International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 02, February 2019, pp. 273–287, Article ID: IJMET_10_02_029
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=02
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
DEVELOPMENT AND PERFORMANCE
EVALUATION OF CRUMB RUBBER – BIO-OIL
MODIFIED HOT MIX ASPHALT FOR
SUSTAINABLE HIGHWAY PAVEMENTS
Modupe Abayomi. E.*, Atoyebi, Olumoyewa D., Basorun, Adebayo. O and Gana A. J
Department of Civil Engineering, Landmark University, Omu-Aran, Nigeria.
Department of Physical Planning and Development, Landmark University, Omu Aran, Nigeria.
Ramonu John A. L
Department of Agric and Biosystems Engineering, Landmark University, Omu-Aran, Nigeria
Raphael O. D.c
Department of Agric and Biosystems Engineering, Landmark University, Omu-Aran, Nigeria
ABSTRACT
The asphalt industry has been perpetually challenged by its hazardous emissions
and its contribution to the ongoing climate change and global warming crises. Likewise,
the environment has been cumbered by the challenge of improper disposal of nondegradable solid wastes especially crumb rubber in form of scrap tyres resulting in
serious environmental degradation. This research investigated the effect of modifying
bitumen with bio-oil from cassava peels upgraded with a nondegradable polymer i.e.
crumb rubber. Performance tests were carried out on the modified bitumen to evaluate
its effect on its rheological properties. The percentage of bio-oil by volume used for
modification of bitumen was 5%, 10%, 15% and 20%. Marshall Stability and flow tests
were also carried out on the bio-asphalt produced. Experimental results of bitumen
modification with cassava peel oil at 5%, 10%, 15% and 20% replacements showed an
increment in flash point of 244°C, 250°C, 252°C & 259°C fire point of 259°C, 265°C,
269°C & 274°C and softening point values of 55°C, 55.5°C, 56.5°C & 57.5°C
respectively of the base bitumen. Due to the high moisture content associated with biooils, properties such as ductility and viscosity were adversely affected. Upgrading with
crumb rubber caused an improvement in the engineering properties of the base bitumen
with penetration grade at 20% modification showed the resultant blend was 40/50
which is suitable for use on airport pavements. The highest Marshall Stability and Flow
values were obtained at 20% modification with bio-oil upgraded with polymer with
values of 26.5kN and 13.33mm as against 9kN and 10.5mm obtained on the control
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Modupe Abayomi. E, Atoyebi, Olumoyewa D., Basorun, Adebayo. O, Gana A. J, Ramonu John
A. L and Raphael O. D.c
sample. Finally, it was observed that the bio-oil could be utilized in the production of
cutback bitumen due to the reduction of viscosity.
Keywords: Bio-oil, Crumb Rubber, Marshall Stability, Flow, Bitumen, Rheological
Properties, Sustainable Pavements, Cassava Peels
Cite this Article: Modupe Abayomi. E, Atoyebi, Olumoyewa D., Basorun, Adebayo. O,
Gana A. J, Ramonu John A. L and Raphael O. D.c, Development and Performance
Evaluation of Crumb Rubber – Bio-Oil Modified Hot Mix Asphalt for Sustainable
Highway Pavements, International Journal of Mechanical Engineering and Technology,
10(2), 2019, pp. 273–287
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1. INTRODUCTION
Bitumen is the main component of asphalt and has been used in road construction for several
years across the world (Kolokolova, 2014). Most bituminous adhesives or binders that are used
for pavement materials are derived primarily from fossil fuels (Airey, et al. 2008).
Nevertheless, due to the petroleum reserves becoming depleted and the ensuing consequences
(global warming, pollution, etc.) of combustion of fossil fuels as well as the subsequent urge to
reduce these effects, there is a drive to develop and produce binders from alternative sources.
The use of these alternative technologies often qualifies the resulting mixture to be classified as
“sustainable”. A sustainable pavement is safe, efficient and environmentally friendly while
meeting the needs of the present generation without affecting the ability of future generations to
meet their needs (Uzarowski, 2008). Sustainable pavements minimize the use of natural
resources, reduce energy consumption, reduce greenhouse gas emissions, limit pollution,
improve health and safety, and ensure a high level of comfort for users. The economic impact
of the use of alternative binders in the construction of flexible pavements should also be
considered when discussing sustainability. Engineers must consider new technologies and
design methodologies to comply with current and future demand for sustainable development.
