Materials Sciences and Applicatio ns, 2011, 2, 53-58
doi:10.4236/msa.2011.21008 Published Online January 2011 (http://www.SciRP.org/journal/msa)
53
Determination of the Pozzolanic Properties of
Olotu Marine Clay and Its Potentials for Cement
Production
Jide Muliu Akande1, Chinwuba Arum2, Fola Micah Omosogbe3
1,3Department of Mining Engineering, The Federal University of Technology, Akure, Nigeria; 2Department of Civil Engineering, The
Federal University of Technology, Akure, Nigeria
Received October 12th, 2010; revised December 16th, 2010; accepted December 31st, 2010.
ABSTRACT
The physical and chemical properties of marine clay at Olotu in Ilaje local government of Ondo State, Nigeria were
investigated. Some of the physical properties investigated include plasticity index, linear shrinkage and firing charac-
teristics (firing colour, shrinkage percentage, and water absorption capacity). The physical properties were determined
using X-ray diffractometry method. The chemical composition was determined using Atomic Absorption Spectroscopy
(AAS) method. All tests were carried out according to proced ures specified b y relevan t British and American Stand ards.
It was established that the physical and chemical properties were adequate to qualify it as pozzolanic material for ce-
ment production when compared with other pozzolanic materials and measured against relevant standards. The cement
produced was tested for compressive streng th and setting times and the results confirmed th e appropriaten ess of the use
of the clay as a pozzolana.
Keywords: Fineness, Spectroscopy, Compressive Strength, Physical Properties, Portland Cement
1. Introduction
As the need for buildings and similar facilities and the
requirement for improved quality of these facilities in-
creased in developing countries, the demand for Portland
cement also rose being the only cementitious product
used for construction in these countries. The high cost of
foreign exchange has been a major constraint in provid-
ing the needed schools, offices, communications infra-
structure and other vital facilities needed in most of the
African countries. There is therefore the need to search
for cheaper alternatives to Portland cement.
The production and use of alternative cement dates
back to the Roman days, and the remains of the great
buildings constructed with it are a testimony to its usage
dating back to antiquity. These alternative binding mate-
rials are known as pozzolanas. A pozzolana is a siliceous
and aluminous material which reacts with calcium hy-
droxide in the presence of water to form compounds
possessing cementitious properties at room temperature
and have the ability to set under water [1]. Pozzolanas
are classified as natural or artificial. Natural pozzolanas
may further be divided into two main groups as:
1) Those derived from volcanic rocks in which the
amorphous constituent is glass produced by fusion.
These include volcanic ashes and tuffs, pumice, scoria
and obsidian.
2) Those derived from rocks or earth for which the sil-
ica constituents contain Opal, either from precipitation of
silica from solution or from the remains of organisms.
Examples of these are diatomaceous earths, cherts,
opaline silica, and lava containing substantial amounts of
glassy component and clay which has been naturally cal-
cined by heat from flowing lava. In Africa, some of the
known sources of natural pozzolanas of volcanic origins
may be found in Cameroon, Cape Verde, Burundi,
Ethiopia, Tanzania, Kenya, Rwanda and Algeria.
Artificial Pozzolanas may be divided into two groups:
those of organic and those of inorganic origin. The most
important artificial pozzolanas of inorganic origin are
obtained from calcined clays and shales, calcined bauxite,
calcined bauxite-waste, calcined spent oil, calcined moler,
calcined gaize “fly ash” (pulverized fuel coal) and brick
powder (surkhi). Kaolinite is the mineral name for an
economic clay commonly called kaoline. It is a group of
clay minerals that consists of kaolinite, dickie, nitrite,
anauxite, halloysite and endellite. They are secondary

Determination of the Pozzolanic Properties of Olotu Marine Clay and Its Potentials for Cement Production 54
minerals formed by weathering hydrothermal alteration
or wall rock alterations of highly feldspathic rocks whose
compositions are only slightly different from each other,
especially in the stacking arrangement of their structures
[2]. The sources of artificial pozzolanas of organic origin
are ashes of rice husk, coffee hulls, coconut shells, sugar
cane bagasses and palm-nut shells and fibers. Investiga-
tions into the use of cocoa pod for pozzolana production
have not been concluded. Of these pozzolanas of organic
origin, rice husk ash has been well investigated and
documented [3]. This research is aimed at determining
the properties of Olotu marine clay in order to verify its
suitability as a pozzolana for the production of cement.
2. Materials and Method
2.1. Materials
The marine clay and periwinkle shell samples used in
this study were collected from Olotu, a town in Ilaje local
government, south western part of Ondo state, Nigeria.
