Effects of various additives on the moisture damage sensitivity of asphalt mixtures

Constructionand Building

Construction and Building Materials 19 (2005) 11–18MATERIALS

www.elsevier.com/locate/conbuildmat

Effects of various additives on the moisture damage sensitivity ofasphalt mixtures

Atakan Aksoy a,*, Kurtulus� S�amlioglu b, S€ureyya Tayfur c, Halit €Ozen d

a Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkeyb General Directorate of Highways, Ankara, Turkey

c ISFALT Asphalt Company, Istanbul, Turkeyd Department of Civil Engineering, Yıldız Technical University, Istanbul, Turkey

Received 15 November 2003; received in revised form 27 April 2004; accepted 5 May 2004

Available online 31 July 2004

Abstract

Effects of four additives, namely two fatty amine (Wetfix I, Lilamin VP 75P), one catalyst (Chemcrete) and a polymer (rubber),

on the moisture damage of asphalt mixtures were studied. Rheological characteristics of the binders were measured using con-

ventional methods both original and thin-film oven aged. Mechanical characteristics of the mixtures were evaluated with Marshall,

indirect tensile and Lottman treatment tests. The additives used in this study reduced the level of damage due to moisture in asphalt

mixtures. Minimum acceptable indirect tensile strength ratio (0.70) is achieved when Chemcrete and 0.2% of Wetfix I, and 0.4–0.6%

of Lilamin VP 75P are used in asphalt mixtures. Indirect tensile strength ratio may decrease due to the relatively higher strength

obtained in dry specimens with respect to the conditioned ones. Indirect tensile strength ratios of asphalt paving specimens were

found to be less than the Marshall Stability ratios.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Additives; Stripping; Marshall Stability and flow; Indirect tensile strength; Marshall Stability ratio; Marshall Stability–flow ratio; Indirect

tensile strength ratio

1. Introduction

In bituminous mixtures, many problems are due to

stripping of the binder from the aggregate. To overcomethis phenomenon, adhesion-improving agents are often

used. Lately, the use of such additives has gained ac-

ceptance by engineers. Some of these are hydrated lime,

sulfur, anti-oxidants, anti-stripping agents, rubber, car-

bon black and a variety of polymers.

In order to improve adhesion and reduce moisture

sensitivity in asphalt mixtures, two different approaches

become apparent. The first, approach suggests the ag-gregate surface to be coated by a suitable agent that will

reverse the predominant electrical charges at the surface

and thus reduce the surface energy of the aggregate. The

second approach is to reduce the surface energy of the

* Corresponding author.

E-mail address: [email protected] (A. Aksoy).

0950-0618/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.conbuildmat.2004.05.003

binder and give an electrical charge opposite to that of

the aggregate surface. To achieve this surface active

agents, the so-called ‘‘surfactants’’ are used. Surfactants,

when used as anti-stripping agents, affect physiochemi-cal properties of both the asphalt and the aggregate.

Usually, asphalt pavements are subjected to extreme

damage because of the adverse effect of moisture. Strip-

ping occurs when the bond between the asphalt and the

aggregate is broken by water. The water may be sent on

or in the aggregate because of incomplete drying or it

may come from some other source after construction.

Water can cause stripping in different ways, such asspontaneous emulsification, displacement, detachment,

pore pressure, hydraulic scouring, and osmosis [1].

Stripping of asphalt concrete has been defined as the

weakening or eventual loss of adhesive bond usually in

the presence of moisture between the aggregate surface

and the asphalt cement in a bituminous mixture. Un-

fortunately, there has been no universally accepted

mail to: [email protected]

Table 1

Chemical composition of Alacatlı aggregate

Properties Value

pH 8.80

Silicon dioxide, SiO2 (%) 2.60

R2O3 (Al2O3 +Fe2O3) (%) 0.15

Ferric oxide, Fe2O3 (%) 0.00

Sulphur trioxide, SO3 (%) 0.04

Aluminum oxide, Al2O3 (%) 0.15

Calcium oxide, CaO (%) 50.95

Magnesium oxide, MgO (%) 5.00

Insoluble residue (%) 3.00

12 A. Aksoy et al. / Construction and Building Materials 19 (2005) 11–18

method to evaluate the proposed aggregate–asphalt

combinations and to determine their water susceptibility

potential or the effectiveness of various anti-stripping

agents [2].

