CHAPTER – 1

INTRODUCTION
1.1 General

Rapid urbanization requires good infrastructural facilities and one among them is transportation
infrastructure. Transportation facilities consist of the construction of new highways, expressways
and some rehabilitation to existing roads. Pavements are constructed with a layered structure and
they are broadly categorized into two types as flexible and rigid. A flexible pavement consists of
bound and unbound layers and in this pavement load transfers in the grain to grain contact.
Flexible pavement covers a major portion of the road network in India due to low initial cost and
good riding comfort.

Surface layer

Base layer
} (Bound layers)

Granular layer (Un-bound layers)

Figure 1.1 Different layers in flexible pavement

1.2 Background

Bitumen is a visco-elastic material, it is black or dark brown in colour. The first application of
bitumen is on waterproofing and later wide applications are increased in the construction
industry and one of the major applications in the present scenario is in the pavement
construction. Various bitumens binders were used in name of natural bitumen (Lake asphalt),
Rock asphalt and Tar. The use of natural bitumen (Lake asphalt) was started around 3000 B.C as
a waterproofing agent, later it has been shifted to use of rock asphalt as gilsonite and coal tar. In
the year 1975 tar was disappeared and bitumen has come into existence for the surfacing of
pavement.

1
The major pavements constructed in India are flexible pavements, these are constructed with
bitumen as a binding material. Basically, bitumen is the residue obtained from the fractional
distillation of crude oil at a higher temperature of around (350 to 400 oC). The residue is further
modified by the air blowing process for the improvement of physical properties. Thus, modified
bitumen is graded as penetration or viscosity grading system. In India, presently viscosity
grading was under use and penetration grading was disappeared in the year 2006.

1.3 Chemical constituents of bitumen

Bitumen contains about 84% carbons, 10% hydrogen, 5% sulfur and around 0.75% of oxygen,
0.5% of nitrogen and some metal traces. The chemical groups of bitumen can be broadly
categorized into two types as asphaltenes and maltenes fractions. Maltenes fractions are further
classified into saturates, aromatics and resins. These fractions were combinedly called as SARA
(Saturates, aromatics, resins and asphaltenes) fractions and can be separated from bitumen by
three major techniques as a) Corbett, b) ASTM D8044 and c) Thin layer chromatography.
Asphaltenes are insoluble solids in n-heptane which are black or dark brown in colour. The
constituents of asphaltenes are carbon, hydrogen, nitrogen, sulfur and oxygen. Asphaltenes are
highly polar compounds and are around 5 to 25% in bitumen. Maltenes constituents around 95 to
75%. Higher the asphaltenes content in bitumen than there will be an increase in high -
temperature rheological properties. Asphaltenes also simulate the aging of bitumen. Bitumen
subjected to aging (Short or long term) then there will be a decrease in maltenes fractions in
bitumen and certainly increases the asphaltenes content.

1.4 Bitumen modification

Modification of base bitumen will enhance the performance of binder towards different climatic
conditions and loadings. Several attempts were made in the past for the improvement of bitumen
performance using additives as polymers, crumb rubber, minerals, and acids. Moreover, PPA has
shown interest in the bitumen modification process. Use of Polyphosphoric acid (PPA) as a
modifier has increased over the past years due to significant hardening of binder in an easy
manner. The addition of PPA was first patented in the year 1973. Base bitumen modified with
PPA has shown decreased penetration, increased softening point which indicates the hardening
effect on the bitumen. The stiffening effect on the binder with PPA modification is due to the

2
formation of asphaltenes network in maltenes as shown in below Figure 1.2. This maltenes
network was formed after PPA chemically reacts with the resins present in the binder. This also
results in the increased asphaltenes content and decreased maltenes fractions of bitumen. Thus,
produced asphaltenes will reduce the further aging kinetics of binder.

Figure 1.2 Modification mechanism of PPA on base binder

1.5 Problem statement

Bitumen is used as a binder for bound layers and the properties of bitumen play a key role in the
performance of mixes. Mixes prepared with conventional bitumen has shown early failures in the
pavement after it’s been subjected to heavy vehicular loading and different climatic conditions.
The performance of these mixes in regards loading and climate shall be enhanced with the use of
high modulus asphalt concrete (HMAC) [1, 2]. HMAC is also known as Enrob à Module Élevé
(EME), was introduced in the year 1980s by France as a solution for the improvement of the
performance of mixes [3, 4]. These HMAC can be produced by using HMAB, further HMAB
can be obtained from three approaches: 1) Hard grade binder (Produced from a refinery), 2)
Binder modified with Gilsonite and 3) Binder modified with polyolefin [5]. Hard grade binder
refers to straight run binder having a penetration of 15/25 or 10/20 at 25 oC [6]. Several attempts
were been made for the development of hard grade binder by using modifiers as Vacuum
residue, Gilsonite, and Novolac [7 – 9]. From there investigation the produced hard grade
bitumen has shown improved performance which can be used for the production of HMAC.
However, there are no specific studies were carried still on the aging kinetics of the produced
hard grade binder.

3
Aging in bitumen is considered as one of the major factor that affects the service life of the
pavement and it is categorized into short term and long term aging. Short term aging of bitumen
takes place during the production and placing of bituminous mixes, whereas long term aging of
the bitumen starts after pavement is opened to traffic and exposed to different climatic conditions
throughout its service life. During the process of short term aging, the bitumen will be exposed to
temperatures greater than 160 oC and thus gets oxidized [10]. The oxidized bitumen will
significantly affect the service life of the pavement [11].

1.6 Study objectives

From the above considerations, the following objectives were selected for the present study.

 To develop a hard grade binder by modifying the base binder.

 To study physical and chemical changes of PPA modified binders.
 To evaluate the high service temperature of binders using Dynamic shear rheometer.
 To evaluate the aging kinetics of base and PPA modified binders.
 To study the morphological changes of PPA modified binders.
 To evaluate bituminous mix characteristics when prepared with base and hard grade binder.
 Cost comparison for 1 km of road stretch.

1.7 Organization of report

The present work is organized into six chapters.

Chapter 1 is an introduction which outlines the background of the study, problem statement and
the framed objectives of the present study.

Chapter 2 briefly describes the review of the literature. The literature presented in the present
chapter was organized into three parts as a) Literature on Polyphosphoric acid-modified binders,
b) Literature on aging and morphology characterization of binder and c) Literature on high
modulus asphalt concrete. Finally, the identified research gap is summarized.

Chapter 3 diagrammatically represents the adopted methodology in the present study.

Chapter 4 widely elaborates on the materials used in the present study, different test procedures
on bitumen and bituminous mixes.

4
Chapter 5 in this chapter the experimental results on PPA modified binder were presented.
Effects of PPA addition on physical and chemical fraction were briefly discussed. Rutting
resistance and aging kinetics of binders were also discussed in this chapter. Performance of
mixes was represented in terms of marshall parameters, Indirect tensile strength, resilient
modulus, and rutting. A cost comparison was explained in detail at the end of the chapter.

Chapter 6 list outs the conclusions made and future scope from the present study.

5
 CHAPTER – 2

LITERATURE REVIEW
2.1 General

In the previous chapter, a brief description was presented on the background of the present study,
objectives and the organization of the thesis. This chapter reviews the literature collected on
aging characterization of binder using asphaltenes and FTIR, the literature on PPA addition in
base binders and literature on the performance of high modulus asphalt mixes.

2.2 Literature on polyphosphoric acid modified binders

 Ylva Edwards et al (2006) [12] conducted a study on bitumen modified with three
commercial waxes (Sasobit, Montan Wax, Polyethylene wax) and polyphosphoric acid.
Waxes were been added by 3 and 6% and PPA with 0.4 and 1%. Modified binders were
tested for complex modulus (G*), phase angle (δ), BBR test (S and m-values) and
hardening index. From his study, wax modified bitumen has shown increased G*/sinδ
when compared with PPA binder. Less amount of Stiffness and high amount of m-values
observed for PPA 1% modified binder when compared with wax modified binders.

 Noemi Baldino et al (2012) [13] studied on two penetration grade binders of 70/100
(source N and C) and 50/70 (source M and P) obtained from two sources when modified
with 0.5, 1.0 and 1.5% PPA. The tests conducted on binders include complex modulus
E*, Loss tangent tanδ, and loss modulus E’’ at 5 to - 30 oC. Findings from his study were,
N binder with 1% PPA and C binder with 1.5% PPA has shown high E* and low loss
tangent. M and P binders with 1% PPA has shown high E* and low loss tangent values.

 Kezhan Yan et al (2013) [14] added PPA from 0 to 2% with an increment of 0.5% in
three bitumens obtained from three different sources. The modified binders were tested
o
for penetration, softening, viscosity at 135 C, ductility, SARA fractions, and
morphological studies. Test results revealed that PPA addition has shown decreased
penetration, increased softening point, increased viscosity and decreased ductility. With
the increase in PPA dosage SARA (saturates, aromatics, resins, and asphaltenes) fractions

6
 was also increased. Bee - like structures present in neat bitumen were dispersed after
modifying with PPA.

 Noemi Baldino et al (2013) [15] performed a study on two grades of bitumen (50/70 and
70/100) obtained from two different sources which were named as P0, M0, N0, and C0.
PPA has been added to each type of bitumen by 0.5, 1 and 1.5% by weight. Complex
modulus and phase angles were determined for the above four bitumen’s using dynamic
shear rheometer. From the results, M0 un-modified has shown high complex modulus
and less phase angle. Hence M0 has shown high G* and low phase angle it has been
further considered for G* and phase angle studies.

 Javier et al (2014) [16] investigated binder of 50/70 penetration grade when modified
with Low - density PE and PPA. Binders were tested for Linear amplitude sweep (LAS)
test and Multiple stress creep recovery (MSCR) test. Generally, LAS has three
parameters A35, B, and af. Higher the A35 it indicates a low amount of loss modulus (G’’).
B value indicates the sensitivity of the binder to an increase in the strain level. Higher the
B value indicates fatigue life of material decreases at a higher rate when strain amplitude
increases. af represents the analysis of damage tolerance, higher the value means material
show a longer crack before the rapid crack propagation. LAS results show that PPA
modified binder has high A35, B and af values. The Percent recovery was observed more
for PPA modified and Non-recoverable compliance revealed that PPA addition has low
rutting levels.

 Ojeyemi et al (2016) [17] in his study natural bitumen (ANB) has been modified with
PPA at 2, 4 and 6%. The tests on ANB and modified samples include penetration,
softening, specific gravity, flash point, fire point, kinematic viscosity, and FTIR. Results
revealed that increase in PPA has shown decreased penetration, increased softening point,
increased specific gravity, decreased flash and fire point and increased viscosity. From
FTIR studies it has been observed that PPA addition has not affected the functional
groups of the binder.

7
 Olga Shulga et al (2016) [18] performed a study on 80/100 penetration grade binder with
the addition of polyphosphoric acid as a modifier. Laboratory tests conducted on binder
are fundamental tests, SARA fractions and rheological studies (PAV samples), Creep
stiffness and m - value. Further study extended on bituminous mixes and the tests
conducted were Resilient modulus, tensile strength, and Hamburg wheel test. Percentage
of carbonyl was less than base bitumen after PAV. The Resilient modulus for base and
modified bitumen was found as 7842 and 8710 ksi at 25 oC respectively. Rut depths for
base and modified bitumen were 7.98 and 4.83 mm at 50 oC after 20k cycles.

