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The Journal of Engineering Research (TJER) Vol. 13, No. 1 (2016) 01-21

Prediction of Permanent Deformation of Foamed and
Emulsified Sulfur Asphalt Soils Mixes

H.I. Al-Abdul Wahhab*, a and G.M.S. Abdullahb

a Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
b Department of Civil Engineering, Najran University, Najran, Saudi Arabia

Received 24 November 2014; accepted 12 August 2015

Abstract: This paper presents a study carried out to evaluate and compare the permanent deformation of
marginal soils. Under consideration were marl, sabkha and dune sand stabilized with foamed and
emulsified sulfur asphalt (FSA, ESA) with mixes of the same soils stabilized with conventional foamed and
emulsified asphalt (FA, EA) for road base construction. Designed mixes at their optimum asphalt content
were evaluated for the dynamic resilient modulus (MR) at 22°C and 40°C and dynamic triaxial at three levels
of deviatoric stress and at 22°C and 40°C. The wheel tracking (WT) test was carried out at 22°C. Permanent
deformation of stabilized mixes with optimum binder contents was modeled and simulated using dynamic
triaxial and WT tests. The developed models were calibrated to predict rutting using VESYS 5W software.
Results indicated that the FSA increased rutting resistance as compared to conventional FA mixes. On the
other hand, ESA increased the rutting susceptibility of marl soil as compared to EA. The calibrated models
of rutting prediction were found to predict the rut depth with 90% accuracy.

Keywords: Rutting, Dynamic triaxial, Wheel tracking, Calibrated models, VESYS.

ooo

(VESYS 5W)

* Corresponding author’s e-mail: hawahab@kfupm.edu.sa

H.I. Al-Abdul Wahhab and G.M.S. Abdullah

1. Introduction

A major stressor in flexible pavement is rutting, as
indicated by the permanent deformation, or rut
depth, sometimes found along wheel paths.
Rutting in flexible pavement usually consists of
longitudinal depressions in the wheel path due to
the accumulation of small amounts of
unrecoverable deformation caused by each load
application (Fig. 1) (Hafeez and Imran H 2009;
Asphalt Institute 1996). Many factors affect the
width and depth of the rut, such as structural
characteristics of pavement layers (thickness and
material quality), traffic loads and environmental
conditions. The accumulation of load-induced
permanent deformation developed from all
individual pavement layers, including the
subgrade forms of surface rutting. A large
percentage of the total rutting will mostly come
from the under layers of pavement such as the
base, subbase, and subgrade when the surface layer
is thin.
Several models have been developed to predict
rutting in asphalt concrete (AC) pavement layers
and were evaluated in National Cooperative
Highway Research Program (NCHRP) publication
1-26 (Barenberg et al. 1990). The study reported that
those models which are related to the log of
permanent strain to the log of load repetition
appear to be the most suitable and versatile for
practical use. This power model is often fitted to
the accumulated permanent deformation curve and
is definitely the most commonly used permanent
deformation formula. The power model usually
plots a straight line on a log-log scale. The slope
and intercept of the power model, when plotted on
a log-log scale, are used as indicators of permanent
deformation resistance (Garba 2002).

Figure 1. Accumulated Plastic Strains in Pavements
(Asphalt Institute 1996).

The basic permanent strain to load repetition
model is expressed as:

ɛp = aNb (1)

This model was initially suggested for subgrade
and unbound materials by Monismith, Carl LM
(1976) and was first used for AC mixes by Khedr,
Safwan AK (1986). Various researchers
consequently used the same model for AC
(Diyaljee and Raymond 1982; Vuong and Peter
1991; Gholam and William 1996), where a and b
are the intercept and slope coefficients and N is the
load repetition. Figure 2 presents graphically the
curve of a power model on a log-log scale between
load repetition and permanent strain.
The progress of rutting with load repetition can
be measured using layer elastic and viscoelastic
theory. In order to get the cumulated permanent
strain in each layer, the following equation is used
(Hafeez, Imran H 2009):

(2)

where

ab
α = 1- b (3)

p = permanent strain (rut value)
N = number of load application
a = intercept coefficient of accumulated permanent

strain versus number of load repetitions curve
on log-log scale;

b = slope coefficient of accumulated permanent
strain versus number of load repetitions curve
on log-log scale; and εr = resilient strain

εr = resilient strain
µ = ratio of plastic to elastic response
α = rate of change of the plastic response.

Thus, the total rut depth can now be calculated
as:

ipi
n
iD hR 1 1 (4)

Figure 2. Log-log form of power model.

