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© Adama Science & Technology University                                                                  https://ejssd.astu.edu.et 

Ethiopian Journal of Science and Sustainable Development (EJSSD) 

p-ISSN 1998-0531                                                                                                  Volume 5 (2), 2018 

Engineering and Chemical Characterisation of Natural 

Bitumen Resources from Nigeria 

Ademila O.* and Ojo F. G. 

Department of Earth Sciences, Adekunle Ajasin University, Akungba-Akoko, Nigeria, 

*corresponding author, e-mail: omowumi.ademila@aaua.edu.ng 

Abstract 

Engineering and chemical properties of bitumen in Agbabu were evaluated for their 

suitability in road pavement construction. Raw samples of natural bitumen were 

collected in Agbagbu, Mile 2 and Mulekangbo, Ondo State, Nigeria. The engineering 

properties analysis involves bitumen penetration, flash and fire points, water content, 

loss on heating and specific gravity. Chemical evaluation includes analysis of heavy 

metals by the use of Atomic Absorption Spectroscopy (AAS) and analysis of Poly 

Aromatic Hydrocarbons (PAHs) using Gas Chromatography/Mass Spectrometer 

(GCMS). Agbabu and Mulekangbo bitumen samples fall within 200/300 penetration 

grade, classified as temperature susceptible bitumen, while samples of Mile 2 fall within 

100/150 penetration grade, classified as conventional paving bitumen. Thus, Agbabu 

and Mulekangbo bitumen can be used in temperate regions of the world, while Mile 2 

bitumen can best be applied in tropics, after upgrading by modifiers. The results of AAS 

indicate a high concentration of iron in the samples in the decreasing order of 

Fe<Zn<Cu<Mn<Pb<Ni. For Agbabu bitumen sample, the concentration indicates Fe 

(509 mg/kg), Zn (16 mg/kg), Cu (14 mg/kg), Pb (1 mg/kg), Ni, Cd and Mn are negligible, 

Mile 2 bitumen sample indicates Fe (8605 mg/kg), Zn (36 mg/kg), Cu (35 mg/kg) Mn 

(27 mg/kg), Ni and Cd are negligible; for Mulekangbo bitumen sample: Fe (8905 

mg/kg), Zn (48 mg/kg), Cu (39 mg/kg),  Mn (37 mg/kg), Pb (7 mg/kg), Mn (37 mg/kg), 

Ni (1 mg/kg) and Cd is negligible. Metals like Pb, Ni, Cd, even though present in small 

concentration can cause environmental hazard. GCMS analysis revealed high 

percentage of PAHs such as Chrysene, Pyrene, Fluorene, Phenanthrene and 

Anthracene in Mulekangbo bitumen sample, while Agbabu and Mile 2 bitumen samples 

indicate low percentage of target PAHs. PAHs present in bitumen sample of 

Mulekangbo can be carcinogenic and mutagenic, thus, exposure to these compounds 

can pose health/environmental risks. This study recommends clean technology during 

refining process to remove hazardous PAHs from the bitumen to prevent human and 

environmental health challenges during utilization. 

Keywords: Natural bitumen, engineering properties, heavy metals, PAHs, pavement 

construction  

1. Introduction 

Bitumen is a mixture of organic 

liquids that are highly viscous, black, 

sticky, composed primarily of highly 

condensed polycyclic aromatic 

hydrocarbons and metals such as nickel, 

iron and vanadium. In other words, 

bitumens contain a complex mixture of 

aliphatic compounds, cyclic alkanes, 

aromatic hydrocarbons, PAHs and 

mailto:omowumi.ademila@aaua.edu.ng


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heterocyclic compounds containing 

nitrogen, oxygen and sulfur atoms, and 

metals (e.g. iron, nickel, and vanadium). 