 Venkat et al (2016) [19] in his study VG 30 grade bitumen was added with PPA from
0.5% to 2.0% with an increment of 0.5%. PPA modified binders were compared with
PMB for fundamental parameters, asphaltenes, and maltenes fractions. The major
findings from his study were increase in PPA content has shown decreased penetration,
increased softening point, decreased viscosity and ductility. Asphaltene content has also
increased with increase in PPA content. Rutting parameter (G*/sinδ) was observed
highest for 2% PPA modified binder.

 Ali Behnood et al (2017) [20] conducted experimental studies on the neat binder of PG
64 – 22 when added with SBS (2, 3 and 4%), GTR (8, 12 and 16%) and PPA (0.3, 0.6,
and 1.2%). The tests conducted on modified binders include PG grading by DSR
(G*/sinδ), BBR (Stiffness and m - value), Multiple stress creep recovery (for creep
compliance) and Frequency sweep test using DSR. For each category of modified binders
G*/sinδ has observed highest for 16% GTR, 1.2% PPA, 4% SBS and PG 64 - 22. In the
case of RTFO aged samples higher G*/sinδ was observed for 16% GTR, 1.2% PPA, 4%
SBS and PG 64 - 22. The Intermediate temperature parameter G*Xsinδ for PAV aged
samples has found higher for 1.2% PPA, 2% SBS, PG 64 - 22 and 12% GTR. Further at -
18 oC, stiffness value less than 300 MPa was observed for 1.2% PPA, 4% SBS, and 8%
GTR also at -18oC all binders has m - value less than 0.30 but higher m-values were been
observed for 1.2, 0.6, 0.3% PPA. Whereas less amount of creep compliance and high
percent recovery has been observed for GTR modified binders.

8
  Dongdong Ge et al (2017) [21] performed laboratory investigation of 40/60 penetration
grade binder when added with 3% sasobit and PPA at 0.5, 1, 1.5 and 2%. The tests
conducted on binders fundamental parameters, Complex modulus G*, Phase angle δ,
Stiffness, m-value, Fluorescence micrographs, and FTIR. From the test results, it has
been revealed that increase in PPA content has shown decreased penetration values,
increased softening point, decreased ductility, and increased the viscosity of binder which
indicates the high-temperature performance of binder was improved. G* and phase angle
values have shown higher at 2% PPA modification for original, RTFO and PAV aged
samples. Further, FTIR studies revealed that no new functional groups were formed after
modifying with PPA.

 Shahriar Alam et al (2017) [22] modified PG 64 – 22 binder with PPA and SBS.
Modified binder was studied for changes in pH, SARA fractions and Gaestel Index. From
this study, it was found that the asphaltene content was increased in binder with the
increase in PPA dosage, whether PPA + SBS modified binder has shown decreased
asphaltene content. Also, found that an increase in asphaltene content has increased the
viscosity of the binder. However, the Gaestel Index has shown colloidal structure for all
binders.

2.3 Literature on aging and morphology characterization of binder

 Naresh Baboo Ramasamy, (2010) [23] modified PG 64 – 22 binder with PPA at 1, 2 and
3%. FTIR study revealed that PPA addition has not created any new functional groups.
The carbonyl index of PPA modified binders was found increased with the increase in
PPA content. Percentage in carbonyl index after RTFO aging for PG 64 – 22, PG 64 – 22
with 1% PPA, PG 64 – 22 with 2% PPA and PG 64 – 22 with 3% PPA was found as
10.2, 22.6, 9.9 and 44%.

 Hui Yao et al (2013) [24] conducted experimental studies on nanoclay and carbon
microfiber modified binders with FTIR. The chemical bonds considered in this study
were ethylene, sulphoxide, aliphatic, aromatic and carbonyl. The carbonyl bond after

9
 modification has found decreased which represents the delay in the oxidation process.
Further, sulphoxide bond was also decreased as similar to the carbonyl bond.

 N. Baldino et al (2013) [15] performed Scanning Electron Microscopy (SEM) test

binders which were modified with 1.4 and 1.5% PPA dosage. From the study, it was
noticed that the solid particles present in the base bitumen were disappeared after
modifying with PPA.

 Dongliang et al (2014) [25] studied the aging resistance of 80/100 grade binder when
modified with anti-aging additives. FTIR spectroscopy was conducted on base and
modified binders and it has found that the carbonyl index of modified binders was
increased only a little amount which indicates higher aging resistance offered by adding
anti-aging additives.

 Olga Shulga et al (2016) [18] conducted FTIR study on PPA modified binder when added
with 0.6 and 1% PPA. The study explores on the aging kinetics of binders by comparing
carbonyl index before and after subjected to aging. Addition of 0.6 and 1% PPA has
shown decreased carbonyl index when compared with unmodified bitumen.

 Bhupendra Singh et al (2017) [26] used Fourier Transform Infrared Spectroscopy for the
aging characterization of VG 10, VG 30, WMA and PMB. Initially, the binders were
tested for physical properties and subsequently all binders were subjected to short term
and long term aging using RTFO and PAV. Carbonyl index (1700 cm-1) and sulphoxide
index (1030 cm-1) are used for the characterization of binders. From the results, it was
revealed that after subjecting to aging all binders has shown increased carbonyl and
sulphoxide indices.

2.4 Literature on high modulus asphalt concrete

 F. Moreno-Navarro et al (2014) [27] conducted experimental work on four types of

asphalt mixes by using limestone as aggregate, calcium carbonate was used as filler for
all the four mixes. The four mixes are

10
 a) B 20/25 bitumen with 5.1% bitumen (as per marshall)
b) B 20/25 bitumen with 5.1% bitumen, 0.3% Acrylic fiber over the total weight of
aggregates (Dry process)
c) B 20/25 bitumen with 5.1% bitumen, 1.5% Crumb rubber over the total weight of
aggregates (Dry process)
d) B 20/25 bitumen with 5.1% bitumen, 1% SBS over the total weight of aggregates
(Wet process)
A cost comparison was conducted on four mixes and tests on mixes include water
sensitivity and wheel-tracking, triaxial, stiffness modulus and fatigue four-point bending.

 Maria Espersson (2014) [2] compared four types of conventional bitumen’s with high
modulus bitumen for their respective percentage reduction in thickness when used as base
course in airports at different temperatures. The conventional bitumen’s used were
B40/50, B60/70, B100/150 and B150/200. The high modulus bitumen is of grade B13/22.
Temperatures considered in the study were -20, - 10, 0, 10 and 20 oC. LEDFAA (Layered
Elastic Design Federal Aviation Administration) program was used for calculating the
thickness of layers for a runway at different temperatures. The high modulus asphalt i.e.,
B13/22 has shown high complex modulus and viscosity at all temperatures. Mixing
temperature for conventional bitumen was 165 oC and for HMAB it is 185 oC. High
modulus bitumen has shown more reduction in thickness for +ve temperatures. In case of
–ve temperatures it has shown less thickness but slightly nearer to conventional mixes.
Cost of four mixes in descending order was 4 > 2 > 3 > 1. ITS of mixes in descending
order were 4 > 1 > 2 > 3.
TSR% of mixes in descending order were 1 > 2 > 3 > 4. Wheel tracking test has shown
mix no. 3 has least rut depth for first 1000 cycles and also for final deformation. Triaxial
test results revealed that the addition of additives has improved the sensitivity again
temperature for permanent deformation. Stiffness modulus of mixes with respect to
temperature with descending order were 2 > 3 > 1 > 4. Fatigue life of mixes in
descending order were 4 > 1 > 2 > 3.

11
 Dong Yu-ming et al (2015) [28] studied the performance of mixes when produced with
hard grade bitumen of grade 10/20 mm and SBS modified bitumen with limestone as
aggregates. Dense gradation was been adopted for the production of asphalt mixes and
tests on mixes include dynamic stability (cycles/mm) (Number of rolls at rut depth
change of 1mm), Resilient modulus (UTM-100) and complex modulus (Simple
performance tester) tests. High modulus asphalt mixes have shown less rut depth and
dynamic stability. Resilient modulus was found higher for high modulus asphalt mix than
SBS mixes when conducted at different temperatures. Complex modulus was also found
higher for hard grade asphalt mix.

 Maria et al (2015) [29] in this work hard grade bitumen 13/22 is compared with
conventional bitumen of grade 60/70 for fatigue life for an airport. Dynamic modulus test
has been conducted for both the asphalt mixes prepared with a conventional and hard
binder. The thickness of the base course was first calculated by using LEEDFAA
software for different CBR values. Later EVERSTRESS program was been used for
finding the number of load cycles to require to cause fatigue failure. The results revealed
that the dynamic modulus in MPa for conventional and high modulus asphalt mixes were
6172 and 13497 MPa. The number of load cycles for fatigue failure is much more for a
hard grade mix when compared with conventional bitumen mix.

 Siksha Swaroopa Kar et al (2016) [30] developed hard grade bitumen conforming to
SHRP guidelines. VG 10 bitumen was mixed with vacuum residue in the proportion of
52: 48. The ITS ratio for mixes prepared with hard grade bitumen and VG 30 were found
as 82 and 84%. Mr values were found as 12900 and 12847 at 25 oC and 3280 and 2584
MPa for mixes prepared with hard grade binder and VG 30. Rut depth after 20,000 cycles
for hard binder, VG 30 and VG 10 was found as 4, 4.8 and 6.2 mm.

 V. Haritonovs et al (2016) [31] in his investigation three types of bitumen of penetration

values 25.3 (B20/30) and 35 (PMB-SBS 10/40), were been used for the preparation of
mixes. Dolomite aggregates were been used the test results revealed that the mix prepared
with PMB and B20/30 has shown a rut depth of 2 and 4 mm after 20k cycles at 60 oC.

12
 Amjad et al (2017) [32] studied the performance of bituminous mixes using two binders
20-30 and 40-50 penetration grade. Rounded shape aggregates have been used in this
study but EME specifies the use of fully crushed fractured aggregate. The tests on
bitumen mixtures include marshall, Indirect tensile test, Uniaxial repeat loading test (Mr)
and Flexural bean fatigue test. Later present serviceability of pavement structure was
compared when the base course is prepared with two different layers using VESYS 5W
software. HMAC (20-30) has shown the stability of 17.50 kN at 4.6% bitumen,
conventional (40-50) has shown 13.40 kN at 3.8% bitumen and HMAC has shown higher
TSR%. Resilient modulus was conducted at 20, 40 and 60 oC and the increase in
temperature has decreased the modulus of mixes. HMAC with 4.6% bitumen has shown
good resistance to rutting and fatigue than conventional and also with HMAC at 4%
bitumen. The fatigue life of HMAC mix at 4.6% bitumen has shown higher life because
of the higher amount of binder increases the film thickness around aggregates thus it
results in lower stress in the binder film. A practical pavement structure was been
considered for determining the PSI with a period of 20 years. Distress is used to define
PSI of pavement. The results have shown that the drop in PSI values for the mix with
HMAC 4.6% is 0.6 at the end of 20 years whereas for a conventional mix the drop was 2.
Hence HMAC has shown good PSI.

 Basim H. Al-Humeidawi et al (2018) [9] in his study developed new bitumen meeting
with the EME2 specifications. Phenol-Formaldehyde (Novolac) and Hexamine with
crumb rubber were used for developing the hard grade bitumen. Conventional bitumen
has a penetration value of 40-50 mm. FTIR, SEM, and Energy disperse x-ray
spectroscopy were conducted for neat and modified bitumens. Conventional bitumen
blended with PF from 1 to 5% with 1% increment, for each percentage of PF Hexamine
was blended with 5, 10, and 15% respectively. Later for the obtained optimal mix crumb
rubber was been added to improve the fatigue resistance with a ratio of 0.5, 0.75 and 1%.
4% PF and 10% Hexamine have shown enough properties for meeting the EME2
specifications. FTIR results have showed that there are any no new functional groups
developed after the modification with PF, Hexamine and crumb rubber. SEM and EDC
have shown an increase in some amount of oxygen content in modified bitumen.

