Journal of Mi nerals & Materials Characterization & Engineering, Vol. 10, No.4, pp.357-366, 2011 Printed in t he USA. All rights reserved
Investigation of the Effect of the Addition of Petroleum Waste
to Interlocking Bricks Const i t u ent
P. O. Atanda 1, O. O. Oluwole2* and I. D. Olumor1
1Department of Materials Science and Engineering O.A.U., Ile-Ife, Nigeria.
2* Mechanical Engineering Department, University of Ibadan.
Corresponding Author:
Incinerator ash was investigated for its potential use as a replacement for sand and cement in
concrete interlocking bricks. The physical characteristics of the raw materials were
examined. Two sets of mixes were prepar ed. For the first set, sand and water quan tities were
fixed while incinerator ash was used at 0% to 100% replacement by weight for cement in
steps of 10%. In the second set, incinerator ash was used at 0% to 100% replacement by
weight for sand while cement and water quantities was fixed. The mixing proportions for
cement, sand and water were 1:3:0.7, respectively. Compressive strength and leachability
tests were performed on the specimens.
Results showed that the replacement of sand by incinerator ash up to 40% exhibited higher
compressive strength than the control mix (0% incinerator ash) after 28 days curing.
Maximum compressive strength of 33.33N/mm2 was obtained after 28 days curing using
using 20% incinerator ash substitution for sand. Replacement of cement by incinerator ash
up to 20% exhibited higher compressive strength than the control mix. Compressive strength
of 28.2 N/mm2 was achieved after 28 days curing period using a 20% ash substitution for
cement. Leaching of heavy metals (Pb and Cd ) present in the ash was observed in
concentrated nitric acid.
Key words: interlocking bricks; sand; cement; replacement; petroleum waste ash;
compressive strength
Interlocking bricks are a form of concrete for pavements and roads arranged to interlock wi th
each other so as to reinforce each other and overcome buckling. They have special
358 P. O. Atanda, O. O. Oluwole and I. D. Olumor Vol.10, No.4
composition that allows for stress resistance without necessarily having to be reinforced with
metal rods as is the case for concrete beams. Concrete generally is a construction material
composed of ce ment as well as oth er materials such as s and, water, aggregates and chemical
admixture s[1]. The word concrete comes from the Latin word “concretus”, which means
“hardened” or “hard” [2]. Interlo cking bricks are engine ering materials designed to withstand
compressive loads.
Investigation of the effect of the addition of petroleum waste ash to interlocking bricks
constituent is a project that aims at investigating the possibility of reducing or even replacing
the cement content of interlocking bricks with waste ash, while the interlocking brick still
maintains desired compressive strength.
Fly-ash, the most commonly used incinerator ash product- is a remarkable material that cost
effectively improves the performance of products it is added to. For instance, in making
concrete, cement mixed with water served as the glue which holds strong aggregates tog ether .
Fly ash works intandem with cement in the production of concrete materials. Concrete
containing fly ash is easier to work because the tiny, glassy beads create a lubricating effect
that causes concrete to flow and pump better, to fill forms more completely and to do it all
using up to 10 percent less water [3].
Because the tiny fly ash particl es fill the microscopic spa ces in the con crete, and because less
water is required, concrete using fly ash is denser and more durable. Fly ash reacts
chemically with lime that is given off by cement hydration, creating more of the glue that
holds concrete together. That makes concrete containing fly ash stronger over time than
concrete made only with cement. According to [4], fly ash is comprised of non-combustible
mineral portion of waste petroleum consumed in a petroleum waste incinerator. Fly ash
particles are glassy, spherical sh aped ball bearings- typically finer than cement particles- that
are collected from the combustion air stream exiting the plant. There are two basic types of
fly ash: clas s F and class C [5]. Both types react in concrete in similar ways. Both under go a
pozzolanic reaction with lime from cement hydration.
The main benefit of fly ash in concrete is that it not only reduces the amount of non durable
calcium oxide (lime), but in the process converts it into calcium silicate hydrate (CSH),
which is the strongest and most durable portion of the paste in concrete. To fully appreciate
the benefits of fly ash in concrete, the basics of producing exceptional concrete must be
understood. Concrete is a composite material which essentially consists of two components:
aggregates and cementiceous paste. To produce good concrete, it is extremely important to
have a smooth gradation of materials from rocks down to the finest particles. In other words,
there must be a good mix of particle sizes so that the smaller rock and sand fill the voids left
between the larger particles [1]. There is a general misconception of durability and strength
when talking about concrete. Durability is the ability to maintain integrity and strength over
time. Strength is only a measure of the ability to sustain loads at a given point in time [6].