Elemental analyses indicate that most 

bitumens contain primarily hydrocarbons, 

i.e. carbon, 79–88%; hydrogen, 7–13%; 

sulphur, traces to 8%; oxygen, 2–8%; 

nitrogen, 3%; and the metals vanadium 

and nickel in parts per million (Speight, 

2000). The exact chemical composition 

of bitumen varies depending on the 

chemical complexity of the original 

crude petroleum and the manufacturing 

processes. Consequently, no two bitumen 

products are chemically identical, and 

chemical analysis cannot be used to 

define the exact chemical structure or 

chemical composition of bitumens. It is 

soluble in carbon disulphide, chloroform, 

ether and acetone, partially soluble in 

aromatic organic solvents, and insoluble 

in water at 20°C (IPCS, 2004). The 

compositional value of its constituents 

influences the industrial applications of 

bitumen. The principal refinery process 

used for the manufacture of bitumen is a 

two-step distillation: atmospheric 

distillation followed by vacuum 

distillation. The distillation is designed to 

remove polycyclic aromatic hydrocarbons 

(PAHs) from bitumen. This results in 

very low concentrations of PAH in the 

final product bitumen. This is sometimes 

followed by air rectification (mild 

oxidation) and/or oxidation (severe 

oxidation) depending on the required final 

product properties (Eurobitume and 

Asphalt Institute, 2015). Bitumen 

originates with chemical and physical 

attributes as immature oil which has 

undergone little secondary migration. 

The greatest amount of natural bitumen 

results from the bacterial degradation 

under aerobic conditions of originally 

light crude oils at depths of about 1,524 

m or less and temperature below 80°C. 

The biodegradation involves loss of most 

of the molecular weight volatile paraffins 

and naphthenes, resulting in a crude oil 

that is very dense, highly viscous, black 

or dark brown and asphaltic (Meyer et al., 

2007). 

Bitumen either in natural form or 

obtained from petroleum consists of four 

fractions namely: saturates, aromatics, 

resins and asphaltenes. PAHs often play 

a key role in the hazard evaluations of 

materials with respect to their impact on 

health and the environment. Recently, 

PAHs have played an important role in 

the outcome of the cancer hazard 

assessment of occupational exposure to 

bitumen and its emissions. Crude oils 

contain low parts of PAH/PAC and as 

such low (ppm) levels may be present in 

bitumen. The PAHs are mainly released 

during the burning of petroleum and its 

derivatives (USEPA, 2007). Hydrocarbon 

having benzene properties are called 

aromatic, and in the presence of two or 

more fused benzene rings, they become 

known as PAHs. According to Lopes 

(2008), the acute symptoms in pavers 

involve: eye irritation, nose and throat 

irritation, headache, dryness and skin 

irritation. Hein et al. (2013) estimated 

that global bitumen and heavy oil 

resources are around 5.6 trillion barrels, 

with most of these located in the Western 

Hemisphere. The high viscosity of 



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bitumen prevents it from flowing to a 

wellbore under in-situ reservoir 

conditions. Natural bitumens are 

naturally occurring deposits of asphalt-

like material, these deposits have 

physical properties that are similar to 

those of petroleum derived asphalt, but 

the composition is different. They exist 

in two main forms; either as pare bitumen 

accumulated down-deep below the earth 

surface or outcrops as oil impregnated 

sand, which is generally known as tar 

sand or oil sand. In Nigeria, natural 

bitumen has been found in Ondo, Ogun, 

Lagos, Edo and Enugu States with a 

combined proven reserve of about 14.86 

billion barrels with a quality estimated to 

be second largest in the world but yet to 

be explored for economic purposes.  

The major applications of bitumen are 

in paving for roads and airfields, 

hydraulic uses (such as dams, water 

reservoirs and sea-defence works), 

roofing, flooring and protection of metals 

against corrosion. More than 80% of 

bitumens are used in many different 

forms of road construction and 

maintenance. It is also the basic 

feedstock for petroleum production from 

tar sands. The extracts from bitumen are 

very rich in aromatics, which makes it a 

suitable feedstock for petrochemical 

industries (Lurgi, 1987). The chemical 

composition of bitumen is a great 

determinant of its grade or quality. 

Bitumen derived from different sources, 

or produced with different manufacturing 

processes and/or crudes can have wide 

variations in chemical compositions and 

other physicochemical properties with 

different levels of service benefits. Any 

bitumen whose chemical composition 

and other physicochemical properties 

deviates significantly from compositions 

of bitumen of standard grades or known 

acceptable qualities can be unreliable in 

service for most engineering applications 

or cause unpredictable problems in its 

service usage (UNEP and ILO, 2004). 