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

where, hi is thickness of the layer.
According to Bevan (2002), α and µ are the
stress- and temperature-dependent nonlinear
parameters and can be used for modeling
permanent deformation of mixes.
Thus, in order to predict the total permanent
deformation of a pavement structure, one has to
determine the properties of material in each layer
and predict the layer rut. The VESYS model was
adopted in this study since it is considered suitable
to predict the layer and total rut depths of the
pavement structure. The model parameters depend
on the results of the experimental work on the
material for each layer. Therefore, the dynamic
triaxial repeated load test, which is a suitable lab
test to obtain the VESYS model parameters, was
conducted on the investigated materials.

2. Experimental Work

Marginal soils cover most of the eastern provinces
of Saudi Arabia. In order to investigate the possible
treatment of the marginal soils to be used in road
construction, dune sand, marl, and sabkha soils
were collected, subjected to basic characterization,
and then stored for use in the experiments. The
basic engineering properties of the soils were
assessed by conducting preliminary
characterization tests, including specific gravity,
plasticity tests, and grain size distribution.
Standard foamed asphalt (FA) and 30/70
foamed sulfur asphalt (FSA) were produced using
a calibrated laboratory scale FA plant WLB 10. The
laboratory mix design procedure was carried out as
outlined in the Wirtgen Cold Recycling Manual to
determine the optimum asphalt content for the
marl, sabkha, and dune sand soil mixes. After
adding FA, 2% cement was added to all mixes to
prevent effecting the optimum moisture content
(Wahhab et al. 2012). A set of test specimens 63.5 ± 6
mm high and 101.6 mm in diameter were prepared
over a range of residual asphalt content. Mixes
were designed using soaked indirect tensile
strength (ITS) test. A relationship between soaked
ITS and residual asphalt content was plotted and
the optimum residual asphalt content, which
provides the maximum soaked ITS, was
determined.
For emulsified soils mixes, a set of test
specimens (63.5 ± 6 mm high and 101.6 mm in
diameter) were prepared over a range of residual
asphalt contents.

Test mixtures were prepared in various increments
of residual asphalt contents using previously
determined amounts of premix water and the
optimum water content required for mixing and
compaction. Prepared mixtures were compacted in
a Marshall mold with 75 blows for each side. After
that, the molds containing the compacted
specimens were placed on a perforated shelf in a
60°C (140°F) forced draft oven for 48 hours
(Asphalt Emulsion Manufacturers Association,
2004). Specimens were soaked under 50 mm Hg of
vacuum pressure in water for one hour and
without vacuum pressure for another hour and
then tested for soaked stability. Based on the
results, a relationship between soaked stability and
residual asphalt content was plotted, and the
optimum residual asphalt content providing the
maximum soaked stability was determined.
Designed FSA and ESA at their optimum binder
contents including marl, sabkha, and dune sand in
addition to the mixes of these soils with
conventional FA and EA were subjected to MR
(AASHTO T-307), dynamic triaxial and wheel
tracking (WT) tests to evaluate their permanent
deformation behavior.

3. Results

The basic properties of the marginal soils (marl,
sabkha and dune sand) used in this study were
determined and the soils were classified. Stabilized
soils treated with FSA and ESA, as well as the
conventional FA and EA were designed utilizing
indirect tensile strength (ITS) and Marshall
stability. Optimum asphalt contents for all mixes
are summarized in Table 1. The designed mixes at
their optimum asphalt content were subjected to
MR and dynamic triaxial (creep) at 22°C and 40°C,
representing relevant temperatures that base layers
are subjected to in the summer and winter and
wheel racking tests at 22°C.

3.1 Basic Soils Properties
The dry and wet grain size distribution curves
for marl, sabkha, and dune sand soils are shown in
Fig. 3. Wet sieving of the sabkha was done with
sabkha brine rather than distilled water in order to
simulate field conditions. The investigated soils
were non-plastic, based on Atterberg limit tests.
The specific gravity values of the marl, sabkha, and
dune sand soils were 2.69, 2.71 and 2.63 kg/m3,
respectively.

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Table 1. Optimum asphalt contents of soils mixes.

Soil Type Additive Type Optimum Asphalt (%)

Marl

FA 9
FSA 9
EA 8.1

ESA 7.2

Sabkha

FA 8

FSA 7

EA 4
ESA 3.6

Sand

FA 7
FSA 8
EA 5.4

ESA 5.4

Figure 3. Grain size distribution of soils.

