Construction and Building Materials 24 (2010) 818–823

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Construction and Building Materials

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Laboratory evaluation of permeability and strength of polymer-modifiedpervious concrete

Baoshan Huang *, Hao Wu, Xiang Shu, Edwin G. BurdetteDept. of Civil and Environmental Engineering, The University of Tennessee, Knoxville, TN 37996, USA

a r t i c l e i n f o a b s t r a c t

Article history:Received 3 February 2009Received in revised form 22 September2009Accepted 15 October 2009Available online 17 November 2009

Keywords:PolymersPerviousConcreteFiber reinforcementDurability

0950-0618/$ - see front matter � 2009 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2009.10.025

* Corresponding author. Tel.: +1 865 974 7713.E-mail address: bhuang@utk.edu (B. Huang).

Pervious concrete has been increasingly used to reduce the amount of runoff water and improve thewater quality near pavements and parking lots. However, due to the significantly reduced strength asso-ciated with the high porosity, pervious concrete mixtures currently cannot be used in highway pavementstructures. A laboratory experiment was conducted in this study to improve the strength properties ofpervious concrete through the incorporation of latex polymer. This study focused on the balance betweenpermeability and strength properties of polymer-modified pervious concrete (PMPC). In addition to latex,natural sand and fiber were included to enhance the strength properties of pervious concrete. The testresults indicate that it was possible to produce pervious concrete mixture with acceptable permeabilityand strength through the combination of latex and sand.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Portland cement pervious concrete (PCPC), also referred to asporous concrete or permeable concrete, is a mixture of portland ce-ment, uniform coarse aggregate, with either a small amount of orwithout fine aggregate, and water. Appropriate amounts of waterand cementitious material are employed to create a paste thatforms a thin coat around aggregate particles but leaves free spacesbetween them. Thus, pores are formed in the pervious materials[1,2]. PCPC has been used for over 30 years in many countries,especially in the United States and Japan. It is increasingly usedin the United States because of its various environmental benefitssuch as controlling storm water runoff, restoring groundwater sup-plies, and reducing water and soil pollution [3–5]. In the meantime,it has the potential to reduce urban heat island effects and can beused to reduce acoustic noise in roads [5,6].

PCPC contains little or no fine aggregate, using an adequateamount of cement paste to coat and bind the aggregate particlestogether to create a system of high porosity and interconnectedvoids that can drain off water quickly. Generally, the void contentof PCPC is between 15% and 25%, and the water permeability is typ-ically about 2–6 mm/s [5,7]. However, relatively low strength isusually associated with the high porosity in PCPC. The low strengthof conventional pervious concrete not only limits its application inheavy traffic highways but also influences the stability and

ll rights reserved.

durability of the structures, because of, for example, susceptibilityto frost damage and low resistance to chemicals. Therefore, PCPCwith low strength can only be utilized in some applications, suchas sidewalks, parking lots, recreation squares and subbases for con-ventional pavement [8–10]. And with some effective improvementin strength and using smaller size aggregate, PMPC could be ap-plied in pavement shoulder and local roads.

However, by using appropriately-selected aggregates, fineaggregates mixtures, and organic intensifiers and by adjustingthe concrete mix proportion, strength and abrasion resistance ofPCPC can be improved greatly [11]. Previous studies show that gra-dation, particle size of aggregate, and mass ratio of aggregate to ce-ment are the primary factors affecting porosity, permeability andcompressive strength of PCPC. Water cement ratio has a minor ef-fect on properties of PCPC [12]. Using smaller size aggregate can in-crease the number of aggregate particles per unit volume ofconcrete, the specific surface of aggregate, and the binding area,which eventually results in an improvement in the strength of per-vious concrete. Wang [10] used river sand to replace approximate7% (by weight) coarse aggregate to improve the concrete strength.Their results indicated that the 7-day compressive strength in-creases from 9.6–14.5 MPa to 22.2–22.7 MPa. Although the voidcontent is reduced due to the fine sand in the mixtures, all voidcontent values are still within an acceptable range (>15%) for PCPCapplications, and the permeability value is still higher than theminimum requirement to drain [10]. Yang and Jiang [11] showedthat use of silica fume (SF) and superplasticizer (SP) in perviousconcrete can enhance its strength significantly. The results also

0%

10%

20%30%

40%

50%

60%

70%80%

90%

100%

0.01 0.1 1 10 100Sieve Size, mm.