This investigation of the engineering 

material is conducted due to the large 

reserves of natural bitumen resources and 

potentials for sustained production in 

large quantity in Nigeria, high demand 

for better strength of road elements, 

lesser road maintenance, increase in 

traffic, poor construction materials and 

continuous road failure caused by rutting, 

cracking and moisture damage. Thus, 

this study is necessitated to provide basic 

information of the quality and 

performance grade of the bitumen for the 

implementation of good resistance roads of 

high performance traffic loading, high 

bearing capacity and to ensure the health 

and safety of workers during the 

execution process of highway works. 

2. Description of the study area 

Bitumen samples were collected from 

four different locations, Agbabu, Mile 2 

(Samples A and B) and Mulekangbo 

sites, where bitumen outcrops occur in 

Odigbo and Okitipupa Local Government 

Areas of Ondo State, called bitumen belt 

of Southwestern Nigeria. It lies between 

latitudes 6° 31’ N and 6° 38’ N and 

longitudes 4° 46’ E and 4° 52’ E (Figure 

1). The location falls within the eastern 

Dahomey Basin and runs through Edo, 



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Ondo and Ogun States (Adegoke et al., 

1980). It is an area of lowlands with few 

ridges about the lowlands, the hills are 

very high which are characteristic of the 

tropical rainforest of southwestern 

Nigeria. The temperature is relatively 

high during the dry season with the 

temperature reaching about 30°C. The 

area is well drained by NE-SW trending 

rivers like Oluwa, Ufara, Omilala, Opeki, 

Shasha, Oba and Ogun. The rivers 

dominate the drainage system of the 

study area and it’s mainly dendritic. 

Some of the sample locations can be 

assessed by roads and footpaths while, 

other locations can only be assessed by 

footpaths. 

3. Geology of the study area 

Geologically, the main bitumen belt 

in Nigeria occurs on the eastern margin 

of a costal sedimentary basin known as 

the Benin Basin. The eastern ward limit 

of the Benin basin is marked by the 

Okitipupa High while, the basin extends 

westwards into Togo and the Volta Delta 

(Ghana). The crystalline basement rocks 

form the foundation of the whole area 

(FMSMD, 2006). The study area falls 

within the sedimentary terrain in the 

Dahomey basin of Southwestern, 

Nigeria. The sedimentary terrain of 

Agbabu falls within the eastern portion of 

the Dahomey Basin. The geologic 

sequence is composed of the Nkporo 

Shale, upper Coal measures, Imo shale 

group, coastal plain sands (Benin 

formation) and quaternary coastal 

alluviumin (Figure 2). The Nkporo Shale 

is made up of shale, sandy clay and lenses 

of sand. The Imo shale group is 

composed off shale while the Coastal 

Plain Sands has alternations of 

clay/sandy clay and clayey sand/sand. 

The Quaternary Coastal Alluvium is 

composed of an alternating sequence of 

sand and silt/clay (Jones & Hockey, 

1964). The aquifer units are sand, 

sandstones, clayey sand and dissolved/ 

fractured limestone which are 

unconfined and confined in nature. The 

study areas belong to the Afowo 

Formation of the Cretaceous Abeokuta 

Group, uncomfortably overlying the 

basement. The Afowo Formation is 

composed of coarse to medium grained 

sandstone with variable but thick 

interbedded shale, siltstone and 

claystone. The sandy facies are tar 

bearing while the shale are organic rich. 

The Dahomey basin is an Atlantic 

margin basin containing Mesozoic-

Cenozoic sedimentary succession 

reaching a thickness of over 3000 m. it 

extends from southeastern Ghana to the 

western flank of the Niger Delta. Its 

stratigraphy is classified into Abeokuta 

Group, Imo Group, Oshosun Formation, 

Ilaro Formation and Coastal Plain sands 

and Alluvium (Jones & Hockey, 1964). 