Marl and sabkha soils were classified as SM and A-
3 according to the Unified Soil Classification
System (USCS) and American Association of State
Highway and Transportation Officials (AASHTO)
soil systems, respectively, based on both dry and
wet sieving methods. However, dune sand was
classified as SP and A-3 based on both dry and wet
sieving methods.

It is clear from dry and wet sieve analysis curves
for marl and sabkha soils that the wet sieving curve
is always above that of the dry curve. This is
ascribed to the fact that water tends to dissolve the

salts between particles of the soil; thus, the
proportion of wet materials passing through a
particular sieve is consistently more than that for
dry sieving. This difference would be higher if
sabkha was sieved with distilled water instead of
sabkha brine.

However, in sand soil, it can be seen that there is
almost no variation between grain size
distributions calculated by both the dry and wet
sieving methods. This is ascribed to the fact that
sand is made up of quartz which is not very
affected by washing.

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

3.2 Resilient Modulus (MR)
A dynamic triaxial test was conducted at 22°C
and 40oC to measure the dynamic MR at these two
temperatures for marl, sabkha, and sand mixed
with FA, FSA, EA and ESA. The dynamic MR was
measured according to the AASHTO T-307
procedure. The specimens were tested under
different combinations of confined pressure
measuring 21–138 kPa (3–20 psi) and deviatoric
stress measuring 34–276 kPa (5-40 psi) to simulate
the traffic loading that the granular base and
subbase materials are subjected to in the road
structures.
The variations of the MR with the deviator stress
for all FA/FSA mixes at 22°C are presented in Fig.
4. The results indicate that there is a significant
effect of the deviator stress variation on MR for all
mixes. The MR increased greatly with the increase
in the deviator stress. These findings are consistent
with the results reported by Li and Liu (2010).
Furthermore, the marl soil mixed with FA or FSA
has the highest MR values, followed by sabkha and
sand mixes. However, FSA mixes have lower MR
values than the FA mixes.
Similarly, FA and FSA mixes were tested for the
MR at 40oC. The relationships between the MR and
the deviator stress are presented in Fig. 5, which
shows that, upon testing at 40 C, the MR values
dropped by a magnitude of about 30% for FA
mixes and 5–10% for FSA mixes, which is
insignificant. The slight reduction in the MR of FSA
mixes under an increased temperature as compared
to FA may be attributed to the stiff bond between
soil particles of the mix, which is improved due to
the small-dispersed stiff droplets of FSA as a result
of the foaming and mixing processes. At low
ambient temperature, stiffness increases at the
points where mineral particles are bounded by
sulfur asphalt droplets while, where there were no
sulfur asphalt droplets, the connection between
particles did not change (Li and Liu 2010). Thus,
when temperatures increase, only the sulfur
asphalt-bounded particles are affected, which are
fewer in comparison to the mineral particles that
are not bounded by sulfur asphalt droplets.
Furthermore, sulfur asphalt has a higher
stiffness and less susceptibility to temperature
differences as compared to plain asphalt, resulting
in a stiffer mixes, which might justify its lower
sensitivity to temperature variation.
The variations of MR with the deviator stress at
22°C for emulsified soils mixes are presented in
Fig. 6, which clearly shows that the MR increased
greatly with an increase in deviator stress.
Additionally, the marl soil treated with EA or ESA

has the highest MR, followed by the sabkha and
lastly by the sand soils treated with the same
stabilizers. The difference, however, is insignificant.
Figure 7 presents the variation of the MR, measured
at 40 C, for the same soils mixed with EA and ESA.
Again, there is a significant effect of deviator stress
on the MR results. The MR increased significantly
with the increase in the applied deviator stress; this
is the same trend noticed for the MR measured at
22°C. The results also show that there is a drop in
the MR values measured at 40°C compared to those
measured at 22 C. This reduction in the MR values
appeared to be small in the ESA mixes compared to
the EA mixes. Thus, the sulfur modified EA mixes
are less sensitive to the temperature effect which is
a great advantage.
In comparison, between the MR for the EA and
ESA mixes, the moduli for the marl-ESA and
sabkha-ESA are slightly higher than those for the
marl-EA and sabkha-EA mixes, whereas the
inverse is true for the sand soil.