Tests for the evaluating stripping potential may bedivided into two types. There are tests to which visually

estimate stripping which measure the time-to-disruption

of mix specimens stressed in some manner in the pres-

ence of water and tests which measure the change in

mechanical properties of mix specimens exposed to

water in some type of conditioning scheme [3].

The main objective of this research is to study the

effects of four additives (Wetfix I, Lilamin VP 75P,Chemcrete and rubber) on stripping of asphalt mixtures.

By adding additives to the asphalt and aggregate com-

binations, it will be determined whether these additives

are improving the performance of asphalt pavements or

not. Asphalt without an additive was ‘‘mixed’’ using the

same procedure as a reference test. Eleven asphalt mix

groups were prepared and tested, each having 30 speci-

mens. Thus engineering properties evaluated on the 330specimens containing additives regarded: Marshall

Stability and flow, Marshall Stability ratio, Marshall

Stability–flow ratio, indirect tensile strength, and ef-

fects of moisture by vacuum-saturation and Lottman

treatments.

1.1. Literature review

Shuler and Douglas [4] investigated stripping prob-

lem in open graded asphalt mixtures. Three different

conventional and polymer-modified asphalt cements

were used with both anti-stripping agents and hydrated

lime. Tests were apted in optimal bitumen. It was con-

cluded that additives decrease stripping. Ramaswamy

and Low [5] indicated that amino additives develop

stripping resistance and Marshall Stability values werefound higher than in the control mixtures. Law [6]

pointed out that amino addition to the bituminous

mixtures increases up to 25% the service life of the road.

Ramanathan et al. [7] determined the adhesion strength

between eight asphalt cements and two aggregates and

claimed that while there is no important difference in

one aggregate–eight asphalts mixtures, it is concerned

statistically big difference when using different type ofaggregate. Parker [8] investigated stripping problem

with siliceous gravels and dolomitic limestones and

cleared that siliceous mixtures showed less tension

strength like expected. Unfortunately dolomitic lime-

stones did not showed the same trend. Tension strength

of the dolomitic limestone mixtures increased unlike the

expecting result. Kennedy indicated that [9] indirect

tensile test could be used for determining water sensi-tivity of the asphalt mixtures and showed good results.

Gharaybeh [10] concluded from his study that there is a

parallel interaction between the visual stripping test and

indirect tensile test results. Maupin [11] founded mis-

leading results using tensile strength ratio for fatty

amine mixed asphalt pavements.

2. Materials and methods

2.1. Aggregate and asphalt cement

Aggregate coming from Alacatlı was chosen due to its

low stripping resistance. Chemical composition was lis-

ted in Table 1.

60–70 penetration asphalt cement was used. Engi-neering properties of the asphalt cement was presented

in Table 2.

2.2. Additives

Wetfix I and Lilamin VP 75P are liquid heat stable

anti-stripping agents specially designed to improve the

adhesion between bitumen and aggregate in hot-mixedasphalt. The heat stability makes the Wetfix I and Lil-

amin VP 75P possible to store in tank for up to one

week. Also they can be injected directly into the bitumen

storage tank. The dosage of these anti-stripping agents is

normally between 0.1% and 0.6% by weight of bitumen,

depending on the aggregate and the bitumen used.

Wetfix I is a mixture of alkyl and alkaline amines. These

agents are manufactured by Scan Road of Nobel In-dustries Sweden and their physical properties were given

in Table 3.

Although these anti-stripping agents are generally

added to the asphalt mix, this study was done by adding

them in the bitumen.

Chemcrete modifier is a catalyst which changes the

molecular structure of bitumen through a series of

chemical reactions which are dependent on the temper-ature and oxygen. Usually, the modifier is added to bi-

tumen at a rate of 2% by weight. Since the Chemcrete

polymerization reaction with bitumen involves air, no

essential changes in the bitumen properties occur until it

has been spread in a thin film over a large surface.