To achieve this, the use of bio-oils as asphalt binders has been proposed. By definition, bio-oils
can be described as dark brown, free-flowing organic liquids that are comprised mainly of
highly oxygenated compounds (Oasmaa, et al., 1999). In other words, it is the liquid produced
from the rapid heating of biomass in vacuum condition (Oasmaa, et al., 2005). Bio-oils have
many synonyms that can be listed as follows: pyrolysis oil, pyrolysis liquid, bio-crude oil
(BCO), wood liquid, wood oil, liquid smoke, wood distillates, and pyroligneous acid (Mohan et
al. 2006 and Oasmaa et al. 2005). Bio-oils are a complex chemical mixture of water, pyrones,
acetic acid, formic acid, and other carboxylic acids with the concentrations of these chemical
components depending on the bio-mass from which the bio-oil had been derived (Mohan et al.
2006). As a result of the presence of cellulose, hemicellulose, and lignin in forestry and
agricultural crops, the production of bio-oils can be described as the rapid and simultaneous
depolymerization and fragmentation of these compounds while rapidly increasing temperature
(Mohan et al. 2006). Bio-oils can substitute for fuel oils and a variety of other chemical
applications (Williams, et al., 2009). Bio-oils are produced by either thermochemical or
biochemical conversion. Thermochemical conversion process, such as pyrolysis and
transesterification allow for a more compact facility as well as a faster conversion time
compared to biochemical conversion (Cantrell, K. et al. 2007). Bio-oils have distinct
advantages when compared to fossil fuel oils. Bio-oils are renewable, environmentally-friendly
and provide energy security. (Uzarowski, 2008). Over the years, bio-renewable resources have
been tested as alternative sources for producing binders and adhesives (Airey, et al. 2008). Due
to the availability of large quantities of bio-renewable sources from different botanical sources,
there are various technical and economic prospects in utilizing them to produce bio-binders
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(Airey, et al. 2008) and through the application of scientific research, a range of different
vegetable oils have been investigated to determine their physical and chemical properties to
determine their applicability to be used as modifiers for binders in the pavement industry (Tan
et al., 2002). Bio-based materials include industrial products, co-products, and by-products
made from agricultural or forestry feed stocks. These feed stocks could be wood, wood waste
and residues, grasses, crops, and co-products of crops. It is essential that the feed stocks for biobased materials do not compete with food or feed supplies. Bio-binders can be utilized in three
different ways to decrease the demand for fossil fuel based bituminous binders summarized as
follows: as a direct alternative binder (100% replacement), as a bitumen extender (25% to 75%
bitumen replacement) and as a bitumen modifier (<10% bitumen replacement) (Williams, et al.
2009). The demand for bio-based fuel and mixtures is gaining popularity as it is not only
sustainable, but also provides secure energy and a positive economic opportunity (Aziz et al.,
2015). A lot of research effort has been put into using bio-binders as a modifier with little or no
work being done on using them as an extender or as direct alternative. Appel and his team used
swine manure to produce oil (Aziz et al., 2015). They successfully converted swine manure to
oil with 50% efficiency at 380oC and 40MPa (around 400 atm) pressure. Fini in his research
produced a bio-oil from swine manure and used it as a partial replacement of bitumen (Fini et
al., 2011). According to Fini, this bio-binder can be an effective material when added to
bitumen binder due to its ability to improve some of the asphalt binder properties (lowtemperature properties and wettability) while also providing economic and environmental
benefits.
