Complete Work

CHAPTER ONE

INTRODUCTION

1.1 PREAMBLE.

In the last fifty years many soil scientists like Taylor (1951),Casagrande and Wilson,

1953 e.t.c were devoted to lateritic soil research and contributed their specific experiences with

soil forming processes. Recycling of industrial and agricultural waste products in the

manufacturing industry has been the focus of research for economical and environmental

reasons. In countries of the tropics and sub tropics, lateritic soils are encountered in various

engineering projects. Geotechnically, soil improvement could either be by modification or

stabilization, or both. Soil modification is the addition of a modifier (cement, lime, etc) to a soil

to change its index properties, while soil stabilization is the treatment of soils to enable their

strength and durability to be improved such that they become totally suitable for construction

beyond their original classification (Alhasan,2008)

The stability of structures founded on soil depends to a large extent on the interaction of

the said soil with water. Some soils of the tropics (e.g., black cotton soil), absorb large amount of

water during the rainy season and do not allow easy passage of such water. This consequently

results in a large volume increase which drastically reduces during the dry season. This

phenomenon has substantial effect on structures founded on such soils. Also, road bases built

with soils that are not easily drained are affected by the development of pore water pressures

which causes the formation of potholes and, eventually, the total failure of such roads. In an

attempt to minimize these effects, such soils are subject to treatments aimed at either disallowing

1

water into them or allowing easy passage (drainage) of water to prevent pore water

development(Alhassan,2008).

A lot of laterite gravels and pisoliths, which are good for gravel roads, occur in tropical

countries of the world, including Nigeria (Osinubi and Bajeh 1994). There are instances where a

laterite may contain a substantial amount of clay minerals that its strength and stability cannot be

guaranteed under load especially in the presences of moisture. These types of laterites are also

common in many tropical regions including Nigeria where in most cases sourcing for alternative

soil may prove economically unwise but rather to improve the available soil to meet the desired

objective (Mustapha, 2005). Experience with soils in the temperate zones revealed that

compositional factors namely grain size distribution and plasticity characteristics exert

significant influence on the engineering properties of soils. Apart from assisting in the

identification and classification of soils, they are indicators of problems in the fundamental

properties of the soil such as compressibility, strength, permeability, swell potential and

workability( Amadi,2010).

Great importance is accorded to the properties listed above when lateritic soil is been

zconsidered for a project . In this regard, they are used to screen materials for various

construction purposes. For example, percentage fines greater than or equal to 30%, percentage

clay greater than or equal to 15%, liquid limit greater than or equal to 20% and plasticity index

greater than or equal to 7% are specified for liner and cover materials to be used in waste

landfills, while for road bases, materials with percentage passing BS 200 sieve greater than 35%,

liquid limit greater than 35% and plasticity index greater than 12% are rejected without further

investigation because such values give indication of poor and undesirable soil qualities for such

purposes (Amadi, 2010). On the basis of this, mixtures of lateritic soil and sawdust ash with

2

varying proportions of sawdust ash were subjected to relevant tests to determine changes in the

index properties. These tests are grain size analysis, Atterberg limits, specific gravity,

compaction and shear strength tests.

1.2 Statement of Problem

The laterite and lateritic soils can be effectively stabilized to improve their properties for

particular uses. However, because of the wide range in lateritic soil characteristics, no one

modifying agent has been found successful for all lateritic materials. Laboratory studies, or

preferably field tests, must be performed to determine which modifying agent, in what quantity,

performs adequately on a particular soil. Some that have been used successfully are:

Cement, asphalt lime and mechanical stabilization. Laterite and lateritic soils can still perform

satisfactorily in a low-cost, unsurfaced road, even though the percent of fines is higher than is

usual in the continental United States. This is believed to be due to the cementing action of the

iron oxide content. Cement and asphalt work best with material of a lower fines content. When

fines are quite plastic, adding lime reduces the plasticity to produce a stable material. (Special

soil problems, chapter 12)

The main by-product of sawmills, unless reprocessed into particleboard, burned in a

sawdust burner or used to make heat for other milling operations, sawdust may collect in piles

and add harmful leachates into local water systems, creating an environmental hazard. This has

placed small sawyers and environmental agencies in a deadlock.

1.3 Justification of the Study

The burning of wood, wood waste, and other biofuels results in a great deal of ash that is

similar in properties to activated carbon. This similarity, due to the incomplete combustion of

3

wood at temperatures greater than 700°C, is what makes wood ash such a beneficial material.

    The carbonization process that occurs during the combustion of wood fuels causes the random

bonding of carbon in ash. This results in defects at the molecular level, forming voids within the

carbon that give wood ash a high surface area. This property of wood ash is what helps it absorb

odors, which makes it a useful additive to compost and bio-solid fertilizers. ( Rosenfield,2000).

In this project the feasibility of modifying the lateritic soil in question with sawdust ash will be

investigated.

1.5 Aims and objectives of the Study

Literarily this work was aimed at the modification of lateritic soil with sawdust ash using

the British Standard heavy compactive effort. The specific objectives include;

(i) Determination of the index properties of the natural lateritic soil and sawdust ash treated soil.

(ii) Determination of the moisture-density relationship of the natural and treated soil using the

British Standard compaction energy.

(iii) Determination of the effect of sawdust ash on the shear strength properties of the treated

soil.

(iv) Determination of the optimal quantity of sawdust ash required to improve the workability of

lateritic soil for use in road construction.

1.6 Scope of Research

This research work was carried out on the modification of lateritic soil treated with up to 5%

sawdust ash content compacted using the British Standard heavy (BSH) compaction energy.