Perc

ent P

assi

ng, %

River sand

Fig. 1. Grain-size distribution of river sand.

B. Huang et al. / Construction and Building Materials 24 (2010) 818–823 819

indicated that SF had a better effect for improving the properties ofpervious concrete than polymer when used with SP. Their resultsindicated that the compressive strength of PCPC can reach50 MPa and the flexural strength 6 MPa. At the same time, therequirements of water penetration, abrasion resistance can alsobe satisfied. Some fibers are helpful in improving the tensilestrength and permeability of pervious concrete. Generally, the fi-bers in PCPC slightly increase the void content, significantly in-crease the permeability, and more significantly improve thesplitting tensile strength of PCPC [10,13]. The addition of polypro-pylene fiber at 0.56% by volume of the concrete causes a 90% in-crease in the indirect tensile strength and a 20% increase in theflexural strength. Polypropylene fiber does not significantly affectthe other mechanical properties [12]. Another effective methodto improve strength is to use some chemical additives, such aspolymer. Kevern [13] also presented that the addition of polymer(styrene butadiene rubber, SBR) significantly improves workability,strength, permeability, and freeze–thaw resistance, which makespervious concrete obtain higher strength at relatively lower ce-ment contents and results in relative higher porosity.

2. Research objective and scope

The objective of the present study is to evaluate the effect ofpolymer modification on the mechanical and physical propertiesof PCPC. The research efforts were made to balance the permeabil-ity and strength of the polymer-modified pervious concrete(PMPC) so that the mixtures are permeable and also strong enoughto support traffic loading.

In this study, three types of single-sized limestone aggregates(12.5 mm, 9.5 mm, and 4.75 mm) were used, and one type of poly-mer (SBS latex) was considered to make the pervious concrete mix-ture. The properties of pervious concrete were evaluated throughair void test, permeability test, compressive strength test, and splittensile strength test.

3. Laboratory experiment

3.1. Materials

Ordinary Type I portland cement was selected in the experiments. Three grada-tions of single-sized sieved limestone were considered as coarse aggregate:12.5 mm, 9.5 mm, and 4.75 mm. The properties of coarse aggregate were measuredaccording to ASTM specifications and listed in Table 1. The grain-size distribution ofthe river sand from the Tennessee River used in this study is shown in Fig. 1.

Latex polymer, styrene butadiene rubber (SBR), was selected and incorporatedinto the mixtures in order to improve the strength of pervious concrete. Styrenebutadiene rubber (SBR) latex is a type of high-polymer dispersion emulsion com-posed of butadiene, styrene and water, etc., which is similar to natural rubber inits resistance to mild solvents and chemicals and, like natural rubber, can be suc-cessfully bonded to many materials. It is one of the popular raw materials in the tiredip fabric industry, because of its good intermiscibility with vinylpyridine latex forfabric dipping. For the application in engineering construction, it can be used tosupply or replace cement as binder to improve tensile, flexural and compressivestrength of concrete. The SBR used in this study is manufactured by anionic solutionpolymerization using an organo-lithium initiator. It is a product with medium sty-rene and high vinyl content. A white thick liquid in appearance, it has good viscositywith 52.7% water content.

In addition to latex, polypropylene fiber was also added into the mixture to fur-ther enhance the mechanical properties of PMPC. Polypropylene fiber has featuresand benefits as follows: inhibits and controls the formation of intrinsic cracking inconcrete; reinforces against impact forces, reinforces against the effect of shattering

Table 1Properties of coarse aggregate.

Aggregate size (mm) Unit weight (kg/m3) Bulk specific gravity

12.5 1426 2.7599.5 1393 2.7584.75 1374 2.760

forces, and provides improved durability. The polypropylene fiber was 100% virginpolypropylene fibrillated fibers containing no reprocessed olefin materials with anaverage length of 20 mm.