Raouf and Williams conducted a study on bio oil in Iowa State University, U.S.A. They
produced different bio-oils from various sources e.g., Oakwood, switch grass and corn stover
(Raouf and Williams, 2010). In the research, bio oil was blended with polymer modifier and
bitumen, and the temperature susceptibility of the mixture was checked afterward. Finally, they
concluded that bio-oil based binders from agricultural wastes behave much rheologically like
bitumen binders. Their behaviour changes when temperature increases and viscosity begins to
decrease making bio-oils more vulnerable to temperature than bitumen binders (Raouf and
Williams, 2010). Agricultural wastes are natural and non-natural by-products produced by
farmers through various farming activities (Ashworth, et al. 2015). These activities or
operations may include dairy farming, horticulture, livestock breeding, market, gardens, nursery
plots and woodlands management (Onu, et al. 2016). It has been estimated that up to 30% of
global agricultural produce are left behind in the farms as wastes (Ugwuanyi, 2013). The use of
these selected bio-masses will provide a means of efficiently managing and even generate
revenue from these waste materials.
Cassava (Manihot esculenta) is extensively cultivated in Nigeria as one of the major staple
food resources. The root of this plant contains high amount of carbohydrates but the main
drawback of this staple food is a poor source of protein. For industrial application, cassava is
used as raw material for glucose, fructose, ethanol, and cassava starch production. During the
process of production, those kinds of industries produce significant amounts of cassava peel
waste. Since the Cassava peel contains cyanogenic glucosides, mainly linamarin, the direct
discharge of this solid waste often creates problem to the environment due to the release of
hydrogen cyanide after hydrolysis by an endogenous linamarin. This further justifies the use of
cassava peel as a bio-mass for the production of bio-oil. Cassava peel has been utilized as a
renewable resource for activated carbon preparation (Sudaryanto et al, 2006), super capacitor
(Ismanto et al, 2010) and as an absorbent (Kosasih et al, 2010); (Kurniawan et al, 2011).
Suryadi et al., (2012), reported in their experiment that bio-oil yield from fast pyrolysis of
cassava peel ranged from about 38.7 % to 51.2 %. The maximum yield of bio-oil was obtained
at temperature of 525oC. Main organic composition of bio-oil can be grouped into acids, esters,
aldehydes, ketones, phenols, alcohols, hydrocarbons, and other organic compounds and some
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Modupe Abayomi. E, Atoyebi, Olumoyewa D., Basorun, Adebayo. O, Gana A. J, Ramonu John
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un-identified organic compounds. The physicochemical properties of bio-oil produced from
pyrolysis of cassava peel were comparable to the ASTM standard for bio-oil. However there
has been no research until now that studies the applicability of utilizing bio oil from cassava
feedstock as partial replacement for bitumen for sustainable pavement works. In order to
explore other sources of biomass, this study evaluated the performance of petroleum-based
mixtures replaced with up to 50% bio-oil produced from agricultural wastes such as cassava
peels.
2. EXPERIMENTAL MATERIALS AND METHOD
2.1. General
The experimental schedule of this study was designed to characterize the bio-oil, modify
conventional bitumen with the developed bio-oil and hence evaluate its effect on the
rheological properties of bitumen, then subsequently produce bio-asphalt with the resultant
blend using the Marshall Mix Design.
2.2. Materials Used
The materials used in this study include: Biomass (from Cassava peels), Bitumen, Mineral
aggregates. The bio-oil was extracted from the bio-mass using a fabricated pyrolysis system as
shown in figure 1.
Figure 1 Pyrolizer
Specifications
The dimensions for the pyrolizer are as follows:
Internal diameter = 30 cm, Radius = 15 cm, Thickness = 2 cm Height = 41 cm, Diameter of
overhead steel pipe = 1.5 cm, Area =
= 3.142 x 1.52 = 7.0695 cm2, Area of pyrolizer =
= 3346.23 cm2, Volume of the pyrolizer =
= 28984.95 cm3
2.3. Material sourcing
The cassava shavings were obtained from the Garri processing plant located at the commercial
farm of Landmark University, Omu-Aran, Kwara State, Nigeria. The bitumen was obtained
from a bitumen processing plant in Akure, Ondo State.
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Figure 2 Cassava Peels
2.4. Experimental Plan
The experimental plan was designed in order to determine the overall characteristics of the biobinders developed from different kinds of bio-oils. The experimental plan was not concerned
only about the rheological properties, which are the main factor in predicting the behaviour of
the developed bio-binders as pavement materials, but the experimental plan emphasized the
overall physical and chemical characteristics in order to have a better understanding of the
applicability of developing bio-binders from bio-oils. The experimental plan included three
different plans, i.e. physical plan, chemical plan and rheological plan.
