This reduction in maximum acoustic

absorption coefficient occurs because for a system with large-size pores, the

fictional losses are low and a considerable portion of the acoustic waves that

enter the pore system gets reflected. The sound absorption coefficient (α) of

pervious concrete were higher than porous asphalt by about 0.1 throughout the

entire frequency range.

It should be noted that porosity is influenced by the pore size, pore to

aperture size ratio and pore length, in addition to aperture length, and it is the

combined effect of all these factors that result in different acoustic absorption

(Neithalath et al., 2005).

5.2.3 Effect of thickness (Test Series C)

Figure 5.9 shows the test samples with three thicknesses, 20 cm, 10 cm

and 6.3 cm. Table 5.8 records the measured sound absorption coefficients for

all the test specimens and Figure 5.10 show the variations in sound absorption

coefficients of pervious concrete and porous asphalt for various pavement

129

thicknesses. For both materials, an increase in specimen thickness led to a

reduction in the frequencies at which the maximum sound absorption

coefficient value occurred. There were very slight increases in the maximum

value of absorption coefficient.

The sound energy has been absorbed by the upper surface section of

the pervious concrete and porous asphalt and thus increasing their thickness

has marginal effect in increasing their sound absorption capacity. On the other

hand, Ahammed and Tighe (2011) who did a study on conventional dense

concrete with varying thickness of 260 mm, 200 mm and 76 mm, noted no

significant effect in sound energy absorption and concluded that increasing the

thickness of the pavement was not beneficial in terms of reducing road noise.

From Figure 5.11, the graphs show that pervious concrete had improved sound

absorption capacity as compared to porous asphalt at all target sample

thickness and frequencies.

5.2.4 Effect of clogging (Test Series D)

Table 5.9 shows the measured sound absorption coefficients for the

pervious concrete and porous asphalt samples with clogging percentage of 0%,

25%, 50%, 75% and 100%. These results are plotted in Figure 5.12. Since the

original pervious concrete and porous asphalt samples had a target porosity of

20%, the porosity of the clogged samples would correspondingly equal to

20%, 15%, 10%, 5% and 1%. For the sample that was 100% clogged, a 0%

porosity is unrealistic as not all the pores in the porous materials can be

clogged up. Three samples were tested at each clogging percentage and their

130

average values are plotted over different frequencies ranging from 100 to 2000

Hz in Figure 5.12.

Table 5.10 details the target and actual porosity of the samples and

Table 5.11 summarizes the highest α value and the frequency at which it

occurred for each porosity level. The peak value of (α) of both pervious

concrete and porous asphalt decreased with percent clogging and this is in line

with the findings of Neithalath et al. (2005). This is because sound waves

enter the matrix of the porous material through the surface pores and travel

around the pore structure; as a result, the sound energy is later converted into

heat energy. The sound energy can be said to be dampened by the porous

material. Therefore with more pores available, more sound waves can be

dampened by the porous material. As such samples with higher porosity have

higher α value.

Traffic noise caused by tire-pavement interaction occurs within the 800

Hz to 1200 Hz range (Neithalath et al., 2005 and Sandberg, 1999). From

Figure 5.12, pervious concrete and porous asphalt samples with 20% initial

porosity can still have relatively good sound absorption capacity even after

their pores are 50% clogged. This can be seen by the marginal decrease in α

value from 0.92 for the 20% porosity sample to 0.78 for the 10% porosity

sample in the case of pervious concrete, and from 0.83 to 0.67 in the case of

porous asphalt. However, further clogging beyond 50% will have a significant

reduction in sound absorption capacity. When fully clogged, the sound

absorption capacities of pervious concrete and porous asphalt were

comparable to the normal weight concrete and dense asphalt respectively.

131

5.3 Sound pressure level dB(A)

The sound pressure level equations commonly used in acoustics

calculations (Munjal, 2013; Ver and Beranek, 2006; Moser, 2009; Fahy, 2001

and Allen and Berkley, 1979) can be used to calculate the overall sound

pressure level (SPL) for each mix. The equivalent continuous A-weighted

sound pressure level (SPL), LAT of the dB(A) is defined by:

LAT = 10log10{[ (1/T) ∫ 𝑃𝐴2 (𝑡)𝑑𝑡]/𝑝𝑟𝑒𝑓

2 }𝑇

0 (5.1)

where,

PA(t) : instantaneous A-weighted SPL in Pa,

pref : reference SPL = 20 x 10-6

Pa,

T: specified time interval in seconds.

The A-weighted sound power level (PWL), LWA is defined by:

LWA = 10log10 (WA/Wref) (5.2)

where,

WA : A-weighted PWL in watts

Wref : reference (PWL), internationally agreed upon as 10-12

watts.

To evaluate traffic noise data efficiently, the overall SPL is calculated

from the A-weighted SPL at an individual centre frequency in accordance to

the 1/3 octave band spectrum as follows:

LAT (overall) = 10log10 (∑ 10𝐿𝐴𝑇,𝑖/10𝑁

𝑖=1) (5.3)

where,

N: total number of centre frequencies,

i : subscript denoting an individual centre frequency.

132

According to Sandberg and Ejsmont (2002), because human hearing

responds not linearly but logarithmically to sound stimulus, the acoustic

parameters are expressed as the logarithm to the base ten of the ratio of the

measured value to a reference quantity. The A-weighted sound level dB(A)

correlates reasonably well with the subjective response of the loudness of

traffic noise.

Using Equation 5.3, the 1/3 octave frequency sound pressure for all

test specimens in Test Series A, B, C and D are summarised in Table 5.12 and

the overall sound pressure level for the specimens are shown in Table 5.13.

Figures 5.13 to 5.16 plot the sound pressure level dB(A) for individual

frequencies of the 1/3 octave band centre frequency (ranging from 100 Hz to

2000 Hz) as well as the overall sound pressure level for the type of mix tested.

For porous asphalt, open-graded asphalt and dense graded asphalt, the LAT

values were referenced from the overall OBSI at 80 km/hr measured from

actual roads in a project with the Land Transport Authority of Singapore

(LTA). For normal weight concrete, LAT values were referenced from

(Donavan, 2011). For pervious concrete, LAT values were assumed similar to

porous asphalt, and for lean concrete, LAT values were assumed similar to

normal weight concrete.

As seen from Figure 5.13, pervious concrete and steel fiber pervious

concrete had comparable sound pressure levels of about 96 dB(A). A

comparison of sound pressure levels between pervious concrete and normal

weight concrete shows a substantial reduction of 4.8 dB(A), which is why

pervious concrete can be classified as a quiet pavement. The difference

between pervious concrete and porous asphalt was marginal at 0.3 dB(A) and

133

when comparing porous asphalt with dense graded asphalt, a significant

reduction of 4.2 dB(A) was noted and this difference in sound pressure level

can be perceived by the human ear. Comparing porous asphalt with open-

graded asphalt, there was an overall sound pressure reduction of 1.2 dB(A).

From Figure 5.14, based on the overall sound pressure levels, pervious

concrete and porous asphalt with porosity ranging from 10% to 25% are all

comparable and in the range of 95 to 96 dB(A). The T-test: Two-samples

assuming unequal variances statistical analysis was conducted and shown in

Annex B Table B-2. Based on the analysis, not all the results was accepted at

the 95% confidence level as most of their P-values were more than 0.05.

Therefore there is not sufficient evidence to reject the null hypothesis and the

results are not statistically different. The results between PC25 and PA10 can

be accepted at the 95% confidence level as the P-values were less than 0.05.

The null hypothesis was rejected in favor of the alternative hypothesis. The

difference in overall sound pressure level between pervious concrete and

porous asphalt was about 0.6 dB(A).

Figure 5.15 demonstrates that when pervious concrete and porous

asphalt sample thicknesses were varied from 63 mm to 200 mm, their overall

sound pressure levels were also in the order of 96 dB(A). That is to say,

increasing sample thickness for porous mixes does not significantly aid in

sound reduction. The sound energy would have been dissipated in the top

layer of the sample. Therefore, in terms of cost efficiency, there is little benefit

in increasing pavement surface course thickness for the purpose of noise

reduction. A T-test: Two-samples assuming unequal variances analysis was

also conducted and shown in Annex B Table B-3. Based on the analysis, not

134

all the results can be accepted at the 95% confidence level as most of their P-

values were more than 0.05. Therefore there was not sufficient evidence to

reject the null hypothesis and the results were not statistically different. The

results between PC6 and PA as well as PC6 and PA4 can be accepted at the

95% confidence level as their p-values were less than 0.05. The null

hypothesis was rejected in favor of the alternative hypothesis. The difference

in overall sound pressure level between pervious concrete and porous asphalt

was in the range of 0.3 to 0.4 dB(A).

Figure 5.16 shows that when fully clogged, pervious concrete and

porous asphalt had comparable overall sound pressure level results of 97.1

dB(A) and 97.3 dB(A) respectively. The effect of clogging on noise reduction

is not significant. After fully clogged, the sound pressure levels of both

pervious concrete and porous asphalt were increased by only 1 dB(A).

5.4 Summary

Comparing the sound absorption capacity, pervious concrete

performed slightly better than porous asphalt and open-graded asphalt, and

significantly better than dense graded asphalt, normal weight concrete and

lean concrete. The use of steel fibers in either pervious concrete or normal

weight concrete had no effect on their sound absorption capacities.

An increase in porous specimen porosity and thickness did not

significantly aid in improving sound absorption capacity. Clogging affected

the sound absorption capacities of both pervious concrete and porous asphalt

in the order of about 1 dB(A) increment even when they were fully clogged.