Tests were carried out in accordance with procedures outlined in BS 1377(1990) and BS

1924(1990)

4

CHAPTER TWO

LITERATURE REVIEW

2.1 General

Bell (1993) defined soil as a material having three components, which includes: solid

particles, air and water. The geological formation is based on rock weathering which can occur

either chemically when the minerals of a rock are altered through a chemical reaction with rain

water, or mechanically through climate effects such as freeze – thaw and erosion.From an

engineering perspective, soil is any un-cemented or weakly cemented accumulation of mineral

particles formed by the weathering of rocks and contains void spaces between particles, which

are filled by water, and air (Bello et al,2006).

Soil is said to be residual soil, if the present location of the soil is that in which the

original weathering of the parent rock occurred, otherwise, the soil is referred to as transported.

Laterite is a soil group, which are formed under weathering systems productive of the process of

laterization (decomposition of ferro alumino – silicate minerals, leaching of the combined silica

and base; and the permanent deposition of sesquioxide within the profiles (Wooltorton, 1975).

The silica that is left unleached after laterization will form secondary clay silicate minerals.

Laterites usually form a poor soil full of concretionary lumps and very unfertile because the

potash and phosphate has been removed in solution, while only iron and silica are left behind

(Gidigasu, 1976).

Laterites have been widely used for foundations and other construction purposes in

subtropical and tropical regions, where they are deposited abundantly. For any soil to be utilized

for Civil Engineering works there is need for its investigation to enable the engineers to use the

5

soil economically, to predict their engineering properties and their performance under field

conditions, with a fairly good degree of accuracy.

2.2 Soil Properties

Soils can be enormously complex systems of organic and inorganic components. Here a few of

the most significant properties, texture, structure, colour, and chemistry are considered

2.2.1 Soil Texture

Soil texture refers to the relative proportion of sand, silt and clay size particles in a sample of

soil. Clay size particles are the smallest being less than 0.002 mm in size. Silt is a medium size

particle falling between 0.002 and 0.05 mm in size. The largest particle is sand with diameters

between 0.05 for fine sand to 2.0 mm for very coarse sand. Soils that are dominated by clay are

called fine textured soils while those dominated by larger particles are referred to as coarse

textured soils. Soil scientists group soil textures into soil texture classes(Michael,2009). A soil

texture triangle is used to classify the texture class (see fig2.0).

Figure 2.0 Soil Texture Triangle

6

The sides of the soil texture triangle are scaled for the percentages of sand, silt, and clay. Clay

percentages on the left side of the triangle are read from left to right across the triangle (dashed

lines). Silt runs from the top to the bottom along the right side and is read from the upper right to

lower left (light, dotted lines). The percentage of sand increases from right to left along the base

of the triangle. Sand is read from the lower right towards the upper left portion of the triangle

(bold, solid lines). The boundaries of the soil texture classes are highlighted in blue. The

intersection of the three sizes on the triangle give the texture class. For instance, if you have a

soil with 20% clay, 60% silt, and 20% sand it falls in the "silt loam" class. Soil texture effects

many other properties like structure, chemistry, and most notably, soil porosity, and

permeability. Soil porosity refers to the amount of pore, or open space between soil particles.

Pores are created by the contacts made between irregular shaped soil particles. Fine textured soil

has more pore space than coarse textured because you can pack more small particles into a unit

volume than larger ones. More particles in a unit volume creates more contacts between the

irregular shaped surfaces and hence more pore space. As a result, fine textured clay soils hold

more water than coarse textured sandy soils. Permeability is the degree of connectivity between

soil pores. A highly permeable soil is one in which water runs through it quite readily. Coarse

textured soils tend to have large, well-connected pore spaces and hence high permeability.

2.2.2 SOIL STRUCTURE

Soil structure is the way soil particles aggregate together into what are called peds. Peds come in

a variety of shapes depending on the texture, composition, and environment(Michael,2009).

7

Figure 2.2 Common soil structure forms

2.2.2.1 Granular

Granular or crumb structures, look like cookie crumbs. They tend to form an open structure that

allows water and air to penetrate the soil. Platy structure looks like stacks of dinner plates

overlaying one another. Platy structure tends to impede the downward movement of water and

plant roots through the soil. Therefore, open structures tend to be better agricultural soils.

2.2.2.2 Bulk Density

The bulk density of a soil is the mass per unit volume including the pore space. Bulk density

increases with clay content and is considered a measure of the compactness of the soil. The

greater the bulk density, the more compact the soil. Compact soils have low permeability,

inhibiting the movement of water. The use of heavy agricultural equipment can cause

compaction of soil, especially in wet clay soil. Soil compaction results in reduced infiltration and

increase runoff and erosion.

8

2.2.3 Soil Chemistry

As plant material dies and decays it adds organic matter in the form of humus to the soil. Humus

improves soil moisture retention while affecting soil chemistry. Cations such as calcium,

magnesium, sodium, and potassium are attracted and held to humus. These cations are rather

weakly held to the humus and can be replaced by metallic ions like iron and aluminum, releasing

them into the soil for plants to use. Soils with the ability to absorb and retain exchangeable

cations have a high cation-exchange capacity. Soils with a high cation-exchange capacity are

more fertile than those with a low exchange capacity.

Hydrogen ion concentration in the soil is measured in terms of the pH scale.  Soil pH ranges

from 3 to 10. Pure water has a pH of 7 which is considered neutral, pH values greater than seven

are considered basic or alkaline, below seven acidic. Most good agricultural soils have a pH

between 5 and 7. Though acidic soils pose a problem for agriculture due to their lack of

nutrients, alkaline soils can pose a problem as well. Alkaline soils may contain appreciable

amounts of sodium that exceed the tolerances of plants, contribute to high bulk density and poor

soil structure. Alkaline soils are common in semi-arid regions.