2.4.1. Physical Testing Plan for bio-oil
Due to the variety of chemical compounds present in bio-oils a well as the complexity
associated with chemically characterizing these oils, physical characterization offers the most
accurate means of determining the properties of the oils. The physical testing of the bio-oils is a
significant phase before using the bio-oils/developed bio-binders as pavement materials. The
following tests were carried out on the produced bio-oils: Density, Viscosity, Specific gravity
which is a very important parameter needed during the design of pavements.
2.4.2. Chemical Testing Plan for bio-oil
The chemical characterization was done using the Gas Chromatography/Mass Spectrometry
tests This test was performed to quantify the amount of oxidative aging that occurred with the
developed bio-binders, and to identify the different types of chemical bonds (functional groups)
presented in the developed/original bio-binders.
2.4.3. Performance based testing plan
Various tests were conducted on bitumen to assess its consistency, gradation, temperature
susceptibility, and safety. These tests include:
I.
Penetration test: Penetration test was performed to determine the consistency of
the modified bitumen sample. This test was conducted by determining the distance
in tenths of a millimeter using a standard needle penetrated vertically into a sample
of the material under fixed conditions of temperature, load, and time. Other tests
conducted are: Ductility test, Flash and Fire Point Test, Loss on Heating Test,
Viscosity, Specific Gravity, water content and Softening point test.
II.
Softening Point Test: Softening point test was conducted to determine the softening
temperature of bitumen by using ring and ball apparatus.
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A. L and Raphael O. D.c
Figure 6 Softening Point Test
2.5. Aggregate Characterization
The mineral aggregates were characterized through the following tests viz: Aggregate Impact
Test, Aggregate Crushing Test, Los Angeles Abrasion Test, and Flakiness & Elongation.
2.6. Marshall Stability and Flow:
Bio-asphalt was produced with the resultant blend of the bio-oil, a suitable polymer and the
conventional bitumen. The bio-asphalt was subsequently subjected to the Marshall Stability and
flow tests to predict the performance criteria of bituminous concrete. Approximately 4000
grammes of aggregates and filler mix was heated to temperature of 175-190°C. Bitumen was
heated to a temperature of 121-125°C with first trial percentage of bitumen (say 3.5 or 4% by
weight of the mineral aggregates). Subsequently, the heated aggregates and bitumen were
thoroughly mixed at a temperature of 154-160°C. The mix was placed in a preheated mould and
compacted by a rammer with 50 blows on either side at temperature of 138°C to 149°C. Upon
complete compaction, the asphalt briquette was extruded from the mould using the extruder as
shown in figure 8.
Figure 8: Extruder and Asphalt Briquette
2.6.1. Properties of the mix
Theoretical Specific Gravity (Gt): This is the specific gravity of the mix without considering the
air voids.
Where: W1 = Weight of coarse aggregate in the mix
W2 = Weight of fine aggregate in the mix
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W3 = Weight of filler in the mix
Wb = Weight of bitumen in the mix
G1 = Apparent specific gravity of coarse aggregate
G2 = Apparent specific gravity of fine aggregate
G3 = Apparent specific gravity of filler
Gb = Apparent specific gravity of bitumen
2.6.2. Bulk specific gravity of the mix (Gm): This is the specific gravity of the mix considering
the air voids.
Where Wm = Weight of mix in air
Ww = Weight of mix in water
Air Voids Percentage (Vv): This represents the percentage of air voids by volume in the mix
2.6.3. Percent by Volume of bitumen (Vb):
2.6.4. Voids in mineral aggregate (Vma):
This is the total volume of voids in the aggregates. It is the sum of air voids and volume of
bitumen.
2.6.5. Voids filled with bitumen (Vfb): This represents the voids in the mineral aggregate
frame work filled with the bitumen.
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Figure 9 Asphalt Briquettes
3. RESULTS AND DISCUSSION
Measured results of samples showed different change of properties towards conventional
bitumen and bio-oil modified bitumen. This involves the data obtained and analysis of results
from tests carried out on bio-oil produced from Cassava peels, bio-oil modified bitumen, Biooil & Polymer Modified bitumen, mineral aggregates and bio-asphalt.
