MEASERMENT RESISTACE OF CRACK SEALANT ASPHALT
CONCRETE UNDER REPEATED LOADING
Ziari Hassan ¹, Khabiri Mohammad Mehdi ²
¹Professor, Department of Civil Engineering, Iran science and Technology University, Iran,Tehran,Narmak,
IUST,Civil Engineering College Zairi Office, Email:H.Ziari@iust.ac.ir
² PhD Student, Department of Civil Engineering, Iran science and Technology University, cuurently lecture
Vali-Asr Rafsenjan university, Iran Iran,Tehran,Narmak. IUST,Civil Engineering College Zairi Office
Abstract: In this paper resistance of cracked and crack sealant asphalt samples were studied by
varying temperature & time of loading to understand the crack sealant pavement behavior under
Iran climatic conditions & to address the problem according to mode of distress. The common cause
of pavement distress in Iran is rutting, which initiates due to uncontrolled axle load & large
variation in temperature. Creep tests were carried out using Universal Testing Machine (UTM 5P)
on the mixes prepared in the laboratory.
Polymer Modified Bitumen has been used as sealing material and is a unique opportunity to
compare the behavior of in crack sealant asphalt concrete. The results of laboratory tests on cracked
and crack sealant asphalt concrete under the influence of load and environmental are presented in
Keywords: Polymer Modified Bitumen, Cracked Sealant, Asphalt Concrete, Universal Testing Machine
(UTM), Premature Failure.
1. INTRODUCTION the crack sealant of pavements to
The main cause of premature failure of withstand the effects of high ambient
pavements in Iran is rutting due to high temperatures. Study of resistant behavior
variations in ambient temperatures, of crack sealant asphalt concrete under
uncontrolled heavy axle loads and varying temperatures and time of loading
limitations of cracked pavement . The has not been given due consideration in
purpose of sealing cracks in asphalt the past due to non availability of relevant
concrete pavements is to protect the testing facilities. L B Chu et al reported
pavement structure from premature that the load carrying capabilities (as
failure. The weakened pavement structure reported by Deflection Bowl Parameters)
can result in load-related failures such as of a flexible pavement is significantly
alligator cracking . affected by environmental factors.M
The road network system in Iran consists Perl et al carried out research on asphalt
of approximately 168,000 KM of flexible performance at low temperature. Its
pavements and about 2100 KM of performance at 20◦ C or less was
Motorways. In the recent polymer investigated and particularly below 0ºC
modified bitumen has been introduced in . He concluded that asphalt can fail to
perform due to deformation (usually 2. TESTING PROGRAM
associated with temperatures above 35ºC) In this research work it was planned to
or by tracking (normally associated with study important property of cracked
temperature less than 10ºC). At high asphalt concrete i.e., Permanent
temperature the accelerated wheel Deformation (Creep). UTM-5P is capable
tracking test offers a mean of measuring of determining permanent deformation
or specifying deformation but at low characteristics of asphalt concrete.
temperatures no standard method is Universal testing machine allows asphalt
available to characterize ductility L to be tested for its ability to withstand
Goodrich considered that at low repeated axial loading at varying
temperatures, the viscous flow of the temperatures. UTM software can replicate
asphalt (which permits creep and thus varying road conditions through increases
resists thermally induced cracking) is in frequency and force of axial loads. the
principally derived from the viscosity of tests were carried out in accordance with
the modified base asphalt . ASTM D-4123 on asphalt samples at 45,
Thus in order to design and/or maintain 55 & 65ºC and on loading pulse period of
road pavements effectively and 1500ms and pulse width of 150ms (.15
economically, the understanding of sec), 300 ms (.3 sec) & 450 ms (.45
environmental influences on the sec). The most important part of this
performance of road structure is very research was to prepare samples of crack
important. The study was carried out to sealant asphalt concrete for laboratory
determine the resistance to permanent testing as shown in Figure 1. A brief
deformation of crack sealant asphalt detail of the samples under is shown in
concrete under repeated loadings at Table 1.
varying temperatures. In order to
determine these properties,UTM-5P has
been used for testing for the first time in
Table 1: Material for cracked, crack sealant and uncracked asphalt samples
Percentage of Aggregate Particles
Sieve Size (mm)
Passing each Sieve
Bitumen kind 60/70 Penetration at 25˚C
Bitumen percent 5.5%(Marshal Method)
Sealant Material Polymer Modified Bitumen
3. REPEATED LOAD UNIAXIAL loading . The test initially applies a
STRAIN TEST (CREEP TEST) static conditioning stress to the specimen
Repeated load uniaxial strain test was and measures the resulting accumulating
performed on the asphalt sample at 100 strain. The magnitude and applied time
kPa loading stress and at 45, 55 & 65ºC duration for conditioning stress were set
temperatures. The loading pulse period of to l0kPa and 600 seconds respectively.