3.2. Mix design

The control pervious concrete mixture was comprised of portland cement,water, and coarse aggregates of three gradations. To improve the overall behaviorof PMPC, latex, fiber, and fine aggregate (natural sand) were selectively added intothe mixture. The mix proportions are presented in Table 2. The basic mix proportionfor the control mix is cement: coarse aggregate: water = 1:4.5:0.35 by weight.When latex and/or fine aggregate were included in the mixture, the solid portionof latex was used to replace 10% cement and natural sand to replace 7% coarseaggregate by weight. The performance and properties of PMPC were compared tothose of the conventional pervious concrete.

3.3. Sample preparation

Pervious concrete mixtures were mixed using a mechanical mixer, and cylindri-cal specimens 152 mm in diameter and 305 mm high were made by applying stan-dard rodding for compaction. The specimens were cured in a standard moisturecuring chamber until the days of testing. Except for the compression test, the sam-ples were cut into about 76 mm thick small specimens for other tests before testing.The specimens were prepared in triplicates.

3.4. Test methods

3.4.1. Air voids testIn order to obtain the air voids content, it is necessary to know the bulk volume

of the compacted concrete. Since the pervious concrete has high interconnected airvoids, it is not suitable to use the submerged weight measurement to obtain thebulk volume. Geometrical measurement of the specimen dimension will not reflectthe surface texture (for different sized aggregates). A vacuum package sealing de-vice, CoreLok, commonly used to measure the specific gravity for asphalt mixtures,was used to obtain the effective air voids for the pervious concrete specimens inthis study. The test was conducted by following the ASTM D 7063 procedures.

3.4.2. Permeability testPermeability is an important parameter of pervious concrete since the material

is designed to perform as drainage layer in pavement structures. Due to the highporosity and the interconnected air voids path, Darcy’s law for laminar flow is nolonger applicable for pervious concrete. In this study, a permeability measurementdevice and method developed by Huang et al. [14] for drainable asphalt mixture(similar to pervious concrete in function) were used. Fig. 2 shows the specimenand device for permeability test.

Two pressure transducers installed at the top and bottom of the specimen giveaccurate readings of the hydraulic head difference during the test. Automatic dataacquisition makes continuous reading possible during a falling head test so that the

Apparent specific gravity Absorption (%) Void content (%)

2.797 0.48 402.801 0.56 432.811 0.66 41

Table 2Mix proportions for PMPC (unit: kg/m3).

Agg. Mix type Cement Latex binder Coarse aggregate River sand Water Fiber

No sand12.5 mm A 320.2 1440.8 112.1

B 314.8 31.5 1416.6 93.6C 320.2 1440.8 112.1 0.9D 314.8 31.5 1416.6 93.6 0.9

9.5 mm A 330.4 1486.9 115.6B 324.9 32.5 1461.9 96.6C 330.4 1486.9 115.6 0.9D 324.9 32.5 1461.9 96.6 0.9

4.75 mm A 352.6 1586.9 123.4B 346.7 34.7 1560.3 103.1C 352.6 1586.9 123.4 0.9D 346.7 34.7 1560.3 103.1 0.9

With sand12.5 mm A 300.6 1352.6 94.7 105.2

B 295.8 29.6 1331.0 93.2 87.9C 300.6 1352.6 94.7 105.2 0.9D 295.8 29.6 1331.0 93.2 87.9 0.9

9.5 mm A 311.9 1403.6 98.3 109.2B 306.9 30.7 1381.2 96.7 91.3C 311.9 1403.6 98.3 109.2 0.9D 306.9 30.7 1381.2 96.7 91.3 0.9

4.75 mm A 329.8 1483.9 103.9 115.4B 324.5 32.5 1460.3 102.2 96.5C 329.8 1483.9 103.9 115.4 0.9D 324.5 32.5 1460.3 102.2 96.5 0.9

Note: A – control; B – latex modified; C – fiber added; D – latex and fiber.

Fig. 2. Permeability test setup and sample.

820 B. Huang et al. / Construction and Building Materials 24 (2010) 818–823

test can be conducted even at very high flow rate, such as in pervious concrete. Thespecimen is placed in an aluminum cell. Between the cell and the specimen is ananti-scratch rubber membrane that is clamped tightly at both ends of the cylindri-cal cell. A vacuum is applied between the membrane and the cell to facilitate theinstallation of the specimen. During the test, a confining pressure of up to103.5 kPa is applied on the membrane to prevent short-circuiting from the speci-men’s side. The top reservoir tube has a diameter of 57 mm and a length of914 mm. The cylindrical specimen has a diameter of 152 mm and a height of76 mm.