3.1. Production and Characterization of Bio-oil
The bio-oil extruded from the cassava peels, rice husk, oil palm, and coconut shell, showed
significant potential as a bitumen modifier because it possesses similar chemical properties with
petroleum binders. The oil was extruded by the pyrolysis process which involves the
combustion of organic matter at high temperatures and in anaerobic conditions i.e. in the
absence of oxygen and consequently producing solids, bio-oil, and gases. It was established by
Raouf et al in 2010 that bio-oils perform poorly without any pre-treatment procedure carried
out on them due to the presence of water and other volatile materials. For this investigation, the
bio-oil was placed in a water bath set at 50°C for 24 hours to attempt to reduce the moisture
content of the bio-oil.
3.1.1 Elemental Analysis
Elemental analysis of the Cassava peel bio-oil was carried out. The results are shown on Table
1. It is important to characterize the bio-oil that is used in the studies as every bio-oil has
different composition depending on its biomass source and the pyrolysis conditions used.
Table 1:
Elemental Analysis of Bio-oil compared to Virgin Bitumen
Elemental Composition (%)
Cassava Peel Bio-oil
Carbon
57
Hydrogen
4.85
Oxygen
38
Nitrogen
0.15
Bitumen
85
11
1
0.3
3.2. Bio-oil modification of bitumen
These results describe the effect of the bio-oil produced on conventional bitumen
3.2.1. Penetration test
It was observed that upon modification with the bio-oil, there was an alteration of the
penetration grade as detailed in Table 2. An increase in the percentage volume by weight of
bio-oil caused an increase in the penetration grade.
Table 2 Effect of bio-oil and Crumb rubber on penetration grade of bitumen
Penetration Value (mm)
Bio-oil percentage by
volume of Bitumen
Bio-oil
Bio-oil +
Crumb rubber
0% (Control)
5%
10%
15%
67
62
76
81
67
61
54
51
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Penetration Grade
Bio-oil +
Bio-oil
Crumb
rubber
60/70
60/70
60/70
60/70
70/80
50/60
80/90
50/60
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20%
93
47
80/100
40/50
The purpose of this test is to classify the modified bitumen into their penetration grades. CT
had penetration grade of 60/70, BO (5%) and BOP (5%) had 60/70, BO (10%) and BOP (10%)
had 70/80 and 50/60 respectively, BO (15%) and BOP (15%) had 80/90 and 50/60 respectively
and BO (20%) and BOP (20%) had 80/100 and 40/50 respectively.
3.2.2 Ductility
It was observed that the addition of the Crumb rubber had an adverse effect on the ductility
value as there is a reduction of ductility as the percentage of crumb rubber added increases as
shown on Table 3. However, it is important to note that the lack of ductility does not indicate
poor quality.
Table 3: Effects of bio-oil modification on ductility of bitumen
Ductility (cm)
Bio-oil percentage by
volume of Bitumen
Bio-oil
Bio-oil + Crumb rubber
0% (Control)
5%
10%
15%
20%
80
82.3
71
69
55
80
83.3
84.7
87.2
87.9
Standard
Requirement
(Minimum)
75
75
75
75
75
3.2.3. Softening Point
The softening point gives an idea of the temperature at which the bituminous material attains a
certain viscosity. Bitumen with higher softening point is used in warmer places. Values are as
shown on Table 4.
Table 4: Effects of bio-oil modification on softening point of bitumen
Softening Point (°C)
Bio-oil percentage by
volume of Bitumen
Bio-oil
Bio-oil +Crumb rubber
0% (Control)
5%
10%
15%
20%
54.5
55
55.5
56.5
57.5
54.5
57.5
58.5
62
62.5
Standard
Requirements
45-60
45-60
45-60
45-60
55-65
3.2.4 Loss on Heating
This test involved weighing out 50 grammes of bitumen, heating it for 5hours at a temperature
of 1630C in a special oven after which it was reweighed. The loss in weight due to heating was
then expressed as a percentage by weight of the original sample. Values are as shown on Table
5.