2000 ms (2 sec) and pulse width of 500 Following the conditioning period, a
ms (0.5 sec) was selected. fixed twenty second time delay is
Vertical deformations must be measured programmed, where the applied stress is
with a linear variable displacement set to zero. When the delay time expires,
transducer (LVDT). Two LVDTs, placed the specimen is then subjected to repeated
diametrically opposite each other, must pulse loading for 3600 cycles with a
be used to measure this deformation. The stress level of 100kPa. As pulse loading
resolution on each LVDT must be better continues, the accumulated strain is
than 0.0025 mm (0.000098 in.). Smooth- measured and displayed as a plot with
loading platens must be used to minimize linear scale axis. The applied force is
the effects of friction on the ends of the open loop controlled and rectangular in
sample. The upper-load platen must be of shape. Figure 2 shows a picture of the
the same diameter as the sample being UTM-5 software interface.
tested to provide for positive centering of
the specimen under load. The upper
platen must be of the floating
compression type to account for minor
deviations in a specimen’s surface.
This test conforms to the requirements of
the design draft issued by the British
standards Institute as a method of
measurement of resistance to permanent Figure 1 .A crack sealant sample after loading
deformation of bitumen mixtures that are (crack widths is 15 mm)
subjected to unconfined uniaxial repeated
Figure 2 .A picture of the UTM-5 software interface.
4. TEST RESULTS AND after 1.5 sec for 3600 pulses. The detailed
DISCUSSION test results are shown in Table 2, whereas
4.1 Resistance to Permanent accumulated strain has been summarized
Deformation of Cracked Asphalt and shown in Table 2.
Concrete From Table 2 it can be observed that the
This test measures the relative relative performance of uncracked
performance of crack sealant asphalt pavement very good with a maximum
samples against permanent deformation accumulated strain of 2.3% at 65ºC as
or rutting. Repeated load uni-axial strain compared to 2.94% of cracked pavement .
test was performed on two samples Permanent deformation performance of
cracked, crack sealant and uncracked at the samples has been shown in Figure 3,
45, 55 & 65ºC. A rectangular loading which shows an accumulated strain of
pulse of 100 kPa was applied for a about 0.99, 1.96 and 1.94% on the
duration of 0.5 sec and period of 2 sec i.e. cracked samples.
load is applied for 0.5 sec and repeated
Table 2. Accumulated strain values for cracked, crack sealant and uncracked asphalt samples
TEMP 45˚C 55˚C 65˚C
Sample Accumulated Accumulated Accumulated
DESCRAPTION Strain% Strain% Strain%
uncracked 0.99 1.72 2.3
crack sealant 1.94 2.28 2.57
cracked 1.96 2.37 2.94
Figure3. Accumulation of strain at 45°C for crack sealant sample
Accumulated strain of the same mixes Stiffness modulus or creep stiffness is
have been plotted at different calculated with the help of following
temperatures and shown in Figure 4, formula.
which shows similar behavior, i.e., σ
increase in strain at higher temperature. Ec =
Less accumulated strain has also been
observed on the uncracked samples.
Ec =Stiffness modulus
εc = accumulated axial strain (creep)
σ = stress applied on the specimen
Accum Strains %
2. crack Sealant Sample
0. 45 55
Tem perature C
Figure 4. Accumulated strain vs temperature for cracked, crack sealant and uncracked asphalt samples
Figure 5 shows the variation of creep uncracked samples is higher as compared
stiffness with temperature. Creep stiffness to cracked samples. Hence, this also
is related with the accumulated strain at shows that accumulation of strain is less
an applied stress value of 100 kPa. This in uncracked samples.
shows that the creep stiffness of
7 UnCraked Sample
crack Sealant Sample
3 45 55 65
Tem perature C
Figure 5. Creep Stiffness vs Temperature for cracked, crack sealant and uncracked asphalt samples
6. CONCLUSIONS 2. Cracked sealant sample constructed
1. uncracked samples, shows encouraging with polymer modified bitumen is
results, i. e., less accumulated strain and expected to perform well in terms of
high creep stiffness values at higher rutting resistance.
temperatures as compared to the 3. Preventive maintenance with cracked
conventional mix. sealant costs 30% more than normal
maintenance but it may save by its long  M Perl et al, Visaco-Elastic-Plastic
term performance and lesser maintenance Constitutive law for A Bituminous
cost. Mixture Under Repeated Loading, TRR,
4. As the load carrying capacity of No 911, 1984.
flexible pavements reduces drastically in  J L Goodrich , Asphalt and Polmer
summer, axle load limit and control is Modified Asphalt Properties Related to
essential to save the premature failures of thePerformance of Asphalt Concrete
pavements. Mixes, Proc. AAPT. Vol 57 , 1988.
 UTM-5P, Universal Testing Machine,
Wykeham Farrance International U K.
7. REFERENCES  ASTM D4123, American Society for
 Khabiri.M.M., 1th Report of PH.D. Testing and Materials, “Annaual Book of
Thesis, "Development a Mathematical Standards”, Vol. 04 08, Test 2434-68,
Model for Increasing Flexible Pavement 1986.
Life Cycle under Preventive British Standard BS 598, Part 3 1995,
Maintenance", Iran Science and Draft for Development for Creep Test,
Technology University, 2006, p. 89–107. DD226, 1986.
L B Chu et al, The Investigation of
Reologoc Properties of Asphalt Concrete,
Taiwan Highway Engineering,1990.