9

Figure 2.3 Soil pH

2.3 ORIGIN AND DEFINITION OF LATERITE

2.3.1 LATERITES AND LATERITIC SOILS

Laterites and lateritic soils form a group comprising a wide variety of red, brown, and yellow, fine-

grained residual soils of light texture as well as nodular gravels and cemented soils. They may vary

from a loose material to a massive rock. They are characterized by the presence of iron and

aluminum oxides or hydroxides, particularly those of iron, which give the colors to the soils. For

engineering purposes, the term “laterite” is confined to the coarse-grained vermicular concrete

material, including massive laterite. The term “lateritic soils” refers to materials with lower

concentrations of oxides. Laterization is the removal of silicon through hydrolysis and oxidation

that results in the formation of laterites and lateritic soils

(www.itc.nl/~rossiter/Docs/FM5-410/FM5-410_Ch12.pdf).The degree of laterization is estimated

by the little mechanical erosion. Laterite country is usually infertile. However, lateritic soils may

10

develop on slopes in undulating topography (from residual soils), on alluvial soils that have been

uplifted.

The soil named “Laterites” was coined by Buchanan (1807) in India from a Latin word “Later”

meaning brick. He described the material as “diffused in great masses, without any appearance

of stratification, and is placed over the granite that forms the basis of Malayala (India). It is full

of cavities and pores, and contains a very large quantity of iron in the form of red and yellow

ochres. In the mass, while excluded from the air, it’s so soft that any iron instrument readily cuts

it and its cut into square masses with a pick axe and immediately cut into the shape wanted with

a trowel or large knife. It very soon becomes as hard as brick and resists the air and water much

better than any bricks I have seen in India’’ (Charman, 1988).

In civil engineering the confusion regarding laterite has been caused largely by the tendency to

apply the term to any red soil or rock in the tropics. The concept of self-hardening has persisted

but several theories have been advanced to account for the origin and formation of laterite.

Latrite occurs in six main regions of the world, which includes Africa, India, South – East Asia,

Australia, central and South America. Lateritic materials constitute the major surfacial deposit of

engineering materials in many parts of Australia, Africa and South America (Charman, 1988).

2.4 ENGINEERING CLASSIFICATION OF LATERITES

The usual methods of soil classification, involving grain-size distribution and Atterberg

limits, should be performed on laterites or suspected laterites that are anticipated for use as fill,

base-course, or surface-course materials. Consideration should be given to the previously stated

fact that some particles of laterite crush easily; therefore, the results obtained depend on such

11

factors as: (1) the treatment of the sample, (2) Amount of breakdown,(3) Method of preparing

the minus No,40 sieve() material. The more the soil’s structure is handled and disturbed, the finer

the aggregates become in grading and the higher the Atterberg limit. While recognizing the

disadvantage of these tests, it is still interesting to note the large spread and range of results for

both laterites and lateritic soils (www.itc.nl/~rossiter/Docs/FM5-410/FM5-410_Ch12.pdf).

2.4.1 Mineralogical /Chemical Characteristics

Mallet (1883) was perhaps the first to introduce the chemical concept for establishing the

ferruginous and aluminium nature of lateritic soils. Fermor (1911) defined various forms of

lateritic soils on the basis of the relative contents of the so-called lateritic constituents (Iron,

Aluminium, Titanium and Manganese) in relation to silica. Also, Lacroix (1913) divided laterite

into:-true laterite, silicate laterite, and lateritic clays depending on the relative contents of the

hydroxides. There are other several attempts by the researchers to classify laterite in terms of

their chemical compositions, but Fox (1936) has demonstrated that such classifications are

inadequate, other than in relations to deposits that may be exploited for their minerals content,

classification based on chemical composition cannot be used to distinguish between indurate and

softer formations. The high content of the sesquioxides of iron or aluminium relative to other

components is a feature of laterite. These essential components are mixed in variable

proportions. Some laterite may contain more than 80% of Fe2O3 and little of Al2O3; while others

may contain up to 60% of Al2O3 and only a little of Fe2O3. Although alkali and alkaline bases are

almost entirely absent in most cases, this is not an absolute criterion. In particular, some

ferruginous tropical soils may contain significant amounts of alkali and alkaline bases

(Opeyemi,2006).

12

Combined silica content is low in sesquioxides. This combined silica is predominantly in the

form of Kaolinite, the characteristic clay mineral of most tropical formation. It was on this basis

that D’hoore (1954) made a theoretical calculation of free Al2O3 content from combined silica

content employing the formula:

Free Al2O3 = TotalAl2O3— (SiO2x0.849) 1

The use of this formula leads to the statement that alumina was present principally in combined

form in laterite of Buchanan’s type. Although alumina is sometimes the main constituent, the

sesquioxides of iron are most common and the most frequent.

2.5 PROFILES OF LATERITIC SOILS

There are many variations of laterites and lateritic profiles, depending on factors such as

the—(1)Mode of soil formation.(2)Cycles of weathering and erosion (3) Geologic history and (4)

Climate(www.itc.nl/~rossiter/Docs/FM5-410/FM5-410_Ch12.pdf). A lateritic soil profile is

characterized by the presence of three major horizons below the humus-stained topsoil. These

horizons include(Opeyemi,2006)

1. The sesquioxide rich lateritic horizon (sometimes gravelly and/or hardened in – situ as

crust);

2. The mottled zone with guidance of enrichment of sesquioxide.

3. The pallid or leached zone (rock suffering chemical and mineralogical change, but

retaining physical appearance) overlying the parent rock. (Gidigasu and Kuma, 1987).