135

Other researchers (Luong et al., 2014; Gonzalez et al., 2013;

Izevbekhai, 2011; Ahammed and Tighe, 2011; Kim and Lee, 2010; Seddeq,

2009; Park et al.,2005; Tiwari et al., 2004 and Neithalath et al., 2005) have

researched on pervious concrete and porous asphalt separately. The current

study is of significance as it makes a comparison of both the sound absorption

capacity and sound pressure level dB(A) for both pervious concrete and

porous asphalt.

136

Table 5.1 Sound Absorption Test Program

Series Test

Variable Type

Mix

ID

Sample

Thickness

(mm)

Target

Porosity

(%)

Remarks

A

Type of

Pavement

Material

Pervious

Concrete PC

63

20 -

Pervious

Concrete PF 20

2% 5D

steel fiber

Normal weight

Concrete NC 1-2

Mix

commonly

used on

roads - No

Steel fiber

Normal weight

Concrete NF 1-2

2% 5D

steel fiber

Lean Concrete LC 1-2 -

Dense Asphalt NA 3-4

W3B -

Mix

commonly

used on

roads

Open-graded

Asphalt OG 10

OGW-

Mix

commonly

used on

roads

Porous Asphalt PA 20 -

B

Porosity of

Pavement

Material

Pervious

Concrete

PC10

63

10 -

PC15 15

PC20 20

Same as

PC

(Series A)

PC25 25 -

Open-graded

Asphalt

PA10 10

Same as

OG

(Series A)

PA15 15 -

Porous Asphalt PA20 20

Same as

PA

(Series A)

PA25 25 -

C

Thickness

of

Pavement

Layer

Pervious

Concrete

PC 63

20

Same as

PC

(Series A)

PC4 100 -

PC6 200

Porous Asphalt

PA 63

20

Same as

PA

(Series A)

PA4 100 -

PA6 200

137

Table 5.1 Sound Absorption Test Program (Cont’d)

Series

Test Variable Type

Sample

Thickness

(mm)

Target

Porosity

(%)

Remarks

D

Degree of

Clogging

Pervious

Concrete

50

20 0% clogged

15 25% clogged

10 50% clogged

5 75% clogged

2-3 100% clogged

Porous

Asphalt

20 0% clogged

15 25% clogged

10 50% clogged

5 75% clogged

2-3 100% clogged

138

Table 5.2 Gradation analysis for coarse and fine aggregates

Mix Small Coarse Aggregate

Fine

aggregate Pervious

concrete

Normal weight

concrete

Lean

Concrete

Sieve

Size (% passing) (% passing) (% passing) (% passing)

25 mm - - 100 -

19 mm - - 85 -

9.5 mm 95 95 - -

4.75 mm 38 38 50 95

2.36 mm 18 18 - 80

1.18 mm 5 5 - 65

0.60 mm - - - 58

0.475

mm - - 23 -

0.30 mm 3 3 - 38

0.15 mm - - - 8

0.075

mm - - 8 -

Pan 0 0 0 0

139

Table 5.3 Mix proportions of concrete samples

Mix

Target

Porosity

Level

[%]

Water/

Cement

Ratio

Cement

[kg/m3]

Water

[kg/m3]

Coarse

Aggregate

[kg/m3]

Sand

[kg/m3]

5D Steel

fibers

dosage

[%]

PC 10 10

0.3

495 148.5

1560 -

-

PC 15 15 400 120.0

PC 20

(Reference) 20 367 110.1

PC 25 25 300 90.0

Steel fiber

pervious

concrete

(PF)

20 367 110.1 2.0

Normal

weight

concrete

(NC)

3-4

0.4 430 172 437.6 705.9

-

Steel fiber

normal

weight

concrete

(NF)

2.0

Lean

concrete

(LC)

1.1 220 242 1143.5 - -

140

Table 5.4 Aggregate gradation and mix composition of asphalt mix designs

Mix Design

Dense graded

Asphalt

W3B

Porous

Asphalt

PA-13

Porous

Asphalt

PA-16

Porous

Asphalt

PA-20

Sieve Size (% passing) (% passing) (% passing) (% passing)

20 mm 100 - - 100

16 mm - - 100 95

13.2 mm 90 100 70 85

9.5 mm - 85 59 72

6.3 mm 63 - - -

4.75 mm - 45 33 22

3.35mm 45 - - -

2.36mm - 30 22 18

1.18mm 26 25 16 -

600um - 20 10 13

300um 14 13 6 9

150um - 10 4 7

75um 6 4 3 6

Asphalt Binder

Content (% by

Weight of

Total Mix)

4.5 to 5.5

Air void

content (%) 3 to 4 8 to 12 15 to 20 20 to 25 or

more

141

Table 5.5 Measured sound absorption coefficients for Series A with different

material types

Frequency

(Hz)

Sound absorption coefficient (α) – PC and PF

PC-1 PC-2 PC-3 Average PF-1 PF-2 PF-3 Average

100 0.38 0.43 0.4 0.40 0.41 0.37 0.37 0.38

150 0.47 0.42 0.41 0.43 0.43 0.39 0.41 0.41

200 0.43 0.46 0.45 0.45 0.45 0.41 0.42 0.43

250 0.46 0.48 0.43 0.46 0.45 0.42 0.43 0.44

300 0.52 0.53 0.5 0.52 0.47 0.43 0.44 0.45

350 0.51 0.54 0.47 0.51 0.51 0.46 0.49 0.49

400 0.59 0.57 0.52 0.56 0.57 0.50 0.55 0.54

500 0.66 0.7 0.65 0.67 0.67 0.62 0.65 0.65

600 0.79 0.78 0.74 0.77 0.76 0.73 0.75 0.75

700 0.9 0.85 0.88 0.88 0.88 0.83 0.85 0.86

800 0.93 0.91 0.92 0.92 0.93 0.88 0.90 0.90

900 0.75 0.7 0.67 0.71 0.70 0.67 0.69 0.69

1000 0.63 0.58 0.56 0.59 0.58 0.55 0.57 0.57

1250 0.55 0.53 0.5 0.53 0.52 0.49 0.50 0.51

1500 0.53 0.5 0.46 0.50 0.52 0.46 0.45 0.48

1750 0.48 0.47 0.44 0.46 0.48 0.40 0.44 0.44

2000 0.5 0.46 0.46 0.47 0.47 0.42 0.47 0.45

142


material types (Cont’d)

Frequency

(Hz)

Sound absorption coefficient (α) – NC and NF

NC-1 NC-2 NC-3 Average NF-1 NF-2 NF-3 Average

100 0.11 0.10 0.09 0.10 0.10 0.09 0.06 0.08

150 0.11 0.12 0.10 0.11 0.11 0.10 0.08 0.10

200 0.10 0.09 0.08 0.09 0.10 0.06 0.05 0.07

250 0.12 0.13 0.11 0.12 0.12 0.09 0.09 0.10

300 0.11 0.13 0.09 0.11 0.11 0.09 0.08 0.09

350 0.11 0.11 0.08 0.10 0.09 0.10 0.05 0.08

400 0.10 0.09 0.08 0.09 0.08 0.07 0.05 0.07

500 0.07 0.05 0.06 0.06 0.07 0.06 0.03 0.05

600 0.09 0.08 0.07 0.08 0.08 0.06 0.05 0.06

700 0.07 0.06 0.05 0.06 0.07 0.04 0.04 0.05

800 0.11 0.10 0.09 0.10 0.11 0.06 0.07 0.08

900 0.11 0.12 0.10 0.11 0.10 0.09 0.07 0.09

1000 0.12 0.10 0.09 0.10 0.10 0.08 0.06 0.08

1250 0.12 0.12 0.09 0.11 0.11 0.09 0.07 0.09

1500 0.12 0.10 0.09 0.10 0.10 0.08 0.06 0.08

1750 0.12 0.11 0.10 0.11 0.11 0.09 0.07 0.09

2000 0.11 0.09 0.07 0.09 0.09 0.07 0.05 0.07

143



Frequency

(Hz)

Sound absorption coefficient (α) – LC and NA

LC-1 LC-2 LC-3 Average NA-1 NA-2 NA-3 Average

100 0.11 0.09 0.07 0.09 0.15 0.09 0.09 0.11

150 0.11 0.10 0.08 0.10 0.17 0.1 0.09 0.12

200 0.11 0.07 0.06 0.08 0.16 0.13 0.16 0.15

250 0.11 0.12 0.10 0.11 0.2 0.16 0.12 0.16

300 0.10 0.11 0.09 0.10 0.13 0.11 0.15 0.13

350 0.10 0.11 0.06 0.09 0.21 0.14 0.13 0.16

400 0.10 0.08 0.06 0.08 0.22 0.16 0.16 0.18

500 0.07 0.06 0.03 0.05 0.17 0.15 0.19 0.17

600 0.09 0.07 0.06 0.07 0.2 0.16 0.18 0.18

700 0.07 0.04 0.04 0.05 0.25 0.17 0.18 0.2

800 0.12 0.07 0.08 0.09 0.24 0.13 0.2 0.19

900 0.11 0.10 0.08 0.10 0.22 0.15 0.14 0.17

1000 0.11 0.09 0.07 0.09 0.15 0.1 0.23 0.16

1250 0.11 0.11 0.08 0.10 0.18 0.17 0.16 0.17

1500 0.10 0.09 0.07 0.09 0.16 0.11 0.12 0.13

1750 0.12 0.10 0.08 0.10 0.2 0.15 0.07 0.14

2000 0.10 0.08 0.06 0.08 0.18 0.13 0.08 0.13

144



Frequency

(Hz)