13
  Huda A. Kadhim et al (2018) [33] worked on the production of HMAC as per EME2
specifications. Crumb rubber has been used for the production of hard grade bitumen and
the tests conducted were Fundamental properties on bitumen, marshall, ITS ratio,
Rutting, and resilient modulus. Faarfiled software was been used for finding the fatigue
life of the entire pavement structure. Rut depth after 10,000 cycles was found as 5 mm for
HMAC. Mr for conventional mix found as 2608 MPa and for HMAC 9263 MPa. The
fatigue life of HMAC was found as 7.2 times more than a conventional mix.

 Mittal A. et al (2018) [8] produced hard grade bitumen by blending VG 30 grade bitumen
with two additives (gilsonite and high-density polyethylene homopolymer). Rut depth
after 20,000 cycles for mix prepared with hard grade bitumen was found as 1.5 mm and
3.5 mm for mix prepared with conventional VG 40 grade bitumen. Resilient modulus
(Mr) was shown higher values for mix prepared with hard grade binder.

2.5 Research Gap

From the above literature study, it has found that Vacuum residue, Gilsonite and Novolac was
been used for the production of hard grade binder. Still, no studies were explored in the
production of hard grade binder with PPA. Addition of PPA has found to stiffen the binder this
may result in decreased penetration and increased softening point of binder. From this, an
attempt was been made for the production of hard grade binder with PPA as additive. Most of the
studies were conducted with the addition of PPA up to 2% dosage. But only a few studies were
explored at higher PPA dosages. Further, no major studies were examined on aging kinetics and
morphology of PPA modified binder at higher dosages. Also, no attempts were been found on
the performance of bituminous mixes with hard grade binder. With these considerations, an
attempt was been made for the production of hard grade binder with PPA.

14
 CHAPTER – 3

METHODOLOGY
3.1 General

In the previous chapter detailed literature with discussion was been presented. This chapter
presents the adopted methodology for the present study.

3.2 Methodology

The present study was divided into 7 stages and the adopted methodology was shown in below
Figure 3.1.

3.2.1 Stages adopted in the present study to accomplish the objectives

Stage – 1: - A brief literature was collected on aging kinetics of binders, different additives for

the production of hard grade and Performance of mixes produced with hard grade

binder.

Stage – 2: - With PPA as additive hard grade binder was produced in the laboratory with a high

stirrer.

Stage – 3: - PPA modified binders were further investigated for fundamental properties,

chemical fractions, rheological studies, aging kinetics, and morphology.

Stage – 4: - Bituminous mixes were prepared with base and hard grade binder with DBM (Dense

Bituminous Macadam) – 2 gradation.

Stage – 5: - Prepared bituminous mixes were evaluated for Marshall, Indirect tensile strength,

Resilient modulus, and rutting characteristics.

Stage – 6: - Using IIT Pave a pavement section was designed for 300 msa of traffic. Different

trials were conducted for determining DBM course thickness. The inputs adopted for

IIT Pave are resilient modulus of the mix.

15
Stage – 7: - For the determined DBM course thickness cost comparison was conducted as per

standard rates given by the central public works department.

Production of hard grade binder PPA content 1.50, 2.25,

3.00, 3.75 and 4.50%

Investigation on PPA modified binders

Physical and Chemical

Rheological study
Aging (FTIR)
Morphology (SEM)

Preparation of DBM mixes with base

and HMAB

Evaluation of mix characteristics

(Marshall, ITS, Resilient Modulus and Rutting)

Determining the DBM thickness for base course using IIT Pave for long life pavement

Cost comparison for 1 km stretch

Figure 3.1 Flow chart representing the adopted methodology

16
 CHAPTER – 4

EXPERIMENTAL PROGRAMME

4.1 General

This chapter widely elaborates on the materials used and their test procedures. Different tests on
bituminous binders and mixes were performed according to Indian standards and MoRTH –
2015 specifications.

4.2 Materials

4.2.1 Bitumen
Base bitumen (VG 30) grade, used in the present study which was provided by TikiTar Industries
Mumbai. The physical properties of VG 30 grade bitumen when compared with IS 73:2013 was
presented in the below Table 4.1.
Table 4.1 Physical properties of VG 30 grade bitumen
Name of the test Test Result Specification Test Method
Penetration, (1/10th) mm 51 45 min IS 1203
Softening point, oC 53 47 min IS 1205
Absolute viscosity at 60 oC, Poises 3400 2400-3600 IS 1206 (Part II)
Kinematic viscosity at 135 oC, cSt 380 350 min IS 1206 (Part III)
Flash point, oC 225 220 min IS 1209
Solubility in trichloroethylene, Percent 99.22 99 min IS 1216
Tests on residue from Rolling thin film oven:
a) Viscosity ratio at 60 oC 2 4 max IS 1206 (Part II)
b) Ductility at 25 oC, cm 55 40 min IS 1208

4.2.2 Modifier
The modifier used for the preparation of hard grade bitumen was Polyphosphoric Acid (PPA).
PPA of grade 115% was procured from Sisco Research Laboratories Mumbai, the specific
gravity and P2O5 concentrations were 2.05 and 83.5%.

17
 Figure 4.1 Modifier used in the present study

4.2.3 Preparation of hard grade bitumen

The preparation of hard grade bitumen consists of heating base bitumen at 160 oC and PPA at
135 oC. PPA was added to the melted base bitumen and the mixture was blended in a shear
stirrer at 150 oC at 1200 RPM for 40 minutes duration as shown in below Figure 4.2. Later the
blended mixture was taken into a container and kept in airtight condition for 24 hours at 25 oC to
retain its morphology.

Figure 4.2 High shear stirrer for the blending process

18
4.3 Tests on bitumen

Base and PPA modified bitumens were tested for physical, chemical (asphaltenes and maltenes)
fractions, and aging kinetics.

4.3.1 Physical tests on bitumen

4.3.1.1 Penetration test

The test measures the consistency of bitumen and it is defined as the distance measured in 1/10th
of a millimeter when a needle penetrates under a standard load of 100 grams for a loading period
of 5 seconds. It is conducted at a standard temperature of 25 oC. and the test apparatus were
shown in the below Figure 4.3.

Figure 4.3 Penetration test on bitumen

4.3.1.2 Softening Point test

The softening point of bitumen was measured using the Ring and Ball apparatus. It measures the
temperature at which bitumen starts initiating into fluid and consistency of bitumen. The test
consists of placing a steel ball of weight around 3.5 grams over bitumen which contained in a
brass ring. Later the sample is placed in water or glycerin bath and the temperature is raised at 5
o
C per minute up to which the ball touches the bottom plate of the metallic plate. The typical
apparatus for conducting the softening point was shown in the below Figure 4.4.

19
 Figure 4.4 Softening point test on bitumen

4.3.1.3 Viscosity test

Viscosity is defined as the resistance of a fluid against applied force or resistance offered by a
fluid due to internal friction. There are two types of viscosities which are generally measured for
fluids. One is absolute viscosity and the other is kinematic viscosity of the fluid. Absolute
viscosity is defined as fluid resistance against externally applied force, whereas kinematic
viscosity is fluid resistance to flow when only gravity is acting upon it. Absolute viscosity and
Kinematic viscosity of bitumen are determined at a temperature of 60 oC and 135 oC. Generally
absolute and kinematic viscosities of bitumen can be determined by using vacuum capillary
viscometers. But in the present study, vacuum capillary viscometer is used only for the
determination of absolute viscosity of base bitumen. Kinematic viscosity of base and modified
binders was determined using Brookfield Rotational Viscometer. The determination of absolute
viscosity of bitumen by using vacuum capillary viscometer consists of determining the time
required for bitumen to flow between pre-marked points. The time multiplied by the constants of
the bulb gives the absolute viscosity of the bitumen. Determination of kinematic viscosity
consists of filling heated bitumen into chambers and placing the chamber into the Brookfield
viscometer. By rotating a standard spindle at known R.P.M it directly displays the absolute
viscosity in centipoise. Below Figure 4.5 shows the vacuum capillary viscometer and Brookfield
viscometer. The principle on which it displays viscosity is by the applied torque on the bitumen

20
its relative resistance to rotation gives viscosity. Then kinematic viscosity will be equal to
absolute viscosity at 135 oC divided by the density of the bitumen.

Figure 4.5 Absolute and Kinematic viscosity test on bitumen

4.3.1.4 Ductility test

Ductility value of bitumen is defined as the distance up to which bitumen placed in standard
briquette mould will elongate without breaking. The test is conducted at a standard temperature
of 25 + / - 2 oC at a pull rate of 50 mm / minute on three moulds. The average elongated length of
three specimens placed in briquette moulds in centimeter is taken as ductility value of bitumen.
Below Figure 4.6 shows the standard briquette mould and the ductility machine used in the
present study.

Figure 4.6 Ductility test on bitumen

21
4.3.1.5 Rolling thin film oven test
Rolling thin film oven test is used to identify the changes in properties of bitumen after subjected
to short term aging process. The test also provides a qualitative measure of loss in volatiles
during the short term aging of bitumen. The test set-up was shown in the below Figure 4.7. The
test procedure consists of pouring heated bitumen into glass bottles and immediately rotating
them in the horizontal plane and cooling for about 60 to 180 minutes. After the bottles are placed
in the RTFO oven carousel and close the door. The temperature should be maintained at 163 oC
for a period of 85 minutes. Later the residue was scrapped from the bottles and the further any
test on RTFO aged sample should be done within 72 hours.

Figure 4.7 Binders simulating to short-term aging by RTFO test

4.3.2 Chemical fractions

Bitumen broadly contains two chemical fractions as asphaltenes and maltenes. These are also
called as solid and liquid or oil phases. Maltenes fractions further consist of three phases, like
resins, aromatics and saturates. Asphaltenes and maltenes fractions are combinedly called as
SARA fractions which abbreviate as Saturates, Aromatics, Resins, and Asphaltenes. The
fractions are named as SARA which represents the increasing order of hydrocarbons.

SARA fractions can be separated by three popular methods, a) Corbett method, b) ASTM D
4124 and c) Thin-layer chromatography and flame ionization detection (Iatroscan TLC-FID). In
this Corbett and ASTM D 4124 are conducted by manually whereas TLC-FID was conducted by
the instrument. In the present study, Corbett method [35] was been used for separation of
asphaltenes and maltenes fractions. The present study is limited to separation of asphaltenes and
maltenes fractions, maltenes were further not separated into three phases. For the separation of

22
two fractions, an instrument is devised in the laboratory as shown in the below Figure 4.8. The
separation procedure consists of taking around 10 grams of bitumen into an Erlenmeyer flask and
adding 100 ml of n-heptane for each gram of bitumen. The sample was stirred while adding n-
heptane and left to stand overnight. Later the mixture was filtered through vacuum filtration with
Whatman grade – 1 filter paper. After the solids retained on paper was dried and weighted as
asphaltenes as shown in Figure 4.9. From the oil phase, n-heptane was separated by simple
distillation process as shown in Figure 4.10 and the residue was weighted as asphaltenes
fractions.