13

For fine-grained soils in lateritic profile over phyllite, it was shown by Gidigasu (1980)

that the particle size distribution, Atterberg limits, compaction characteristics, swell and bearing

properties for soils in the three horizons vary considerably. However, in the mottled and pallid

zones the fines content predominate except for un-weathered quartz in the parent rocks (Gidigasu

and Kuma, 1987).

2.5.3 Modification of Lateritic Soils

Modification may be defined as any process by which the shear strength properties of a soil

material is improved. The goals of modification are therefore to improve the soil strength, to

improve the bearing capacity, durability and durability under adverse moisture and stress

condition.

2.5.5 Engineering Properties of Lateritic Soils

Geotechnical characteristics and field performance of lateritic soils, as well as their reaction to

different modifying agents may be interpreted in the light of all or some of the following

parameters (Gidigasu, 1976):

14

(i) Genesis and pedological factors (parent material, climate, topography, vegetation, period

of time in which the process have operated)

(ii) Degree of weathering (decomposition, sesquioxides enrichment and clay-size content,

degree of leaching)

(iii) Position in the topographic site, and

(iv) Depth of soil in the profile

2.5.6 Particle Size Distribution of Lateritic Soils

Particle size distribution may provide the following information:

(i) A basis for identification and classification of soils.

(ii) The compaction characteristics

(iii) Permeability

(iv) Swellability and

(v) A rough idea of deformation characteristics of the soil mass.

Texturally, lateritic soils are very variable and may contain all fractions sizes; boulders, cobbles,

gravel, sand, silt, and clay as well as concretionary rocks.

Pre-testing preparation of lateritic soils for sieve analysis may have the following effects on the

size distributions (Gidigasu, 1976):

(i) Re-molding and removal of free iron oxides increases the content of fines between 35and

65% (this will be a function of the dispersing agent)

(ii) Degree of drying and time of mixing of the sample prior to testing influence the degree of

dispersion of some lateritic soils

15

(iii) Cementing effects of sesquioxides, which bind the clay and silt fractions into coarser

fraction.

2.5.7 Plasticity Characteristics of Lateritic Soils

The interaction of the soil particles at the micro scale is reflected in the Atterberg limits of the

soil at micro scale level. Knowledge of the Atterberg limits may provide the following

information(Opeyemi,2006):

i. A basis for identification and classification of a given soil

ii. Texture

iii. Strength and compressibility characteristics swell potential of the soil or the water

holding capacity.

Atterberg limits depend on: -

i. The clay content; plasticity increases with increase in clay content (Piaskowski, 1963)

ii. Nature of soil minerals; only minerals with sheet-like or plate-like structures exhibit

plasticity. This is attributed to the high specific surface areas and hence the increased contact in

plate shaped particles

iii. Chemical composition of the soil environment; the absorptive capacity of the colloidal

surface of the cations and water molecules decrease as the ratio of silica to sesquoixides

decreases (Baver, 1930)

iv. Nature of exchangeable cations; this has a considerable influence upon the soil plasticity

(Hough, 1959).

v. Organic matter; high organic matter increases plasticity ( Skempton, 1953)

16

Pre-test preparation, degree of moulding and time of mixing, dry and re-wetting, and irreversible

changes may affect plasticity. Drying drives off adsorbed water, which is not completely

regained, on re-wetting (this is the case in both oven and air drying) (Fookes, 1997).

Studies on the relationship between the natural moisture content and the liquid limits and plastic

limits have shown that generally the natural moisture contents is less than the plastic limit in

normal lateritic soils (Vargas, 1953). However, the lateritic soils from high rainfall areas may

have moisture contents as high as the liquid limit (Hirashima, 1948).

2.5.8 Compaction Characteristics of Lateritic Soils

The compaction characteristics of lateritic soils are determined by their grading

characteristics and plasticity of fines. These in turn can be traced to genetics and pedological

factors. The significant characteristics of lateritic soils are influenced by the strength of

concretionary coarse particles on compaction. Most lateritic soils contain a mixture of quartz and

concretionary coarse particles, which may vary from very hard to very soft. The strength of these

particles has major implications in terms of field and laboratory compaction results and their

subsequent performance in road pavements. The higher the iron oxides content the more the

degree of dehydration in the lateritic soil, the harder the concretionary particles become.

Placement variable (moisture content, amount of compaction, and type of compaction

effort) also influences the compaction characteristics. Varying each of these placement variables

has an effect on permeability, compressibility, swellability, strength and stress-strain

characteristics (Lambe, 1958). For example, soil compacted on the dry side of optimum moisture

content swells more than soils compacted on the wet side because the soils compacted on the dry

17

side have a greater moisture deficiency and a lower degree of saturation (Mitchel et al., 1969).

On the other hand, soils compacted on the wet side of the optimum moisture content will shrink

more on drying than a soil compacted on the dry side (Lambe, 1958).

2.5.8 Shear Strength Characteristics of Lateritic Soils

The main objective of shear strength test in soil engineering, is generally to determine the

shear strength parameters (i.e., the cohesion and angle of internal friction) in terms of total or

effective stresses under known test condition. It’s determination directly or indirectly enters into

virtually every soil engineering problems.

The cohesion is attributable to the resultant of inter particle forces which are mainly

associated with the clay-size particle of soils and will vary with the particle size of the particle

and the distance separating them. Some of the inter particle forces which are believed to

contribute to soil cohesion includes(Opeyemi,2006):

(a) Valence forces associated with surface

(b) Ionic forces associated with ions dissociated from polar materials

(c) Dipole forces and moments associated with polar materials

(d) Molecular attraction or van der Waal’s forces.