Sound absorption coefficient (α) – OG and PA

OG-1 OG-2 OG-3 Average PA-1 PA-2 PA-3 Average

100 0.24 0.20 0.22 0.22 0.33 0.28 0.30 0.30

150 0.32 0.29 0.30 0.30 0.41 0.35 0.35 0.37

200 0.39 0.34 0.35 0.36 0.39 0.36 0.38 0.38

250 0.39 0.35 0.36 0.37 0.40 0.35 0.38 0.38

300 0.45 0.37 0.41 0.41 0.43 0.40 0.42 0.42

350 0.46 0.40 0.43 0.43 0.48 0.41 0.45 0.45

400 0.50 0.46 0.48 0.48 0.52 0.45 0.50 0.49

500 0.61 0.53 0.59 0.58 0.62 0.57 0.58 0.59

600 0.71 0.65 0.64 0.67 0.70 0.65 0.69 0.68

700 0.60 0.56 0.58 0.58 0.80 0.75 0.78 0.78

800 0.54 0.50 0.51 0.52 0.85 0.80 0.83 0.83

900 0.50 0.45 0.48 0.48 0.60 0.52 0.55 0.56

1000 0.46 0.40 0.43 0.43 0.55 0.48 0.50 0.51

1250 0.40 0.35 0.40 0.38 0.53 0.40 0.46 0.46

1500 0.40 0.36 0.36 0.37 0.45 0.38 0.42 0.42

1750 0.37 0.33 0.34 0.35 0.40 0.36 0.39 0.38

2000 0.33 0.26 0.32 0.30 0.35 0.31 0.33 0.33

145

Table 5.6 Porosity of specimens for Series B on materials type

Target

Porosity

(%)

Measured Porosity (%)

Pervious Concrete Porous Asphalt

10 Average (11.5, 12.9, 13.2) = 12.5 Average (11.9, 12.3, 13.1) =12.4

15 Average (16.23, 17.14, 17.86) = 17.1 Average (16.1, 16.8, 17.3) =16.7

20 Average (20.31, 21.56, 22.05) = 21.3 Average (20.9, 21.8, 22.0) = 21.5

25 Average (25.13, 25.41, 26.05) = 25.5 Average (25.4, 25.9, 26.1) = 25.8

Table 5.7 Peak sound absorption coefficient for pervious concrete and porous

asphalt specimens for Series B test with different porosities

Porosity

(%)

Peak sound absorption coefficient (α)


10 0.80 at 500 Hz 0.75 at 500 Hz

15 0.93 at 500 Hz 0.83 at 500 Hz

20 0.92 at 600 Hz 0.82 at 600 Hz

25 0.84 at 600 Hz 0.77 at 600 Hz

146

Table 5.8 Measured sound absorption coefficients for Series C with different

thicknesses of pavement layer

Frequency

(Hz)

Sound absorption coefficient (α) – thickness: 63 mm

PC-1 PC-2 PC-3 Average PA-1 PA-2 PA-3 Average

100 0.40 0.35 0.37 0.37 0.3 0.32 0.35 0.32

150 0.43 0.37 0.39 0.40 0.41 0.35 0.37 0.38

200 0.46 0.41 0.41 0.43 0.36 0.39 0.38 0.38

250 0.43 0.38 0.40 0.40 0.33 0.38 0.35 0.35

300 0.51 0.45 0.44 0.47 0.42 0.43 0.4 0.42

350 0.53 0.46 0.50 0.50 0.45 0.48 0.41 0.45

400 0.57 0.50 0.55 0.54 0.52 0.5 0.45 0.49

500 0.83 0.70 0.77 0.77 0.68 0.62 0.55 0.62

600 0.92 0.85 0.85 0.87 0.8 0.85 0.82 0.82

700 0.85 0.75 0.80 0.80 0.75 0.7 0.8 0.75

800 0.70 0.64 0.68 0.67 0.6 0.62 0.65 0.62

900 0.60 0.54 0.58 0.57 0.55 0.5 0.52 0.52

1000 0.53 0.47 0.50 0.50 0.45 0.42 0.4 0.42

1250 0.50 0.42 0.45 0.46 0.4 0.45 0.37 0.41

1500 0.44 0.38 0.38 0.40 0.33 0.36 0.36 0.35

1750 0.39 0.34 0.36 0.36 0.28 0.31 0.26 0.28

2000 0.42 0.34 0.38 0.38 0.33 0.32 0.35 0.33

147


thicknesses of pavement layer (Cont’d)

Frequency

(Hz)


PC4-1 PC4-2 PC4-3 Average PA4-1 PA4-2 PA4-3 Average

100 0.34 0.27 0.36 0.32 0.25 0.26 0.28 0.26

150 0.42 0.34 0.39 0.38 0.36 0.31 0.3 0.32

200 0.41 0.34 0.39 0.38 0.28 0.33 0.35 0.32

250 0.46 0.37 0.40 0.41 0.42 0.31 0.32 0.35

300 0.60 0.48 0.54 0.54 0.62 0.47 0.36 0.48

350 0.75 0.61 0.72 0.69 0.71 0.64 0.55 0.63

400 0.90 0.83 0.82 0.85 0.8 0.8 0.77 0.79

500 0.91 0.86 0.89 0.89 0.83 0.85 0.8 0.83

600 0.84 0.79 0.82 0.82 0.76 0.79 0.81 0.79

700 0.78 0.71 0.74 0.74 0.68 0.65 0.72 0.68

800 0.66 0.56 0.61 0.61 0.41 0.57 0.67 0.55

900 0.54 0.41 0.46 0.47 0.35 0.4 0.48 0.41

1000 0.45 0.35 0.39 0.40 0.26 0.3 0.36 0.31

1250 0.36 0.29 0.34 0.33 0.25 0.26 0.3 0.27

1500 0.34 0.28 0.27 0.30 0.22 0.24 0.25 0.24

1750 0.36 0.30 0.34 0.33 0.26 0.3 0.32 0.29

2000 0.49 0.41 0.44 0.45 0.38 0.35 0.43 0.39

148


thicknesses of pavement layer (Cont’d)

Frequency

(Hz)


PC6-1 PC6-2 PC6-3 Average PA6-1 PA6-2 PA6-3 Average

100 0.34 0.31 0.31 0.32 0.25 0.28 0.25 0.26

150 0.57 0.47 0.52 0.52 0.56 0.36 0.46 0.46

200 0.77 0.70 0.72 0.73 0.76 0.66 0.6 0.67

250 0.94 0.89 0.89 0.91 0.85 0.86 0.83 0.85

300 0.90 0.86 0.89 0.88 0.84 0.83 0.8 0.82

350 0.88 0.80 0.82 0.83 0.76 0.7 0.68 0.71

400 0.83 0.72 0.79 0.78 0.74 0.6 0.65 0.66

500 0.66 0.61 0.63 0.63 0.6 0.55 0.57 0.57

600 0.58 0.52 0.55 0.55 0.5 0.5 0.48 0.49

700 0.54 0.46 0.51 0.50 0.45 0.48 0.4 0.44

800 0.50 0.46 0.49 0.48 0.4 0.41 0.37 0.39

900 0.49 0.39 0.47 0.45 0.4 0.38 0.3 0.36

1000 0.48 0.41 0.49 0.46 0.35 0.45 0.4 0.40

1250 0.46 0.40 0.40 0.42 0.3 0.33 0.32 0.32

1500 0.46 0.39 0.37 0.41 0.29 0.35 0.4 0.35

1750 0.39 0.33 0.37 0.36 0.27 0.33 0.31 0.30

2000 0.36 0.32 0.33 0.34 0.26 0.27 0.3 0.28

149

Table 5.9 Target porosity and measured porosity of the samples for Series D

with different degrees of clogging

Target

Porosity (%)


Measured

Porosity (%)

Mean

Porosity (%)

Measured

Porosity (%)

Mean

Porosity (%)

20

20.15

20.64

20.60

19.53 22.35 19.01

19.41 18.97

15

14.68

14.88

14.46

14.21 16.01 14.20

13.95 13.96

10

9.96

9.54

9.09

9.08 10.46 8.97

8.19 9.19

5

6.45

6.27

4.16

4.77 6.03 5.42

6.33 4.72

1

1.86

1.83

1.79

1.62 1.67 1.59

1.97 1.47

150


degrees of clogging

Frequency

(Hz)

Sound absorption coefficient (α) – 0% clogged


100 0.38 0.43 0.4 0.40 0.28 0.33 0.3 0.30

150 0.47 0.42 0.41 0.43 0.41 0.35 0.35 0.37

200 0.43 0.46 0.45 0.45 0.36 0.39 0.38 0.38

250 0.46 0.48 0.43 0.46 0.38 0.4 0.35 0.38

300 0.52 0.53 0.5 0.52 0.42 0.43 0.4 0.42

350 0.51 0.54 0.47 0.51 0.45 0.48 0.41 0.45

400 0.59 0.57 0.52 0.56 0.52 0.5 0.45 0.49

500 0.66 0.7 0.65 0.67 0.58 0.62 0.57 0.59

600 0.79 0.78 0.74 0.77 0.7 0.69 0.65 0.68

700 0.9 0.85 0.88 0.88 0.8 0.75 0.78 0.78

800 0.93 0.91 0.92 0.92 0.85 0.83 0.8 0.83

900 0.75 0.7 0.67 0.71 0.6 0.55 0.52 0.56

1000 0.63 0.58 0.56 0.59 0.55 0.5 0.48 0.51

1250 0.55 0.53 0.5 0.53 0.53 0.46 0.4 0.46

1500 0.53 0.5 0.46 0.50 0.45 0.42 0.38 0.42

1750 0.48 0.47 0.44 0.46 0.4 0.39 0.36 0.38

2000 0.5 0.46 0.48 0.48 0.35 0.31 0.33 0.33

151


degrees of clogging (Cont’d)