3.3 Dynamic Triaxial (Creep)
A dynamic triaxial repeated load test was

conducted on specimens 100 mm in diameter by
200 mm in height prepared at the optimum water
and FA, FSA, EA and ESA contents and compacted
to the maximum dry density. The specimens were
tested under 10 psi (68.95 kPa) of confining
pressure and a 40–80 psi range of deviator stress
(276–552 kPa) to simulate the traffic loading that
the granular base and subbase materials are
subjected to in the roads. The deviatoric stress was
applied in the form of a sinusoidal (haversine)
wave pulse with a loading time of 0.1 second
followed by a reset period of 0.9 seconds. Repeated
load tests were applied for treated mixes samples at
lab temperatures of 22°C and 40°C and with
deviator stress levels of 60, 70, and 80 psi (414, 483,
and 552 kPa) for stiff materials and 40, 50, and 60
psi (276, 345, and 414 kPa) for less stiff materials.

The results of the dynamic triaxial tests for the
marl, sabkha and dune sand soils treated at the
optimum percentages with FA and FSA and tested
at 22°C are presented below (Figs. 8–10). It is clear
that the marl soil has a high resistance to rutting,
followed by sabkha and sand soils. Furthermore,
the FSA mixes, except sand soil, reflect high rutting
resistance in comparison to the FA mixes, which is
considered a great advantage for newly
investigated FSA.

However, for the sand soil, the difference is not
as high, and the permanent deformation is high
either for the standard FA mixes or the modified
FSA mixes.

H.I. Al-Abdul Wahhab and G.M.S. Abdullah

Figure 4. Variation of MR with deviator stress for the foamed soils at 22°C.

Figure 5. Variation of MR with deviator stress for foamed soils at 40°C.

Deviator Stress, kPa

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Figure 6. Variation of MR with deviator stress for emulsified soils at 22°C.

Figure 7. Variation of MR with deviator stress for emulsified soils at 40°C.

Deviator Stress, kPa

H.I. Al-Abdul Wahhab and G.M.S. Abdullah

Figure 8. Dynamic triaxial test results for marl-FA/FSA at 22°C.

Figure 9. Dynamic triaxial test results for sabkha-FA/FSA at 22°C.

Figure 10. Dynamic triaxial test results for sand-FA/FSA at 22°C.

Load Repetitions

Load RepetitionsLoad RepetitionsLoad Repetitions

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

The increase in the resistivity of the sulfur modified
mixes to the permanent deformation may be
ascribed to the increased asphalt stiffness.
Similarly, Figs. 11–14 show the results of the
dynamic triaxial test for the same soils tested at
40 C. The same trend as was found at 22°C is
noticeable for the sabkha soil and marl, in which

FSA mixes have higher resistance to permanent
deformation. In addition to that and based on the
results of the dune sand mixes shown in Figs. 13
and 14, in spite of the weakness of the sand mixes,
the FSA mix is more resistant to permanent
deformation than the FA mix when tested at 40°C,
particularly under low to medium loading stresses.

Figure 11. Dynamic triaxial test results for marl-FA/FSA at 40°C.

Figure 12. Dynamic triaxial test results for sabkha-FA/FSA at 40°C.

Load Repetitions

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Figure 13. Dynamic triaxial test results for sand-FA at 40 C.

Figure 14. Dynamic triaxial test results for sand-FSA at 40 C.

Figures 15–17 show the results of the dynamic
triaxial tests of EA and ESA mixes conducted at
22oC. Contrary to the foamed mixes, the addition
of the modified ESA to the soils increased the
possibility of rutting, especially for marl and sand
soils. Sabkha soil ESA mixes showed less
permanent deformation than the EA mixes, but
they reached to the failure stage earlier than EA
mixes, particularly at high stress levels. Such
behavior may be attributed to the reduction in the
shear strength parameters (C and ф) of the soils
when treated with ESA rather than conventional
EA. It should be noted that the internal friction
angle of traded soils did not change significantly
due to the treatment type while the cohesion has

dropped considerably when ESA was used instead
of EA.
Figures 18–20 show the dynamic triaxial test
results for the same three soils tested at 40°C.
Based on the results for the marl soil, the same
trend found when testing at 22°C is clearly present
[Fig. 18]. Here, the mixes remained in the second
stage of the creep curve and did not reach to the
failure stage as happened when testing at 22°C and
under 80 psi (552 kPa) of loading, which means that
sulfur mixes perform well at higher temperatures.
On the other hand, sabkha and sand soils show
the inverse trend. ESA mixes are less sensitive to
rutting in comparison to conventional mixes which
were found to fail rapidly (Figs. 19–20).

Load Repetitions

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Furthermore, the mixes did not reach the failure
stage, particularly at low to medium loading for
sand and for all levels of loading in the case of the
sabkha soil. In addition, the slope (b) and intercept
(a) of the permanent deformation curves are low

which leads to a high and low µ for rutting
model parameters, resulting in low rutting
prediction. Hence, the sulfur modified emulsion
mixes have lower temperature susceptibility than
conventional mixes.