The angle of internal friction included the effect of interlocking. The interlocking effect

itself is affected to some degree by the shape of particles and the grain–size distribution. The

interlocking action varies with the density and the angle of internal friction increases with

increase in density. The two parameters cohesion (c) and angle of friction (ø) depends on the

18

following factors; grading, particle shape and void ratio. The cohesion also depends on degree of

saturation, while angle of internal friction does not (Gidigasu, 1976).

The shear strength characteristics of lateritic soils have been found to depend

significantly on the parent materials, and the degree of weathering (i.e., degree of decomposition,

laterization and dessication) which depends on the position of the sample in the soil profile and

compositional factors as well as the pretest preparation of the samples (Cruz, 1969; Lohnes et al.,

1971 and Wallace, 1973). The higher the degree of laterization the more favourable are the shear

strength parameters (Baldovin, 1976).

2.10 General Use of Laterites

Laterites are widely used for different purposes. In agriculture, it is used for construction of fish

ponds but not suitable for farming because of lack of potash and phosphate in the soil. Laterite

have various engineering uses(Opeyemi,2006):

i. They are used on clays for pudding, for making tiles, and as mortar in rough work.

ii. Kankar, a mineral component of laterite has filled an important part as cement in many

engineering works (in India).

iii. Where the iron concretion has been worked out by rains or by artificial treatment (often

in the form of small short-like pellets) they serve as iron ore in parts of India and Africa.

iv. Laterite has also been successfully used in the construction of slopes, embankments,

foundations, reinforced retaining walls and dams in both tropical and sub-tropical regions.

2.11 Sawdust Ash.

19

Sawdust ash (SDA) is obtained from sawdust; an industrial waste produced in several

tonnes in Nigeria.SDA is obtained by burning saw dust at a controlled temperature in the

presence of air for about 24hrs. The most striking advantage of SDA is the high silica content as

well as free lime content. The pozzolanic activity of the ash is best obtained in the amorphous

phase. To realize this, the ranges of temperature are essential especially for commercial

production quantity (Tashima et al 2004). Sawdust is an industrial waste in the timber industry

and posses a nuisance to both the health and

environment when not properly managed. It has pozzolanic properties and has been shown to

react chemically with the calcium hydroxide released from the hydration of Portland cement, to

form cement compounds (Elinwa and Mahmood, 2002). Active pozzolans gain their binding

properties when they react with calcium hydroxide in lime or cement in presence of water.

Questions about the science behind the determination of sawdust being an environmental hazard

remain for sawmill operators (though this is mainly with finer particles), who compare wood

residuals to dead trees in a forest. Technical advisors have reviewed some of the environmental

studies, but say most lack standardized methodology or evidence of a direct impact on wildlife.

They don’t take into account large drainage areas, so the amount of material that is getting into

the water from the site in relation to the total drainage area is minuscule.

The advantages of using SDA for concrete production are numerous. It acts as a retarder

prolonging the setting times, reduces the heat of hydration, encourages a healthier environment

by reducing green gas emission and abundantly available as a waste. SDA has been used as

partial replacement in mortar and concrete works (Elinwa and Mahmood, 2002; Elinwa and

Ejeh, 2004). It has also been used as a powder material in the production of self compacting

20

concrete (SCC) (Elinwa and Mamuda, 2008) and in combination with metakaolin as a ternary

blend with 3 % added to act as an admixture(Elinwa et al, 2005). Udoeyo and Dashibil, (2002)

described the use of sawdust ash as a cement replacement. According to the test results, the use

of sawdust ash decreased slump and increased the expansion of the ash/cement mortar as it

hardened.The ash also caused an increase in the initial and final setting times for the concrete

mixes. This is due to slower hydration and a slower evolution of heat.

CHAPTER THREE

MATERIALS, METHODS AND RESULTS

3.1 Materials

3.1.1 lateritic soil

The soil sample used for this study was collected by method of disturbed sampling from a

borrow pit in Shika area of Zaria (Longitude 7° 45’ E latitude 11° 15’ N) along Zaria - Funtua

road before the new Ahmadu Bello University Teaching Hospital. The soil sample belongs to the

group of ferruginous tropical soils derived from acid igneous and metamorphic rocks(Ovey,

2010).The samples used for the analysis were collected at a depth of between 1.5 and 2m

corresponding to the B - horizon usually characterized by accumulation of material leached from

the overlying A - horizon. The oxide composition of the lateritic soil from the study borrow pit is

given in table 3.1.

3.1.2 Sawdust Ash

21

The sawdust was obtained locally from a timber-shed situated in Sabon Gari local

government area in Zaria, Kaduna state. The sawdust was collected, air-dried and burnt under

atmospheric conditions. The remains is the ash that was collected in sacks and transported to the

soil mechanics research laboratory. The ash was then passed through the BS No200 sieve(75μm

aperture) to meet the requirement of ASTM class N pozzolanas(ASTM C618-78). The chemical

analysis of sawdust ash was carried out using Flame Photometer and the Atomic Absorption

Spectrophotometer (AAS) (Pye-Unicam Model SP 1900).

Table 3.1 Chemical composition of lateritic soil from study borrow pit(after sinubi,1998a)

22

Oxide Composition(%)

CaO 0.228

SiO2 35.6

Al2O3 27.4

Fe2O3 2.4

MgO 85

SO3 -

Mn2O3 -

P2O5 -

Loss of ignition 146

3.2 Methods

Preliminary classification tests were performed on the soil in accordance with BS 1377

(1990), while treated soil were tested in accordance with BS 1924(1990).

3.2.1 Preparation and Testing of Specimen

The natural soil sample was air-dried and crushed until it passed BS sieve No.