Figure 4.8 Separation of asphaltenes fractions by filtration

Figure 4.9 Residual asphaltenes on filter paper

23
 Figure 4.10 Simple distillation process for separation of maltenes fraction

Bitumen

Precipitate in n-heptane

Maltenes Solubles Filter Insolubles Asphaltenes

Figure 4.11 Flow chart for the separation of asphaltenes and maltenes fractions

4.3.3 Rheological study

Dynamic shear rheometer (DSR) is generally used to analyze the viscoelastic properties of
binders. One of the major parameter measured from rheological study is the high service
temperature of binder. It is measured as a parameter called as rutting resistance and denoted by
G*/sinδ as per ASTM D7175. In this test binders were tested for un - aged and RTFO aged
condition with a 25 – mm diameter steel plate with a gap 1 mm at frequency of 10 rad/s. Binders
were tested from 52 oC with an increment of 6 oC up to which the G*/sinδ reaches a value of
1.00 and 2.20 kPa for un - aged and RTFO aged binders. As G*/sinδ value is high the binder will

24
have more resistance towards rutting at elevated temperature. Below Figure 4.12 shows the DSR
instrument used in the present study.

Figure 4.12 Dynamic shear rheometer

4.3.4 Fourier transform infrared spectroscopy

Fourier Transform Infrared Spectroscopy is used to analyze the absorbance or emittance infrared
spectrum of materials. The wavelength of the spectrum ranges from 400 to 4000 cm-1. In this
study, FTIR was employed to quantify the degree of aging taken place after modification with
PPA and subsequent subjecting to short term aging. JASCO 4600 model was used in the present
study as shown in below Figure 4.13. The observed FTIR spectrum helps in identifying the
changes in functional groups before and after aging in bitumens. Further with the FTIR spectra,
the carbonyl index of bitumen before and after subjecting to short term aging was evaluated
using below equation 1 [35] for twelve bitumens. For the below equation 1 the area for the
centered and between the spectral bands was calculated using Origin Software.

Figure 4.13 FTIR spectroscopy instrument (JASCO 4600)

25
 Area of carbonyl band centered around 1700cm-1
Carbonyl Index: 1
∑ Area of the spectral band between 600 and 2000 cm-1

4.3.5 Morphological study

Scanning electron microscopy was conducted by using Apreo LoVac model as shown in below
Figure 4.14, un - aged VG 30 and PPA modified samples. SEM images will be generated by
scanning the surface with the high-energy focused beam. Thus scanned images will give
information on the surface topography, chemical composition, and structure of the sample. In
this study, microstructural changes in bitumen samples were magnified by 600, 1200 and 2500
times with a size of 100, 50 and 30 µm respectively.

Data storage
unit

Figure 4.14 Scanning electron microscopy instrument (Apreo LoVac model)

4.4 Tests on aggregate

Crushed natural aggregates were used in the present study which was purchased from a nearby
supplier. Aggregates were tested for their physical properties to fulfill the MoRTH - 2015
specifications for DBM course. The following tests were conducted on coarse and fine
aggregate.

26
4.4.1 Specific gravity and water absorption test
The specific gravity of aggregates can be defined as the mass of aggregates to the mass of
reference substance with equal volume. It gives an indication of the strength of aggregates and it
plays an important role in the volumetric properties of bituminous mixes.

Water absorption test on aggregates gives an identity on the porosity of aggregates. Aggregates
with high porosity are not preferred because it may degrade the pavement performance. In this
study, specific gravity and water absorption test were performed as per IS: 2386 (Part III) –
1963.

4.4.2 Impact test

Impact test on aggregates gives a relative measure on the resistance towards the sudden impact
due to heavy vehicles. This impact from vehicles on aggregates may breakdown the aggregates
into small pieces. Hence aggregates should have sufficient toughness to resist the impact loads.
In this study, the test was performed according to IS: 2386 (part IV) – 1963.

Figure 4.15 Impact test apparatus

4.4.3 Crushing test

Aggregates used in the pavement construction should be capable to resist the crushing load
imposed by the vehicles. The resistance of these aggregates towards crushing under the gradually
applied compressive load is called an aggregate crushing value. Higher the resistance then lower

27
will be the crushing value. The test is conducted as per procedure laid out in the IS: 2386 (Part
IV) - 1963.

Figure 4.16 Crushing test apparatus

4.4.4 Abrasion test

Abrasion test measures the hardness property of aggregates. Aggregates and pneumatic tyres of
vehicles subject to abrasion action after opening to traffic if the resistance of aggregates is least
towards abrasion this may lead to wearing of aggregates. The resistance of aggregates for
wearing effect is determined by the Los Angeles Abrasion test and the test is conducted in this
study as per IS: 2386 (part IV) – 1963.

Figure 4.17 Los Angeles test apparatus

4.4.5 Flakiness and Elongation index test

This test measures the relative shape of aggregates. Aggregates with flaky are elongated may
easily break under the moving load of heavy vehicles. Use of flaky and elongated aggregates
may not be desirable for achieving the better interlocking between aggregates. In this study
combined flakiness and elongation test was conducted as per IS: 2386 (part I) – 1963.

28
 Figure 4.18 Flakiness and Elongation test apparatus

4.5 Marshall mix design

Samples were cast with Marshall Mix design method with DBM – 2 gradation as per ASTM
D6927. Initially, the specific gravities of coarse aggregate, fine aggregate, filler, and bitumen
were determined as per IS 2386 – Part III and IS 1202 – 1978. Aggregates of size 26.5 mm were
replaced with 22.4 mm in this study.

Hammer

Load cell
Vertical LVDT
Marshall sample

Data acquisition
unit

Figure 4.19 Automatic compactor with Marshall testing apparatus

Aggregates were heated at 175 oC for 2 hours and bitumen was added and mixed at the pre-
determined mixing temperature. Later the sample was kept in oven up to which it attains the
desired compaction temperature. The mix was then placed in 101.6 mm diameter mould and
compacted with 4.54 kg rammer on each face with 75 blows as per ASTM D6927. Each sample
was measured for compacted height and stability corrections were applied. Samples were
allowed to cool at room temperature for 24 hours and later samples were kept in a water bath at

29
60 oC for 30 to 40 minutes duration. The samples were tested as per ASTM D6927 - Method B
(Using an automatic load and deformation recorder) as shown in below Figure 4.19. Bitumen
content corresponding to 4% air voids as per MS – 2 guidelines was considered as optimum
binder content in this study. Further, the stability, flow, and volumetric parameters were checked
to satisfy with the established requirements.

4.6 Indirect tensile strength test

Indirect tensile strength is used to determine the resistance of mixes against cracking. The test is
conducted in this study as per AASHTO T 283 with the obtained optimum binder content. ITS of
bituminous mix calculated by using below equation 2 and the test apparatus was shown in below
Figure 4.20.

ITS = 2

Where, P = Failure load in Newton

d = Diameter of the sample in mm

t = Thickness of sample in mm

Figure 4.20 ITS test apparatus

30
4.7 Resilient modulus of mixes

Resilient modulus evaluates the mechanistic property of bituminous mixes. The test was
conducted at 35 oC as per ASTM D7369. 10% of the failure load corresponding to ITS was
applied by the computer-controlled program as shown in below Figure 4.21. The vertical and
horizontal deformations for the specimens were captured through the computerized data
acquisition unit as shown in the below Figure. Below equations 3 and 4 evaluate the resilient
properties of mixes.

Hydraulic unit
Data acquisition unit

Load cell

Vertical LVDT

Horizontal LVDT

Figure 4.21 Repeated load test set-up

P(0.27 + u)
Mr = 3
t . dh

dh
u =3.59 dv 4

Where, Mr = Instantaneous resilient modulus

u = Instantaneous resilient poisons ratio

4.8 Rutting characteristics

In this study rut resistance of mixes were evaluated using wheel rutting machine as per
AASHTO T 324. The rutting machine consists of a steel wheel with a total surcharge weight of
705 N. The wheel travels for a distance of 230 mm for one pass which is approximate with a
speed of 1.46 kmph. Mixes were cast in the rectangular mould of size 40 X 30 X 5 cm using an

31
automatic slab compactor as shown in below Figure 4.22. The air temperature in this study is
considered as 35 oC.

Hydraulic unit

Surcharge load

Pressure
controller

Steel wheel

Compacted
slab

Figure 4.22 Automatic slab compactor with wheel rutting machine

32
 CHAPTER – 5

RESULTS AND DISCUSSIONS

5.1 General

In the previous chapter, several test procedures were explained on bitumen and bituminous
mixes. This chapter briefly elaborates and discuss the test results of PPA modified bitumen and
bituminous mixes.

5.2 Physical properties of base and PPA modified bitumen

The physical properties of base and PPA modified binders were shown in below Table 5.1. From
the results, it has been revealed that addition of PPA to base binder has decreased the penetration
value ranging from 51 dmm for the base binder to 23 dmm for 4.50% PPA added binder. It
indicates that the addition of PPA has stiffened the binder which significantly improves the
rutting potential of the binder. The softening point of PPA modified binders was increase with
the increasing PPA content, the addition of 4.50% PPA to base binder has shown the softening
point of 70 oC whereas base binder shown 53 oC. From this, it indicates that binder modified
with PPA will increase resistance towards temperature susceptibility.

Table 5.1 Physical properties of base and PPA modified bitumen

Type of Penetration Softening Ductility Kinematic Penetration
bitumen (dmm) (oC) (cm) viscosity (cSt) index (PI)
Base 51 53 95 380 -0.43
Base + 1.50 PPA 41 57 68 480 -0.05
Base + 2.25 PPA 38 61 49 550 0.57
Base + 3.00 PPA 35 63 36 690 0.76
Base + 3.75 PPA 31 66 25 1030 1.02
Base + 4.50 PPA 23 70 18 1160 1.06

Accordingly, the ductility value of PPA modified binders was decreased with the increasing PPA
content, this is due to the stiffening of a binder. However, for 4.50% PPA modified binder the
ductility value found as 18 cm which is more than the minimum required ductility value of 10

33
cm for hard grade binder [2]. The kinematic viscosity of PPA modified binders was increased
with increasing PPA content. This may be due to the increase in asphaltenes content in PPA
modified binders, as asphaltenes are the viscosity builders in binder [22]. The penetration index
(PI) of base and PPA modified binders were calculated using Pfeiffer and Van Doormaal formula
i.e.,
20 - 500A (log 800 - log )
PI = ,A=
1 + 50A ( - 25)

Increase in PPA content has shown the increased PI values of binders. The PI range for binders
was – 3 for highly temperature susceptible binders and + 7 for highly low temperature
susceptible binders. PI of PPA modified binders were within the stipulated range. The required
properties of hard grade bitumen were shown in below Table 5.2. When compared with PPA
modified binders, base binder modified with 4.50% PPA has satisfied with the required values
for hard grade binder.
Table 5.2 Specifications of hard grade binder
Property Required value for hard grade binder
Penetration (1/10th) mm 15 – 25
Softening oC 55 – 71
Viscosity at 135 oC cSt ≥ 550

5.3 Effects of PPA addition on physical properties

Penetration retention rate (PRR), Softening point increment (SPI), Retained ductility (RD) and
Viscosity increment (VI) are considered for determining the effects of PPA addition on physical
properties of bitumens. These four parameters were computed from below formulas 5 to 8 and
the effects were shown in below Figure 5.1.