Figure 15. Dynamic triaxial test results for marl-EA/ESA at 22°C.

Figure 16. Dynamic triaxial test results for sabkha-EA/ESA at 22°C.

Load Repetitions

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Figure 17. Dynamic triaxial test results for sand-EA/ESA at 22°C.

Figure 18. Dynamic triaxial test results for marl-EA/ESA at 40°C.

Figure 19. Dynamic triaxial test results for sabkha-EA/ESA at 40°C.

Load Repetitions

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Figure 20. Dynamic triaxial test results for sand-EA/ESA at 40°C.

3.4 Wheel Tracking (WT)
A WT test is considered one of the best tests to
simulate field conditions. Thus, rutting behavior of
compacted base mixes was simulated using a wheel
track tester. Two slabs for each mix were
compacted to their maximum dry density, which is
the same density as in the dynamic triaxial test
specimens, using dynamic compaction. From the
marl, sabkha or sand mixed with FA, FSA, EA, and
ESA, 24 slabs measuring 45 cm x 22 cm x 10 cm
were prepared. The slabs were then cured at 40°C
for 72 hours for foamed mixes and at 60°C for 48
hours for emulsified mixes and tested dry under a
wheel load of 80 psi (552 kPa) at 22°C. Figure 21
shows samples of some tested slabs.
The results shown in Figs. 22–24 are the
measured rut depths for the FA- and FSA-treated
slabs of marl, sabkha, and sand soils, respectively.
Results clearly show the same rankings as were
obtained from the dynamic triaxial test; marl soil
had the highest rutting resistance followed by
sabkha and sand soil. Furthermore, the modified
FSA mixes had less rutting susceptibility than the
conventional foam mixes. Results also showed that
the sand treated with FA or FSA is very sensitive to
rutting and exhibited higher permanent
deformation (>15 mm within the first thousand
load repetitions) compared to the other marl and
sabkha mixes. The test section was considered
failed when the vertical deformation was ≥25mm (1
inch).
The results shown in Figs. 25–27 are the
measured rut depths for EA and ESA mixes for
marl, sabkha, and sand, respectively. Again, the
same trend and ranking as in the dynamic triaxial

was observed in which marl soil has the highest
rutting resistance, followed by sabkha and sand
soils. This means that rutting can be predicted from
any of the test methods and compared reasonably
well with other. Results also indicate that the ESA
mixes showed lower rutting resistance than the
emulsion mixes. In comparison to either normal or
sulfur modified foam mixes, emulsified mixes are
less resistant to permanent deformation than
foamed mixes. This can be attributed to the fact that
the FA treatment mechanism is different from that
of the EA treatment. While EA tends to coat soil
particles with a very fine asphalt layer, FA works
more like a soil stabilized with lime whereas FA
mostly binds the finer particles of the soil,
improving its structure. As such, FSA has a stiff
bond between fine soil particles of the mix
(droplets constituted of FSA).
Results also showed that sand treated with EA
or ESA is very sensitive to rutting and exhibited
higher permanent deformation (>15 mm within the
first thousand load repetitions) as compared to
marl and sabkha mixes.
Generally, marl asphalt mixes are more resistant
to permanent deformation than sand or sabkha
mixes due to the higher internal friction angle of
marl asphalt mixes, resulting in a longer secondary
stage of permanent deformation. The low friction of
dune and sabkha soils is attributed to the spherical
nature of the particles.
In general, the relative performance ranking of
accelerated pavement tests (APT) represented here
by a loaded WT test and a dynamic triaxial
repeated load test was found to be the same for all
investigated mixes in this study.

Load Repetitions

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Figure 21. Permanent deformation in WT samples.

Figure 22. Results of the permanent deformation for the marl-FA/FSA mixes using a wheel track machine,
dry at 22°C.

Figure 23. Results of the permanent deformation for the sabkha-FA/FSA mixes using wheel track machine,
dry at 22°C.

Load Repetitions

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Figure 24. Results of the permanent deformation for the sand-FA/FSA mixes using a wheel track machine,
dry at 22°C.

Figure 25. Results of the permanent deformation for the marl-EA/ESA mixes using a wheel track machine,
dry at 22 C.

Figure 26. Results of the permanent deformation for the sabkha-EA/ESA mixes using wheel track machine,
dry at 22 C.