4(4.76mmaperture). Samples were weighed appropriately and mixed thoroughly with sawdust

ash to obtain uniform colour. Plate 3.1 shows the sample preparation in progress

Plate 3.1 Sample preparation in progress

3.2.2 Natural moisture content

The natural moisture content was determined in accordance with Test 1(A) of BS 1377

(1990). Known weights of pulverized soil samples were weighed in a container whose weight

was pre-determined. The container and its contents were weighed and and placed in an oven at a

temperature between 105 and 1100C for a period of 24 hours. After drying, the container and its

content were re-weighed. The natural moisture content was calculated by the relationship.

23

W =W 2−W 1W 3−W 1

×100 (3.1)

where, W= Moisture content in percentage

W1= Weight of container (g)

W2= Weight of container and wet soil (g)

W3=Weight of container and dry soil (g)

3.2.3 Specific gravity

The specific gravity (GS) was determined in accordance with the procedure outlined in BS 1377

1990: Part 2. Three density bottles were used in determining the specific gravity of all samples.

The specific gravity of each sample was calculated from the following equation:

GS=M 2−M 1

(M 4−M 1)−(M 3−M 2 ) (3.2)

where; M1 = mass of dry glass bottle, g

M2 = mass of bottle + soil sample, g

M3 = mass of bottle + soil sample + water, g

M4 = mass of bottle + water, g

24

Ordinary tap water was used in conducting the specific gravity test. An average of the value was

reported on specific gravity of each sample.

Plate 3.2 Specific gravity test in progress

3.2.4 Particle size distribution

200 g of the lateritic soil was taken for each of the soil samples with 0 to 5% SDA

concentration by dry mass of soil and soaked for 24 hours, washed through BS No 200 sieve size

(75 μm aperture). The materials retained were collected and oven-dried for 24 hours. The washed

materials passing through No 200 sieve size was used for sedimentation test.

Dry sieving and sedimentation methods were adopted for the particle size distribution

test. The sieve analysis was done in accordance with procedure outlined in BS 1377 1990: Part 2

on the oven-dried sample, which was subjected to sieving through a set of BS sieve between 2.4

mm to 75 μm diameter in sieve sizes. The percentages of soil passing were then calculated. Also,

sedimentation test was done on the solution kept in 1000 ml cylinder by using hydrometer

analysis, in accordance with procedure outlined in BS 1377 1990: Part 2: Section 9.5. In this

analysis, a dispersing agent (Sodium Hexa-metaphosphate) was added to the soil suspension in

water, in order to ensure separation of discrete particles of the soil. The percentage of fines was

25

calculated and combined with percentage of soil passing in dry sieve analysis to establish the full

particle size distribution (grading curve). Plate 3.3 shows sieve analysis test being performed

Plate 3.3 Sieve analysis test in progress.

3.2.5 Atterberg limits

3.2.5.1 Liquid limit

The air dried natural soil sample was pulverized and passed through sieve no.4. 200g of

the sample was taken. The liquid limit test was conducted at six different sets of soil-sawdust ash

mixture on Cassangrade’s liquid limit device. These samples were placed in a circular brass cup,

after being mixed thoroughly with tap water into a paste and a groove of 2 mm wide was made in

the soil separating it into two halves. The cup was then lifted to a height of 10 mm and allowed

to drop into a hard rubber base. The number of such blows to cause the two soil halves to come

together over a distance of 13 mm was recorded and the moisture content of the samples were

determined in accordance with outlined procedure in BS 1377 1990: Part 3: Section 3.2. The test

was repeated for 1,2,3,4 and 5% sawdust ash treatment and a graph of moisture content against

number of blows (usually within the range of (10 -50 blows) was plotted. The moisture content

at 25 blows was defined as the Liquid limit (LL). The average moisture content values were

26

plotted against the corresponding number of blows and the best line of fit was drawn. The

procedure was repeated for 1,2,3,4 and 5% sawdust ash content The liquid limit are shown in

Plate 3.4 shows the liquid test being performed

Image 3.4 Performing the liquid limit test

3.2.5.2 Plastic limit

Part of mature hydrated sample of about 20 g for each respective sample was used to carry out

the plastic limit test, in accordance with procedure outlined in BS 1377 1990: Part 2: Section 5.3.

The 20 g sample was first kneaded, and shaped into a ball, it was then divide into two portions

each of about 10 g and further divided into four equal parts. Each quarter part was rolled between

two fingers of one on the surface of the glass plate, into about 6 mm diameter by using a steady

pressure. The rolling was done until the threads crumbled, when it had been rolled to about 3

mm diameter. The crumbled threads were then kept in the moisture containers, weighed and

oven-dried for about 24 hours, after which, the dry samples were weighed again. The moisture

content was determined by using eq (3.1) Two replicate moisture content samples were taken as

previously done above. The average of the two moisture contents gives the plastic limit (PL).

27

The values of the plastic limit for various percentages of soil treatment with sawdust ash was

recorded and tabulated.

3.2.5.3 Plasticity Index

Plasticity index which is the numerical difference between the liquid limit and the plastic

limit was calculated. Using the equation:

PI=¿−PL

3.3Compaction Characteristics

Compaction test was carried out on soil samples by using British Standard heavy (BSH)

energy in accordance with BS 1377 1990: Part 2. Each compaction involved five trials. In this

test, about 3000 g sample was shared into three parts after thorough mixing with tap water, each

portion was placed in 1000 cm3 cylindrical mould and 27 blows was applied from a 4.5 kg

rammer falling from a height of 300 mm, which is equivalent to a west Africa compactive effort.