Frequency

(Hz)



100 0.35 0.37 0.34 0.35 0.27 0.29 0.26 0.27

150 0.39 0.41 0.38 0.39 0.33 0.35 0.32 0.33

200 0.42 0.47 0.43 0.44 0.35 0.4 0.36 0.37

250 0.44 0.5 0.48 0.47 0.36 0.42 0.4 0.39

300 0.5 0.54 0.52 0.52 0.4 0.44 0.42 0.42

350 0.5 0.56 0.53 0.53 0.42 0.48 0.45 0.45

400 0.57 0.56 0.55 0.56 0.5 0.49 0.48 0.49

500 0.63 0.68 0.68 0.66 0.55 0.6 0.6 0.58

600 0.79 0.75 0.8 0.78 0.7 0.66 0.64 0.67

700 0.85 0.8 0.83 0.83 0.75 0.7 0.73 0.73

800 0.74 0.7 0.73 0.72 0.66 0.62 0.6 0.63

900 0.69 0.61 0.6 0.63 0.58 0.5 0.49 0.52

1000 0.58 0.53 0.51 0.54 0.5 0.45 0.43 0.46

1250 0.51 0.49 0.48 0.49 0.44 0.42 0.38 0.41

1500 0.47 0.48 0.45 0.47 0.39 0.4 0.37 0.39

1750 0.46 0.43 0.43 0.44 0.38 0.35 0.35 0.36

2000 0.43 0.42 0.44 0.43 0.32 0.31 0.33 0.32

152



Frequency

(Hz)



100 0.31 0.34 0.33 0.33 0.2 0.22 0.24 0.22

150 0.38 0.4 0.37 0.38 0.3 0.32 0.29 0.30

200 0.41 0.46 0.42 0.43 0.34 0.39 0.35 0.36

250 0.44 0.43 0.47 0.45 0.36 0.35 0.39 0.37

300 0.51 0.5 0.52 0.51 0.41 0.4 0.42 0.41

350 0.52 0.58 0.55 0.55 0.4 0.46 0.43 0.43

400 0.55 0.57 0.57 0.56 0.48 0.5 0.46 0.48

500 0.61 0.69 0.67 0.66 0.53 0.61 0.59 0.58

600 0.77 0.76 0.81 0.78 0.68 0.67 0.65 0.67

700 0.7 0.68 0.66 0.68 0.6 0.58 0.56 0.58

800 0.64 0.61 0.6 0.62 0.54 0.51 0.5 0.52

900 0.61 0.56 0.59 0.59 0.5 0.45 0.48 0.48

1000 0.54 0.51 0.48 0.51 0.46 0.43 0.4 0.43

1250 0.47 0.47 0.45 0.46 0.4 0.4 0.35 0.38

1500 0.44 0.48 0.44 0.45 0.36 0.4 0.36 0.37

1750 0.38 0.44 0.34 0.39 0.37 0.34 0.33 0.35

2000 0.38 0.35 0.33 0.35 0.33 0.3 0.28 0.30

153



Frequency

(Hz)



100 0.26 0.24 0.21 0.24 0.23 0.21 0.18 0.21

150 0.31 0.32 0.28 0.30 0.25 0.26 0.22 0.24

200 0.31 0.35 0.33 0.33 0.24 0.28 0.26 0.26

250 0.38 0.38 0.33 0.36 0.3 0.3 0.25 0.28

300 0.41 0.39 0.38 0.39 0.31 0.29 0.28 0.29

350 0.44 0.45 0.45 0.45 0.32 0.33 0.33 0.33

400 0.43 0.44 0.47 0.45 0.36 0.35 0.38 0.36

500 0.46 0.48 0.5 0.48 0.38 0.4 0.42 0.40

600 0.44 0.45 0.47 0.45 0.35 0.36 0.37 0.36

700 0.4 0.43 0.4 0.41 0.3 0.33 0.3 0.31

800 0.38 0.4 0.35 0.38 0.28 0.3 0.25 0.28

900 0.4 0.38 0.33 0.37 0.29 0.27 0.22 0.26

1000 0.33 0.36 0.31 0.33 0.25 0.28 0.23 0.25

1250 0.33 0.31 0.32 0.32 0.26 0.24 0.22 0.24

1500 0.33 0.3 0.28 0.30 0.25 0.25 0.2 0.23

1750 0.26 0.29 0.24 0.26 0.25 0.24 0.19 0.23

2000 0.26 0.25 0.22 0.24 0.24 0.23 0.2 0.22

154



Frequency

(Hz)



100 0.2 0.19 0.18 0.19 0.15 0.13 0.12 0.13

150 0.22 0.22 0.2 0.21 0.16 0.14 0.15 0.15

200 0.25 0.22 0.23 0.23 0.18 0.15 0.16 0.16

250 0.27 0.27 0.25 0.26 0.21 0.19 0.17 0.19

300 0.28 0.26 0.27 0.27 0.21 0.18 0.2 0.20

350 0.29 0.29 0.26 0.28 0.2 0.2 0.22 0.21

400 0.3 0.29 0.29 0.29 0.23 0.22 0.24 0.23

500 0.28 0.27 0.27 0.27 0.2 0.19 0.22 0.20

600 0.27 0.26 0.25 0.26 0.18 0.17 0.2 0.18

700 0.29 0.28 0.26 0.28 0.19 0.18 0.21 0.19

800 0.28 0.26 0.24 0.26 0.18 0.16 0.19 0.18

900 0.28 0.25 0.23 0.25 0.17 0.16 0.18 0.17

1000 0.24 0.2 0.25 0.23 0.16 0.14 0.18 0.16

1250 0.22 0.22 0.23 0.22 0.15 0.15 0.16 0.15

1500 0.24 0.23 0.25 0.24 0.16 0.16 0.17 0.16

1750 0.18 0.2 0.19 0.19 0.15 0.17 0.14 0.15

2000 0.19 0.2 0.18 0.19 0.14 0.15 0.13 0.14

155

Table 5.11 Peak α values for different porosity and the frequency that they

occur at for clogging series D

Final target

porosity

(%)

Percentage

clogging

(%)

Pervious

concrete

peak

sound

absorption

coefficient

(α)

Porous

asphalt

peak

sound

absorption

coefficient

(α)

Frequency at

which peak α

occurs

(Hz)

20 0 0.92 0.83 800

15 25 0.83 0.78 700

10 50 0.78 0.69 600

5 75 0.48 0.40 500

1 100 0.29 0.22 400

156


A, B, C and D)

Type of

Pavement

Material

(Series A)

1/3 octave band centre frequency sound pressure dB(A)

Frequency (Hz) PC PF NC NF LC NA OG PA

100 68.0 68.1 73.8 73.8 73.8 67.3 67.5 68.3

125 75.6 75.7 74.8 74.8 74.8 73.2 74.2 75.9

160 76.8 76.9 75.8 75.8 75.8 75.6 75.8 77.0

200 80.6 80.6 77.8 77.9 77.8 82.7 81.2 80.8

250 83.1 83.1 78.7 78.8 78.8 83.8 83.0 83.3

315 85.4 85.6 79.7 79.8 79.8 85.1 84.7 85.7

400 86.6 86.6 80.8 80.8 80.8 86.2 85.8 86.8

500 90.0 90.1 83.9 83.9 83.9 89.8 89.1 90.3

630 87.0 87.1 85.8 85.9 85.9 90.9 88.3 87.4

800 85.3 85.4 93.8 93.8 93.8 92.1 88.7 85.7

1000 85.2 85.3 95.8 95.8 95.8 93.4 88.9 85.4

1250 84.1 84.2 91.8 91.8 91.8 92.2 87.9 84.3

1600 83.0 83.1 93.8 93.8 93.8 91.1 86.7 83.2

2000 81.8 81.8 89.8 89.9 89.9 89.8 85.6 82.1

Porosity of

Pavement

Material

(Series B)

1/3 Octave band centre frequency sound pressure dB(A)

Frequency (Hz) PC10 PC15 PC20 PC25 PA10 PA15 PA20 PA25

100 68.2 68.0 68.1 68.2 68.3 68.2 68.4 68.5

125 75.7 75.5 75.7 75.8 75.9 75.8 76.0 76.0

160 76.9 76.7 76.9 76.9 77.0 77.0 77.2 77.2

200 80.4 80.5 80.6 80.6 80.8 80.8 80.8 80.9

250 82.9 83.0 83.0 83.1 83.1 83.2 83.3 83.4

315 85.3 85.4 85.4 85.4 85.4 85.6 85.6 85.7

400 85.9 85.7 86.5 86.5 86.2 86.1 86.5 86.8

500 89.6 89.1 90.0 90.0 89.7 89.4 90.2 90.3

630 87.2 87.0 86.6 87.3 87.4 87.4 87.0 87.2

800 86.3 86.3 86.0 86.3 86.5 86.6 86.3 86.7

1000 85.6 85.3 85.3 85.4 85.8 85.7 85.6 85.7

1250 84.4 84.1 84.2 84.3 84.6 84.5 84.5 84.6

1600 83.2 82.9 83.0 83.1 83.5 83.3 83.3 83.4

2000 82.0 81.6 81.9 82.1 82.2 82.0 82.1 82.2

157


A, B, C and D) (Cont’d)

Thickness of

Pavement Layer

(Series C)