Other materials include locally fabricated laboratory size
electric furnace for calcining the marine clay and peri-
winkle shell, a thermocouple which automatically con-
trols the heating and cooling of the furnace, a laboratory
size ball mill for milling the calcined materials and a set
of laboratory sieves. Other equipment used included the
Vicat apparatus for testing the setting time of cement and
a crushing machine for determining the compressive
strength of moulded cubes.
2.2. Method
2.2.1. Production Procedure
The samples of Olotu marine clay were moulded into
balls of about 30 mm in diameter and dried in the sun to
reduce the moisture content. At a temperature of 700˚C,
the dried clay was calcined in the electrically heated fur-
nace for about 3 hours. This temperature was maintained
with the aid of a thermocouple and a suction fan at the
exhaust. After 24 hours the calcined clay was pulverized
and milled in the ball mill and later sieved using a set of
laboratory sieves with sieve shaker to fines of 1.18 mm.
The periwinkle shell was heated at 750˚C for 1.75
hours in the furnace with the temperature controlled us-
ing the thermocouple, and the carbon dioxide gas (CO2)
pressure reduced or controlled by the suction fan at the
exhaust. The fan sucked out the emitted CO2 by the shell,
reducing the pressure in the furnace and thereby avoiding
re-carbonation of the quicklime produced. The dis-
charged quicklime was slaked by manually sprinkling
some quantity of water (55 liters per 200 kg i.e., 27.5%
of shell weight) on it. The slightly moist and hot slaked
lime was left to dry out and cool for 24 hours, after
which it was pulverized and milled in the ball mill and
then sieved through 1.18 mm mesh.
The processed materials were batched by weight in the
ratios 3:1 and 2:1 corresponding to three pozzolana to
one lime and two pozzolana to one lime [4,5]. Regrind-
ing of the mix was done in the ball mill to produce fines
of 125-106 microns (120-150 mesh) after sieving. The
Lime-Pozzolana Cement (LPC) was bagged in polyeth-
ylene-lined bag and ready for use.
2.2.2. Tests for Setting Time
The Vicat apparatus was used for the purpose of deter-
mining the setting time and standard consistency of the
lime-pozzolana cement in accordance with the provisions
of [6], with a needle diameter 1.30 mm and load 300 g.
The needle was released at the surface of the hydrated
cement paste at intervals until it penetrated only to a
point 5 mm ± 1 mm from the bottom of the mould. When
the paste attained this degree of stiffness, it was said to
have reached initial set. A second needle, similar to the
first but with an attached concentric ring was then used
to determine final setting time. This was reached when
the needle made an impression on the surface of the paste
but did not penetrate the 0.5 mm necessary for the ring to
mark the surface.
2.2.3. Compressive Strength Tests
2.2.3.1. Moulding and Testing of Cubes
Various cubes were made using 150 mm cube moulds.
Table 1 shows the mix proportions of the mortar used for
the cubes (A to C) cast from different cements as propor-
tions by weight of Cement: Sand: Water. A constant
volume of water was used [4].
Cubes A1 and A2 were produced from Ordinary Port-
land Cement (OPC) and served as control for B1, B2 and
C produced from Lime-Pozzolana Cement (LPC). The
compressive strengths of the cubes were obtained at ages
7, 14, 21 and 28 days. The densities of the cubes were
calculated when wet and when dry.
3. Results and Discussion.
3.1. Results
3.1.1. Physical Properties
The firing characteristics of Olotu clay are shown in Ta-
Table 1. Mortar mix proportions for different cements.
Cube mark Composition
OPC Sand Water
A1 1 3 0.6
A2 1 2 0.6
LPC Sand Water
B1.1 1 3 0.6
B1.2 1 2 0.6
B2.1 1 3 0.6
B2.2 1 2 0.6
(OPC:LPC) Sand Water
(7:3) C
1 3 0.6

Determination of the Pozzolanic Properties of Olotu Marine Clay and Its Potentials for Cement Production 55
ble 2 while the results of its essential geotechnical index
properties are presented in Table 3.
3.1.2. Chemi c al Comp osition
The result of the analysis of Olotu marine clay for
chemical composition is shown in Table 4 while the
chemical composition of the periwinkle shells is shown
in Table 5.
3.1.3. Setting Time
The results of the tests for the setting times of the various
cements are presented in Table 6.
3.1.4. Compressive Strength
The result of the compressive strengths of mortar cubes
cast from the various cements, including their weights
and densities, is presented in Table 7.