Omatsola & Adegoke (1981) recognized 

three formations belonging to the 

Abeokuta Group. These are: Ise 

Formation (Neocomian-Albian) consisting 

essentially of continental sands, grits and 

siltstones, overlying the basement 

complex. Overlying the Ise Formation is 

the Afowo Formation (Turonian-

Maastrichtian) consisting of coarse to 



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medium grained sandstones with 

interbeds of shale, siltstones and clay. 

The Araromi Formation (Maastrichtian-

Paleocene) conformably overlies the 

Afowo Formation and consists of sands, 

overlain by dark-grey shales with 

interbeds of limestones and marl.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1. Location map of the study area showing the sample locations 

 

4. Material and Method 

4.1. Sample collection 

Four natural bitumen samples were 

collected at four different locations 

within the richest bitumen spots at 

Agbabu, Mile 2 (Samples A and B) and 

Mulekangbo. One sample was collected 

from a standard extraction hole drilled 

with metal casing by early explorers of 

bitumen in Agbabu. Two bitumen 

samples were collected from the deposits 

within a water logged area, some 

kilometers away from Agbabu 

community and the last bitumen sample 

was collected at the well drilled by the 

early explorers of Mulekangbo 

community in a cocoa plantation site. 

The sample collection involved the use of 

dip stick, hand trowel, sterilized plastic 

containers, marker, GPS (each sample 

location was plotted using a global 

positioning system) and paper tape. The 

samples were collected and properly kept 

in a well labeled plastic containers and 

were later taken to the laboratory for the 

required analysis.



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Figure 2. Geological map of the study area

4.2. Determination of flash and fire 

points 

The flash point tells the critical 

temperature above which suitable 

precautions are required to be taken to 

eliminate the danger of fire during 

heating. The flash-point is the 

temperature at which bitumen fume may 

flash, or spark. This temperature is 

usually 230°C or higher for common 

paving bitumen. The flash-point provides 

an indication of fire hazard and the test is 

frequently used to indicate whether a 

given product has been contaminated 

with materials of lower flash-point 

(ASTM D92-01 (2001)). 

Test cup, a thermometer and a bunsen 

burner were used for the fire point 

experiment. The test cup used was filled 

with the bitumen sample to the standard 

level; thermometer was inserted into the 

cup and heated at the rate of 5°C/min. 

The test flame was lighted and adjusted 

to a diameter of 3.8 to 5.4 mm. The test 

flame was applied when the temperature 

read on the thermometer has reached 

each successive 2°C mark. A lighted 

flame was passed across the sample at 

interval of 15 seconds. The flash point 

was considered as the lowest liquid 

temperature at which application of the 

test flame caused the vapors of the 

sample to flash, while the fire point was 

considered as the temperature at which 

the test flame causes the sample to ignite 

and remain burning for at least 5 seconds. 



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4.3. Determination of loss on heating 

Bitumen sample was scooped into the 

test cup and weighed to an accuracy of 

0.01 gm at room temperature. Then it was 

place in an oven and was heated for five 

hours at 163°C. After that, the sample 

from the oven was brought out and 

cooled to room temperature and the 

weight was taken at an accuracy of 0.01 

gm, with the value noted and recorded. 

Calculation 

i) Loss on heating = Weight of 

bitumen before heating – weight 

of bitumen after heating. 

ii) Percentage of loss on heating = 

Loss on heating / Weight of 

bitumen before heating * 100. 

 

4.4. Determination of Water Content 

(water-in-bitumen) 

100 g of bitumen sample was 

measured and transferred to a cylindrical 

container. Sufficient trichloroethylene 

free from water was added to permit 

refluxing to take place and then bolt on 

the cover with a dry gasket in position 

and fixed the receiver and condenser in 

place. Adequate flow of water through 

the condenser and heat to give a steady 

reflux action was ensured. Continuous 

heating was ensured until the volume of 

water in the receiver remained constant. 

Then the volume of water was then 

measured and its mass was recorded. 

Then, the water content was calculated as 

a percentage by mass of original sample 

to the nearest 0.1%.  

4.5. Determination of specific 

gravity 

Bitumen sample was heated in oven 

to melt. 100 g of the heated sample was 

weighed into a gravity bottle of a known 

weight and volume. The weights of the 

bottle plus the sample was taken and 

recorded. The sample was allowed to 

cool for about 30 minutes and the solvent 

(trichloroethylene) was added to the 

sample in the bottle to the standard mark. 

