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Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2):194-200 (ISSN: 2141-7016)
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Laboratory Assessment of Highways Asphalt Bitumen inSouthwest of Nigeria
I. Akiije and V. A. Moyinwin
Department of Civil and Environmental Engineering,
University of Lagos, Lagos, Nigeria
Corresponding Author: I. Akiije
___________________________________________________________________________AbstractThis paper reports laboratory tests conducted while evaluating some properties of bitumen used in the
production of hot mixed-hot laid asphalt of three different asphalt plants in southwest of Nigeria. The bitumen
properties investigated included determination of the purity or contamination of the bitumen sample.Determination of the temperature at which bitumen sample used will attain standard fluidity for the purpose of
mixing with aggregate. The bitumen properties also investigated included determination of the sample grade atthe temperature of 25C and 60C. These properties were investigated through Solubility, Softening Point,
Penetration and Saybolt Viscosity tests respectively. Although all the three asphalt plants samples passed the
Softening Point and the Solubility tests but could not satisfy the specification values set up as standards for
Penetration and Saybolt Viscosity tests. Southwest of Nigeria is in the tropical region and the standardspecification values for Penetration test should be AC 60/70 but the results obtained are of about AC 85/100that is meant for temperate climate regions. It is pertinent to note that the harder the grade of bitumen, the
lower the penetration value and the better its use for the production of quality asphalt in tropical region. Thesignificance of this study is that results of experiments on bitumen samples from the three selected asphalt
plants in southwest of Nigeria are unsatisfactory when related to the expected standard approved grades of
both Penetration and Saybolt Viscosity tests. Unsatisfactory results from Penetration and Saybolt Viscosity
tests as shown in this study could significantly affect the performance of asphalt leading to the premature
failure of flexible pavements as presently prominent in southwest of Nigeria.__________________________________________________________________________________________
Keywords:solubility, softening, penetration, viscosity, flexible, pavement
INTRODUCTIONBitumen in this study is referring to asphalt cement,
a binder in the production hot mixed-hot laidasphalt of flexible pavement. A mixture of bitumenfrom fractional distillation during the refining
petroleum crude and non-volatile oil such as
propane, butane or pentane by heating can produce
graded bitumen of usable consistency for flexiblepavement Wright (2003). Bitumen is usually graded
in accordance with its viscosity or penetration at aspecified temperature, Kadyali and Lal (2008),
Garber and Hoel (2010). Bitumen is useful in the
production of asphalt primarily because of theirexcellent binding or cementing power and their
waterproofing properties, as well as their relativelylow cost, Adedimila (2000). Asphalt is a relatively
thin high quality bituminous surface material on topof series of granular layers of a flexible pavement,Akiije and Oyekan (2012).
A flexible pavement is a structure that maintains
intimate contact with and distributes loads to the
subgrade and depends on the interlock, particle
friction, and cohesion for highway stability.Highway is a system which its functions allow for
traffic movement in six recognizable stages of
main, transition, distribution, collection, access andtermination AASHTO (2008).
Hot mixed-hot laid asphalt is usually produced byproperly blending bitumen, coarse aggregate, fine
aggregate, and filler (dust) at temperatures ranging
from about 80C to 165C. The surface of flexible
pavement varies depending on the type of bitumenused and climatic conditions. Flexible pavement
distresses do occur where unsatisfactory bitumenproperties manifested in the asphalt used for a
highway. Distress is defined as an indication of
unfavourable pavement performance or signs ofimpending failure, or any unsatisfactory
performance of pavement sort of failure Oguara(2006). Too much bitumen in asphalt can cause
distortion. Pavement distortion is any change of thepavement surface from the original shape inform ofrutting, corrugation, shoving and depressions. A rut
is a longitudinal surface depression which maydevelop in the wheel paths. Corrugation is a form of
plastic movement typified by ripples across the
bituminous pavement surface that occurs usually at
points where traffic starts and stops. Corrugationsare usually caused by lack of stability of asphalt
layers in warm weather or lack of aeration of
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(2): 194-200
Scholarlink Research Institute Journals, 2013 (ISSN: 2141-7016)jeteas.scholarlinkresearch.org
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asphalt mixture. Shoving is a lateral displacementof paving material due to action of traffic generally
resulting in the bulging of the surface caused bylack of stability in bituminous layers.