Load Repetitions

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Figure 27. Results of the permanent deformation for the sand-EA/ESA mixes using wheel track machine,
dry at 22 C.

4. Prediction of Permanent Deformation
Using the VESYS Model

The VESYS model includes two different flexible
pavement rutting models: system and layer rutting.
One advantage of the layer rutting model is its
capability to predict both surface rutting and the
permanent deformation in each layer of the
pavement structure. The permanent deformation in
each finite layer can be estimated as the product of
the layer material permanent deformation law
associated with that layer and the elastic
compression at that layer which, in layer theory, is
given by the difference in deflections of the top and
bottom of the layer. Thus, the rut depth in any
finite layer can be calculated from the following
equation (Zhou and Scullion 2002):

RD (N) = (W+-W-)* N (1- αi) (5)

where,

RD = the permanent deformation (rutting) level
after N load repetitions;

W+, W- = the elastic deflection amplitudes of the
top and bottom surfaces of the layer, respectively;
µi, αi = the laboratory permanent deformation
parameters for the each layer (i) material;

μ , α = 1- b (6)
εr = (7)

In this study, VESYS 5W software was used to
analyze the pavement structure and conduct
performance analysis. The two main input
parameters in the VESYS 5W rutting model are the
permanent deformation parameters, α and µ, for
each layer.
To calculate the MR of the stabilized mixes,
regression models with high coefficients of
correlation in terms of deviator stress, confining
pressure, and temperature were developed using
Minitab software, Version 16 (Minitab, Inc., State
College, Pennsylvania, USA) based on the results of
the MR tests. Tables 2 and 3 present the MR models
for FA and EA mixes, respectively.

The permanent deformation parameters ( and
for each mix were obtained by representing the

accumulated permanent strain versus the number
of load repetitions, represented as a curve resulting
from the dynamic triaxial test on a log-log scale.
The intercept and slope coefficients were
determined and then and µ were calculated
according to Eqn. 6. Regression models were
created using Minitab software, Version 16 to
express these two parameters as functions of stress
levels and temperature for foamed and emulsified
mixes as shown in Tables 4 and Table 5,
respectively.

Load Repetitions

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Table 2. Regression models of MR for FA mixes.

Material
Type

Type of
Additive MR R

Marl
FA MR = 260 - 6.47 T + 0.004 c + 4.92 d 0.989

FSA MR = 147 - 1.77 T - 0.692 c + 4.00 d 0.982

Sabkha
FA MR = 256 - 6.16 T + 0.079 c + 4.51 d 0.986

FSA MR = 115 - 1.53 T - 0.393 c + 3.82 d 0.988

Sand
FA MR = 135 - 3.57 T + 0.152 c + 4.36 d 0.977

FSA MR = 112 - 2.20 T - 0.371 c + 3.88 d 0.991
MR = resilient modulus; FA = foamed asphalt; FSA = foamed sulfur asphalt.

Table 3. Regression models of MR for EA mixes.

Material
Type

Type of
Additive MR R

Marl
EA MR = 128 - 2.26 T - 0.513 c + 4.52 d 0.98

ESA MR = 119 - 2.49 T - 0.257 c + 4.61 d 0.993

Sabkha
EA MR = 158 - 3.07 T - 0.346 c + 4.05 d 0.988

ESA MR = 139 - 2.39 T - 0.417 c + 4.25 d 0.99

Sand
EA MR = 151 - 3.21 T - 0.093 c + 3.79 d 0.99

ESA MR = 86.1 - 1.05 T - 0.329 c + 4.01 d 0.992
MR = resilient modulus; EA = emulsified asphalt; ESA = emulsified sulfur asphalt.

Table 4. Regression models of μ and α for FA mixes.

Soil
Type

Stab-
ilizer μ R

2 α R2

Marl
FA μ = - 5.81 + 0.0161 T + 0.0133 d 0.97 α = 1.15 + 0.000037 T - 0.000598 d 0.95

FSA μ = - 1.53 + 0.0189 T + 0.00325 d 0.934 α = 1.04 - 0.00115 T - 0.000334 d 0.974

Sabkha
FA μ = - 3.80 + 0.0502 T + 0.0125 d 0.95 α = 0.805 + 0.000926 T - 0.000181 d 0.962

FSA μ = - 1.88 + 0.0204 T + 0.00776 d 0.882 α = 0.865 - 0.000741 T - 0.000181 d 0.892

Sand
FA μ = - 14.7 + 0.345 T + 0.0261 d 0.85 α = 1.93 - 0.0247 T - 0.00154 d 0.902

FSA μ = - 15.1 + 0.232 T + 0.0346 d 0.678 α = 1.37 - 0.00148 T - 0.00149 d 0.505
FA = foamed asphalt; FSA = foamed sulfur asphalt.