It was ensured that the bottle was shaken 

while adding the solvent to allow for 

outright dissolution of the sample. The 

bottle was then put in the water bath at 

25°C for about one hour and refilled to 

the mark due to a little decrease in the 

level of the solvent in the bottle and 

weighed. 

The specific gravity of the bitumen 

sample was calculated as: 

Specific gravity = density of natural 

bitumen/density of water at 4°C 

following standard procedure.  

4.6. Determination of penetration 

The penetrometer used for the 

conduction of this test was made up of a 

needle assembly with a total weight of 

100 g and a device for releasing and 

locking in any position. The bitumen 

samples from each location was scooped 

in a test cup and heated until pouring 

temperature, and then cooled to room 

temperature. The sample container was 

then placed in the transfer dish with water 

at the required temperature of 25°C, from 

the constant temperature bath, the sample 

being completely covered with water at 

all times. The needle was then released 



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for 5 secs and relocked immediately at 

the end of the period and the penetration 

value was obtained from its digital 

indicator. Care was taken not to disturb 

or jolt the apparatus when releasing the 

needle. This was repeated for all the 

samples. 

4.7. Determination of Chemical 

Composition 

The chemical composition includes 

the heavy metals and PAHs analysis. The 

heavy metal is determined majorly by the 

use of Atomic Absorption 

Spectrophotometer. The Polycyclic 

Aromatic Hydrocarbons were determined 

by the use of the GCMS. The materials 

used for this analysis include; measuring 

cylinder, beaker, conical flask, funnel, 

filter paper, hot plate, fume cupboard, 

AAS, and the reagent used are: Aqua 

regia (HCl + HNO3) and perchloric acid. 

Procedure: 0.5 gm of samples was 

weighed into a digesting flask and 

digestion was carried out with 10ml of 

mixture of conc. HNO3 and HCl (aqua 

regia) with few drops of perchloric acid 

added. The mixture were heated on 

digesting block until the fume of the acid 

ceased and made up with distilled water 

into a 500 ml standard flask. Analysis 

was carried out with AAS VGP 210 

following the standard procedure as 

described by the operation manual of the 

equipment. 

4.8. PAH Analysis 

The bitumen sample was extracted 

using Methanol and the extracts was 

transferred to 100 ml pear-shaped flasks 

and evaporated to nearly dryness under 

reduced pressure of 150 mbar at 35°C 

using a rotary evaporator fitted with 

thermostated heating bath). An 

additional 10 ml n-hexane was added to 

the concentrated extracts and evaporated 

to a small volume (about 1 ml). Then the 

sample was transferred to 1.5 ml 

chromatographic vial for gas 

chromatography analysis. The PAHs 

were quantified by internal calibration 

performed with a GCMS (Agilent 

GC6890/5973MSD). For PAHs analysis, 

a HP-5 MS column (Aglient, length 30 

m, i.e. 0.25 mm, film thickness of 0.25 

mm) was employed with the following 

temperature program: 60–280°C at 6°C 

min−1, isothermal holding at 280°C for 20 

min using helium as the carrier gas. The 

instrument was operated with an initial 

flow of 1.2 ml min−1, head pressure 0.03 

Mpa, and injection mode as follows: 

splitless (1 ml), temperature of injector: 

280°C. The Mass Spectrometer (MS) 

was operated using the electron impact 

(EI) ionization mode at 70 eV (electron 

volt), scanning from 50 to 550 mass units 

at 0.82 s scan-1. All PAHs were 

determined by selective ion monitoring. 

5. Result and Discussion 

5.1. Engineering Properties of 

bitumen samples 

The values obtained for flash and fire 

points of the natural bitumen samples of 

the study area are as shown in Table 1. 

The values ranged from180°C - 241°C 

and 220°C - 288°C for flash and fire 

points respectively. Mulekangbo 



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bitumen sample has the lowest flash and 

fire point values, while Mile 2 (Sample 

B) bitumen has the highest values. This 

result is similar with that of previous 

study by Guma et al (2012) for two tested 

natural bitumen samples. 