Penetration value of the modified bitumen

PRR = Penetration value of unmodified bitumen 5

SPI = Softening point of modified bitumen – Softening point of unmodified bitumen 6

Ductility value of the modified bitumen

RD = Ductility value of unmodified bitumen 7

34
VI = Viscosity of modified bitumen- Viscosity of unmodified bitumen 8

From Figure 5.1 it was observed that the addition of 4.50% PPA to base bitumen has shown
more influence on physical properties rather than 1.50 - 3.75% addition. PRR for a PPA content
increment from 3.75 to 4.50% PPA has decreased twice when compared with other incremental
percentages. While softening point increment was shown linearity with the increase in PPA
content. Increase in PPA content has decreased the retained ductility of bitumens. Viscosity
increment was increased drastically for increment in PPA from 3.75 to 4.50%. From this, it is
evident that the addition of 1.50 - 3.75% PPA has shown a slightly lower effect on physical
properties whereas 4.50% PPA content has shown a significant effect on physical properties.

90 18

16

80 14
Softening Point Increment (oC)
Penetration Retention Rate (%)

12
70 10

8
60
6

4
50
2

0
40
1.50 2.25 3.00 3.75 4.50
1.50 2.25 3.00 3.75 4.50
Percentage of PPA
Percentage of PPA

80 900

800
70
700
60
Viscosity Increment (Cst)
Retained Ductility (%)

600
50
500
40
400
30
300
20 200

10 100

0 0
1.50 2.25 3.00 3.75 4.50 1.50 2.25 3.00 3.75 4.50
Percentage of PPA Percentage of PPA

Figure 5.1 Effects of PPA addition on physical properties

35
5.4 Asphaltenes and maltenes fractions of base and PPA modified bitumen

From the experimental results as shown in below Table 5.3 it is clearly found that the increase in
PPA content has increased the asphaltenes content of bitumen. The increase in asphaltenes
concentration may be due to the conversion of resins into asphaltenes. Also, the maltenes
fractions were decreased, this may be due to the shift of saturates and aromatics to resins [14,
22].
Table 5.3 Asphaltenes and Maltenes fractions of bitumen
Name of the bitumen Asphaltenes (%) Maltenes (%)
Base 16 84
Base + 1.50 PPA 21 79
Base + 2.25 PPA 24 76
Base + 3.00 PPA 26 74
Base + 3.75 PPA 28 72
Base + 4.50 PPA 32 68

5.5 Rheological study results

Dynamic Shear Rheometer (DSR) test was carried on PPA modified binder for evaluating the
performance at high service temperature. The basic condition for determining the high service
temperature of binders is the G*/sinδ value shall be a minimum of 1.00 kPa for un – aged binder
and for RTFO aged binder the G*/sinδ value should be minimum of 2.20 kPa. Table 5.4
summarizes the obtained G*/sinδ values for base and modified binders corresponding to un –
aged and RTFO aged condition. Addition of PPA to base binder has shown the enhanced high
temperature grade of binders. Base binder modified with 3.75 and 4.50% PPA has shown a high
service temperature of 76 oC.
Figure 5.2 graphically represents the rutting resistance of binders when tested at 70 oC. Base
binder when modified with PPA has shown increased G*/sinδ parameter which indicates that the
PPA modified binders has increased resistance towards rutting.

36
 Table 5.4 Rheological parameters of base and PPA modified binders
Name of the G*/sinδ minimum, 1.00 kPa for un-aged High
bitumen and 2.20 kPa for RTFO aged binder Performance
Un-aged RTFO aged grade
Base 1.589 2.214 PG 64 – XX
Base + 1.50 PPA 1.314 2.497 PG 70 – XX
Base + 2.25 PPA 1.554 3.332 PG 70 – XX
Base + 3.00 PPA 1.771 3.724 PG 70 – XX
Base + 3.75 PPA 1.019 2.711 PG 76 – XX
Base + 4.50 PPA 1.067 2.993 PG 76 – XX
Note: - Above values are corresponding to passing temperature

6 Un-aged RTFO aged

G*/sinδ in KPa at 70 oC @ 10 rad/s

0
0.00 PPA 1.50 PPA 2.25 PPA 3.00 PPA 3.75 PPA 4.50 PPA
Percentage of PPA

Figure 5.2 Rutting parameter of base and PPA modified binders

37
5.6 Fourier transform infrared spectroscopy analysis

FTIR spectroscopy test was carried for a total of twelve bitumens of un - aged and RTFO aged in
nature. The spectral absorbance ranging from 400 to 2000 cm-1 for six bitumens with their
corresponding RTFO aged absorbance spectrum was shown in Figure 5.3. The reason for
selecting the specified bandwidth is to clearly fingerprint the effect of short term aging on
changes in functional groups. From the spectral absorbance, it has found that short term aging
has not created any new functional groups. The only difference between un - aged and aged
bitumens was the changes in the intensities of absorbance.
1.0
1.0 1.0
1.0
Un-aged
Un-aged RTFO aged
RTFO aged Un-aged
Un-aged RTFOaged
RTFO aged

0.8
0.8 0.8
0.8
(a.u.)

(a.u.)
Absorbance(a.u.)

Absorbance(a.u.)
0.6 0.6
0.6 0.6
Absorbance

Absorbance

0.4 0.4
0.4 0.4

0.2 0.2
0.2 0.2

0.0 0.0
0.0 400 600 800 1000 1200 1400 1600 1800 2000 0.0 400 600 800 1000 1200 1400 1600 1800 2000
400 600 800 1000 1200 1400 1600 1800 2000 400 600 800 1000 1200 1400
-1 1600 1800 2000
Wavenumber (cm-1) Wavenumber (cm )
Wavenumber (cm-1) Wavenumber (cm-1)
a) Base b) 1.50 PPA
a) Base b) 1.50 PPA
1.0 1.0
1.0 Un-aged RTFO aged 1.0 Un-aged RTFO aged
0.9 0.9
Un-aged RTFO aged Un-aged RTFO aged
0.9 0.9
0.8 0.8
0.8 0.8
0.7 0.7
(a.u.)(a.u.)

(a.u.)(a.u.)

0.7 0.7
0.6 0.6
Absorbance

Absorbance

0.6 0.6
0.5 0.5
Absorbance

Absorbance

0.5 0.5
0.4 0.4
0.4
0.3 0.4
0.3

0.3
0.2 0.3
0.2

0.2
0.1 0.2
0.1

0.1
0.0 0.1
0.0
400 600 800 1000 1200 1400 1600 1800 2000 400 600 800 1000 1200 1400 1600 1800 2000
0.0 0.0
Wavenumber (cm-1) Wavenumber (cm-1)
400 600 800 1000 1200 1400 1600 1800 2000 400 600 800 1000 1200 1400 1600 1800 2000
Wavenumber (cm-1)
c) 2.25 PPA d) 3.00 (cm
Wavenumber PPA
) -1

1.0
c) 2.25 PPA 1.0
d) 3.00 PPA
Un-aged RTFO aged Un-aged RTFO aged
1.0 0.9
1.0

0.8 Un-aged RTFO aged 0.8 Un-aged RTFO aged

0.9

0.8 0.7
0.8
(a.u.) (a.u.)

(a.u.) (a.u.)

0.6 0.6
0.7
Absorbance

Absorbance

0.5
0.6 0.6
38
Absorbance

Absorbance

0.4 0.4
0.5
0.3
0.4 0.4
0.2 0.2
0.3
0.1
0.2 0.2
 0.1 0.1

0.0 0.0
400 600 800 1000 1200 1400 1600 1800 2000 400 600 800 1000 1200 1400 1600 1800 2000
Wavenumber (cm-1) Wavenumber (cm-1)

c) 2.25 PPA d) 3.00 PPA

1.0 1.0
Un-aged RTFO aged Un-aged RTFO aged
0.9

0.8 0.8

0.7
Absorbance (a.u.)

Absorbance (a.u.)
0.6 0.6

0.5

0.4 0.4

0.3

0.2 0.2

0.1

0.0 0.0
400 600 800 1000 1200 1400 1600 1800 2000 400 600 800 1000 1200 1400 1600 1800 2000
Wavenumber (cm-1) Wavenumber (cm-1)

e) 3.75 PPA f) 4.50 PPA

Figure 5.3 Spectral absorbance graphs of base and PPA modified binders

The carbonyl index as shown in equation 1 was used for quantifying the bitumen aging
characteristics. The area for evaluating the index was calculated using Origin software. The
calculated carbonyl index of un - aged and aged bitumens was shown in the below Figure 5.4.
The carbonyl index centered at 1700 has been considered as an aging factor by previous authors
(18, 23) for PPA modified bitumens. It has been observed that the addition of PPA has decreased
the carbonyl content in modified bitumen when compared with the base bitumen. From, the
previous researches also similar findings were been observed (18, 23). After the bitumens were
subjected to short term aging the carbonyl index was increased this is due to the absorption of
oxygen during the aging process. Higher the increase in carbonyl index after aging indicates the
more absorption of oxygen which seriously indicates a higher degree of aging (24). From the
experimental results, an increase in PPA content has shown increased carbonyl index of
bitumens. Addition of 4.50% PPA has shown carbonyl index of 0.0268, whereas for base
bitumen it has shown 0.0306. When compared with short term aged bitumens all samples have
shown increased carbonyl index which is due to absorption of oxygen during the aging process.
The percentage increase in carbonyl index after subjecting to short term aging were found as
0.98, 11.85, 2.27, 3.91, 5.04 and 2.61 % for the base, 1.5 PPA, 2.25 PPA, 3.0 PPA, 3.75 PPA and
4.50% PPA modified bitumen. From this, the hard grade bitumen produced with the addition of
4.50% PPA to base bitumen has found a lesser percentage increase in carbonyl index but very
closer to the 2.25% PPA modified bitumen.

39
 0.035
Un-aged RTFO aged

0.030
Carbonyl Index

0.025

0.020

0.015
0.00 PPA 1.50 PPA 2.25 PPA 3.00 PPA 3.75 PPA 4.50 PPA
Percentage of PPA

Figure 5.4 Carbonyl index of base and PPA modified binders

5.7 Morphology analysis

Scanning Electron Microscopy images were used to study the microstructural changes of base
and PPA modified bitumen. Figure 5.5 (a to f) depict the captured images from SEM with three
magnifications as 600, 1200 and 2500 times. The SEM image of the base bitumen as shown in
Figure 5.5a appears as rough with some fine and coarser particles are distributed unevenly over
the surface, whereas with the addition of PPA the surface is changed to smooth and the particles
are disappeared. The addition of 1.50% PPA to base bitumen has exhibited clustered and
overlapped phases. Further increase in PPA content has decreased the clusters and improved the
surface homogeneity of the bitumen. Addition of 4.50% PPA has improved the morphology to
homogeneous when compared with other binders.

(a) Base bitumen with 600x, 1200x and 2500x magnifications

40
(b) Base and 1.50% PPA modified bitumen with 600x, 1200x and 2500x magnifications

(c) Base and 2.25% PPA modified bitumen with 600x, 1200x and 2500x magnifications

(d) Base and 3.00% PPA modified bitumen with 600x, 1200x and 2500x magnifications

(e) Base and 3.75% PPA modified bitumen with 600x, 1200x and 2500x magnifications

41
 (f) Base and 4.50% PPA modified bitumen with 600x, 1200x and 2500x magnifications
Figure 5.5 SEM images for base and modified binders

5.8 Marshall test results

In the present experimental study DBM – 2 gradation was considered and samples were cast as
per ASTM D6927. For the preparation of mixes, crushed natural aggregates were procured from
a nearby quarry and the physical properties when tested as per Indian Standards were shown in
below Table 5.5. Midpoint method was adopted as per MoRTH - 2015 specifications and the
below Figure 5.6 shows the considered gradation with an upper limit, lower limit, and the
selected mid limit.