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Table 5 Effect of bio-oil modification on the loss on heating of bitumen
Loss on Heating (%)
Bio-Oil
Bio-Oil + Crumb Rubber
0.88
0.88
0.92
0.89
0.96
0.81
1.02
1.18
1.18
1.39
Bio-oil percentage by volume of
Bitumen
0% (Control)
5%
10%
15%
20%
3.2.5. Specific Gravity
This parameter is of great importance to obtain volumetric measurements for the mix design.
Marshall Mix Design is used for mix design of bituminous concrete. Marshall Mix Design is a
volumetric mix design process, so the result obtained from Marshall Mix design will be in
terms of volume. However, while making the mix, we mix different constituents in terms of
their weight. For finding out this weight, we need the value of Specific Gravity.
Weight = Specific Gravity * Volume
Apart from this, specific gravity is found out for Quality Control purpose. i.e. 80/100 bitumen will have
a certain specific gravity value which will be different from 40/50 bitumen.
Table 6 Effect of bio-oil modification on Specific Gravity of Bitumen
Bio-oil percentage by
volume of Bitumen
0%
5%
10%
15%
20%
Specific Gravity
Bio-oil
Bio-oil + Crumb Rubber
0.98
0.973
0.991
1.012
1.03
0.98
1.03
0.98
0.97
0.96
Standard
Requirement
0.96-1.02
0.96-1.02
0.96-1.02
0.96-1.02
0.96-1.02
3.2.6. Moisture Content
This test is carried out to determine the content of water in a sample of bitumen. Results are as
shown on Table 7.
Table 7: Effect of bio-oil modification on the Moisture content of bitumen
Bio-oil percentage by volume of
Bitumen
0%
5%
10%
15%
20%
Moisture Content (%)
Bio-Oil
0.09
0.11
0.19
0.21
0.29
Bio-Oil + Crumb Rubber
0.09
0.1
0.14
0.16
0.19
3.2.7. Flash and Fire Point
The lower the flash point temperature, the greater the risk. This classification is then used to
warn of a risk and to enable the correct precautions to be taken when using, storing or
transporting the liquid. Table 8 highlights the performance enhancement of the bio-oil on
bitumen.
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Table 8: Effect of bio-oil modification on the Flash & Fire point of bitumen
Bio-oil
percentage by
volume of
Bitumen
0%
5%
10%
15%
20%
Flash Point (°C)
Bio-oil
Bio-Oil +
Crumb Rubber
Standard
Requirement
240
244
250
252
259
250
252
267
270
271
175
175
175
175
175
Fire Point(°C)
Bio-Oil +
BioCrumb
oil
Rubber
240
250
259
266
265
274
269
283
274
`287
Standard
Requirement
205
205
205
205
205
The flash and fire point of the modified bitumen were within the required safety limits. The
modification improved this property, making it possible to mix bitumen safely at higher
temperatures.
3.2.8. Viscosity Test
Table 9 Effect of bio-oil modification on the Viscosity of bitumen
Viscosity (s)
Bio-oil
275
275
272
270
269
Bio-oil percentage by volume of Bitumen
0%
5%
10%
15%
20%
Bio-Oil + Crumb Rubber
275
278
284
291
298
3.3. PRODUCTION OF BIO-ASPHALT
Of the two types of asphalt (i.e. hot-mix asphalt and Mastic Asphalt), hot-mix asphalt was
produced using the bio-polymer modified bitumen blend. The material is practically impervious
to water, with the fines, filler and bitumen forming a mortar in which coarse aggregate was
scattered in order to increase its overall bulk.
3.3.1 Characterization of aggregates
3.3.1.1. Coarse Aggregate Testing
Table 10 highlights the tests carried out on the aggregates, the test results and comparisons to
the standard requirements of those values.
Table 10 : Coarse Aggregate Characterization
Tests Carried Out
Aggregate Impact Test
Aggregate Crushing Test
Los Angeles Abrasion Test
Flakiness Index
Elongation Index
Density
Test Results Obtained
24.98%
44.93%
56.03
28.62
29.53
1492.267kg/m3
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Standard Test Values
30% Maximum
45% Maximum
60% Maximum
30% Maximum
30% Maximum
1500 kg/m3
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Specific Gravity
2.8
2.8
All the test results were satisfactory meaning the coarse aggregates were found suitable for
use in flexible pavement works.