Another sort of distress that can be caused byunsatisfactory bitumen is pavement disintegration.
Disintegration of asphalt is the breaking up of apavement into small, loose fragments that dislodged
aggregate particles and if not stopped in its early
stages can progress until the pavement requirescomplete rebuilding. Two common types of
disintegration are potholes and ravelling. Potholesare bowl-shaped holes of various sizes in the
pavement surface resulting from localizeddisintegration by weakness in the asphalt resulting
from too little bitumen among other causes.Ravelling is the progressive disintegration ofaggregate particles in a pavement from the surface
downward or edges inward. Ravelling is caused bytoo little bitumen in the mix, or overheating of the
bituminous mix. Skid hazard due to slippery on
pavement surfaces can be the result of a film of
bitumen bleeding from the asphalt surface.
The aim of this paper therefore is to carry out
laboratory tests on bitumen samples used in theproduction of hot mixed-hot laid asphalt for
highway pavement from three different asphaltplants in southwest of Nigeria. The objective is to
evaluate some properties while determining both
consistency and quality of the bitumen samplesobtained by evaluating their conformity with the
relevant established standard specifications.Specifically, to carry out the following laboratory
tests on the samples obtained that includes
Solubility Test, Softening Point Test, PenetrationTest and Saybolt Viscosity Test. The scope of work
in this study is on the determination of the bitumengrade at temperature of 25C and 60C. Another
work is the determination of the temperature atwhich bitumen attained its standard fluidity for the
purpose of mixing with aggregate.
Also, work done is on the determination of the
purity of bitumen and contamination in bitumen.
The purpose of this study is to identify statistically
the satisfactory performance of the asphaltproduced for the construction of highway
pavements from three asphalt plants within the
southwest of Nigeria for safety considerations. Thesignificance of this study is that majority of asphalt
bitumen being used in the southwest of Nigeria
which is in tropical region are of materials meant
for temperate climate and this is a fatal reason for
premature failure of their flexible pavements.Premature failure of roads makes highways
dangerous and leading to high rate of fatal accidentsof vehicles which is a trend to loss of lives and
properties.
MATERIALSBitumen used for road construction are viscous
liquid or semi-solid materials that is black to brownin colour with less free carbon and consisting
essentially of hydrocarbons and their derivatives,
which are soluble in trichloroethylene Brennan andOFlaherty (2002). According to Wright (2003)
bitumen produced from petroleum is softer but asthe bitumen cools down to room temperature, it
becomes a semisolid viscous material. The
consistency of the residues produced duringpetroleum refinery can be further modified to
paving bitumen by the solvent deasphalting, or thesolvent extraction processes. Bitumen produced
from the vacuum-steam distillation exists as asemisolid at room temperature, and usually proper
workability can be attained by heating it to atemperature of 120C to 165C to liquefy it for
purpose of mixing it with heated aggregates. Table
1 is showing the typical uses of bitumen that arecategorized into Viscosity gradedoriginal,
Viscosity gradedresidue and Penetration graded
which is useful in the selection of any particular
type of pavement construction. The consistency of
bitumen materials is important in flexible pavementconstruction because it is a tool to indicate the
grade or class of the available bitumen at aspecified or a particular temperature. It is important
that the temperature at which the consistency isdetermined be specified as in Tables 2 and 3, since
temperature significantly affects consistency of
asphalt materials. Tables 2 and 3 are showing thepenetration and viscosity grades of bitumen or
asphalt cement that are normally available in themarket for the production of asphalt for flexible
road pavements respectively.