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Table 5. Regression models of μ and α for EA mixes.

Soil
Type

Stab-
ilizer

μ R2 α R2

Marl
EA μ = - 0.113 -0.00005 T + 0.00113 d 0.914 α = 0.812 + 0.00326 T + 0.00004 d 0.949

ESA μ = - 10.9 + 0.037 T + 0.0278 d 0.826 α = 1.14 - 0.000296 T - 0.000518 d 0.916

Sabkha
EA μ = - 3.31 + 0.0247 T + 0.0137 d 0.867 α = 1.17 - 0.00444 T - 0.000979 d 0.715

ESA μ = - 0.91 - 0.0719 T + 0.0157 d 0.811 α = 0.341 + 0.0146 T + 0.000036 d 0.915

Sand
EA μ = - 5.63 + 0.107 T + 0.00897 d 0.714 α = 2.17 - 0.0280 T - 0.00178 d 0.918

ESA μ = -2.51 - 0.0454 T + 0.0124 d 0.706 α = 0.735 + 0.0181T - 0.00123 d 0.895
EA = emulsified asphalt; ESA = emulsified sulfur asphalt.

Table 6. Calibration factors for α and µ.

Soil
Type Treatment Type αCF µCF

Marl
FA 0.8904 1.058

FSA 0.9638 2.50

Sabkha
FA 1.0959 1.429

FSA 0.8267 0.351

Sand
FA 0.6604 1.16

FSA 0.7843 1.098

Marl
EA 0.7912 2.941

ESA 0.9412 1.331

Sabkha
EA 1.321 1.77

ESA 0.60 0.903
Sand EA 0.93 1.191

A = foamed asphalt; FSA = foamed sulfur asphalt; EA = emulsified asphalt; ESA = emulsified sulfur asphalt.

where,

and permanent deformation properties of the
materials;

T = temperature in degree

d = deviator stress in kPa

4.1 Validation and Calibration of Rut Depth
Prediction Models

Simulation in accelerated pavement tests (APT),
such as through a WT test, is the most effective
manner to simulate the impact of traffic loading
and environmental conditions on pavement
configurations. These tests are also known as the
Hamburg WT and used for the Superpave
evaluation process. The rutting prediction models
derived in this study are based on the dynamic

triaxial test, which is different from wheel tracking
(WT) in many respects such as boundary
conditions and traffic loading. However, both
methods remain only a simulation of actual
behavior of the material (Jawad et al. 2013). It is
necessary to verify and calibrate these models with
the results of the WT test, which presents a better
simulation of actual field conditions.
Figure 28 shows the procedure of the calibration
process. First, the permanent deformation
properties of the materials ( and µ) were
calculated from the developed triaxial models at a
temperature of 22 C and under a deviator stress of
552 kPa (similar to a WT test) for each mix. Data
were entered into VESYS 5W software and rut
depths were predicted. The predicted rut depths
were compared with the rut depths measured
using the WT tests. If the predicted rut depth was
similar to the measured rut depth (within 90% of
the calculated value), then it was determined that

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

there was no need for calibration and the model
could be used for rutting prediction. Otherwise,
and µ were multiplied by the ratio of the recent
predicted rut depth (RD+1) to the rut depth
predicted in the previous step (RD) and called i+1
and μi+1 as shown in the flowchart. i+1 and μi+1
were re-entered into the VESYS 5W software and
the process was repeated until the predicted rut
depth was within 90% of the WT-measured rut
depth. Finally, calibration factors for the permanent
deformation properties ( and µ) for each mix
were determined (Table 6). It is worth mentioning

that these factors were used only for the marginal
soils (marl, sabkha, and dune sand) whose basic
properties and classifications are listed in this
paper.
Figures 29 and 30 show the WT-measured and
VESYS 5W-predicted rut depth curves for the marl
treated with FSA and ESA, respectively, as an
example of the rutting prediction using calibrated
models. It is clear from the figures that the
calibrated models have predicted the rutting values
close to that measured using a WT test.

Figure 28. Model calibration flowchart.

H. I. Al-Abdul Wahhb and G.M.S. Abdullah

Figure 29. Measured and predicted for marl-FSA mixes.

Figure 30. Measured and predicted for marl-ESA mixes.