3.3.1.2. Particle Size Analysis
Table 11 shows the particle size distribution for coarse aggregates, while Table 12 shows the
particle size distribution for fine aggregates.
Table 11 Particle Size Distribution for Coarse Aggregates
Sieve No
(#)
Sieve Size
(mm)
19
12.7
4
10
16
30
40
50
Weight of aggregates
retained (g)
% retained on
each sieve
Cumulative %
Cumulative
retained on
% passing
each sieve
0
0
0
100
28.56
20.36
8.41
12.7
5.16
9.5
9.83
2.42
28.56
48.92
57.33
70.03
75.19
84.69
94.52
96.94
71.44
51.08
42.67
29.97
24.81
15.31
5.48
3.06
526
9.52
4.75
2
1.18
0.6
0.425
0.3
375
155
234
95
175
181
44.5
3.3.2. Marshall Mix Design
In order to obtain the optimum bitumen content for the mix, several trial aggregate-binder
blends were evaluated. The design ratio is:
Where 5% represents the binder, 45% represents the coarse aggregate, 30% represents the
filler
20% represents the fine aggregate.
3.3.3. Marshall Stability and Flow Values
This aims to provide a means of predicting the performance of bituminous concrete for use in
flexible pavement. The stability portion of the test measures the maximum load a specimen can
support. The load is applied until the specimen fails and this maximum load is considered as
stability. During the loading, an attached dial gauge measures the specimen’s deformation
(plastic flow) due to loading.
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Development and Performance Evaluation of Crumb Rubber – Bio-Oil Modified Hot Mix Asphalt for
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Table 12 Marshall Properties for Bio-oil Modification
%
Bio-oil
0%
5%
10%
15%
20%
PMB
Stability
Flow (mm)
Vv
Vb
Vfb
Vma
Gm
OBC (%)
Bio-Oil
Bio-Oil
Bio-Oil
Bio-Oil
12.5
12
15.67
19
10.67
10.83
11.17
11.5
3.8
3.9
4.5
4.4
17
17
16.9
16.9
81.9
81.3
79
79.5
20.7
20.9
21.3
21.2
2.3
2.3
2.3
2.3
5.7
5.2
5.6
5.6
Table 13: Marshall Properties for Bio-oil & Crumb Rubber Modification
%
Bio-oil
0
5
10
15
20
PMB
Stability
Flow
(mm)
Vv
Vb
Vfb
Vma
Gm
OBC
(%)
Bio-oil + Crumb Rubber
Bio-oil + Crumb Rubber
Bio-oil + Crumb Rubber
Bio-oil + Crumb Rubber
19.33
21.33
25.67
26.5
11.17
11.33
12.83
13.33
4
3.7
4.1
3.3
16.9
17
16.9
17
79.4
82.2
80.4
83.8
21.3
20.7
21
20.4
2.3
2.3
2.3
2.3
5.4
5.9
5.1
5.1
4. CONCLUSION
The objectives of this study were to produce and characterize bio-oil from cassava peels,
modify bitumen with the bio-oil and a selected polymer and determine its effects on the
rheological properties of bitumen and hence produce bio-asphalt and determine its Marshall
Stability and Flow Values. From the obtained results, it was observed that modification with the
bio-oil increased the penetration grade of the bitumen (i.e. made the bitumen softer) making it
suitable for use in cold climates. The penetration values were improved upon modification with
Crumb rubber. The penetration grade of bitumen was 60/70 and got reduced to 60/70, 70/80,
80/90 & 80/100 for modifications at 5%, 10%, 15% and 20% respectively. However, the values
were 60/70, 50/60, 50/60 and 40/50 for crumb rubber modification of 5%, 10%, 15% and 20%
respectively. The ductility values and penetration grade were found proportional to each other.