Frequency (Hz) PC PC 4 PC 6 PA PA 4 PA 6

100 68.1 68.3 68.3 68.3 68.4 68.4

125 75.7 75.8 75.8 75.8 76.0 76.0

160 76.9 77.0 76.5 77.0 77.1 76.7

200 80.6 80.8 79.7 80.8 80.9 79.9

250 83.2 83.2 81.6 83.4 83.4 81.8

315 85.5 85.3 84.3 85.7 85.5 84.5

400 86.6 85.6 85.8 86.8 85.8 86.2

500 89.7 89.2 90.1 90.2 89.5 90.3

630 86.9 87.0 87.9 86.9 87.1 88.1

800 86.2 86.4 86.8 86.4 86.6 87.0

1000 85.5 85.8 85.6 85.7 86.0 85.8

1250 84.3 84.7 84.4 84.5 84.8 84.7

1600 83.3 83.5 83.2 83.4 83.6 83.4

2000 82.0 81.8 82.1 82.1 82.0 82.3

158


A, B, C and D) (Cont’d)

Degree of

Clogging -

Pervious

Concrete

(Series D)


Frequency

(Hz) PC 0% PC 25% PC 50% PC 75% PC 100%

100 68.0 68.2 68.2 68.5 68.6

125 75.6 75.7 75.8 76.0 76.2

160 76.8 76.9 76.9 77.1 77.4

200 80.6 80.6 80.6 80.9 81.1

250 83.1 83.0 83.1 83.3 83.6

315 85.4 85.4 85.4 85.8 86.1

400 86.6 86.6 86.6 86.9 87.3

500 90.0 90.0 90.1 90.6 91.1

630 87.1 87.1 87.1 88.2 88.6

800 85.3 86.0 86.4 87.1 87.4

1000 85.2 85.4 85.4 85.9 86.2

1250 84.1 84.2 84.3 84.7 84.9

1600 83.0 83.1 83.2 83.6 83.7

2000 81.7 81.9 82.1 82.4 82.5

Degree of

Clogging -

Porous

Asphalt

(Series D)


Frequency

(Hz) PA 0% PA 25% PA 50% PA 75% PA 100%

100 68.3 68.4 68.5 68.5 68.7

125 75.9 75.9 76.1 76.1 76.3

160 77.0 77.1 77.1 77.3 77.5

200 80.8 80.8 80.8 81.1 81.3

250 83.3 83.2 83.3 83.5 83.8

315 85.7 85.7 85.7 86.0 86.3

400 86.8 86.8 86.8 87.1 87.5

500 90.3 90.3 90.3 90.8 91.3

630 87.4 87.5 87.5 88.4 88.8

800 85.7 86.4 86.7 87.3 87.6

1000 85.4 85.6 85.7 86.1 86.4

1250 84.3 84.5 84.5 84.9 85.1

1600 83.2 83.3 83.3 83.6 83.9

2000 82.1 82.2 82.2 82.4 82.6

159

Table 5.13 Overall sound pressures for all specimens (Series A, B, C and D)

Type of Pavement Material (Series A) Overall sound pressure dB(A)

PC 96.0

PF 96.1

NC 100.8

NF 100.8

LC 100.8

NA 100.5

OG 97.4

PA 96.3

Porosity of Pavement Material (Series B) Overall sound pressure dB(A)

PC10 96.2

PC15 96.0

PC20 96.0

PC25 95.8

PA10 96.4

PA15 96.3

PA20 96.2

PA25 96.1

Thickness of Pavement Layer (Series C) Overall sound pressure dB(A)

PC 96.1

PC 4 96.1

PC 6 96.0

PA 96.4

PA 4 96.3

PA 6 96.2

Degree of Clogging (Series D) Overall sound pressure dB(A)

PC 0% 96.0

PC 25% 96.1

PC 50% 96.2

PC 75% 96.7

PC 100% 97.1

PA 0% 96.3

PA 25% 96.4

PA 50% 96.5

PA 75% 96.9

PA 100% 97.3

160

(a) 100 mm diameter sample

(b) 150 mm diameter sample

Figure 5.1 Sample holder for acoustic absorption tests

ϕ 100 mm

ϕ 150 mm

161

(a) 0% clogged (b) 25% clogged

(Final target porosity of 20%) (Final target porosity of 15%)

(c) 50% clogged (d) 75% clogged


(e) 100% clogged

(Final target porosity of 0%)

Figure 5.2 Pervious concrete samples – (a) 0% clogged; (b) 25% clogged;

(c) 50% clogged; (d) 75% clogged; (e) 100% clogged

162

(a) 0% clogged (b) 25% clogged


(c) 50% clogged (d) 75% clogged


(e) 100% clogged

(Final target porosity of 0%)

Figure 5.3 Porous asphalt samples – (a) 0% clogged; (b) 25% clogged;

(c) 50% clogged; (d) 75% clogged; (e) 100% clogged

163

(a)

(b)

Figure 5.4 (a) Impedance tube setup for frequencies 100 -500 Hz;

(b) Impedance tube setup for frequencies 600 - 2000 Hz

164

Figure 5.5 Low and high frequency sound waves

Note: PC = Pervious concrete; PF = Steel fiber reinforced pervious concrete; NC =

Normal weight concrete; NF = Steel fiber reinforced normal weight concrete; LC =

Lean concrete; PA = Porous asphalt; OG = Open-graded asphalt and NA = Dense

asphalt.

Figure 5.6 Sound absorption coefficient values for eight road materials

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

NC NF LCPC PF NAOG PA

Low frequency

sound wave

Impedance tube

diameter (100 mm)

High frequency

sound wave

Impedance tube

diameter (29 mm)

165


(b) Porous Asphalt

Figure 5.7 Sound absorption coefficient values for (a) pervious concrete (b)

porous asphalt at varying porosities in Test Series B

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

So

un

d A

bso

rpti

on

Co

effi

cien

t (α

)

Frequency (Hz)

PC10 PC15

PC20 PC25

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PA10 PA15

PA20 PA25

166

(a) Pervious Concrete and Porous Asphalt with Porosity 10%

(b) Pervious Concrete and Porous Asphalt with Porosity 15%

Figure 5.8 Comparison of sound absorption coefficient values for pervious

concrete and porous asphalt at individual target porosities in Test

Series B

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PC10 PA10

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PC15 PA15

167

(c) Pervious Concrete and Porous Asphalt with Porosity 20%

(d) Pervious Concrete and Porous Asphalt with Porosity 25%

Figure 5.8 Comparison of sound absorption coefficient values for pervious

concrete and porous asphalt at individual target porosities in Test

Series B (Cont’d)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PC20 PA20

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PC25 PA25

168

Figure 5.9 Sample thicknesses

(a) 200 mm

(b) 100 mm

(c) 63 mm

169

Note: PC = 63 mm; PC 4 = 100 mm and PC 6 = 200 mm.


Note: PA = 63 mm; PA 4 = 100 mm and PA 6 = 200 mm.

(b) Porous Asphalt

Figure 5.10 Sound absorption coefficient values for pervious concrete and

porous asphalt at different thicknesses in Test Series C

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound a

bso

rpti

on c

oef

fici

ent

(α)

Frequency (Hz)

PC

PC 4

PC 6

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound a

bso

rpti

on c

oef

fici

ent

(α)

Frequency (Hz)

PA

PA 4

PA 6

170

(a) Thickness = 63 mm

(b) Thickness = 100 mm

Figure 5.11 Comparison of pervious concrete and porous asphalt by thickness

in Test Series C

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound a

bso

rpti

on c

oef

fici

ent

(α)

Frequency (Hz)

PA PC

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound a

bso

rpti

on c

oef

fici

ent

(α)

Frequency (Hz)

PA 4 PC 4

171

(c) Thickness = 200 mm

Figure 5.11 Comparison of pervious concrete and porous asphalt by thickness

in Test Series C (Cont’d)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound a

bso

rpti

on c

oef

fici

ent

(α)

Frequency (Hz)

PA 6 PC 6

172


(b) Porous Asphalt

Figure 5.12 Sound absorption coefficient values for pervious concrete and

porous asphalt at varying clogging percentages in Test Series D

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PC 0% clogged

PC 25% clogged

PC 50% clogged

PC 75% clogged

PC 100% clogged

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Sound A

bso

rpti

on C

oef

fici

ent

(α)

Frequency (Hz)

PA 0% cloggedPA 25% cloggedPA 50% cloggedPA 75% cloggedPA 100% clogged

173

(a) Sound pressure levels of different road materials in Test Series A

b) Overall sound pressure levels of different road materials in Test Series A

Figure 5.13 (a) Sound pressure levels dB(A) at 1/3 octave frequencies and (b)

overall sound pressure levels dB(A) for different road

materials in Test Series A

0

10

20

30

40

50

60

70

80

90

100

110

100 125 160 200 250 315 400 500 630 800 1000125016002000

Sound L

evel

dB

(A)

1/3 Octave Band Centre Frequency (Hz)

PC PF NC NF LC NA OG PA

0

10

20

30

40

50

60

70

80

90

100

110

PC PF NC NF LC NA OG PA

Over

all

Sound L

evel

dB

(A)

Different Road Materials

174

(a) Sound pressure levels for pervious concrete of different porosities

in Test Series B

(b) Sound pressure levels for porous asphalt of different porosities in

Test Series B

Figure 5.14 Sound pressure levels dB(A) at 1/3 octave frequencies for (a)

pervious concrete (b) porous asphalt and (c) overall sound pressure

levels dB(A) for pervious concrete (PC) and porous asphalt (PA)

of varying porosity

0

10

20

30

40

50

60

70

80

90

100

Sound L

evel

dB

(A)


PC10 PC15 PC20 PC25

0

10

20

30

40

50

60

70

80

90

100

Sound L

evel

dB

(A)