Table 5.5 Properties of aggregates

Property Result MoRTH Specifications Test Method

(Maximum)
Specific gravity (Coarse aggregate) 2.63 - IS 2386 Part 3
Specific gravity (Fine aggregate) 2.61 - IS 2386 Part 3
Water absorption (%) 0.4 2%
Aggregate Impact value (%) 16 27% IS 2386 Part 4
Abrasion value (Los Angeles) (%) 21 35% IS 2386 Part 4
Combined index (F & E) (%) 19 30% IS 2386 Part 1

42
 100
Upper limit Lower limit Mid value
90

80

70

60

% Passing
50

40

30

20

10

0
0.01 0.1 1 10 100
Sieve Size (mm)

Figure 5.6 DBM - 2 Gradation as per MoRTH – 2015 specifications

5.8.1 Mixing and compaction temperature of bitumen

Brookfield rotational viscometer (DV-E model) was used in the present study for determining
the temperature versus viscosity relationship of base and laboratory-developed hard grade
bitumen. The viscosity of two bitumens was determined from 125 oC to 195 oC with an
increment of 10 oC and it is shown in the below Figure 5.7. The mixing and compaction
temperatures corresponding to 0.17 and 0.28 Pa.s for two bitumens were tabulated in below
Table 5.6.

1.0
0.9 Virgin Hard grade bitumen
0.8
0.7
0.6

0.4
Viscosity Pa.s

0.3
Compaction Temperature

0.2
Mixing Temperature

0.1

110 120 130 140 150 160 170 180 190 200
o
Temperature C

Figure 5.7 Temperature versus Viscosity

43
 Table 5.6 Mixing and Compaction Temperatures of two binders
Description Base HMAB
o
Mixing temperature C (0.17 Pa.s) 163 186
Compaction temperature oC (0.28 Pa.s) 145 175

5.8.2 Preparation of mixes

For the preparation of mixes initially, aggregates were heated at 175 oC for 2 hours and later the
bitumen was added and the mixture was mixed at the pre-determined mixing temperature. Later
the sample was kept in oven up to which it attains the desired compaction temperature. On each
face of the sample, 75 blows were applied in accordance with ASTM D6927. Bitumen content
corresponding to 4% air voids as per MS – 2 guidelines was considered as optimum binder
content in this study. Further, the stability, flow, and volumetric parameters were checked to
satisfy with the established requirements as per MoRTH - 2015 guidelines.

Table 5.7 Marshall parameters for mix prepared with base binder
Percentage Stability Bulk density Percentage Flow (mm) VFB (%) VMA (%)
of bitumen (kN) (g/cc) of air voids
4.5 13.27 2.313 5.25 3.25 69.13 17.01
5.0 16.09 2.323 4.43 3.47 72.02 15.82
5.5 14.51 2.331 3.58 4.13 77.12 15.65
6.0 12.99 2.314 3.35 5.45 80.18 16.92
6.5 11.14 2.287 3.03 5.95 82.53 17.35

Table 5.8 Marshall parameters for mix prepared with 4.50% PPA modified binder
Percentage Stability Bulk density Percentage Flow (mm) VFB (%) VMA (%)
of bitumen (kN) (g/cc) of air voids
4.5 14.14 2.315 5.55 3.15 67.00 16.82
5.0 17.29 2.325 4.75 3.25 69.82 15.74
5.5 15.97 2.335 3.93 3.68 74.79 15.57
6.0 13.99 2.316 3.55 4.25 78.40 16.45
6.5 12.80 2.292 3.36 4.45 80.35 17.12

44
The marshall parameters for base and PPA modified binder were tabulated in above Table 5.7
and 5.8 and also the value of each respective sample was summarized in Appendix A and B.
Marshall plots were graphically presented in the below Figure 5.8. Bitumen content
corresponding to 4% air voids for two mixes were evaluated from graphs and further 3 samples
were cast for each mix and tested for Marshall stability, flow value, bulk specific gravity and
volumetric properties. Below Table 5.9 shows the obtained test results for two mixes
corresponding to 4% air voids which are satisfied with MoRTH - 2015 requirements. From the
results, it was revealed that the marshall parameters were satisfied with the established
requirements as specified in MoRTH - 2015. The stability of mix produced with HMAB has
found higher than base mix. However, flow value is found lower for HMAC. This may be due to
higher stiffness offered by the mix.

Table 5.9 Marshall parameters for base and HMAC mixes corresponding to 4% air voids
Property Base HMAC MoRTH - 2015
Specifications
Bitumen content (%) 5.27 5.46 Min 4.5
Stability (kN) 15.16 16.14 Min 9
Flow (mm) 3.73 3.51 2–4
VMA (%) 15.60 15.48 Min 12
VFB (%) 73.10 73.36 65 – 75
Bulk density (g/cc) 2.325 2.331 -

18 2.35
Base 4.50 % PPA Base 4.50 % PPA
17 2.34

16
2.33
Bulk Density (g/cc)

15
Stability (kN)

2.32
14
2.31
13
2.30
12

11 2.29

10 2.28
4.5 5.0 5.5 6.0 6.5 4.5 5.0 5.5 6.0 6.5
Percentage of bitumen Percentage of bitumen

6.0 7.0
Base 4.50 % PPA Base 4.50 % PPA
45 6.5
5.5

6.0
5.0
air voids

5.5
m)

4.5
 2.30
12

11 2.29

10 2.28
4.5 5.0 5.5 6.0 6.5 4.5 5.0 5.5 6.0 6.5
Percentage of bitumen Percentage of bitumen

6.0 7.0
Base 4.50 % PPA Base 4.50 % PPA
5.5 6.5

6.0
5.0
Percentage of air voids

5.5

Flow (mm)
4.5
5.0
4.0
4.5
3.5
4.0

3.0 3.5

2.5 3.0
4.5 5.0 5.5 6.0 6.5 4.5 5.0 5.5 6.0 6.5
Percentage of bitumen Percentage of bitumen

90 18.0
Base 4.50 % PPA Base 4.50 % PPA
17.5
85
Voids in mineral aggregate (%)
Voids filled with bitumen (%)

17.0
80

16.5

75
16.0

70
15.5

65 15.0
4.5 5.0 5.5 6.0 6.5 4.5 5.0 5.5 6.0 6.5
Percentage of bitumen Percentage of bitumen

Figure 5.8 Marshall parameters of bituminous mixes

5.9 Indirect tensile strength

For determining the indirect tensile strength of mixes three samples were cast for each individual
mix with the obtained optimum binder content. The average ITS value of three samples for base
and HMAC was found as 1.10 and 1.45 MPa and shown in below Figure 5.9. It has found that
the ITS of mix prepared with HMAB was 1.32 times higher than base mix.

46
 1.8

1.6

Indirect tensile strength (MPa)

1.4

1.2

1.0

0.8

0.6

0.4
Base 4.50 % PPA

Figure 5.9 Indirect tensile strength of bituminous mixes

5.10 Resilient modulus of mixes

The resilient modulus of mixes was determined by applying repeated load in haversine form at
35 oC. The test was conducted up to 500 cycles and the 5 cycles after 100 cycles were considered
for calculating the resilient modulus of the bituminous mix. The resilient modulus results were
tabulated in below Table 5.10. The resilient modulus of HMAC has shown 1.98 times higher
than base mix. This can subsequently increase resistance to rutting and fatigue in the base course
and also reduces the thickness of the layer.
Table 5.10 Resilient modulus parameters
Type of bituminous Test Load Horizontal Resilient modulus
mix temperature (oC) (N) deformation (um) in (MPa)
Base 35 1100 6.15 1746
HMAC 35 1450 4.27 3310

5.11 Rutting characteristics of bituminous mixes

Base and HMAC were evaluated for the rutting as per AASHTO T 324. With the obtained OBC
for the base and HMAC two slabs of size 40 X 30 X 5 cm were cast using automatic compactor
and after 24 hours the slabs were tested for rut depth in dry condition. Two slabs were subjected
to 20,000 cycles with a load of 705 N. Rut depth of two slabs after each 500 cycles were
summarized in Appendix C and graphically presented in the below Figure 5.10. HMAC have

47
shown more resistance towards rutting when compared with the base mix. The rut depth of
HMAC and the base mix has found 3.88 mm and 6.50 mm respectively after 20,000 cycles.

0
1 Base 4.50 % PPA

2
3.88
3
Rut depth in (mm)

6.50
4
5
6
7
8
9
10
0 4000 8000 12000 16000 20000
Number of cycles

Figure 5.10 Number of cycles versus rut depth in (mm)

5.12 Design of pavement section for heavily trafficked road as per IRC: 37-2018 guidelines

As per IRC: 37-2018 guidelines a pavement section was designed for traffic of 300 msa. For
attaining 300 msa of design traffic the allowable vertical compressive strain at top of sub – grade
and the allowable horizontal tensile strain in bottom of bituminous layer was computed by below
equations 9 and 10 as per IRC: 37-2018 guidelines. For attaining strains less than the allowable
limits a trial section was considered and designed using IIT Pave, the design inputs were
tabulated in below Table 5.11. CBR value of sub-grade was considered as 8% and thickness of
granular layer as 450 mm. For bituminous layers the surface course (BC) thickness is kept
constant as 50 mm and the base course (DBM) thickness is computed by conducting several
trials using IIT Pave. Below Table 5.12 shows the allowable and computed strains and the
corresponding pavement composition. Figure 5.11a and 5.11b pictorially represents the
computed pavement composition when base and HMAB used in DBM mixes respectively. From
the Figure 5.11 the use of HMAB in base course has reduced the DBM thickness by 40 mm. The

48
reduction in 40 mm in bituminous layer will saves materials like aggregates and especially the
reduced usage of large amount of bitumen.
NR = 1.4100 * 10-08 * [1/εv] 4.5337 (for 90% reliability) -9

Nf = 0.5161 * C * 10-04 * [1/εt] 3.89 * [1/MRm] 0.854 (for 90% reliability) - 10

Table 5.11 Design inputs for IIT Pave

Type of bituminous mix
Type of Base HMAC
course Resilient Poisson’s ratio Resilient Poisson’s ratio
modulus (MPa) modulus (MPa)
B.C 1746 0.35 1746 0.35
DBM 1746 0.35 3310 0.35
Granular 208 0.35 208 0.35
Sub-grade 66 0.35 66 0.35

Table 5.12 Allowable and computed strains for design traffic of 300 msa
Type of bituminous Horizontal tensile strain Vertical compressive strain
mix Allowable Computed Allowable Computed
Base 0.000118 0.000117 0.000250 0.000190
HMAC 0.000103 0.000102 0.000250 0.000195

B.C D.B.M Granular

50 mm
50 mm
240 mm 200 mm

450 mm 450 mm

a) b)

Figure 5.11 Pavement composition with base and HMAC in DBM mix

49
5.13 Cost analysis

Further, with the obtained pavement composition cost analysis was carried out. For the analysis
only DBM course i.e., 240 and 200 mm for base and HMAC was considered because the B.C
and granular layer thickness will be same for both types of sections. In this only materials cost
was considered and the standard rates were taken from the recent schedule of rates (2018) of
central public works department. Below Table 5.13 shows the cost comparison for pavement
with 4 - lane highway for 1 kilometer of road stretch for a designed traffic of 300 msa. From the
below results, it has been observed that pavement constructed with HMAB in DBM course has
increased the cost for 1 cum quantity, whereas for 1 km road stretch the cost has decreased by
33.10 lakhs which is equal to 12.33%.