3.2. Discussion of Results
3.2.1. Firing Characteristics
The moist samples were dark and light to dark grey in
colour but later exhibited colour change when fired. Two
groups of fired colours were obtained: reddish brown/
pinkish and buff colours. These colours showed depend-
ence on the amount of iron and titanium (as pigment)
oxides present. The clays with iron oxides between 2-3
percent give reddish brown and pink colour (Table 2).
This result is somewhat similar to those obtained by Og-
bukagu [7] for argillacious clays of Suthern Nigerian
sedimentary basin. It has been established [8] that clays
with iron oxide exceeding 2-3 percent usually give pink-
ish and/or reddish brown colour upon firing whereas,
Table 2. Firing characteristics of Olotu marine clay.
Sample
No. Moist colour Firing colour Shrinkage (%)
Water
absorption
(%)
1. DG RB 17.23 13.50
2. LG CBU 14.50 11.40
3. DG P 13.63 13.34
4. DG RB 13.42 13.22
5. G C 12.57 12.58
Table 3. Some geotechnical index properties of Olotu ma-
rine clay.
Sample
No. Clay + Silt (%) Sand (%)
Plastic
Limit
(%)
Plasticity
Index Linear Shrinkage (%)
1. 88.0 12.0 64.7 43.7 13.50
2. 82.0 18.0 52.5 35.4 11.38
3. 95.0 15.0 36.7 36.5 11.42
4. 86.0 14.0 58.7 39.3 11.60
5. 90.0 10.0 68.3 46.3 12.30
Table 4. Chemical composition of Olotu marine clay (%).
Sample SiO2Al2OFe
2O3TiO2 MgO CaO K2O NaOLOI
BH152.3012.713.441.02 0.38 2.55 0.30 0.5126.80
BH248.7318.523.460.86 0.51 2.42 0.41 0.4724.59
BH354.2024.022.551.05 0.22 1.97 0.47 0.6414.88
BH451.4023.652.851.20 0.40 2.51 0.38 0.5217.09
BH545.6622.623.851.10 0.31 2.35 0.43 0.4623.22
Table 5. Chemical composition of periwinkle shell (%).
SiO2AL2O3Fe2O3CaOMgO NaO LOITotal
1.18 0.51 0.35 66.13 0.02 0.11 33.5699.86
Table 6. Experimentally determined setting times of differ-
ent cements.
Cube mark IST (Hr) MFST (Hr)
A 0.72 10.25
B1 1.38 16.08
B2 1.20 15.50
C 1.00 13.75
those with lower percentage of iron oxide develop
creamy, whitish or buff shades. In the present work,
about two of the samples developed cracks on firing. It
was observed that those samples with high content of
coarser material have this property while those with high
content of fine material developed no cracks on firing.
3.2.2. Geotechnical Index Properties
Table 3 contains the results of the geotechnical index
property tests. All the clay samples are fine grained,
characterized by high proportions of clay plus silt frac-
tions, the rest of the material being considered as sand.
Close examination of the sand particles revealed that
they were made up of a mixture of quartz and iron grains.
These were as a result of tropical weathering of rocks.
The clay is very plastic. This property reflects in the
narrow range of the plasticity index (35.4-46.3), which is
attributed to very low percentage of sand and significant
amount of clay and silt. These two physical properties
are responsible for high linear shrinkage values (11.38
-13.50%) obtained. It could be inferred that the higher
the plasticity, the higher the percentage shrinkage and the
higher the clay contents.
3.2.3. Chemi cal and Mi neralogical Comp o s i tion o f
Olotu Marine Clay
The clay contained some amount of lime (CaO), alkali
and magnesia oxides less than 1%. The low amount of
sodium oxide indicates low proportion of montmorilonite
in the samples and the low amount of potassium oxide
indicates low amount of illite present.

Determination of the Pozzolanic Properties of Olotu Marine Clay and Its Potentials for Cement Production 56
Table 7. Compressive strength of mortar cubes.