PA10 PA15 PA20 PA25

175

(c) Overall sound pressure levels of pervious concrete and porous

asphalt of different porosities in Test Series B


pervious concrete (b) porous asphalt and (c) overall sound pressure

levels dB(A) for pervious concrete (PC) and porous asphalt (PA)

of varying porosity (Cont’d)

90.0

91.0

92.0

93.0

94.0

95.0

96.0

97.0

PC10 PC15 PC20 PC25 PA10 PA15 PA20 PA25

Over

all

Sou

nd

Lev

el d

B(A

)

Porosity

176

(a) Sound pressure levels for pervious concrete and porous asphalt

materials of different thicknesses in Test Series C

(b) Sound pressure levels for pervious concrete and porous asphalt

materials of different thicknesses in Test Series C

Figure 5.15 (a) Sound pressure levels dB(A) at 1/3 octave frequencies and (b)

overall sound pressure levels dB(A) for pervious concrete (PC)

and porous asphalt (PA) of varying thickness in Test Series C

0

10

20

30

40

50

60

70

80

90

100

Sound L

evel

dB

(A)


PC PC 4 PC 6 PA PA 4 PA 6

90.0

91.0

92.0

93.0

94.0

95.0

96.0

97.0


Over

all

Sou

nd

Lev

el d

B(A

)

Thickness

177

(a) Sound pressure levels for pervious concrete of different degrees of

clogging in Test Series D

(b) Sound pressure levels for porous asphalt of different degrees of

clogging in Test Series D


pervious concrete (b) porous asphalt and (c) overall sound

pressure levels dB(A) for pervious concrete (PC) and porous

asphalt (PA) of varying clogging percentage in Test Series D

0

10

20

30

40

50

60

70

80

90

100

Sound L

evel

dB

(A)


PC0% PC25% PC50% PC75% PC100%

0

10

20

30

40

50

60

70

80

90

100

Sound L

evel

dB

(A)


PA0% PA25% PA50% PA75% PA100%

178

(c) Overall sound pressure levels for pervious concrete and porous asphalt

of different clogging percentages in Test Series D


pervious concrete (b) porous asphalt and (c) overall sound

pressure levels dB(A) for pervious concrete (PC) and porous

asphalt (PA) of varying clogging percentage Test Series D

(Cont’d)

90

91

92

93

94

95

96

97

98

PC

0%

PC

25%

PC

50%

PC

75%

PC

100%

PA

0%

PA

25%

PA

50%

PA

75%

PA

100%

Over

all

Sound L

evel

dB

(A)

Clogging Percentage

179

CHAPTER 6 CONCLUSION

6.1 Review of work done

In this study, the physical and mechanical properties, clogging and

sound absorption characteristics of pervious concrete with and without steel

fibers were investigated. Tests were carried out to examine the effect of

cement content, coarse aggregate size, water-cement ratio and fiber content on

the compressive and flexural strength as well as the porosity and permeability

of pervious concrete. A steel fiber-reinforced pervious concrete mix was

established, giving the desired flexural strength, permeability and porosity for

use in urban road liable to flash flooding. The clogging effects of residual soils

in pervious concrete were also studied and compared to those in porous

asphalt. In addition, the sound absorption characteristics of pervious concrete

was determined experimentally and compared to other pavement materials

including porous asphalt.

6.2 Summary of main findings

From the studies carried out on pervious concrete, the following conclusions

can be drawn:

6.2.1 Physical and mechanical properties of pervious concrete

(a) To achieve a highly permeable and porous pavement with reasonable

compressive and flexural strengths, the CA/C ratio is recommended to

be in the region of 4.0, water-cement ratio of around 0.3 to 0.35 and

cement in the range of 360 kg/m3 to 400 kg/m

3. Mixes with smaller

coarse aggregates performed marginally better than mixes with larger

180

coarse aggregates due to the regular and more even arrangement of the

aggregates in the concrete matrix.

(b) Steel fibers aid in increasing the compressive and flexural strengths of

pervious concrete. The hook end configuration of the steel fibers did

not lead to significant differences in permeability and porosity of

pervious concrete.

(c) A minimum dosage of 1.5% steel fiber per volume of concrete is

recommended to achieve the target flexural strength of 3.5 MPa,

permeability of 10 mm/s and porosity of 20%.

6.2.2 Clogging characteristics of pervious concrete

(a) The permeability and clogging resistance of pervious concrete

increased substantially when the mixture porosity was more than 20%.

Pervious concrete specimens gave higher initial permeability than the

porous asphalt specimens with the same porosity.

(b) Pervious concrete was less susceptible to clogging compared to porous

asphalt with the same porosity, and the incorporation of steel fibers up

to about 2% did not affect the results.

6.2.3 Sound absorption capacity of pervious concrete

(a) Pervious concrete performed comparatively better than porous asphalt,

open-graded asphalt, dense asphalt, normal weight concrete and lean

concrete. The use of steel fibers in pervious concrete and normal

weight concrete did not affect their sound absorption capacity

significantly.

181

(b) An increase in porous specimen porosity and thickness did not

significantly aid in improving sound absorption capacity.

(c) Even with increased clogging, the sound absorption capacity of

pervious concrete was not significantly compromised.

(d) Based on the overall sound pressure level, pervious concrete with or

without steel fibers were comparable in performance and these mixes

achieved a significant overall sound pressure reduction of more than

4.5 dB(A) when compared to normal weight concrete and dense graded

asphalt mixes.

6.3 Recommendations for further research

Further work may be carried out in the following areas.

1. The test results obtained in this study could be calibrated with actual

pervious concrete road site construction and field testing.

2. Fatigue testing of pervious concrete slabs incorporating wet and dry

cycles can be done to mimic actual road conditions.

3. With a view in the reduction of urban heat island effect (ACI

Committee Report 522, 2010), thermal conductivity test can be carried

out on pervious concrete.

4. A possible problem with the use of steel fibers in pervious concrete is

the corrosion of the steel fibers which would then affect the long

performance of the pervious concrete. A study on the effect of

corrosion of steel fibers in pervious concrete can be carried out.

182

5. With the prospect that repeated traffic loadings may cause wear and

polishing of the pervious concrete surface, the Los Angeles Abrasion

test can be carried out.

183

LIST OF PUBLICATIONS

Journals:

1. T. F. Fwa, Lim E. and K. H. Tan. (2015). Comparison of Permeability

and Clogging Characteristics of Porous Asphalt and Pervious

Concrete Pavement Materials, Journal of the Transportation Research

Board (TRB), No. 2511, pp 72-80.

2. Lim, E., Tan, K.H and Fwa, T.F. (2013). Effect of Mix Proportion on

Strength and Permeability of Pervious Concrete for Use in Pavement,

EASTS/ ATS Journal, Volume 10, pp. 1565-1575.

3. Lim, E., Tan, K.H and Fwa, T.F. (2013). High-strength high-porosity

pervious concrete pavement, Advanced Material Research Journal,

Vol. 723, pp. 361-367.

Conferences:

1. Tan, K.H, Lim, E and Fwa, T.F. (2015). Steel fiber-reinforced pervious

concrete for urban roads, USMCA 14th

International Symposium on

New Technology for Urban Safety of Mega Cities in Asia, October 29

– 31, Kathmandu, Nepal.

2. Lim, E., Tan, K.H and Fwa, T.F. (2015). Laboratory Evaluation of

Clogging Behavior of Pervious Concrete Pavements, EASTS Eastern

Asia Society for Transportation Studies Conference, September 11 -

14, Cebu, Philippines.

3. Lim, E., Tan, K.H and Fwa, T.F. (2015). Laboratory Evaluation of

Clogging Behavior of Porous Asphalt Pavement, 6th International

conference bituminous mixtures and pavements, June 10 - 12,

Thessaloniki, Greece.

184

4. Lim, E., Tan, K.H and Fwa, T.F. (2013). Effect of Mix Proportion on

Strength and Permeability of Pervious Concrete for Use in Pavement,

EASTS Eastern Asia Society for Transportation Studies Conference,

September 9 – 12, Taiwan Taipei.

5. Lim, E., Tan, K.H and Fwa, T.F. (2013). High-strength high-porosity

pervious concrete pavement, 8th ICPT International Committee on

Road and Airfield Pavement Technology Conference, 14 – 18 July,

Taiwan, Taipei.

6. Lim, E., Tan, K.H and Fwa, T.F. (2013). Pervious concrete pavement

mix design, 18th Singapore Symposium on Pavement Technology

Conference (SPT), 31 May, National University of Singapore.

185

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211

ANNEX A: Residual Normality Analysis

Assumptions for regression model:

Fitting a regression model requires several assumptions. Estimation of

the model parameters requires assumption that the errors are uncorrelated

random variables with mean zero and constant variance. Test of hypotheses

and interval estimation require that the errors be normally distributed. In

addition, it is assumed that the order of the model is correct, that is if a simple

linear regression model is fitted, it is assumed that the phenomenon usually

behaves in a linear or first-order manner. The residuals from the regression

model are defined as ei = yi – yn, i = 1,2,…,n (Montgomery et al., 2011 and

2006).

The residuals for the equations shown below are normally distributed

as the P-value were more than 0.05 using the Anderson-Darling Normality

Test as shown in Figures A.9 to A.16 below.