Therefore, all normal procedures and practices can be

Table 2

Conventional rheological properties of asphalt cement

Test Standard AC 60–70

Penetration (100 g, 5 s, 25 �C), 0.1 mm ASTM D5-73 75


Penetration ratio ASTM D5-73 33.3

Ductility (25 �C, 5 cm/min), cm ASTM D113-79 100+

Ductility after loss of heating test, cm ASTM D113-79 100+

Solubility in trichloroethylene, % ASTM D2042-76 99.7

Softening point, �C ASTM D36-76 48.5

Flash point, �C ASTM D92-78 260+

Loss of heating, % ASTM D1754-78 0.02

Properties of the TFOT Residue

Spot test AASHTO T102-83 –


Ductility (25 �C, 5 cm/min), cm ASTM D113-79 100+

Specific gravity, g/cm3 ASTM D70-76 1.038

Viscosity at 135 �C, cSt ASTM D2170-85 166.97

A. Aksoy et al. / Construction and Building Materials 19 (2005) 11–18 13

used for the mixing, placing and compaction of asphalt

materials produced with Chemcrete-modified bitumen.

After mixing and placing, the properties of the

Chemcrete-modified bitumen will be changed gradually

until the catalytic process stops. The primary effect of

this process is that some of the weak electrostatic forces,

which link conventional asphalt molecules, are replaced

with strong irreversible chemical bonds. Different testsperformed by the manufacturer have shown that the

modification of the rheological properties induced by

the Chemcrete modifier produces on asphalt with de-

creased temperature susceptibility, thus improved high

temperature strength, and improved deformation resis-

tance, greater adhesion [12]. Therefore Chemcrete

modified bitumen will improve the performance of the

pavement. The Transport and Research Laboratorystated that Chemcrete binder has a significant effect on

the predicted life of the road structure increasing it by a

factor of 4–6 over the same thickness of conventional

bituminous construction. So for a given design life the

instruction of Chemcrete would lead to a reduction in

the design thickness of bound materials of between 15%

and 30% [13].

Rubber is added to the asphalt during mixing. Therubber ingredient (1.2, 0.6 and 0.4 mm of size) was

mixed the asphalt at 165–200 �C temperature, 0.25% by

total weight of blend. The major purpose of using the

rubber was to decrease the temperature susceptibility

Table 3

Some properties of the Wetfix I and Lilamin VP 75P

Properties Wetfix I Lilamin VP 75P

Visual appearance at

20 �CBrown liquid Brown liquid

Pour point, �C <0 )15Flash point, �C >160 120

Density at 20 �C, g/cm3 0.975 1.010

and increase the resilient modulus. That is, the rubber

asphalt improves the resistance against the deformation

due to its high viscosity, and alleviate the initiation and

propagation of the reflection crack and the temperature

crack due its resiliance modulus. The rubber asphalt also

increases the oxidation resistance of the binder by the

antioxidants and enhances the lasting quality of the

asphalt mix by building a thick film around the aggre-gate particles. The rubber is added to the mix either in

the plant or in a premix manner [14].

2.3. Effects on the properties of asphalt mixtures

Eleven series of asphalt mixtures were prepared with

the combination of AC 60–70 pen. Asphalt and four

types of additives, namely anti-stripping agents (Wetfix Iand Lilamin VP 75P), Chemcrete-modified asphalt, the

rubber. The rubber ingredient (1.2, 0.6 and 0.4 mm of

size) was mixed the asphalt at 165–200 �C temperature,

0.25% by total weight of blend.

2.3.1. Moisture sensitivity on loose mixtures

ASTM D1664 Test Method for uncompacted (loose)

mixtures was used. In this test, coarse aggregate (9.5–6.35 mm) coated with asphalt cement is immersed in

water for 24 h and the degree of stripping is determined

by visual inspection after a condition time. Test results

were given in Table 4.

2.3.2. Mixture design

Alacatlı aggregate was used with the AC 60–70 (with

and without additives) brought from Alia�ga refinery. Toevaluate the characteristics of each material, standard

tests were performed and results for each material were

presented (see Fig. 1).

Los Angeles Abrasion test result of the aggregate was

found to be as 20.1%. Sodium sulphate soundness was

Table 4

Visual stripping resistance of aggregate with the two different asphalt

and additives

Additive choice Visual stripping resistance

(for loose mixtures) retaining

(%)

AC 60–70 AC 120–150

Control 25–30 30–35

With Wetfix I (0.2%) 90–95 70–75

With Wetfix I (0.4%) 95–100 80–85

With Wetfix I (0.6%) 95–100 85–90

With Lilamin VP 75P (0.2) 60–65 60–65

With Lilamin VP 75P (0.4) 80–85 70–75

With Lilamin VP 75P (0.6) 80–85 85–90

With rubber (1.2 mm) 75–80 65–70

With rubber (0.6 mm) 80–85 70–75

With rubber (0.4 mm) 80–85 70–75

With Chemcrete 85–90 80–85

Table 6

Specific gravities of aggregate

Fraction Specific gravities (g/cm3)