The values of loss on heating ranged 

from 1.15% - 2.52%. The result indicates 

that Mile 2 (Sample A) bitumen has the 

lowest value of percentage loss of water 

during heating, while Agbabu bitumen 

sample has the highest value of 

percentage loss of water on heating. 

Based on this result, only Mile 2 (Sample 

A) bitumen of all tested bitumen samples 

meets the requirement of 1% loss on 

heating (ASTM 1998) bitumen grading. 

The percentage of water present in the 

bitumen samples of Mulekangbo and 

Mile 2 (Sample A) is 3.9% (Table 1). 

Agbabu bitumen sample has the lowest 

percentage of water of 1.9%. The high 

value obtained for Mulekangbo and Mile 

2A samples may be due to their presence 

in waterlogged area. This high value in 

moisture in bitumen requires 

modification/upgrading of the bitumen in 

the study area to prevent reduction in 

adhesiveness of bitumen to aggregate 

during compaction in pavement 

construction. The specific gravity (Gs) of 

the bitumen samples ranged from 0.68 – 

0.84. The specific gravity of each sample 

compares favourably with that for 

asphalt standard of 1 maximum as given 

by ASTM D5-97 (1998). 

The penetration of bituminous 

material is a measure of the consistency 

of bitumen at a given temperature. This 

property in-turn indicates the quality and 

grade of bitumen. As can be observed 

from Table 1, the values of penetration of 

bitumen fall in the range of 100 – 300 

dmm. The penetration value of Mile 2 

(Samples A and B) bitumen fall in the 

range of 100/150 for bitumen of 

acceptable grades commonly used to 

manufacture asphalt mixes, cut-back 

bitumen, bitumen emulsions and 

modified bitumen. An increase in 

penetration value of bitumen implies 

hardening of the material. This hardening 

of bitumen has a negative effect on the 

quality of bitumen. Hardening of 

bitumen has been emphasized to be 

responsible for distresses such as 

breakdown and rupture in the pavement 

which led to premature failure of road 

(Nassar et al, 2012). Based on the 

bitumen grade summarized in Table 2, 

two of the four bitumen samples 

collected (Mile 2 bitumen (Samples A 

and B)) fall within the grade 100/120 and 

120/150 respectively, classified as 

conventional paving bitumen can be 

applied on road construction in the tropic 

regions like Nigeria, when appropriately 

upgraded or modified in order to provide 

a variety of properties such as good 

resistance to aging, durability, high 

performance traffic loading and high 

bearing capacity. Abgabu (Sample C) 

and Mulekangbo (Sample D) bitumen 

flow at room temperature classified as 

temperature susceptible bitumen and can 

be best applied for road pavement in 

temperate regions of the world. 



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Table 1. Summary of the engineering properties of bitumen samples 

Sample  Location Water-in-

bitumen 

(%) 

Penetratio

n at 25 °C 

(dmm) 

Gs Loss on 

heating 

(%) 

Flash 

Point 

(°C) 

Fire 

Point 

(°C) 

Sample A (Mile 2A) 3.9 110   0.84     1.15  196 240 

Sample B (Mile 2B) 2.2 150 0.68 2.35 241 288 

Sample C (Agbabu) 1.9 206 0.68 2.52 238 277 

Sample D (Mulekangbo) 3.9 226 0.82 2.25 180 220 

Table 2. The grade of bitumen 

Bitumen location Grade Best possible use 

Mile 2A (Sample A) 100/120 Conventional paving bitumen 

Mile 2B (Sample B) 120/150 Conventional paving bitumen 

Agbabu (Sample C) 200/300 Temperature susceptible bitumen 

Mulekangbo (Sample D) 200/300 Temperature susceptible bitumen 

 

5.2. Trace metals in bitumen samples 

The concentration of trace metals in 

bitumen samples are shown in Table 3. 