5. Conclusion

This paper summarizes a laboratory investigation
to evaluate the permanent deformation of marl,
sabkha and dune sand soils treated with FSA and
ESA as well as conventional FA and EA by
conducting dynamic triaxial and WT tests and
developed and calibrated models for rutting
prediction. Based on the results of this study, the
following conclusions are drawn:

1. The MR of FSA mixes are slightly less than
those of FA mixes. However, the MR of ESA
mixes are slightly higher than EA mixes.

2. FSA mixes showed superior rutting resistance
compared with FA mixes and less temperature
susceptibility.

3. ESA was found to increase the permanent
deformation susceptibility of soil mixes.

4. Permanent deformation prediction models for
the investigated mixes were developed and
calibrated with the WT test results, and the
calibrated models were found to predict the rut
depth with 90% accuracy.

5. The VESYS 5W program is suitable to predict
rut depth since it can predict the layer rut
depth and the total rut depth of the pavement
structure with a 90% degree of accuracy.

Prediction of Permanent Deformation of Foamed and Emulsified Sulfur Asphalt Soils Mixes

Acknowledgment

The authors would like to acknowledge the
support provided by King Fahd University of
Petroleum and Minerals (KFUPM) for the execution
of this research.

References

Abdullah and Wahhab, Gamil MSA, Hamad I. Al-
Abdul W (2015), Evaluation of foamed sulfur
asphalt stabilized soils for road applications.
Construction and Building Materials 88: 149–158.

Abdullah, Gamil MSA (2014), Modeling the
behavior of sulfur modified foamed and
emulsified asphalt soils mixes for local road
applications. Ph.D Dissertation, King Fahd
University of Petroleum and Minerals, Dhahran,
Saudi Arabia.

Asphalt Emulsion Manufacturers Association
(AEMA) (2004), A basic asphalt emulsion
manual. Manual Series (MS) No. 19.

Asphalt Institute (1996), Superpave TM mix design.
Superpave Series SP-2, Lexington, Kentucky,
USA.

Barenberg, Ernest JB, Marshall RT (1990),
Calibrated mechanistic structural analysis
procedures for pavements phase 1 & II of
NCHRP project 1-26. National Cooperative
Highway Research Program”. Transportation
Research Board. Washington, DC.

Bevan WS (2002), Development of flow number
and flow time candidate simple performance test
for asphalt mixtures. MS Thesis. Department of
Civil and Environmental Engineering, Arizona
State University.

Diyaljee, Vishnu AD, Gerald PR (1982), Repetitive
load deformation of cohesionless soil. Journal of
the Geotechnical Engineering Division. Proc. ASCE
108(10): 1215-1229.

Garba, Rabbira G (2002), Permanent deformation
properties of asphalt concrete mixtures. PhD

Thesis, Norwegian University of Science and
Technology.

Gholam AB, William OY (1996), Determination of
elastic and plastic subgrade soil parameters for
asphalt cracking and rutting prediction. Transp.
Res. Rec. 1540, Transportation Research Board,
Washington DC. 97-104.

Hafeez, Imran H (2009), Impact of hot mix asphalt
properties on its permanent deformation
behavior. 05- UET/ PhD-CE-22, University of
Engineering and Technology, TAXILA.

Jawad H, Douglas JW, Theunis FPH, David A
(2013), Comparing results between the repeated
load triaxial test rand accelerated pavement test
on unbound aggregate. Journal of Materials in Civil
Engineering 26(3): 476–483.

Khedr, Safwan AK (1986), Deformation mechanism
in asphaltic concrete. Journal of Transportation
Engineering ASCE112(1): 29-45.

Li, Liu, Peng L, Juanyu L (2010), Characterization
of asphalt treated base course material. (No.
FHWA-AK-RD-10-07). Alaska University
Transport Centre. Alaska, USA.

Monismith, Carl LM (1976), Rutting prediction in
asphalt concrete pavements. Transp. Res. Rec.
616, Transportation Research Board, Washington,
D.C. 2-8.

Vuong B, Peter A (1991), Repeated load triaxial
testing on the subgrade from mulgrace ALF site.
Australian Road Research Board, WD RI91/023.

Wahhab, Hamad IA, Mirza MB, Isam MA, Hisham
MK (2012), Study of road bases construction in
Saudi Arabia using foam asphalt. Construction
and Building Materials 26: 113–121.

Zhu and Scullion, Fujie Z, Thomas S (2002),
VESYS5 rutting model calibrations with local
accelerated pavement test data and associated
implementation. Report No. FHWA/TX-03/9-
1502-01-2, Texas Transportation Institute, College
Station, TX.