Apparent Bulk Standard

Coarse aggregate 2.707 2.680 ASTM C127

Fine aggregate 2.697 2.667 ASTM C128

Filler aggregate 2.716 – ASTM C128

Effective specific grade

of blended aggregate

2.690 – ASTM D2041

Bulk specific grade of

blended aggregate

2.675

Apparent specific grade

of blended aggregate

2.702

Table 7

Summary of Marshall design results

Design parameters Values Board specification in Turkey

Minimum Maximum

Bulk specific gravity,

Gmb

2.408 – –

Marshall Stability, kg 1160 900 –

Air voids, Pa, % 3.6 3 5

Void filled with

asphalt, Vf , %77 75 85

Flow, F, 1/100 in. 3.20 2 4

Filler/bitumen 1.24 – 1.5

Asphalt cement, Wa

(by weight of agg.)

5.0

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

80,00

90,00

100,00

0,01 0,10 1,00 10,00 100,00

Sieve Size, mm

Per

cent

age

Pas

sing

, %

Fig. 1. Aggregate gradation chart.


performed and it was found as 1.21%. The chemical

properties of aggregate are listed in Table 1. The prop-

erties of the AC 60–70 penetration asphalt cement had

been given in Table 2. The combined gradation of ag-

gregates used in the study is given in Table 5.Aggregate-specific gravities were presented in Table 6.

Table 5

Design gradation of aggregates

Sieve Sieve (mm) Passing (%) Lower–upper limits

3/4 in. 19.1 100 100

1/2 in. 12.7 86 77–100

3/8 in. 9.52 75 66–84

No. 4 4.76 58 46–66

No. 10 2 35 30–50

No. 40 0.42 13.8 12–28

No. 80 0.177 9.1 7–18

No. 200 0.074 6.2 4–10

Determining optimal asphalt cement content both

conventional and modified asphalt mixtures Marshall

Method (ASTM D1559) was applied. Three identical

samples were prepared for all alternatives (same asphalt

cement content) and seven different addition ratios were

used. The results of the Marshall Test results were

summarized in Table 7.

Eleven series of Marshall specimens were preparedand tested, including 30 reference specimens containing

no additives. For each aggregate-binder combination, 24

specimens were selected according to their bulk specific

gravities. The other six specimens were disregarded. All

specimens were prepared using at 5.0% asphalt content

which is the optimum asphalt content of Alacatlı ag-

gregate and Alia�ga asphalt (see Table 8).

Table 8

Samples identification

Type of additive Additive content

Control Low Medium High

Wetfix I c wl (0.2%) wm (0.4%) wh (0.6%)

Lilamin VP 75P ll (0.2%) lm (0.4%) lh (0.6%)

Rubber rs (0.4mm) rm (0.6 mm) rh (1.2 mm)

Chemcrete cc (2%)


The Marshall specimens were prepared from each

batch. Compaction was accomplished by a mechanical

Marshall compactor with 75 blows per side at 135 �C for

all specimens. Specimens with Chemcrete-modified as-

phalt were placed in the oven for 2 h before compactionto maintain its chemical reaction.

2.3.3. Moisture damage on compacted mixtures

Resistance to moisture and effect of additives on

moisture-induced damage of asphalt concrete mixtures

were evaluated by using Marshall conditioning (24 h at

60 �C), and retained tensile strength ratio after vacuum

saturation and after Lottman-accelerated moistureconditioning (vacuum saturation followed by freezing

and warm water soaking).

The Lottman wet-to-dry tensile strength ratio should

be used in conjunction with the ACMODAS (Asphalt

Concrete Moisture Damage Analysis System) computer

program developed by Lottman and Leonard to predict

changes in fatigue life because of additives and to pre-

dict field life benefit-to-cost ratios for different additives[15].