The mould was fitted with a detachable collar which enabled the soil to be compacted to a level

slightly above the rim of the mould itself. It was then removed and the surface was carefully

trimmed with a knife. The bulk density (ρb) was obtained by weighing the mould and a small

portion of the soil was taken to determine the moisture content (MC). Thereafter, the moisture

content – dry density curves were plotted, the maximum dry density (MDD) and optimum

moisture content (OMC) for 0 to 5% of sawdust ash of dry weight of soil were estimated by

using curve fitting method. Plate 3.5 shows the compaction test being performed.

28

Plate 3.5 Compaction test in progress

3.4 Shear Strength Characteristic

3.4.1 Undrained triaxial compression

The triaxial test was carried out in accordance with the procedure outlined in BS

1377 1990: Part 7: Section 8 using triaxial apparatus. of cylindrical specimens 38 mm in

diameter and 76 mm length. The cylindrical specimen was prepared by using British Standard

heavy compactive effort at optimum moisture content. The compacted soil was then

extruded,and carefully placed in the cell axial compression was applied on a set of three

specimens A, B and C which were subjected to different confining cell pressures (310, 210 and

100 kN/m,2 respectively) respectively, to obtain the undrained shear strength parameters.

Each specimen was carefully trimmed to the required size and weighed. The weighed

specimens fitted into membranes were placed vertically on the pedestal of the cell. Suction was

applied through the tube in which the membrane was attached by sucking with the mouth, so as

to draw the membrane tightly against the specimen. The suction was maintained while lowering

the tube carefully over the specimen, thereafter, the suction was released so that the membrane

clings to the specimen, the membrane ends were then rolled gently onto end caps, making a

29

smooth fit with no entrapped air and all necessary precautions were taken to avoid the membrane

from being wrinkled or twisted.

The cell was then tightened and the load rammer was gently released to make contact

with the vertically aligned specimens. The cell was filled with tap water and placed on the

triaxial machine. For specimens A, B and C, their respective confining pressures were applied to

the cell. A sketch of the triaxial compression apparatus is shown in fig. 3.1

30

Figure 3.1 Triaxial apparatus

The machine was then switched on to record the readings of the load dial gauge at the regular

strain intervals (see plate 3.6). The test continued until 3 or 4 consecutive readings showed a

decreasing or constant value, after which the machine was stopped. The cell was loosened and

the specimen was carefully removed from the membrane, part of the specimen was placed in a

moisture container, weighed and oven-dried to obtain the moisture content.

Image 3.6 Performing the Triaxial compression test.

The failure value was calculated using eq(3.3)

σ 1−σ 3=[ R ×CR ×(1−ε)×1000A ]

where: σ 1 = Principal compressive stress, kN/m2

σ 3 = cell confining pressure, kN/m2

R= failure value

CR=Proving dial constant

ɛ=Strain

31

Furthermore, the value of principal or major stress and confining pressure for the three

specimens were used to plot the Mohr circles and envelopes in order to obtain the value of

cohesion (c) and angle of internal friction (ø) for all samples.

CHAPTER FOUR

RESULTS AND DISCUSSIONS

4.1 Preliminary Tests

4.1.1 Index properties of natural soil

The results of tests for identification of the natural soil and the determination of its

properties before modification are presented in Table 4.1. The soil is classified as an A-7-6

(GI=9) based on AASHTO classification system which says if the natural soil has liquid limit

greater than 41% and plasticity index also greater than 11% then the soil is either an A-7-5 or an

A-7-6. But since PI is greater than (LL-30), then the soil is termed A-7-6. It is a reddish brown

well-graded fine-grained soil with inorganic clay of medium plasticity. The clay content is about

10%, the soil is adjudged unsuitable for direct use as base or sub-base material. On the basis also

32

of both the plasticity and percentage passing BS No. 200 sieves. The properties of the natural

soil are summarized in Table 4.1

Table 4.1 Properties of natural lateritic soil

Property QuantityNatural moisture content, % 14.7Passing No.200 BS Sieve 53.2Liquid limit % 43.5Plastic limit % 28.5Plasticity index % 15.0Specific gravity 2.68AASHTO Classification A-7-6Group index 9Unified Soil Classification System CLMaximum dry density Mg/m3 1.88Optimum moisture content % 13.60Cohesion, c KN/m2 70Angle of internal friction (0) 20

Colour Reddish brown

4.1.2 Chemical Composition of Sawdust Ash

The chemical composition of the sawdust ash used in this study is summarized in Table 4.2.

Table 4.2 Oxide Composition of sawdust ash

Oxide Concentration(% by weight)

SiO2 67.20Al2O3 4.09MgO 5.8Fe2O3 2.26Na2O 0.08K2O 0.11CaO 9.98P2O5 0.48SO3 0.45MnO 0.01

4.2 The Effect of Sawdust Ash on Lateritic Soil

33

4.2.1 Particle size distribution

The particle size distribution curves for the natural and treated soils are shown in fig 4.2.

It can be observed that with increase in sawdust ash contents, the particle size distribution curve

shifted to the right, thereby showing a reduction in the percentage of fines at 1,2,3,4 and 5% of

ash contents accordingly after an initial increase between 0 and 1% ash contents, respectively.