Table 1: Typical Uses Of Bitumen
Source: Wright, 2003
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Table 2: Penetration Grades of Bitumen
Source: Wright, 2003
Table 3: Viscosity Grades Of Bitumen
Source: Wright, 2003
METHODOLOGYThe particular grade of bitumen or asphalt cement
is designated by its penetration and viscosity, bothof which will give an indication of the consistencyof the material at a given temperature. In this study
bitumen examined were samples from threeselected asphalt plants that produce asphalt for
pavement construction in Lagos, Ogun, Oyo, Osun,Ondo and Ekiti States within the southwest of
Nigeria. Representative samples of bitumen were
collected from three selected asphalt plants for fourdifferent months. Laboratory tests were carried on
bitumen samples obtained from the three selectedasphalt plants at the department of Civil and
Environmental Engineering, University of Lagos.Solubility Test was carried out for it was used tomeasure the amount of impurities in the bitumen
material. Softening Point Test, Penetration Test andSaybolt Viscosity Test were also carried out in the
course of this study. Three tests were carried out on
each of the monthly collected representative sampleof bitumen per asphalt plant. The mean value of the
three tests was considered as the sample
representation for the monthly Solubility, Softening
Point, Penetration and Saybolt Viscosity Tests pereach asphalt plant.
Solubility Test2 g of bitumen sample from the plant was dissolved
in 100 ml of trichloroethylene a solvent for 30minutes and the solution was filtered through a
filter paper into a crucible. The material thatretained on the filter paper was then dried and
weighed and used to calculate the percentage of the
weight of the original bitumen sample. Thesolubility test of bitumen sample with full detail of
the equipment used is fully described in theAASHTO D T44-03 (2006).
Softening Point TestThe bitumen sample obtained from the plant was
heated to a temperature between 75C and 100C asa consideration for approximate softening point to
be in complete fluid form. Heated bitumen was then
poured into standardized two rings of 16 mm insidediameter and 6.5 mm high attached to a metal plate
and left for 30 minutes to cool at room temperature.After which a steel ball of 10 mm was placed on
each of the bitumen of the standardized two rings.
The assembled instrument of the rings, bitumen andsteel balls was placed inside a beaker with distilled
water. The boiling water was then stirredcontinuously while noticing the temperature change
using an emerged thermometer. As the temperatureincreases gradually the bitumen softened and
thereby permitting the ball to eventually sink to thebottom plate etched 25 mm below the rings. Thetemperature at which the balls touched the bottom
plate were observed and recorded of the meanvalue. Details of Softening Point Test on bitumen
sample with full detail of the equipment used are
fully described in the ASTM D36-95 (2000).
Penetration TestThe bitumen sample was softening to a pouring
consistency temperature between 75C and 100Cand stirred to make it homogenous and free from air
bubbles and water. The sample was then pouredinto a standard container to a depth of 15 mm more
than the expected penetration depth. The bitumen
sample container was then placed in a temperaturecontrolled water bath at a temperature of 25C for
one hour and after then it was removed and laterplaced at the penetrometer equipment for the
penetration test. Here, the penetrometer needle was
brought in contact with the surface of bitumensample and the reading of dial was set at zero. After
which the standard needle with a load of 100 g wasallowed to penetrate the bitumen sample for exactly
5 seconds. The penetration is given as the distancein units of 0.1 mm as the needle penetrates the
bitumen sample. AASHTO D T49 (2006) gives full
details of the penetration test.
Saybolt Viscosity Test
The Saybolt Furol Viscometer with tube 10.8 cm
long and 4 cm in diameter. An orifice of 0.3 cmdiameters is connected to an opening of 1 cm
diameter at the bottom of the tube. The standard
tube was then placed in a larger water bath of theinstrument fitted with an electric heater and astirring device. A heated bitumen sample that has
been filtered through a 100m mesh was placed
directly into the viscometer tube closed with a
stopper at the 1 cm diameter opening until the levelwas above the flow rim. The bitumen sample was
then heated to 60C temperature. Immediately uponreaching the 60C temperature, the stopper was
removed, and the time in seconds for exactly 60 ml
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of the asphalt material to flow through the orificewas recorded. Description in full details of the
equipment for the Saybolt Viscosity Test is inAASHTO T72-97 (2001).
RESULTS AND DISCUSSIONThe summary of the bitumen representation sample
results on the solubility test obtained from the threeselected asphalt plants in the southwest of Nigeria
is in Table 4. Table 4 is showing how the results of
the solubility test are in conformity to AASHTO DT 44-03 (2006) and the FMW (2007). It is also
obvious in Table 4 that the bitumen samplerepresentation from each of the three asphalt plants
passed the solubility test at a level of higher free ofimpurities contamination. Assurance could also be
noted that the material tested for asphalt productionis not tar for in tars case the presence of impuritieswill be higher and will not conform to the standard
specification although they both have black tobrown colour. Moreover, it must be noted that the
solubility value of bitumen sample tested is not
lower than that of the standard specification values.