Cement normally gains most of its strength within 28 days, thus the reasoning behind
specification normally requiring determination of 28 days strength as standard. As lime from
Vol.10, No.4 Investigation of the Effec t of the Addit ion o f Petrole um Waste 359
cement hydration becomes available, it reacts with fly ash. Typically, concrete made from fly
ash will be slightly lower in strength than straight cement concrete up to 28 days, equal
strength at 28 days and substantially higher strength within a year. Conversely, in straight
cement concrete, lime remains intact and over time is susceptible to effects of weathering
resulting in loss of strength and durability [7].
2.1 Sample preparation
The test specimens were prepared as 2cm diameter by 4cm length cylinders. Moulds for the
cylindrical specimens were made of rigidly constructed non-absorbent plastic tubes to
facilitate removal of the moulded specimen without damage (Fig.1).
Fig.1: Plastic moulds
The sand used was thoroughly washed and dried sieved. Sand used for ramming were not
more than 1.4mm size after sieving. Distilled water was used for mixing and curing of the
concrete specimens.
The ash used was obtained from Delta Environmental Logistics, Port-Harcourt, Nigeria
(Fig.2). The ash sample was ground in a cer amic mortar and sieved. 125µ m size of ash was
used for the experiment folowing BS 410 full tolerance test sieve.
360 P. O. Atanda, O. O. Oluwole and I. D. Olumor Vol.10, No.4
Fig.2: Unsieved ash
In the first set of samples, percentage of sand and water in the mixes were kept constant
while cement content was reduced in steps of 10 % and supplementing the cement reduction
with with ash additive to the same tone of reduction (Table 1).
Table 1: Proportioning mix for samples with Ash used as substitute for Cement.
identification %wt of ash Weight of cement
(g) Weight of Ash (g)
A second set was prepared with water and ce ment contents kept constant while sand content
was reduced from in steps of 10% and replaced with ash.(Table 2). A mixture of sand,
cement and water in the proportion 3:1:0.7 were prepared. Control sample had a mix
proportion of of 22.340g of sand, 5.210g of water and 7.450g of Portland cement.
2.2 Moulding Specimens
During the asse mbly of the plastic moulds, the joints and bo ttom of the moulds were covered
with a thin film of petroleum jelly and wrapped with polyethene in order to ensure that no
water escaped during ramming and setting. The assembled moulds wer e then placed on a flat
Vol.10, No.4 Investigation of the Effec t of the Addit ion o f Petrole um Waste 361
surface and held f ir mly. Immediately after mixing, the whole of the mortar were p laced in th e
mould cavity and then subsequently compacted and rammed for about 2 minutes.
Table 2: Proportioning mix for samples with Ash used as substitute for Sand.
identification %wt of ash
Weight of sand
(g) Weight of ash
2.3 Curing Specimens
The specimens were left undisturbed in a relatively humid environment for about 24 hours
after ramming had been completed. At the end of this period, the specimens were removed
from the moulds and submerged completely in clean fresh water and kept there until taken
out just prior to testing. The water in which they were completely submerged were renewed
every 7 days (for curing periods of 28 days) and maintained at ambient temperature. Care was
taken that samples were not allowed to get dry until curing test was conducted (Fig.3)
Fig.3: Cured Brick Samples
2.4 Compressive Tests
362 P. O. Atanda, O. O. Oluwole and I. D. Olumor Vol.10, No.4
The specimens were tested for compressive strength immediately after removal from the
curing chamber whil e they were still wet. Su rface water and grit were wiped of f the samples
and all projected fins were removed gently with the aid of a hand file. Thre e samples per each
mix proportion were tested and the average was found. The load was then steadily and
uniformly applied starting from zero until the test piece just fractures(Fig.4). The fracture
load was noted and recorded.
Fig.4: Brick fracturing during compression
The compressive strengths for the specimens were calculated from the crushing load and the
cross sectional area over which the load was applied by using the equation:
Compressive strength = P/A
Where P= crushing load, A= cross sectional area of the specimen. Comparison of result was
made with value of bricks with no ash additives which is 23.5 N/mm2[8]. Requirements for
general use concrete is about 21 N/mm2 [8].
2.5 Leaching Test
Leaching test was carried out on the sample with maximum strength i.e. sample with 20% ash
substituted for cement. Leaching test was performed at room temperatures. The sample was
first finely ground and separated into particle sizes of 2.8mm, 1.4mm, 1.1mm, 300µm and
250µm using the BS 410 full tolerance test sieve. Concentrated nitric acid was used for
leaching. 3g each of the ground samples were then measured and poured into five separate
beakers. The acid solution was then poured into the beakers and agitated for an hour.