For pervious concrete with:

10% Porosity: k = 2.453e-0.338N

R2 = 0.996 (4.7)

15% Porosity: k = 13.019e-0.271N

R2 = 0.948 (4.8)

20% Porosity: k = 15.790e-0.304N

R2 = 0.989 (4.9)

25% Porosity: k = 17.117e-0.062N

R2 = 0.952 (4.10)

For porous asphalt with:

10% Porosity: k = 2.127e-0.291N

R2 = 0.992 (4.11)

15% Porosity: k = 4.927e-0.416N

R2 = 0.978 (4.12)

20% Porosity: k = 7.668e-0.290N

R2 = 0.992 (4.13)

25% Porosity: k = 15.272e-0.211N

R2 = 0.992 (4.14)

212

Regression method:

k = a1eb1N

(A.1)

ln(k) = ln(a) + b1(N) (A.2)

Figure A.1 Porous Asphalt 10%


y = -0.2904x + 0.1628

R² = 0.9919

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle

Porous Asphalt 10%

y = -0.4109x + 0.9707

R² = 0.9738

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle

Porous Asphalt 15%

213



y = -0.293x + 1.4759

R² = 0.9909

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle

Porous Asphalt 20%

y = -0.2128x + 2.1971

R² = 0.9885

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle

Porous Asphalt 25%

214

Figure A.5 Pervious Concrete 10%


y = -0.3382x + 0.3143

R² = 0.996

-5.5

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

) Clogging Cycle

Pervious Concrete 10%

y = -0.2704x + 1.9552

R² = 0.9491

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle


215



y = -0.3109x + 2.2825

R² = 0.9805

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle


y = -0.0839x + 2.5085

R² = 0.9668

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity l

n k

(m

m/s

)

Clogging Cycle


216

Normality Plots

Figure A.9 Porous Asphalt 10% residuals

The normality assumption is acceptable as the residuals plot for PA10 show

that they are normally distributed since they have a p-value of 0.868 which is

greater than 0.05.




greater than 0.05.

217




greater than 0.05.




greater than 0.05.

218

Figure A.13 Pervious Concrete 10% residuals

The normality assumption is acceptable as the residuals plot for PC10 show


greater than 0.05.




greater than 0.05.

219




greater than 0.05.




greater than 0.05.

220

ANNEX B: Statistical analysis using T-Test: Two samples assuming

unequal variances for selected mixes

Assumptions for two-sample inference:

i. X11, X12,…, 𝑋1𝑛1, is a random sample from population 1.

ii. X21, X22,…, 𝑋2𝑛2, is a random sample from population 2.

iii. The two populations represented by X1 and X2 are independent.

iv. Both populations are normal.

B-1) Statistical analysis using T-Test: Two samples assuming unequal

variances for permeability deterioration of pervious concrete and porous

asphalt

Figure 4.5 Comparison of permeability deterioration curves of porous asphalt

and pervious concrete mixtures

0123456789

101112131415161718192021222324252627

0 1 2 3 4 5 6 7 8 9 10

Per

mea

bil

ity C

oef

fici

ent,

k (

mm

/s)

Clogging Cycle

PA 10% PA 15%PA 20% PA 25%PC 10% PC 15%PC 20% PC 25%

Legend:

PA = Porous Asphalt

PC = Pervious Concrete

Numerical values indicate

PC 25%

PC 20%

PA 25%

PC 15%

PA 20% PA 15%

PC 10%

PA 10%

221

Hypothesis Testing Statement

Null hypothesis: 𝐻0: 𝜇1 = 𝜇2

Alternative hypotheses:

𝐻𝑎: 𝜇1 ≠ 𝜇2 , or

𝐻𝑎: 𝜇1 < 𝜇2 , or

𝐻𝑎: 𝜇1 > 𝜇2

Table B.1 details the p-values and conclusions drawn from the

hypothesis testing.

Based on the T-test: Two-samples assuming unequal variances test,

most of the results from the comparison of permeability deterioration of

porous asphalt and pervious concrete mixtures could be accepted at the 95%

confidence level as most of their p-values were less than 0.05. The null

hypothesis was rejected in favor of the alternative hypothesis as shown in

Table B-1.

Some of the porous mixture combinations have p-values more than

0.05 and these were highlighted in bold. As their p-value was greater than

0.05, therefore the results were not statistically significant at the 95%

significance level. The null hypothesis was not rejected and the results were

not statistically different.

222

Table B.1. P-values and conclusions for the comparison of permeability

deterioration (mm/s) of porous asphalt and pervious concrete mixtures from

the T-test: Two samples assuming unequal variances

Cycle 0 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)

Conclusion [Permeability (mm/s)]

PC10

PC15 0.001623


Alternative hypotheses: 𝐻𝑎: 𝜇1 < 𝜇2, i.e.

PC10 has lower permeability than PC15.

As the p-value was less than 0.05, the null hypothesis

is rejected in favor of the alternative hypothesis.

PC20 0.003556






PC25 0.000033






PA10 0.414961


Alternative hypotheses: 𝐻𝑎: 𝜇1 > 𝜇2, i.e.

PC10 has higher permeability than PA10.

As the p-value is greater than 0.05, therefore the

results are not statistically significant at the 95%

significance level. The null hypothesis is not rejected

and the results are not statistically different.

PA15 0.132539



PC10 has lower permeability than PA15.





PA20 0.006180






PA25 0.006000






223

Cycle 0 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.004808






PC25 0.000084






PA10 0.003991






PA15 0.004643






PA20 0.049362






PA25 0.041662






224

Cycle 0 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.003548






PA10 0.000013






PA15 0.000172






PA20 0.000539






PA25 0.268559








PC25

PA10 0.000825






PA15 0.000129






PA20 0.000218






PA25 0.013122






225

Cycle 0 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.037896



PA10 has lower permeability than PA15.



PA20 0.002519






PA25 0.013136






PA15

PA20 0.001405






PA25 0.017696






PA20 PA25 0.038628






PA25 PA25 - -

226

Cycle 1 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.003219






PC20 0.001204






PC25 0.000197






PA10 0.284609








PA15 0.316823








PA20 0.012264






PA25 0.001574






227

Cycle 1 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.015597






PC25 0.001053






PA10 0.006154






PA15 0.009056






PA20 0.049487






PA25 0.041662






228

Cycle 1 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.016123






PA10 0.000640






PA15 0.000087






PA20 0.000334






PA25 0.341377








PC25

PA10 0.002246






PA15 0.002636






PA20 0.001132






PA25 0.015004






229

Cycle 1 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.002819






PA20 0.004315






PA25 0.007154






PA15

PA20 0.002186






PA25 0.009025






PA20 PA25 0.024622






PA25 PA25 - -

230

Cycle 2 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.003077






PC20 0.004180






PC25 0.003538






PA10 0.259230








PA15 0.242377








PA20 0.005414






PA25 0.000489






231

Cycle 2 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.086140








PC25 0.018951






PA10 0.009798






PA15 0.013208






PA20 0.106163








PA25 0.047964






232

Cycle 2

/Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.049791




As the p-value was less than 0.05, the null hypothesis is

rejected in favor of the alternative hypothesis.

PA10 0.000074






PA15 0.000002






PA20 0.001554






PA25 0.264994




As the p-value is greater than 0.05, therefore the results

are not statistically significant at the 95% significance

level. The null hypothesis is not rejected and the results

are not statistically different.

PC25

PA10 0.009249






PA15 0.010758






PA20 0.021876






PA25 0.063552








233

Cycle 2 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.018240






PA20 0.018240






PA25 0.000560






PA15

PA20 0.000918






PA25 0.003647






PA20 PA25 0.006740






PA25 PA25 - -

234

Cycle 3 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.004023






PC20 0.001268






PC25 0.003958






PA10 0.311942








PA15 0.267060








PA20 0.005840






PA25 0.006038






235

Cycle 3 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.227923








PC25 0.019913






PA10 0.011146






PA15 0.015424






PA20 0.149764








PA25 0.160627








236

Cycle 3 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.043097






PA10 0.004779






PA15 0.006359






PA20 0.034033






PA25 0.314613








PC25

PA10 0.010057






PA15 0.011557






PA20 0.023952






PA25 0.040277






237

Cycle 3 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.001941






PA20 0.003291






PA25 0.010628






PA15

PA20 0.005083






PA25 0.013664






PA20 PA25 0.068790








PA25 PA25 - -

238

Cycle 4 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.021615






PC20 0.009774






PC25 0.004446






PA10 0.030685






PA15 0.231346








PA20 0.003938






PA25 0.011864






239

Cycle 4 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.451347







and the results are not statistically different..

PC25 0.004245






PA10 0.018073






PA15 0.023879






PA20 0.258056








PA25 0.221953







240

Cycle 4

/Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.006204






PA10 0.008071






PA15 0.011112






PA20 0.141870








PA25 0.215991







are not statistically different..