As the penetration grade changed with increasing percentages of Cassava bio-oil, the ductility
values also did. The ductility became 82.3cm, 71cm, 69cm, 55cm for bio-oil modification of
5%, 10%, 15% & 20% respectively. The ductility only improved at 5% modification. The
addition of the crumb rubber made the bitumen mixture stiffer, hampering the ductility values
as they became 55cm, 50cm, 48cm and 39cm for 5%, 10%, 15% and 20% respectively. It was
observed that there was an increase in the softening point with the addition of bio-oil and a
greater improvement as a result of the polymer modification. For bio-oil modification of 5%,
10%, 15% and 20%, the softening points became 55°C, 55.5°C, 56.5°C and 57.5°C respectively
and for the polymer modification of 5%, 10%, 15% and 20%, the softening point became
57.5°C, 58.5°C, 62°C and 62.5°C respectively. The percentage lost on heating for bio-oil
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Modupe Abayomi. E, Atoyebi, Olumoyewa D., Basorun, Adebayo. O, Gana A. J, Ramonu John
A. L and Raphael O. D.c
modification of 5%, 10%, 15% and 20%, was 0.92%, 0.96%, 1.02% & 1.18% and 5%, 10%,
15% and 20%, polymer modification caused 0.89%, 0.81%, 1.18% and 1.39% respectively.
This was an increase on the 0.88% lost from CT. This is as a result of the introduction of more
volatile substances being added to bitumen. The specific gravity of bitumen is to be in the range
of 0.96-1.02. The modification with Cassava Peel bio-oil had 0.973, 0.991, 1.012 and 1.03 for
5%, 10%, 15% and 20% respectively. For polymer modification 5%, 10%, 15% and 20%, the
results were 1.03, 0.98, 0.97 and 0.94 respectively. The moisture content of bitumen was
increased with the modification with Cassava peel bio-oil due to the relatively high moisture
content in the oil. 5%, 10%, 15% and 20% modification caused the moisture content to become
0.11, 0.19, 0.21 and 0.29 respectively, while the addition of crumb rubber in the following
proportion 5%, 10%, 15% and 20% caused 0.1, 0.14, 0.16 and 0.19 moisture content
respectively. The flash and fire point of the resultant blends were higher compared to virgin
bitumen. 5%, 10%, 15% and 20% modification increased the flash and fire point to 244°C,
250°C, 252°C & 259°C (flash point) and 259°C, 265°C, 269°C and 274°C (fire point)
respectively. With the addition of the crumb rubber, these values further increased to 252°C,
267°C, 270°C and 271°C (flash point) and 266°C, 274°C, 283°C and 287°C (fire point) for 5%,
10%, 15% and 20% modification. The viscosity of the blend was negatively affected by the
addition of the bio-oil as 5%, 10%, 15% and 20% caused 75s, 72s, 70s and 69s viscosity.
However, with an addition of crumb rubber in the proportion 5%, 10%, 15% and 20%, the
viscosity increased to 78s, 84s, 91s and 98s respectively.
The Marshall Properties of bio-polymer modified bituminous concrete mixture (BPMBCM)
were determined from the results of the Marshall Stability Test. The properties that were tested
for were Marshall Stability, Flow Value, Volume of Bitumen in the mix, Voids in the mineral
aggregate, Voids filled by bitumen, Volume of voids and the Bulk Density of the mix. It was
observed that with the bio-oil and polymer modified bitumen mix had higher Marshall
properties compared to the bituminous mix modified with the bio-oil alone. This implies that
the bio-polymer mix is a suitable material for the modification of bitumen for use in flexible
pavement. The flow values were within the range of 10-14mm and in accordance with the
Asphalt Institute for heavy traffic at 75 blows. The lower the flow, the higher the mixture’s
resistance to deformation. Based on knowledge obtained from this research, the use of Cassava
peel bio-oil can be recommended for modification of bitumen for use in flexible pavement,
especially for the production of cutback bitumen since the penetration grades after modification
suggested softer bitumen. The oil can serve as a suitable substitute for kerosene in the cut-back
bitumen production process. I also recommend that the optimum combination volumes of both
bio-oil from cassava peel and crumb rubber be investigated. The use of bitumen modified with
bio-oil and crumb rubber for use in the construction of flexible pavements is recommended to
reduce agricultural wastes and other environmental pollution issues as well as reducing road
construction costs.
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Sustainable Highway Pavements
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