Afterwards the mixtures were filtered through a filter paper. The filtrate was collected and
Vol.10, No.4 Investigation of the Effec t of the Addit ion o f Petrole um Waste 363
analyzed usi ng a tomic absorption spectro metry (AAS). The results ob ta in ed from the analy s is
are presented in Table3. Immobilization coefficient of leaching was calculated using the
Immobilization coefficient = (leached value of pure ash – leached value of concrete)/leached
value of pure ash) [9].
3.1 Results
The compressive strengths of the various sand/cement/ash and water admixtures are
presented in Figures 5 and 6. Figure 5 shows the case where ash is substituted for cement
while Figure 6 shows the situation where ash is substituted for sand sa mples. It could be seen
in Figure 5 that compressive strength of bricks substituted with ash up to 20% in place of
cement and cured for 28days were stronger than bricks without any ash content. In Figure 6,
bricks with ash substituted up to 40% in place of sand and cured for 28days had compression
strengths higher than bricks without ash content. The two plots also showed that curing at 28
days gave best compressive strengths. The plots also showed that all the samples cured for
less than 28 days had compressive strengths less than bricks with no ash content cured for
020 40 60 80100120
% W t. A sh
Compre ssive Strength(N/
7 Days Curing
14 Days Curing
21 Days Curing
28 Days Curing
Fig.5: Compressive Strength versus %wt ash substituted for cement; with sand and water
content kept constant.
364 P. O. Atanda, O. O. Oluwole and I. D. Olumor Vol.10, No.4
0 20406080100120
% W t. Ash
Compressive Strength (N/
7 Days Curing
14 Days Curing
21 Days Curing
28 Days Curing
Fig.6: compressive strength versus %wt ash substituted for sand; with cement and water
content kept constant.
Figure 7 shows particle size effect on leaching of heavy metals present in the ash in the
bricks. The result showed that leaching increased with decreasing particle size of bricks.
Table 3 presents the immobilization coefficient for the leaching reactions. It showed
immobilization coefficient was highest for smallest particle size and lowest for the biggest
particle size.
Particle size of crushed samples(mm)
Amount leached(ppm)
Fig.7: Effect of crushed concrete particle size on Concentrated Nitric acid leaching of heavy
metals present in the ash incorporated in the bricks.
Vol.10, No.4 Investigation of the Effec t of the Addit ion o f Petrole um Waste 365
Table 3: Immobilization coefficient for leaching operations.
identification Immobilization coefficient
(Pb)(%) Immobilization coefficient
2.8mm 43.7 44.0
1.4mm 57.7 55.2
1.1mm 63.4 62.7
300µm 74.6 72
250µm 83.1 83.2
3.2 Discussion
Replacement of sand by incinerator ash(Fig.5) up to 40% exhibited a higher compressive
strength than the control mix (0% incinerator ash) after 28 days of curing. The maximum
compressive strength of 33.33N/mm2 was achieved using 20% incinerator ash after 28 days
of curing.
Specimens prepared using 20% incinerator ash replacement for cement (Fig.6)yielded a
higher compressive strength than the control mix after 7 and 28 days of curing. The
maximum compressive strength of 28.2N/mm2 was achieved after 28 days curing period.
From Fig.7, the results for leaching show that as the particle size of the crushed brick
increases, the leachability of heavy metals decreases. This is expected because the finer the
communition, the easier it is for the leachant to reach the species in the interlocking bricks.
Water when used as leaching agent, showed no detectable leaching of heavy metals at the
temperature, leaching time and particle sizes used.
Also, there was substantial amount of heavy metal (Pb and Cd) leaching for all replacement
of cement by ash in interlocking bricks. The immobilization coefficients for the concrete
crushed to various particle sizes showed the obvious pattern reflected in the leaching
operation.The smaller sized particles leached better and had higher immobilization values.
This work has shown that the fly-ash generated from the Nigerian petroleum waste
incineration plants can be suitably substituted for cement up to 20% replacement in use as
interlocking bricks constituent. At this level of replacement, the bricks will achieve a
compressive strength of 15.81 N/ mm2, 22.11 N/mm2 and 28.20 N/mm2 for 3 days, 7 days and
28 days curing periods respectively which fall under the acceptable values for compressive
strengths of interlocking bricks as stipulated by BSI 4550:Part 5:1972.
366 P. O. Atanda, O. O. Oluwole and I. D. Olumor Vol.10, No.4
The results for leaching show that as the particle sizes of the crushed concrete increases, the
leachability of heavy metals decreases being locked in the mass of brick.
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