Initially, 15 Marshall specimens were prepared at the

same bitumen content (5%) for the asphalt mixes with

and without an additive. Of these 15 specimens, three

specimens yielded different bulk specific gravities as with

respect to the remaining 12 specimens. The remaining

specimens are then divided in two groups; the average

specific gravity of the specimens of the each group shallbe equal. First group specimens were placed in water

bath at 60 �C for 35 min. And then loaded at a ratio of 2

in./min, and the stability and flow values were recorded

(which is named unconditioned specimens). The second

group of specimens was placed in water bath at 60 �Cfor 24 h. And then the same loading as described above

was applied. The Marshall Stability ratio (MSR) was

then found by using the average stability of each groupusing the following formula MSR¼ 100� (MScond:/

MSuncond:), where MSR: Marshall Stability ratio,

MScond: Average Marshall Stability for unconditioned

specimens (kg) and MScond: Average Marshall Stability

for conditioned specimens (kg).

An index of retained stability can be used to measure

the moisture susceptibility of the mix being tested. A

ratio of stabilities for ‘‘conditioned’’ specimens to ‘‘un-conditioned’’ specimens is the criterion to identify a

moisture susceptibility of a mix [3].

The ratio of retained Marshall Stability to flow

(MSFR) and the ratio of average Marshall Stability to

flow for each group of specimens were determined using

the following formula MSFR¼ 100� ((MS/F)cond:/(MS/

F)uncond:) where MSFR, Marshall Stability flow ratio;

(MS/F)cond: Ratio of average Marshall Stability to flowfor conditioned specimens (kg/mm) and (MS/F)uncond:;Ratio of average Marshall Stability to flow for uncon-

ditioned specimens (kg/mm).

Indirect tension test involves loading a cylindrical

specimen with vertical compressive loads. This generates

a relatively uniform tensile stress along the vertical di-

ametral plane. Failure usually occurs by splitting along

this loaded plane.Fifteen specimens of each mixture were prepared to

determine the tensile strength values. Of these 15 spec-

imens, three were rejected which have different bulk

specific gravity. The remaining 12 specimens were di-

vided into two groups (six specimens each). The two set

of cylindrical specimens 2.5 in.� 4 in. diameter was

compacted to the expected pavement density. First set

was preconditioned by vacuum saturation. That is, 55–80% of the air voids were filled with water. Specimens

showing above 80% saturation after the vacuum soaking

were discharged since they were accepted as severely

saturated; this process was repeated with a new speci-

men. If saturation has not reached 55% in a conditioned

specimen after the initial vacuum soaking, then the

specimen was returned for additional vacuum soaking

until a minimum saturation level of 55% is reached.These specimens were weighted in water and saturated

surface-dry conditioned in air. Results related with sat-

uration levels are given in Table 9 for only control

specimens. Specimens were wrapped in plastic bags and

put in a freezer for 16 h at )18 �C.After the specimens were put into a water bath for 24

h at 60 �C, finally they were placed in a water bath for 2

h at 25 �C. Second set is tested at 25 �C in indirecttension at 2 in./min deformation rate. The load at failure

was determined. The tensile strength of specimens was

found by the following formula; St ¼ ð2� PultÞ=ðp� d � tÞ, where St, tensile strength of conditioned or

unconditioned specimens, psi; Pult, ultimate applied load

required to fail specimens, lb; t, thickness of the speci-

mens, inches; d, diameter of the specimens, in.

The indirect tensile strength ratio (ITSR), which iscalculated as the ratio of preconditioned indirect tensile

strength to dry indirect tensile strength) that is

ITSR¼ (Stcond:/Stdry)� 100, where Stcond: Average ten-

sile strength of conditioned specimens, psi and Stdry

average tensile strength of unconditioned specimens, psi

is used to predict the stripping susceptibility of the

mixtures. The minimum ITSR necessary to ensure good

pavement performance has not been identified inT€urkiye, however 0.70 is generally considered to be

reasonable minimum value. Mixtures with tensile

strength ratios less than 0.70 are moisture susceptible

and mixtures with ratios greater than 0.70 are relatively

resistant to moisture damage [16].

Marshall Stability test results were summarized in

Table 10 and indirect tensile test results were given in

Table 11.In Fig. 2, the relationships between Marshall Stability

(MS) and type of asphalt mixes, Flow, F and type of

asphalt mixes for both conditioned and unconditioned

Table 9

Degree of saturation in Marshall specimens for control specimens (Gmm¼ 2.500)

Sample

number

Weight in

air (A)

Weight in water

(C)

Sat. Surf. Dry.