Table 5.13 Cost comparison for two types of DBM courses for 1 km road stretch
Type of bituminous Volume for 1 km Cost per 1 cum Cost for 1 km road
mix stretch (Rupees) stretch (Lakhs)
Base 4080 6575.67 268.28
HMAB 3400 6917.08 235.18
Net savings (Lakhs) 33.10
Percentage savings 12.33

50
 CHAPTER – 6

CONCLUSIONS

6.1 General

This chapter describes on the conclusions made from this study. Conclusions were been
elaborated on the effect of PPA addition on bitumen properties, aging kinetics and morphology.
The performance of mixes with HMAB was also elaborated in this chapter.

6.2 Conclusions

 Addition of PPA to base binder has shown decreased penetration, increased softening
point, decreased ductility and increased viscosity, this indicates the stiffening effect on
base binder with PPA addition.
 Asphaltenes fractions of PPA modified binder were found to increase with increase in
PPA content this may be due to formation of asphaltenes network in maltenes phase.
 Addition of 4.50% PPA has shown much effect on physical rather than 1.50 to 3.75%
PPA addition.
 Rutting parameter (G*/sinδ) was increased with the increase in PPA content. The high
service temperature of binders was found to increase with the increase in PPA content.
 3.75 and 4.50% PPA modified binder has shown high service temperature of 76 oC, but
4.50% PPA modified binder has shown high G*/sinδ value when compared with other
PPA modified binders.
 FTIR studies revealed that there is no any new functional groups were formed after
modification with PPA and consequent subjecting to short term aging.
 The carbonyl indexes of PPA modified bitumens were found lower than un-modified
bitumen. The percentage increase in carbonyl index after aging for PPA modified
bitumens were found least for 2.25% PPA modified bitumen.
 SEM images clearly evident that fine and coarser particles found in the un-modified
bitumen were dispersed after PPA modification. Clusters present in 1.5% PPA modified
bitumen were changed to homogeneous surface with the addition of 4.5% PPA.
 Mixes prepared with HMAB was found improved marshall parameters when compared
with base mix.

51
 Indirect tensile strength of mix prepared with HMAB was found 1.32 times higher than
base mix.
 Resilient modulus of mixes when tested at 35 oC was found as 3310 and 1746 MPa for
mixes prepared with HMAB and base binder. From this study, mix with HMAB was
approximately twice the mix prepared with base binder.
 Rut depth for bituminous mixes prepared with HMAC was found as 3.88 mm and for
base mix it is 6.50 mm. The difference between rut depths for two mixes was obtained as
2.62 mm.
 Pavement section designed for traffic of 300 msa with HMAC was found to decrease the
thickness of base course by 40 mm when compared with base mix.
 Pavement designed with HMAC in DBM course has reduced the materials cost by 33.10
lakhs which is equal to 12.33% savings.

6.3 Future scope

 A comparative study can be conducted on hard grade bitumen produced with different
additives like gilsonite, polyolefin with PPA.
 Low temperature and MSCR test can be conducted on PPA modified binders.
 Aging kinetics can be reduced by using anti-aging additives.
 Rheological study can be conducted on hard grade bitumen produced with PPA.
 Reclaimed asphalt pavements and recycled aggregates can be utilized for producing
HMAC.
 Fatigue life of produced HMAC can be further studied at different temperatures.

52
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57
 APPENDICES

Appendix A - Marshall parameters for mix prepared with base binder

Percentage Stability Bulk density Percentage Flow VFB VMA

of bitumen (kN) (g/cc) of air voids (mm) (%) (%)
12.50 2.298 5.74 3.12 68.24 16.71
4.5
13.34 2.336 5.02 2.99 70.08 16.91
13.98 2.304 4.98 3.65 69.08 17.41
16.05 2.318 4.44 3.48 72.14 16.03
5.0
17.04 2.312 4.61 3.18 71.37 15.92
15.18 2.338 4.24 3.75 72.54 15.50
15.07 2.321 3.61 3.75 76.92 15.64
5.5
13.94 2.332 3.44 4.50 78.06 15.57
14.51 2.339 3.70 4.14 76.38 15.73
14.15 2.313 3.69 5.66 80.10 17.07
6.0
10.85 2.325 2.91 5.32 80.80 16.74
13.96 2.305 3.46 5.37 79.64 16.95
11.98 2.274 3.72 5.52 81.67 17.72
6.5
10.38 2.303 3.16 6.23 83.12 17.31
11.05 2.284 2.21 6.09 82.79 17.02

58
 Appendix B - Marshall parameters for mix prepared with 4.50% PPA modified binder

Percentage Stability Bulk density Percentage Flow VFB VMA

of bitumen (kN) (g/cc) of air voids (mm) (%) (%)
14.34 2.292 5.31 3.12 67.14 16.83
4.5
14.11 2.336 5.48 2.99 67.04 16.98
13.98 2.317 5.87 3.35 66.83 16.64
16.26 2.327 4.62 3.28 69.88 15.68
5.0
18.12 2.331 4.57 3.14 70.65 15.55
17.48 2.318 5.07 3.32 68.92 16
15.84 2.328 4.02 3.88 74.46 15.69
5.5
16.11 2.349 3.77 3.62 75.87 15.42
15.96 2.328 3.99 3.54 74.04 15.61
14.15 2.321 3.59 4.28 78.41 16.77
6.0
13.85 2.311 3.71 4.09 77.97 16.06
13.96 2.317 3.36 4.37 78.82 16.52
12.98 2.298 3.62 4.62 79.83 17.48
6.5
12.38 2.309 3.26 4.43 80.25 17.21
13.05 2.269 3.21 4.29 80.96 16.66

59
 Appendix C - Rut depth of base and HMAC mixes after every 500 cycles

Number of cycles Rut depth in (mm) for base mix Rut depth in (mm) HMAC mix
0 0 0
500 1.14 1.05
1000 1.32 1.18
1500 1.45 1.27
2000 1.65 1.38
2500 1.79 1.52
3000 1.86 1.57
3500 1.99 1.61
4000 2.12 1.63
4500 2.28 1.64
5000 2.41 1.64
5500 2.65 1.66
6000 2.91 1.77
6500 3.38 1.87
7000 3.60 1.89
7500 3.81 1.93
8000 3.96 2.03
8500 4.05 2.11
9000 4.29 2.13
9500 4.50 2.27
10000 4.51 2.43
10500 4.61 2.61
11000 4.73 2.66
11500 4.79 2.71
12000 4.83 2.80
12500 4.96 2.95
13000 5.18 3.04
13500 5.30 3.06

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14000 5.41 3.15
14500 5.54 3.17
15000 5.66 3.25
15500 5.79 3.31
16000 5.85 3.36
16500 5.97 3.45
17000 6.13 3.51
17500 6.22 3.55
18000 6.27 3.61
18500 6.36 3.66
19000 6.38 3.73
19500 6.46 3.81
20000 6.50 3.88

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 PUBLICATIONS

Title of the paper Name of the Journal Status of the paper

Design of Bituminous Mixes for International Journal of
Published
Heavily Trafficked Roads – A Boon Technical Research &
to Indian Roads Science
Laboratory Study on Physical
Construction and Building Under Review
Properties, Aging Kinetics and
Materials
Morphology of Hard Grade Bitumen
Produced with PPA Addition

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DESIGN OF BITUMINOUS MIXES FOR

HEAVILY TRAFFICKED ROADS – A BOON
TO INDIAN ROADS
G Sandeep Reddy1 and Penki Ramu2

E-Mail Id: sandeepreddy974@gmail.com

1
M.Tech Student, Civil Engineering Department, V.N.R Vignana Jyothi Institute of Engineering and
Technology, Hyderabad, Telangana, India
2
Assistant Professor, Civil Engineering Department, V.N.R Vignana Jyothi Institute of Engineering and
Technology, Hyderabad, Telangana, India

Abstract-

A large number of road construction projects are currently under design and construction stage in India. If these
projects are constructed with high modulus bituminous mixes then there will be a huge amount of savings in
materials, reduced maintenance cost and increased service life of the pavement. High modulus bituminous mixes can
be produced by using hard grade bitumen. The present experimental study aims at production of hard grade bitumen
with PPA as modifier for the preparation of high modulus bituminous mixes. Bituminous mixes were prepared with
Dense Bituminous Macadam (DBM) gradation for both conventional and laboratory produced hard grade bitumen.
The tests conducted on prepared mixes were Marshall stability, Indirect tensile strength (ITS) and Resilient modulus
(Mr). From the test results the optimum binder content was found as 5.27 % and 5.46 % for virgin and hard grade
bituminous mixes. The marshall stability and ITS of mixes prepared with hard grade bitumen was found as 1.14 and
1.32 times higher than the virgin bituminous mixes. Resilient modulus at 35 oC found as 3310 MPa for mix prepared
with hard grade bitumen and 1746 MPa for the virgin mix. Further, a pavement section was designed for 300 msa as
per IRC: 37-2018 guidelines by using IIT Pave. After conducting several trials in IIT Pave the thickness of the base
course is decreased by 40 mm by considering the bituminous mix prepared with hard grade bitumen.

Keywords- Hard grade bitumen, High modulus mix, Marshall stability and Resilient modulus .

1. INTRODUCTION
At present in India, a massive amount of road construction projects are undergoing under various schemes. Most of
the pavements constructed under them are flexible in nature and their performance is most important for the
effective service life of the pavement. If these pavements are constructed with high modulus bituminous mix in the
base course then there will be an increase in performance of pavement and thus saves material and maintenance cost
(1). These savings in material and maintenance can be used for other road projects. Several research works (2 - 4),
has reported that the construction of flexible pavement with high modulus bituminous mixes in the base course will
effectively reduce the failures in pavement and also increases the service life of the pavement. These high modulus
bituminous mixes can be produced by using hard grade bitumen which can resist rutting and fatigue in the pavement
(5, 6). In the year 1990 France has developed Enrobe a Module Eleve (EME) technology for heavily trafficked
roads. Generally, Enrobe a Module Eleve is hot mix asphalt (HMA) prepared with a bitumen of 10/20 or 15/25
penetration (7). Later, South Africa and Australia have developed their known hard grade bitumens for the
development of high modulus mixes for high volume roads (8). From their study, it has found that the mixes
produced with such hard bitumen increased the modulus of mixes and resistance to rutting and fatigue (9). However,
such a high modulus layer will also strengthen the pavement and protect the underneath layers by heavy volumes
(10).

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Polyphosphoric Acid (PPA) is one of the commonly used stiffener for the production of hard grade bitumen. PPA
was first added to the bitumen in the year 1973. Studies conducted from past researchers (11, 12) revealed that
addition of PPA as modifier has shown a hardening effect on bitumen. Bitumen modified with PPA has shown
decreased penetration and increased softening point. Also, (13) has revealed that the PPA modified bitumen has
increased the high-performance grade (PG) without much decreasing the low PG grade.

The aim of the present study is to develop a high modulus bituminous mixes for heavily trafficked roads. In this
study, hard grade bitumen was developed in the laboratory with PPA as a modifier. The properties of bituminous
mixes studied were Marshall parameters, ITS and Mr. Finally, a pavement section was designed with high modulus
bituminous mix as a base course in IIT Pave.

2. MATERIALS AND METHODS

2.1 Bitumen

Bitumen of VG 30 grade provided by TikiTar industries Mumbai was used in the present investigation as virgin
bitumen. Polyphosphoric acid (PPA) of grade 115 % was procured from Sisco research laboratories Mumbai was
used as a modifier to the bitumen. The hard grade bitumen was developed in the laboratory by heating virgin
bitumen to 160 oC. PPA was also heated at 135 oC and added to virgin bitumen, later the prepared mixture was
blended for 40 minutes at 1200 R.P.M.