This is because such a situation will lower the hot
mixed-hot laid asphalt bonds and finally causeuntimely deterioration of the pavement under the
traffic.
In the case of softening point tests, summary of thebitumen representation sample results obtained
from the three selected asphalt plants in the
southwest of Nigeria is in Table 5. The results ofTable 5 on softening point tests are in conformity to
ASTM D36-95 (2000) and FMW (2007). Theconformance of the tested samples to standard
specifications is an indication that the bitumen
materials when used for hot mixed-hot laid asphaltwill be of higher workability, proper enhanced
mixing with aggregates and the possibility of fireoutbreak is eliminated.
Table 6 contains the summary of the penetrationtest result values on bitumen representation samples
obtained from the three selected asphalt plants inthe southwest of Nigeria. The table is showing how
the results of the penetration test are validated using
AASHTO D T 49-06 (2006) and FMW (2007)
standard specification values. A glance at thesample results of penetration tests of Table 6 and
comparing it to standard penetration grades
specification of bitumen of Table 2 it is obviousthat one third of the results conformed to AC 60/70while two thirds conformed to AC 85/100. It is to
be noted that AC 60/70 is a harder bitumen material
while AC 85/100 is a softer one. However, it could
be argued that the majority of the bitumen materialsin used for asphalt production in southwest of
Nigeria which is in tropical region are suitable fortemperate climate region countries. It is the
addition of solvent such as propane, butane and
pentane used on soft vacuum-steam-refinedbitumen from petroleum refinery that brings about
harder asphalt bitumen materials. The additionaluse of solvents during further distillations to
produce harder bitumen warrants more cost and
manufacturers may want to elude this process oreconomise that will not satisfactorily produce
bitumen of AC 60/70. Marketers will buy thematerials they found on ground or go for cheaper
bitumen and for this reason unsuitable bitumen may
be imported into Nigeria at the expense of usingsame to produce unsatisfactory asphalt in
Southwest of Nigeria.
Table 7 contains the summary of the viscosity testresult values on bitumen representation samples
obtained from the three selected asphalt plants inthe southwest of Nigeria. The table is showing howthe results of the viscosity test are validated using
AASHTO T 72-97 (2001) and FMW (2007)standard specification values. Comparing the
sample results of viscosity tests of Table 7 to
standard viscosity grades specification of bitumen
of Table 3 it is obvious that the whole results is not
conforming to grade AC 20. Bitumen of AC 20 isthe recommended grade as found in Table 1 for the
production of hot mixed-hot laid asphalt forhighways, airports and parking areas in tropical
regions of which southwest of Nigeria is a part.Bitumen at the viscosity grade of AC 20 will
provide a uniform film for binding action in tropical
regions whereas bitumen with higher viscosity willresists compacting effort and bitumen with lower
viscosity will only lubricates the aggregate particles(Gupta and Gupta, 2007).
Table 4: Bitumen Sample Solubility Tests
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Table 5: Bitumen Sample Softening Tests
Table 6: Bitumen Sample Penetration Tests
Table 7: Bitumen Sample Viscosity Tests
Figure 1: Viscosity Bitumen Sample at Location A
Figure 2: Viscosity Bitumen Sample at Location B
Figure 3: Viscosity Bitumen Sample at Location C
It is apparent in Table 3 that the bitumen samples
tested are of AC 2.5, AC 5 and AC 10 whilerelating results obtained and that the bitumen arenot useful for hot mixed-hot laid asphalt in
southwest of Nigeria being a tropical region. Thebitumen samples tested revealed that the materials
could be useful for the production of hot mixed-hot
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laid asphalt in temperate regions or used forbitumen-aggregate applications of surface
treatments in tropical regions as shown in Table 1.Figures 1 through 3 are charts presented in order to
vividly illustrate and compare viscosity bitumen
sample results from the three selected asphalt plantsin the southwest of Nigeria. It is obvious from the
three charts that none of the bitumen from theasphalt plants of comply with standard
specifications of AASHTO T 72-97 (2001) and
FMW (2007).