Weig. (B)

Volume of specimen

(D¼B)C)

Bulk specific grav-

ity (Gmb ¼ A=D)Air voids

Pa ¼ ðGmm � GmbÞ=Gmm

Before saturation

C6 1201.0 701.5 1202.3 500.8 2.398 4.1

C8 1202.9 701.6 1203.5 501.9 2.397 4.1

C13 1204.1 701.3 1204.6 503.3 2.393 4.3

C15 1189.5 693.9 1189.6 495.7 2.400 4.0

C24 1200.5 700.5 1201.8 501.3 2.397 4.1

C25 1192.6 691.4 1193.6 502.2 2.377 4.9

After saturation

Weight in

water (E)

Sat. Surf. Dry.

Weig. (F)

Volume of specimen

(G¼F)E)

Bulk specific gravity

(Gbw ¼ A=G)Air voids Paw ¼ðGmm�GbwÞ=Gmm

Degree of saturation (S*)

S ¼ ðF � AÞ= ðPawGÞ10; 000

C6 716.0 1216.2 500.2 2.401 4.0 76.8

C8 716.8 1216.6 499.8 2.407 3.7 73.5

C13 716.4 1218.4 502.0 2.399 4.1 70.2

C15 707.8 1203.0 495.2 2.402 3.9 69.6

C24 715.1 1214.4 499.3 2.404 3.8 72.8

C25 708.0 1205.1 497.1 2.399 4.0 62.3

Table 10

Summary of effects of additives on mixture properties for Marshall Test

Property Marshall test results

Bulk specific

gravity (Gmb)

Air voids,

% (Pa)Stability 35 min

at 60 �C MS1

(kg)

Flow F1(mm)

Stability 24 h

at 60 �C MS2

(kg)

Flow F2(mm)

MSFR, % ðMS2=F2ÞðMS1=F1Þ MSR, %

(MS2=MS1)

Control 2.408 3.7 1290 2.78 1178 3.16 80.4 91.3

Wetfix I (0.2%) 2.398 4.1 1371 2.86 1351 3.37 84.3 98.5

Wetfix I (0.4%) 2.412 3.5 1264 2.88 1202 3.13 87.5 95.2

Wetfix I (0.6%) 2.411 3.6 1221 3.07 1158 3.23 90.1 94.8

L.VP 75P (0.2%) 2.412 3.5 1330 3.00 1274 3.39 85.0 95.8

L.VP 75P (0.4%) 2.420 3.2 1376 3.42 1366 3.50 96.9 99.3

L.VP 75P (0.6%) 2.417 3.3 1442 3.66 1416 3.98 90.1 98.2

Rubber (1.2 mm) 2.420 3.2 1224 3.06 1181 3.39 86.8 96.5

Rubber (0.6 mm) 2.414 3.4 1410 2.95 1309 3.22 85.6 92.8

Rubber (0.4 mm) 2.419 3.2 1439 2.88 1412 3.11 91.1 98.1

Chemcrete (2%) 2.394 4.2 2232 3.21 1662 3.44 69.3 74.5

Table 11

Summary of effects of additives on mixture properties for indirect tensile test

Property Indirect tensile test results

Bulk specific

gravity (Gmb)

Air voids,

% (Pa)Maximum load

(kg) P(dry)

St (psi)(dry)

Maximum load

(kg) P(cond.)

St (psi)(cond.)

ITSR St(cond.)/St(dry)

Control 2.397 4.1 525 74.3 255 36.0 0.485

Wetfix I (0.2%) 2.417 3.3 424 60.8 337 48.3 0.794

Wetfix I (0.4%) 2.394 4.2 610 86.2 409 57.6 0.668

Wetfix I (0.6%) 2.392 4.3 658 93.2 358 50.7 0.544

L.VP 75P (0.2%) 2.390 4.4 740 105.1 402 57.2 0.544

L.VP 75P (0.4%) 2.418 3.3 868 125.5 772 111.8 0.891

L.VP 75P (0.6%) 2.408 3.7 1088 158.3 800 116.6 0.737

Rubber (1.2 mm) 2.415 3.4 1036 149.9 325 47.1 0.314

Rubber (0.6 mm) 2.414 3.4 941 134.8 379 54.5 0.404

Rubber (0.4 mm) 2.419 3.2 929 133.5 505 72.3 0.542

Chemcrete (2%) 2.423 3.1 1971 283.5 1604 230.4 0.813


0

20

40

60

80

100

c wl wm wh ll lm lh rs rm rh ccMixture

Mar

shal

l Sta

bilit

y R

atio

,%

Fig. 4. Effects of additives on Marshall Stability ratio.