2.2 Aggregates

For the present experimental work aggregates were procured from nearby quarry and the physical properties were
shown in below Table 2.1. Bituminous mixes were prepared with DBM - 2 gradation and midpoint method was
adopted as per MORTH 5th specifications. The gradation of DBM - 2 was shown in below Fig. 2.1 with an upper
limit, lower limit and the considered mid limit.

Table-2.1 Properties of Aggregates

Property Result MORTH Specifications (Maximum) Test method

Aggregate Impact value 16 % 27 % IS 2386 Part 4
Abrasion value (Los Angeles) 21 % 35 % IS 2386 Part 4
Combined index (F & E) 19% 30 % IS 2386 Part 1
Specific gravity 2.63 - IS 2386 Part 3

100
Upper limit Lower limit Mid value
90

80

70

60
% Passing

50

40

30

20

10

0
0.01 0.1 1 10 100
Sieve Size (mm)

Fig.2.1 DBM - 2 Gradation as Per MORTH 5th Specifications

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2.3 Mixing and compaction temperature of bitumen

Brookfield rotational viscometer (DV-E model) was used in the present study for determining the temperature
versus viscosity relationship of virgin and laboratory developed hard grade bitumen. The viscosity of two bitumens
was determined from 125 oC to 195 oC with an increment of 10 oC as shown in below Fig. 2.2. The mixing and
compaction temperatures corresponding to 0.17 and 0.28 Pa.s for two bitumens were tabulated in below Table 2.2.

Table-2.2 Mixing and Compaction Temperatures of Two Bitumens

Description Virgin Hard grade bitumen

Mixing temperature oC (0.17 Pa.s) 163 186
Compaction temperature oC (0.28 Pa.s) 145 175
1.0
0.9 Virgin Hard grade bitumen
0.8
0.7
0.6

0.4
Viscosity Pa.s

0.3
Compaction Temperature

0.2
Mixing Temperature

0.1

110 120 130 140 150 160 170 180 190 200
o
Temperature C

Fig. 2.2 Temperature versus Viscosity

2.4 Mix design

Samples were cast with Marshall Mix design method with DBM – 2 gradation. Initially, aggregates were heated at
175 oC for 2 hours and bitumen was added and mixed at the pre-determined mixing temperature. Later the sample
was kept in oven up to which it attains the desired compaction temperature. On each face of the sample, 75 blows
were applied in accordance with ASTM D6927. Bitumen content corresponding to 4 % air voids as per MS – 2
guidelines was considered as optimum binder content in this study. Further the stability, flow and volumetric
parameters were checked to satisfy with the established requirements.

2.5 Indirect tensile strength test (ITS)

Indirect tensile strength is used to determine the resistance of mixes against cracking. The test is conducted in this
study as per AASHTO T 283. ITS of bituminous mix calculated by using below formula.

ITS =

Where, P = Failure load in Newton

d = Diameter of sample in mm

t = Thickness of sample in mm

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2.6 Resilient modulus of mixes (Mr)

Resilient modulus evaluates the mechanistic property of bituminous mixes. The test was conducted at 35 oC as per
ASTM D7369. 10 % of the failure load corresponding to ITS was applied by the computer controlled program. The
vertical and horizontal deformations for the specimens were captured through the computerized data acquisition
unit.

3. RESULTS AND DISCUSSION

3.1 Physical properties of conventional and developed hard grade bitumen

Virgin (VG 30) bitumen was blended with PPA for several trials for the production of hard grade bitumen. Finally,
the addition of 4.5 % PPA has found to be optimum dosage for obtaining hard grade bitumen. The physical
properties of virgin and laboratory produced hard grade bitumen with the corresponding requirement of hard grade
bitumen (10) are given in below Table 3.1.

Table-3.1 Properties of Conventional and Developed Hard Grade Bitumen

Property Virgin Hard grade bitumen Required value for hard grade bitumen
Penetration (1/10th) mm 51 24 15 – 25
Softening oC 52 70 55 – 71
Viscosity at 135 oC cSt 380 1160 ≥ 550

3.2 Marshall Properties

The marshall stability, flow value, bulk specific gravity and volumetric properties of two bitumens at 4% air voids
were shown in below Table 3.2. From the results, it has revealed that the marshall parameters were satisfied with the
established requirements as specified in MORTH. The stability of mix produced with hard grade bitumen has found
higher than virgin mix. However, flow value is found lower for hard grade bituminous mix. This may be due to
higher stiffness offered by the mix.

Table-3.2 Marshall Parameters of Mixes

Property Virgin mix Hard grade mix MORTH Specifications

Bitumen content (%) 5.27 5.46 Min 4.5 %
Stability (kN) 14.09 16.14 Min 9 kN
Flow (0.25 mm) 3.75 3.5 2 – 4 mm
VMA (%) 15.60 15.48 Min 12 %
VFB (%) 73.10 72.36 65 – 75%
Bulk density (g/cc) 2.325 2.328 -

3.3 Indirect Tensile Strength

With the obtained optimum bitumen content three samples were cast for each individual mix and tested for indirect
tensile strength. The average ITS value of three samples for virgin and hard grade bituminous mixes was found as
1.1 and 1.45 MPa. It has found that the ITS of mix prepared with hard grade bitumen is 1.32 times higher than virgin
mix.

3.4 Resilient Modulus of mixes

The resilient modulus of mixes was determined by applying repeated load in haversine form at 35 oC. The test was
conducted up to 500 cycles and the 5 cycles after 100 cycles were considered for calculating the resilient modulus of

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bituminous mix. The resilient modulus results were shown in below Table 3.3. The resilient modulus of hard grade
bituminous mix has shown 1.98 times higher than virgin mix. This can subsequently increases resistance to rutting
and fatigue in base course and reduces the thickness of layer.

Table-3.3 Resilient Modulus Test Results

Type of bitumen used Test temperature Load Horizontal Resilient modulus in

in bituminous mix (oC) (N) deformation (um) (MPa)
Virgin 35 1100 6.15 1746
Hard grade 35 1450 4.27 3310

4. DESIGN OF PAVEMENT SECTION FOR HEAVILY TRAFFICKED ROAD AS PER

IRC: 37-2018
As per IRC: 37-2018 guidelines a pavement section is designed for traffic of 300 msa. The allowable vertical
compressive strain at top of sub – grade and the allowable horizontal tensile strain in bottom of bituminous layer
was computed by below equations 1 and 2 as per IRC: 37-2018 guidelines. In this study, for attaining strains less
than the allowable limits a trial section was considered with CBR value of sub-grade as 8 % and thickness of
granular layer as 450 mm. For bituminous layers the surface course (BC) thickness is kept constant as 50 mm and
the base course (DBM) thickness is computed by conducting several trials using IIT Pave. Below Fig. 4.1a and 4.1b
shows the computed pavement composition when virgin and hard grade bitumen used in DBM mixes respectivley.
From the Fig. 4.1b the use of hard grade bitumen in base course has reduced the DBM thickness by 40 mm. The
reduction in 40 mm in bituminous layer will saves materials like aggregates and especially the reduced usage of
large amount of bitumen.

NR = 1.4100 * 10-08 * [1/εv] 4.5337 (for 90 % reliability) -1

Nf = 0.5161 * C * 10-04 * [1/εt] 3.89 * [1/MRm] 0.854 (for 90 % reliability) -2

B.C D.B.M Granular

50 mm
50 mm
240 mm 200 mm

450 mm 450 mm

a) b)

Fig. 4.1 Pavement Composition with Virgin and Hard Grade Bitumen in DBM Mix

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CONCLUSION
 Physical properties of laboratory produced hard grade bitumen have found to resist more towards high
temperature than virgin bitumen.
 Stiffer bitumen produced with PPA can resist more against plastic deformation than the virgin bitumen.
 Marshall stability and Indirect tensile strength of bituminous mix prepared with hard grade bitumen has
found higher than conventional mix.
 Resilient modulus of hard grade bituminous mix is approximately twice the virgin mix.
 Use of hard grade bituminous mix in base course has reduced pavement thickness by 40 mm.

REFERENCE
[1] Abhishek Mittal, Khusboo Arora, Gajendra Kumar and Pramod Kumar Jain, Comparative studies on
performance of bituminous mixes containing laboratory developed hard grade bitumen, Advances in civil
engineering, 2017.
[2] Amjad H. K. Albayati and Roaa H. Lateif, Evaluating the performance of high modulus asphalt concrete
mixture for base course in Iraq, Journal of engineering, Vol. 23, pp 14-33, June, 2017.
[3] Maria Espersson, Effect in the high modulus asphalt concrete with the temperature, Construction and
building materials, 71, pp 638-643, 2014.
[4] Siksha Swaroopa Kar, Khusboo Arora, Chandrakant Mani and Dr P.K. Jain, Characterization of bituminous
mixes containing harder grade bitumen, Transportation research procedia, pp 349-358, 2016.
[5] Maria Inmaculada Garcia Hermamdez, High modulus asphalt concrete: a long life asphalt pavement,
Journal of civil & environmental engineering, Vol. 5, Issue 5, 2015.
[6] Hyun Jong Lee, Jung Hun Lee and Hee Mun Park, Performance evaluation of high modulus asphalt
mixtures for long life asphalt pavements, Construction and building materials, pp 1079-1087, 2007.
[7] V Haritonovs, J Tihonovs and M Zaumanis, Performance evaluation of high modulus asphalt concrete
mixes, 3rd International conference on competitive materials and technology processes, IOP Publishing,
2016.
[8] Erik Denneman, Laszlo Petho, Benoit Verhaeghe, Julius Komba, Wynand Steyn,Rob Vos, Trevor Distin,
Piet Myburgh, Andrew Beercroft and Jonathon Griffin, High modulus asphalt (EME) technology transfer to
South Africa and Australia: shared experiences, 11th Conference on asphalt pavements for southern Africa,
CAPSA, 2015.
[9] Basim H. Al-Humeidawi, Mutaz Kadhim Medhlom, Kassim Kadhim Hameed and Huda A. Kadhim,
Production of hard grade bitumen for using in high modulus asphalt concrete, Journal of university of
Babylon for engineering sciences, Vol. 26, No. 6, 2018.
[10] Laszlo Petho and Erik Denneman, High modulus asphalt mix (EME) for heavy duty application and
preliminary laboratory test results in Australia, 15th AAPA International Flexible Pavements Conference,
Brisbane, Australia, September, 2013.
[11] Kezhen Yan, Henglong Zhang and Hongbin Xu, Effect of polyphosphoric acid on physical properties,
chemical composition and morphology of bitumen, Construction and building materials, 47, pp 92-98,
2013.
[12] Shahriar Alam and Zahid Hossain, Changes in fractional compositions of PPA and SBS modified asphalt
bitumens, Construction and building materials, 152, pp 386-393, 2017.
[13] Zahid Hossain, Md Shahriar Alam and Gaylon Baumgardner, Evaluation of rheological performance and
moisture susceptibility of polyphosphoric acid modified asphalt bitumens, Road materials and pavement
design, 2018.
[14] ASTM D6927, Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures, ASTM
International, West Conshohocken, PA, 2015.
[15] IRC: 37-2018:- Guidelines for the Design of Flexible Pavements.
[16] AASHTO T 283, Standard method of test for resistance of compacted asphalt mixtures to moisture-Induced
damage.
[17] ASTM D 4123, Standard test method for indirect tension test for resilient modulus of bituminous mixes
[18] Asphalt mix design methods, Manual series – 2, 7th edition.
[19] Ministry of Road Transport and Highways, Specifications for Road and Bridge Works, 2013.

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CERTIFICATE

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 SHOW AND TELL

Presenting project at Show and Tell

Poster prepared for Show and Tell presentation

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