CONCLUSIONThe main conclusions derived from the bitumen
samples obtained from the three selected asphaltplants in the southwest of Nigeria after the
laboratory tests are as follows:1. The three selected asphalt plants representative
bitumen samples passed the laboratory
solubility tests with the experimental resultscope within 99.90% - 99.99% when compared
to standard specifications of 99.00% - 99.99%
of AASHTO T 44-03 (2006) and FMW
(2007).
2. The three selected asphalt plants representativebitumen samples also passed the laboratory
softening tests because ASTM D36-95 (2000)and FMW (2007) specification for same is
within the range of 40% - 55% while theexperimental result scope is 44C- 55C.
3. Considering the penetration tests carried out in
the laboratory on the three selected asphaltplants representative bitumen samples,
validating results obtained with 60/70penetration values at 25C temperature of
AASHTO T 49-06 (2006) and FMW (2007)
specification show that:i. Asphalt plant A bitumen sample
passed the test once of the four testscarried out therefore having a score of
25% compliance.ii. Asphalt plant B bitumen sample also
passed the test once of the four tests
carried out therefore having a score of25% compliance.
iii. Asphalt plant C bitumen sample
passed the test twice of the four tests
carried out therefore having a score of50% compliance.
4. The three asphalt plants representative bitumen
samples failed the Saybolt Viscosity laboratorytests at 60C temperature because AASHTO T72-97 (2001) and FMW (2007) specification
for same is within the range of 1600 - 2400
poise while the experimental results scope are
as following :i. Asphalt plant A bitumen sample
Saybolt Viscosity laboratory tests at60C temperature results are within
the range of 170.24 - 940 poise.
ii. Asphalt plant B bitumen sampleSaybolt Viscosity laboratory tests at
60C temperature results are withinthe range of 171.20 - 988 poise.
iii. Asphalt plant bitumen sample Saybolt
Viscosity laboratory tests at 60Ctemperature results are within the
range of 598.00 - 1033.60 poise.5. The unsatisfactory results from Penetration and
Saybolt Viscosity tests as shown in this study
could significantly affect the performance ofasphalt leading to the premature failure of
flexible pavements as presently prominent insouthwest of Nigeria.
RECOMMENDATIONThe general practice in Nigeria is in using imported
bitumen of which the majority is from temperatecountries where they use different bitumen grade
that is not conforming to asphalt being produced inNigeria. In view of this it recommended that
1. The Federal Government of Nigeria should
endeavour to establish at least a factory for
now in each of the six geopolitical zones of the
nation to be importing bitumen for the purposeof upgrading same to the required 60/70
penetration and 1600 - 2400 poise of viscositygrade.
2. The suggestion by the Asphalt Institute (1965)that 85/100 penetration could be used for
paving highways and streets in Hot climate for
medium to light traffic should be discouragedin Nigeria. This is because asphalt produced by
manufacturers using bitumen of 85/100penetration meant for medium to light traffic
could end up been used for heavy traffic
highways and streets that can lead to prematurefailure of the pavements.
REFERENCESAASHTO T 44-03, (2006): Solubility ofBituminous Materials, in Standard Specificationsfor Transportation Materials and Methods of
Sampling and Testing, Twenty-Sixth edition,American Association of State Highway and
Transportation Officials, Washington, D.C
AASHTO T 49-06 (2006): Penetration ofBituminous Materials, in Standard Specifications
for Transportation Materials and Methods of
Sampling and Testing, Twenty-Sixth Edition,American Association of State Highway andTransportation Officials, Washington, D.C
AASHTO T 72-97 (2001): Saybolt Viscosity,
Standard Specifications for TransportationMaterials and Methods of Sampling and Testing,
Twenty-Sixth edition, American Association ofState Highway and Transportation Officials,
Washington, D.C
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AASHTO, (2008): A Policy on Geometric Designof Highways and Streets, American
Association of State Highway and TransportationOfficials, Washington, D.C
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