PC25

PA10 0.004107






PA15 0.004677






PA20 0.010216






PA25 0.006663






241

Cycle 4 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.043281






PA20 0.002901






PA25 0.010180






PA15

PA20 0.001179






PA25 0.013010






PA20 PA25 0.066933








PA25 PA25 - -

242

Cycle 5 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.001542






PC20 0.009964






PC25 0.008194






PA10 0.005257






PA15 0.005746






PA20 0.012439






PA25 0.005850






243

Cycle 5 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.212083








PC25 0.013096






PA10 0.000038






PA15 0.000084






PA20 0.224685








PA25 0.278253








244

Cycle 5

/Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.008194






PA10 0.008872






PA15 0.011029






PA20 0.131029








PA25 0.494903








PC25

PA10 0.005257






PA15 0.005688






PA20 0.012439






PA25 0.005850






245

Cycle 5 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.213213








PA20 0.000597






PA25 0.017261






PA15

PA20 0.001010






PA25 0.021076






PA20 PA25 0.212490








PA25 PA25 - -

246

Cycle 6 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.025175






PC20 0.000142






PC25 0.007950






PA10 0.032656






PA15 0.356435








PA20 0.025103






PA25 0.000931






247

Cycle 6 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.110971








PC25 0.005375






PA10 0.015905






PA15 0.024898






PA20 0.423702








PA25 0.058304








248

Cycle 6

/Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.016329






PA10 0.000254






PA15 0.000397






PA20 0.075916








PA25 0.142466








PC25

PA10 0.007110






PA15 0.007964






PA20 0.004981






PA25 0.018997






249

Cycle 6 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.003658






PA20 0.015343






PA25 0.002893






PA15

PA20 0.024668






PA25 0.003854






PA20 PA25 0.041582






PA25 PA25 - -

250

Cycle 7 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.039111






PC20 0.000293






PC25 0.008386






PA10 0.031325






PA15 0.341138








PA20 0.033985






PA25 0.029696






251

Cycle 7 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.092526








PC25 0.005439






PA10 0.029720






PA15 0.040290






PA20 0.456072








PA25 0.170563






252

Cycle 7 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.017388






PA10 0.000233






PA15 0.001905






PA20 0.047990






PA25 0.420865








PC25

PA10 0.007890






PA15 0.008438






PA20 0.005014






PA25 0.009106






253

Cycle 7 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.021020






PA20 0.025433






PA25 0.024568






PA15

PA20 0.034979






PA25 0.030322






PA20 PA25 0.153763








PA25 PA25 - -

254

Cycle 8 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.049653






PC20 0.001594






PC25 0.006703






PA10 0.043992






PA15 0.361687








PA20 0.059300








PA25 0.014387






255

Cycle 8 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.008723






PC25 0.009418






PA10 0.043416






PA15 0.051173








PA20 0.437635








PA25 0.029984






256

Cycle 8 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.014457






PA10 0.001519






PA15 0.001646






PA20 0.008095






PA25 0.220488








PC25

PA10 0.006583






PA15 0.006729






PA20 0.009266






PA25 0.005231






257

Cycle 8 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.043685






PA20 0.051466








PA25 0.013508






PA15

PA20 0.061186








PA25 0.014607






PA20 PA25 0.026224






PA25 PA25 - -

258

Cycle 9 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.020689






PC20 0.004789






PC25 0.008332






PA10 0.041989






PA15 0.198869








PA20 0.017322






PA25 0.023049






259

Cycle 9 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.018178






PC25 0.010940






PA10 0.019348






PA15 0.021445






PA20 0.449983








PA25 0.068258








260

Cycle 9 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.013681






PA10 0.004603






PA15 0.004893






PA20 0.028799






PA25 0.403573








PC25

PA10 0.008265






PA15 0.008366






PA20 0.011240






PA25 0.005981






261

Cycle 9 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.024383






PA20 0.021571






PA25 0.022297






PA15

PA20 0.023719






PA25 0.023452






PA20 PA25 0.082314








PA25 PA25 - -

262

Cycle 10 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC10

PC15 0.026341






PC20 0.010850






PC25 0.009765






PA10 0.094921








PA15 0.163082








PA20 0.002353






PA25 0.013319






263

Cycle 10 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC15

PC20 0.165886








PC25 0.012218






PA10 0.024982






PA15 0.027135






PA20 0.463185








PA25 0.092085








264

Cycle 10

/Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PC20

PC25 0.013046






PA10 0.010418






PA15 0.011096






PA20 0.111092








PA25 0.268199








PC25

PA10 0.009710






PA15 0.009795






PA20 0.011868






PA25 0.013862






265

Cycle 10 /Clogged

permeability

Mix

T-test

Two

samples

assuming

unequal

variances

(p-value)


PA10

PA15 0.036190






PA20 0.002251






PA25 0.012860






PA15

PA20 0.002399






PA25 0.013581






PA20 PA25 0.079196








PA25 PA25 - -

266


variances for Sound Pressure Level dB(A) for Series B – Porosity

Figure 5.14 Overall sound pressure levels of pervious concrete and porous

asphalt of different porosities in Series B.

Based on the T-test: Two-samples assuming unequal variances test, not

all the results from Series B could be accepted at the 95% confidence level as

most of their P-values were more than 0.05. Therefore there was not sufficient

evidence to reject the null hypothesis and the results were not statistically

different.

The results between PC25 and PA10 accepted at the 95% confidence

level as their p-values were less than 0.05. The null hypothesis was rejected in

favor of the alternative hypothesis. Table B.2 detailed the p-values and

conclusions drawn from the hypothesis testing.

90.0

91.0

92.0

93.0

94.0

95.0

96.0

97.0

PC10 PC15 PC20 PC25 PA10 PA15 PA20 PA25

Over

all

Sou

nd

Lev

el d

B(A

)

Porosity

267

Table B.2. P-values and conclusions for the overall sound pressure level

dB(A) from the T-test Two samples assuming unequal variances for Series B

Series B Mix

T-test: Two-

samples

assuming

unequal

variances

(p-value)

Conclusion [Overall sound level dB(A)]

PC10

96.2 dB(A)

PC15 0.178



PC10 has higher dB(A) than PC15.

As the P-value is greater than 0.05, therefore the




PC20 0.130



PC10 has higher dB(A) than PC20





PC25 0.096



PC10 has higher dB(A) than PC25





PA10 0.178



PC10 has lower dB(A) than PA10.





PA15 0.274








PA20 0.500


Alternative hypotheses: 𝐻𝑎: 𝜇1 ≠ 𝜇2

No difference in dB(A).





PA25 0.274



PC10 has higher dB(A) than PA25.





268

Series B Mix

T-test:

Two-

samples

assuming

unequal

variances

(p-value)


PC15

96.0

dB(A)

PC20 0.500


Alternative hypotheses: 𝐻𝑎: 𝜇1 ≠ 𝜇2, i.e.




significance level. The null hypothesis is not

rejected and the results are not statistically

different.

PC25 0.241








different.

PA10 0.069



PC15 has lower dB(A) than PA10





different.

PA15 0.099








different.

PA20 0.178








different.

PA25 0.311








different.

269

Series B Mix

T-test:

Two-

samples

assuming

unequal

variances

(p-value)


PC20

96.0

dB(A)

PC25 0.225








different.

PA10 0.058








different.

PA15 0.051








different.

PA20 0.130








different.

PA25 0.259








different.

270

Series B Mix

T-test: Two-

samples

assuming

unequal

variances

(p-value)


PC25

95.8 dB(A)

PA10 0.040






PA15 0.060








PA20 0.096








PA25 0.142








PA10

96.4 dB(A)

PA15 0.311



PA10 has higher dB(A) than PA15.





PA20 0.178








PA25 0.099








271

Series B Mix

T-test:

Two-

samples

assuming

unequal

variances

(p-value)


PA15

96.3

dB(A)

PA20 0.274








different.

PA25 0.115








different.

PA20

96.2

dB(A)

PA25

0.274








different.

PA25

96.1

dB(A)

PA25

-

-

272


variances for Sound Pressure Level dB(A) for Series C – Thickness

Figure 5.15 Sound pressure levels for pervious concrete and porous asphalt

materials of different thicknesses in Series C.

Based on the T-test: Two-samples assuming unequal variances test, not

all the results from Series C could be accepted at the 95% confidence level as

most of their P-values were more than 0.05. Therefore there is not sufficient

evidence to reject the null hypothesis and the results were not statistically

different. The results between PC6 and PA as well as PC6 and PA4 can be

accepted at the 95% confidence level as their P-values were less than 0.05.

The null hypothesis was rejected in favor of the alternative hypothesis. Table

B.3 detailed the p-values and conclusions drawn from the hypothesis testing.

90.0

91.0

92.0

93.0

94.0

95.0

96.0

97.0


Over

all

Sou

nd

Lev

el d

B(A

)

Thickness

273

Table B.3. P-values and conclusions for the overall sound pressure level

dB(A) from the T-test Two samples assuming unequal variances for Series C

Series C Mix

T-test Two

samples

assuming

unequal

variances

(p-value)

Conclusions [Overall sound level dB(A)]

PC

96.1

dB(A)

PC4 0.500


Alternative hypotheses: 𝐻𝑎: 𝜇1 ≠ 𝜇2, i.e.


As the P-value is greater than 0.05, therefore

the results are not statistically significant at the

95% significance level. The null hypothesis is

not rejected and the results are not statistically

different.

PC6 0.225



PC has higher dB(A) than PC6.





different.

PA 0.061



PC has lower dB(A) than PA.





different.

PA4 0.115



PC has lower dB(A) than PA4.





different.

PA6 0.274



PC has lower dB(A) than PA6.





different.

274

Series C

Mix

T-test Two

samples

assuming

unequal

variances

(p-value)


PC4

96.1 dB(A)

PC6 0.144








different.

PA 0.051



PC4 has lower dB(A) than PA.





different.

PA4 0.091








different.

PA6 0.248








different.

PC6

96.0 dB(A)

PA 0.027



PC6 has lower dB(A) than PA.

As the p-value was less than 0.05, the null

hypothesis is rejected in favor of the alternative

hypothesis.

PA4 0.040




As the p-value was less than 0.05, the null

hypothesis is rejected in favor of the alternative

hypothesis.

PA6 0.110








different.

275

Series C Mix

T-test Two

samples

assuming

unequal

variances

(p-value)


PA

96.4

dB(A)

PA4 0.274



PA has higher dB(A) than PA4.


the results are not statistically significant at

the 95% significance level. The null

hypothesis is not rejected and the results are


PA6 0.144



PA has higher dB(A) than PA6.






PA4

96.3

dB(A)

PA6

0.274









PA6

96.2

dB(A)

PA6

-

-

Documents

A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF … · 2018. 1. 8. · characteristics of pervious concrete for pavement use lim emiko (b.eng (hons), m.eng, national university of