In this test, the falling head method was used. From the paper of Huang et al.[14] hydraulic head difference vs. time curve obtained from the two pressuretransducers:

h ¼ a0 þ a1t þ a2t2 ð1Þ

where, a0, a1 and a2 are regression coefficients.Then, differentiate equation,

dhdt¼ a1 þ a2t ð2Þ

where a1 and a2 are regression coefficients for differential equation of head and time.Therefore, the discharge velocity is expressed as:

v ¼ dQdt¼ A1

A2

dhdt¼ r2

1

r22

dhdt

ð3Þ

Time (s)

Hea

d (m

m)

Time vs. Head

Fig. 3. Hydraulic head vs. time.

Hydraulic Gradient : i

Hydraulic Gradient vs. Discharge Velocity

Dis

char

ge v

eloc

ity:

v (

mm

/s)

Fig. 4. Hydraulic gradients vs. discharge velocity.

0

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15

20

25

30

35

Control mix Mix with latex Mix with latexand sand

Mix with latex,sand, and fiber

Poro

sity

(%)

12.5 mm 9.5 mm 4.75 mm

Fig. 5. Effect of latex on porosity.

25

)

12.5 mm 9.5 mm 4.75 mm

B. Huang et al. / Construction and Building Materials 24 (2010) 818–823 821

where A1; A2; r1; r2 are the cross section areas and radius of upper cylindrical reser-voir and the specimen.

According to Fig. 3 and Fig. 4, the pseudo-coefficient of permeability K0 and theshape factor m can be obtained. Based on the results, the relationship betweenhydraulic gradient and discharge velocity is v = 7.6208i0.3538 so the K0 is7.621 mm/s.

3.4.3. Compressive strengthThe compressive strength was tested at 7-days by following the ASTM C39 test-

ing procedures. The compressive strength test was conducted on an INSTRON load-ing frame on triplicate cylindrical specimens with 152-mm diameter and 305-mmheight.

3.4.4. Split tensile strengthThe split tensile test was conducted on triplicate cylindrical specimens of 152-

mm diameter and 76-mm thickness. The test was performed on an MTS loadingframe in accordance with the procedures ASTM C 496/C 496 M. The vertical loadwas continuously recorded and split tensile strengths were obtained through thetests.

0

5

10

15

20

Control mix Mix with latex Mix with latexand sand

Mix with latex,sand, and fiber

Perm

eabi

lity

(mm

/s

Fig. 6. Effect of latex on permeability.

4. Results and discussion

4.1. Porosity

Fig. 5 presents the porosity results for all pervious concretemixtures and the effect of latex on porosity. It is seen that mostof the mixtures had porosities within the range from 20% to 30%,which is acceptable. The three coarse aggregates with differentsizes exhibited similar porosity, indicating that aggregate grada-tion did not have a significant effect on the porosity results.

It also can be seen form Fig. 5 that the addition of latex and sandresulted in a slight decrease in porosity. However, the combinationof latex, sand, and fiber did not further decrease the porosity val-ues. The mix made with latex, sand, and fiber could still achievethe porosity and the acceptable permeability as expected.

4.2. Permeability

The permeability results are presented in Fig. 6 as well as theeffect of the introduction of latex on permeability of pervious con-crete. It is evident from Fig. 6 that all the pervious mixtures hadpermeability values between 10 and 20 mm/s, which is high en-ough to be used as a drainage layer for pavement structures. Theaggregate gradation did not show consistent influence on the per-meability. The mixtures made with three different size aggregatesexhibited similar permeability values.

According to Fig. 6, the effect of latex, natural sand, and fiber onpermeability was similar to that on porosity. Although the additionof sand and latex could lead to a reduction in permeability, the per-meability value was comparable and acceptable compared to thegeneral requirement of drainage.