Trace metals have been employed in the 

natural bitumen characterization. Iron 

(Fe) concentrations range from 509 to 

8905 mg/kg. High level of Iron (Fe) in 

sample collected from Mile 2 (8905 

mg/kg) and Mulekangbo (8605 mg/kg), 

in contrast to the sample collected from 

Agbabu (509 mg/kg). The concentration 

of the elements for all the samples in 

decreasing order is as follow: Fe > Zn > 

Cu >Mn>Pb. The concentration of iron is 

the highest (8905 mg/kg) while Pb is the 

lowest (1.00 mg/kg). The concentration 

of heavy metals in the samples shows 

slight similarities with the work obtained 

by Bakare et al. (2015). The exceptional 

high concentration of iron for sample 

collected from Mile 2 (Sample A) may be 

as a result of the presence of the sample 

in waterlogged area. The regular occurrences 

of the high rainfall and flooding have 

contributed to the leaching of most trace 

elements and this has contributed to the 

increased level of these metals. The 

relatively high levels of Fe, Pb and Ni 

observed in the result of some of the 

samples may be associated with the 

bitumen sample obtained from the 

marine environment. The presence of 

Manganese (Mn) and Lead (Pb) in sample 

from Mile 2 and Mulekangbo, may pose 

environmental hazard and catalytic 

poisons during the refining of the 

bitumen. 

The differences that occur with other 

studies may be due to the fact that 

previous studies of Ipinmoroti and 

Aiyesanmi (2001) and Adebiyi and 

Omole (2007) were conducted on 

bituminous sand while the present study 

used flow bitumen obtained from 



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observatory wells. During the process of 

extraction of bitumen from bituminous 

sand, some of the metal contents might 

have been leached out from the sample, 

hence, the relatively lower concentrations of 

some metals reported. It is observed that 

work has not been carried on Mulekangbo 

observatory well. The result of Mulekangbo 

bitumen sample indicates high concentration 

of Fe, Mn, Pb, and Zn. These heavy 

metals when present in high quantity 

cause environmental hazards. The 

exceptionally high concentration of heavy 

metals may be due to contaminations 

during collection of the sample, because 

the sample was found in contact with 

biogenic materials and with water 

emanated from the well beneath.

Table 3: Concentrations of trace metals (ppm) in bitumen samples 

 Sample locations 

Heavy metals (mg/kg) Agbabu Mile 2 Mulekangbo 

Zn 16.00 48.00 36.00 

Cu 14.00 39.00 35.00 

Pb 1.00 7.00 5.00 

Ni ND 1.01 ND 

Cd ND ND ND 

Mn ND 37.00 27.00 

Fe 509.00 8905.00 8605.00 

ND: not detected 

5.3. Polycyclic Aromatic Hydrocarbons 

The asphalt binders (or bitumen) 

release fumes which have PAHs. The 

PAHs belong to a class of complex 

chemical compound whose structure is in 

the form of linked benzene rings, and is 

widely distributed in the atmosphere. 

However, some PAHs are considered to 

have carcinogenic and/or mutagenic 

potential. Bitumen emissions, generated 

upon heating, may contain two-ring to 

seven-ring PAHs, several of which are 

mutagenic and carcinogenic (IARC, 

2011). In mammalian cells, exposure to 

bitumen emissions or their condensates 

produced mutagenic intermediates and 

DNA adducts. 

Analysis of the sample from Mile 2 

contains wide spectrum of PAHs (Figure 

3). In the sample, 37 PAHs have been 

found, with Hexadecane showing a 

higher percentage of 6.56%, others like 

Phenanthrene, Naphthalene and its 

derivatives show lower percentage. The 

United States Environmental Protection 

Agency (USEPA, 2000), ranked sixteen 

PAHs as priority in relation to health and 

the environment: Naphthalene (Na), 

Acenaphthalene (Ac), Acenaphthene (Ace), 

Fluorene (Flu), Phenanthrene (Ph), 

Anthracene (An), Pyrene (Py), Chrysene (Ch), 

Fluoranthene (FL), Benzo [a] anthracene 

(BaA), Benzo [b] fluoranthene (BbF), Benzo 

[k] fluoranthene (BKF), Benzo [a] pyrene 

(BaP), Dibenzo [a, h] anthracene (DA), Benzo 



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[g, h, i] perylene (BPE) and Indeno [1,2,3-c, d] 

pyrene (IP). Possible long-term damage 

caused by chronic health hazard has diverted 

more attention to PAHs.  