Compressive strength (MPa)
Cube
mark
Wet weight
(kg)
Density
(kg/m3)
Dry weight
(kg)
Density
(kg/m3) 7 days 14 days 28 days
A1
7.51
7.56
7.43
2225
2240
2201
6.41
6.42
6.39
1902
1893
1899
6.91
7.11
7.02
9.96
10.06
10.18
15.40
15.41
15.42
A2
7.60
7.58
7.62
2252
2245
2258
7.23
7.24
7.22
2142
2143
2139
10.10
11.11
11.12
11.12
14.50
14.60
18.15
18.13
18.11
B1
B1.1
7.28
7.32
7.32
B1.2
7.37
7.38
7.35
2157
2168
2168
2183
2186
2177
6.84
6.82
6.86
6.94
6.98
6.95
2026
2021
2032
2056
2068
2059
3.76
3.89
3.77
4.75
4.74
4.76
5.60
5.54
5.56
7.32
7.30
7.28
7.83
7.81
7.79
10.01
10.03
10.05
B2
B2.1
7.40
7.42
7.38
B2.2
7.52
7.53
7.51
2192
2198
2186
2228
2281
2225
6.96
6.98
6.94
6.98
7.10
6.95
2062
2063
2056
2068
2077
2059
2.99
2.13
2.17
2.91
2.96
2.92
2.90
3.01
3.03
4.40
4.20
4.02
4.60
4.63
4.66
5.66
5.64
5.62
C
7.45
7.58
7.42
2207
2216
2198
7.02
7.04
7.03
2080
2085
2082
5.33
5.31
5.24
8.55
8.50
8.45
12.38
12.40
12.44
The X-Ray Diffraction (XRD) anaysis showed that
kaoline was the main clay mineral present in the sample.
It is recognized on the diffractograms at 2θ values of
26.60, 50.12, 20.13 and 68.08 (Figure 1). Quartz (60.03,
54.05, 36.30 and 12.40) is the principal non-clay mineral
in all the samples. The illite mineral appears at values
70.50, 72.50 and 76.80. The kaolinite and quartz peaks
are the most prominent on the diffractogram. Kaolinite is
the dominant clay mineral in the deposit and quartz is the
main subsidiary non-clay mineral detected from the XRD
trace.
3.2.4. Chemical Composition of Periwinkle Shell
Analysis of periwinkle shells presented in Tabl e 5 shows
a large percentage of CaO, which is a common charac-
teristic of shells. Its low magnesia content is a proof that
it possesses the general properties of calcium limes [9].
This is one of the criteria that qualified it as source of
lime in this research work.
3.2.5. Setting T i me of LPC
From the results of the tests for setting time shown in
Table 6, the times for LPC (B1) are longer than that of
Portland cement but still within the limit specified by BS
12 [10]. The longer times of the LPC are due to low
fineness of the materials compared with Portland cement.
The water content of the paste is another factor that af-
fects the setting time of cements. The higher the water
content of the paste, the longer it will take for the hydra-
tion product to form a structure with the chosen resis-
tance to penetration. Water to cement ratio of 0.60 tested
in Britain and favored in other European countries and in
USA is adopted in this work: Table 1 [4,10]. The factors
put together contributed to the differences shown in Ta-
ble 6. As shown in the table, the initial setting time of C
is low compared to those of B1 and B2. This is as a result
of the presence of OPC which boosted the hydration
process.
3.2.6. Compressive Strength of LPC
Table 7 shows a high positive correlation between the
density of a cube and its compressive strength. It shows
that the higher the density the higher the compressive
strength of the cube.
The major factor responsible for variations in strength
between group A and B is the variation in silicate content.
Group B1 has higher strength than B2 because the ce-
ment has the proportion of silicates needed for good
strength and so preferred to B2. Figure 2 illustrates the
variation in strengths of cubes made from different ce-
ments, with B1 having a steady increase in strength after
the seventh day.
4. Conclusions
From the results of this work the following conclusions
are apt.
1) The clay exhibits properties that qualify it as poz-
zolanic material for cement production, having 66.5% of
the oxides of silicon, aluminium and iron and 2.36% of

Determination of the Pozzolanic Properties of Olotu Marine Clay and Its Potentials for Cement Production 57
Figure 1. X-ray diffraction pattern of Olotu marine clay.
0
2
4
6
8
10
12
14
16
18
20
1
A
2
A
B1.1
B1.2
B2.1
B2.2
C
Compressive strength (MPa)
07th14th 28th
Figure 2. Relationship between the age of mortar and its compressive strength, for different cements.
calcium oxide in line with the recommendations of the
American Society for Testing and Materials (ASTM).
2) The delay in the setting times of the lime pozzolana
cements is as a result of its low fineness compared with
Portland cement.
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Determination of the Pozzolanic Properties of Olotu Marine Clay and Its Potentials for Cement Production 58
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Notation
OPC Ordinary Portland Cement
LPC Lime Pozzolana Cement
C Cream
CBU Cream Buff
DG Dark Grey
G Grey
LG Light Grey
P Pinkish
RB Reddish Brown
IST Initial Setting Time
MFST Maximum Final Setting Time