4.3. Compressive strength

The effects of latex, sand, and fiber on the compressive strengthare shown in Fig. 7. As expected, the smaller the coarse aggregatesize, the higher the compressive strength. It is evident that theaddition of sand or latex could both increase the compressivestrength of concrete mixtures. The addition of natural sand in-creases the amount of cement mortar and thus increases the con-tact area between neighboring aggregate particles. Subsequently,the increased contact area will result in strength improvement.The addition of latex can also increase the contact area betweenneighboring aggregate particles. More importantly, the latex and

02468

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Control mix Mix withlatex

Mix withsand

Mix withlatex and

sand

Mix withlatex, sand,

and fiber

Com

pres

sive

stre

ngth

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)

12.5 mm 9.5 mm 4.75 mm

(a) Effects of latex and sand

0

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Control mix Mix with fiber Mix with fiberand sand

Mix with fiber,sand, and latex

Com

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stre

ngth

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)

12.5 mm9.5 mm4.75 mm

(b) Effect of fiber

Fig. 7. Comparisons of compressive strength results.

0

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Mix withsand

Mix withlatex and

sand

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and fiber

Tens

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12.5 mm 9.5 mm 4.75 mm

(a) Effects of latex and sand

0

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Control mix Mix with fiber Mix with fiberand sand

Mix with fiber,sand, and latex

Tens

ile s

treng

th (M

Pa)

12.5 mm 9.5 mm 4.75 mm

(b) Effect of fiber

Fig. 8. Comparison of tensile strength result.

822 B. Huang et al. / Construction and Building Materials 24 (2010) 818–823

the cement hydration products commingle and create two inter-penetrating matrices which work together, resulting in improvedstrength [15]. It is also observed from Fig. 7a that the combined ef-fect of latex and sand resulted in a further increase in the compres-sive strength.

Fig. 7b presents that fiber seemed to have only a minor effect onthe compressive strength. When fiber was added into control mixwithout latex or sand, fiber appeared to increase the compressivestrength significantly. However, after sand and/or latex were alsoincorporated into the mix, addition of fiber could not further im-prove the strength (Fig. 7). One of the reasons for the reducedeffectiveness was that the fiber used in the study could not be fullydispersed and evenly distributed in the mixture.

4.4. Split tensile strength

Fig. 8 compares the effects of latex, sand, and fiber on the splittensile strength. Similar to the compressive strength, concrete mix-tures containing smaller size aggregates had higher split tensilestrength. From Fig. 8, the effect of sand on the split tensile strengthwas not as much as on the compressive strength. Mixtures madewith sand sometimes even had lower split tensile strength thanmixtures without sand. However, the effect of latex was still signif-icant in improving the split tensile strength of pervious concrete.This is attributed to the latex network formed during the commin-gling and inter-penetration of the latex and cement hydrationproducts [15]. Unlike the brittle cement mortar, the latex networkis relatively strong in tension, which will contribute significantly tothe split tensile strength of pervious concrete.

According to Fig. 8b, it is seen that the effect of fiber on splittensile strength was similar to the effect on compressive strength.The addition of fiber appeared to lead to a significant increase inthe split tensile strength of the control mix. However, addition ofsand and/or latex compromised the effectiveness of fiber. Use of fi-ber did not lead to the increase of split tensile strength of perviousconcrete mixtures containing sand and/or latex.

5. Summary and conclusions

A laboratory experiment was conducted to investigate the per-meability and strength characteristics of polymer-modified pervi-ous concrete. The effects of latex, natural sand, and fiber wereevaluated based on the laboratory test results. Based on this study,the following conclusions can be drawn:

� Use of the combination of latex, natural sand, and fiber couldproduce acceptable pervious concrete with both enough drain-age and strength properties.

� Latex and sand could both decrease the porosity and permeabil-ity of pervious concrete and increase the compressive strengthof pervious concrete. However, only the addition of latex couldincrease the split tensile strength of pervious concrete.

� Fiber did not have a significant effect on the strength propertiesof pervious concrete in this study. This was due to the fact thatfiber was not fully dispersed and evenly distributed in the pervi-ous concrete mixture. Special methods are recommended forgood separation and dispersion of fibers in the mixtures. Forexample, use of short fibers might be easier to acquire a uniformdistribution of fibers in the mixtures.

6. Future research

This is a preliminary laboratory study on the effect of polymermodification on the performance of pervious concrete with theemphasis on the permeability and strength properties. The durabil-ity of polymer-modified pervious concrete should be included infuture studies to evaluate the abrasion resistance of PMPC.

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