According to WHO (1998), apart 

from PAHs, several other substances 

potentially harmful to health are 

asphaltenes, straight and branched aliphatic 

hydrocarbons, naphthene aromatics and 

resins. From the analysis of Agbabu 

bitumen sample, Duodecane, ethyl ester 

shows a wide spectrum (Fig. 4) and the 

presence of benzene (target) ranged from 

1.16 to 2.57%. Spectrum of PAHs values 

of bitumen sample collected at 

Mulekangbo is shown in Fig. 5. The 

result of PAHs from bitumen sample 

collected at Mulekangbo indicates higher 

amount of Pyrene, and a considerable 

high amount of the entire target PAHs 

like Chrysene, Fluorene, Anthracene, 

Phenanthrene, Triphenylene and 

Fluoranthrene, but Triphenylene, Benz 

[a] anthracene, and Cyclohexane are 

negligible. The effects of PAHs present 

in Mulekangbo bitumen sample are 

considered to have carcinogenic and/or 

mutagenic potential. Exposure to these 

compounds through inhalation or even 

absorption through the skin during 

application to streets and roads can cause 

skin cancer (Gasthauer et al., 2007). The 

emissions generated during the 

production and application of the 

bitumen from this location would pose 

health and environmental risk to those 

involved. Also, these PAHs can leach 

into the environment through the 

degradation of the road surface and 

contaminate water bodies. When 

bitumen is applied during mixing in 

asphalt binders, it is usually handled at 

elevated temperatures, so trace amounts 

of PAHs may occur in the hot bitumen 

fume and cause cancers risk to the 

workers handling the mixing.

 

 

 

 

 

 

 

 

 

 

  

 

 

Figure 3. Spectrum of PAHs values of bitumen sample collected at Mile 2. 



Ademila O. & Ojo F.G.                                                                                EJSSD, V 5 (2), 2018 

79 
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Figure 4. Spectrum of PAHs values of bitumen sample collected at Agbabu. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5. Spectrum of PAHs values of bitumen sample collected at Mulekangbo 

 

6. Conclusion 

The engineering and chemical 

properties of natural bitumen samples 

collected from Agbabu and its environs 

have been determined using standard 

methods. The water content of bitumen 



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and loss on heating of the samples in the 

locations are greater than the 

recommended values of 0.2% and 1 max 

respectively. The specific gravity of the 

samples is below the standard value of 

1.01 for bitumen of good grade. From the 

penetration values, the bitumen are 

classified into two grades. Agbabu and 

Mulekangbo bitumen samples are 

classified as temperature susceptible 

bitumen while, Mile 2 (sample A and B) 

are classified as conventional paving 

bitumen. Mile 2 bitumen can be applied 

successfully in road construction in the 

tropics, but this can only be achieved 

after they must have been upgraded. 

The AAS test carried out showed that 

Agbabu, Mile 2 and Mulekangbo have a 

low concentration of heavy metals except 

for the high concentration of iron. 

However, low concentrations of lead and 

nickel in all the samples may pose 

environmental hazard and catalytic 

poisons during the refining of the 

bitumen. The GCMS revealed high 

percentage of PAHs in the bitumen 

sample collected from Mulekangbo and 

the targets PAHs like Pyrene, Anthracene, 

Fluorene, etc. are carcinogenic and 

mutagenic in nature. Exposure to these 

target PAHs during application to streets 

and roads through inhalation and 

absorption through the skin tend to pose 

health hazards. Therefore, exploitation of 

Mulekangbo bitumen must undergo the 

primary bitumen refining process 

“distillation” in order to remove the 

PAHs from the bitumen. The percentage 

of targets PAHs like Naphthalene in the 

samples collected from Agbabu and Mile 

2 are low with no Pyrene, Anthracene 

and Fluorene. Thus, Agbabu and Mile 2 

bitumen would have no impact on health 

and the environment during exploitation 

and utilization. This study recommends 

standard exploration and clean 

technology (distillation) during refining 

process to remove hazardous PAHs from 

the bitumen.

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