0

500

1000

1500

2000

2500


Mar

shal

l Sta

bilit

y at

60o C

, kg

MS1 (35 min. stability)

MS2 (24 hrs. stability)

Fig. 2. Effects of additives on Marshall Stability.

0

20

40

60

80

100


Mar

shal

l Sta

bilit

y Fl

ow R

atio

,%

Fig. 5. Effects of additives on Marshall Stability flow ratio.


situation are illustrated, respectively. There were sig-

nificant increases in both conditioned and uncondi-

tioned stability due to the addition of Chemcrete (CC)

as compared to control mixes (C). Slight increase instability for Wetfix I at 0.2% (WL), Lilamin VP 75P at

all percent (LL, LM, LH) and rubber at 0.6 and 0.4 mm

of size (RM and RS) were achieved. One of the reasons

for increased stability for Chemcrete was that Chem-

crete-modified asphalt had high viscosity. Increases in

the percent of Wetfix I yielded decrease in Marshall

Stability, thus Wetfix I should be used at low percents.

By increasing the amount of Lilamin VP 75P, higherMarshall Stabilities are obtained. On the other hand,

better performances were observed with smaller sizes of

rubber additives.

As shown in Fig. 3 all additives increased slightly

Marshall Flow for both conditioned and unconditioned

specimens compared to control mixes. In Fig. 4, the

relationship between Marshall Stability ratio (MSR)

versus type of asphalt mixes was shown. All additives

0

2

4

6


Flow

at 6

0o C, m

m

F1 (35 min. flow)

F2 (24 hrs. flow)

Fig. 3. Effects of additives on Marshall flow.

increased the Marshall Stability ratio as compared to

control mixes except for Chemcrete.

Fig. 5 shows the relationship between Marshall Sta-bility–flow ratio (MSFR) and types of asphalt mixes. All

additives increased the MSFR except for Chemcrete.

However, Chemcrete increased Marshall Stability and

flow, the ratio of stability over flow was decreased.

Indirect tensile strength versus asphalt mixes type in

Marshall Specimens was shown in Fig. 6 for Stcond: and

0

50

100

150

200

250

300


Indi

rect

Ten

sile

Str

engt

h, p

si

dry mixtures

conditioned mixtures

Fig. 6. Effects of additives on indirect tensile strength.

0

20

40

60

80

100


Indi

rect

Ten

sile

Str

engt

h R

atio

, %

Fig. 7. Effects of additives on indirect tensile strength ratio.


Stuncond: Chemcrete, Lilamin VP 75P, and rubber in-

creased tensile strength significantly; Wetfix I increased

the strength slightly. Tensile strengths of dry specimens

and moisture-conditioned specimens generally increased

when additives were used. The increase in conditioned

strength was less than the increase in dry strength.

The relationship between ITSR and different type of

asphalt mixtures was illustrated in Fig. 7. The specimenswith 0.4% of Lilamin VP 75P have the maximum indi-

rect tensile strength ratio (89.1). There were little dif-

ferences between Wetfix I-modified asphalts and control

mixes in terms of stability and tensile strengths. Rubber-

modified asphalts increased the stability and indirect

tensile strengths but decreased the indirect tensile

strength ratio. Chemcrete significantly increased the

Marshall Stability and tensile strength values of allmixes, so Chemcrete increased the moisture resistance of

mixes as determined by the Lottman procedure.

3. Conclusion

The additives used in this study reduced the level of

moisture-induced damages in asphalt mixtures. Mini-mum acceptable indirect tensile strength ratio (0.70) is

achieved when Chemcrete and 0.2% of Wetfix I, and

0.4–0.6% of Lilamin VP 75P are used in asphalt mix-

tures. Indirect tensile strength ratio may decrease due to

the relatively higher strength obtained in dry specimens

with respect to the conditioned ones. Indirect tensile

strength ratios of asphalt paving specimens were found

to be less than the Marshall Stability ratios.

The relative performance of different additives seems

to be different. The choice for any field application

should therefore be made on the basis of field trials or at

least by conducting a simulation model study to assess

their relative performance because long term effective-ness of the amino additives is still controversial.

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Documents

Effects of various additives on the moisture damage sensitivity of asphalt mixtures