This was probably due to the flocculation as a result of ion exchange there by leading to a

reduction in the clay size particles. A little change is noticed in the coarser sizes. The changes in

the shape of the curves are very apparent at 600μm and more marked at 212μm down to clay

particle size. This is an indication that with increases in sawdust ash content, modification

reaction between sawdust ash and clay minerals increased, which facilitated the formation of

heavier pseudo-sands particles(Mua’zu, 2006)

0.001 0.01 0.1 1 100

20

40

60

80

100

120

0% sawdust 1% sawdust 2% sawdust 3% sawdust4% sawdust 5% sawdust

SDA content, %

Perc

enta

ge p

assin

g, %

Fig. 4.2 Variation of particle size distribution with sawdust ash content

34

4.2.2 Atterberg Limits

4.2.2.1 Liquid limit

As shown in figure 4.3 the liquid limit of the soil sawdust ash mixture reduced from a

value of 43.5 to a value of 35.7%. This was due to the effect of sawdust ash contents on the

modified soil. The liquid limit (LL) reduces with increasing sawdust ash content.  The possible

explanation for this is that as sawdust ash (a pozzolana) content increased which aided

flocculation and aggregation of the clay particles. This increased the effective grain size due to

agglomeration of the clay particles. The agglomeration turned clayey soil to a silty soil and thus,

by itself decreased the liquid limit of the soil because of the lower surface area and plastic limit

increased.

4.2.2.2 Plastic limit

The plastic limit of the soil-sawdust ash mixture icreased from a value of 28.51 to a value

of 28.78% then suddenly reduced to a value of 28.57 at the 3% SDA content then finally

increased. This was due to the effect of sawdust ash contents on the modified soil. The plastic

limit (PL) increased with increasing sawdust ash content.  The possible explanation for this is

that as sawdust ash content increased which aided flocculation and aggregation of the clay

particles. More water was required for hydration of sawdust ash content this increased the

effective grain size due to agglomeration of the clay particles.

4.2.2.3 Plasticity index

The plasticity index of the soil sawdust ash mixture reduced from a value of 14.99 to a

35

value of 7.57%. The reduction in plasticity was due to a reduction in liquid limit. The effect of

sawdust ash content on liquid limit, plastic limit may not be unconnected with pozzolanic action

of sawdust ash in aiding the flocculation and aggregation of the clay particles. This brought

about increase in effective grain size due to agglomeration of the clay particles. The

agglomeration turned the clayey soil to a silty soil and this by itself decreased the liquid limit of

the soil because of the surface area, thus consequently increases the plastic limit. This is in

agreement with(Osinubi,1995).

4.2.3 Specific gravity

As indicated in Table 3.2, the specific gravity of the study soil is 2.68 which is within

the range of 2.6 and 3.4 reported by [28,29] for lateritic soils. The incorporation of sawdust ash

with specific gravity of 2.27 resulted in mixtures with lower specific gravity i.e. 2.64, 2.61,

2.53, 2.49,2.41 respectively for 1,2,3,4, and5% sawdust ash contents. The generally low specific

gravity of sawdust ash which resulted in reduced unit weight of lateritic soil - sawdust ash

mixtures as compared to the soil alone is an attractive property for its use in geotechnical

applications.

Figure 4.7 Graph of specific gravity at various SDA content

36

From the consideration of the plasticity characteristic and grain size, the direct use of the

materials as pavement material are not met for any of the sawdust ash contents considered, but

the grain size requirement were met with the respect to the percentage passing BS sieve No. 200.

FIG; 4.2 Variation of plastic limit(PL) with sawdust ash content.

37

0 1 2 3 4 5 627.4

27.6

27.8

28

28.2

28.4

28.6

28.8

29

SDA content,%

PLAS

TIC

LIMIT

, %

0 1 2 3 4 5 620

25

30

35

40

45

FIG; 4.3 Variation of liquid limit(LL) with sawdust ash content

FIG; 4.4 Variation of plastic Index(PI) with sawdust ash content

38

0 1 2 3 4 5 620

25

30

35

40

45

0 1 2 3 4 5 66789

10111213141516

Variation of PI with SDA content

Series2

 4.2.2 COMPACTION CHARACTERISTICS

  The compaction curves representing the moisture content – dry density

relationship for Sawdust ash-soil mixture with the BSH compactive effort are shown in Fig. 4.9.

These compaction curves are similar to that of the natural lateritic soil sample Fig 4.9. Curves

fitting method was utilized in evaluating the OMC and MDD of the soil samples. Values of

OMC ranged from 13.65 to 24.5% and MDD values ranged from 1.45 to 1.69 Mg/m3.

The effect of Sawdust ash on the maximum dry density (MDD) on the modified soil-sawdust

ash mixture is shown in Figure4.5, for BSH Compaction While the corresponding optimum

moisture contents is shown in Figure 4.6, accordingly. Result shows increasing OMC and

decreasing MDD as the percentages of sawdust ash content increased. The initial reduction in

dry density was as a result of flocculation and agglomeration of clay particles occupying larger

space leading to a corresponding drop in dry density. It is also as a result of initial coating of the

soils by the sawdust ash to form large aggregates, which consequently occupy larger spaces

[Mu’azu,2006]. The increase in OMC as the sawdust ash contents increased was as the result of

extra water required for hydration and pozzolanic reaction to take place

39

0 1 2 3 4 5 61.5

1.55

1.6

1.65

1.7

1.75

1.8

1.85

1.9

SDA Content,%

MAx

imum

dry

den

sity

Mg/

m3

Figure 4.5 Variation of MDD with sawdust ash content

Figure 4.6 Graph of OMC at varying ash content

40

0 1 2 3 4 5 61.5

1.55

1.6

1.65

1.7

1.75

1.8

1.85

1.9

SDA Content,%

MAx

imum

dry

den

sity

Mg/

m3

0 1 2 3 4 5 612

12.513

13.514

14.515

15.516

16.517

17.518

SDA Content,%

Opti

mum

moi

stur

e co

nten

t %

4.2.3 SPECIFIC GRAVITY

4.2.3SHEAR STRENGTH CHARACTERISTIC

The effect of bagasse ash contents on the cohesion of the soil-cement-bagasse ash

mixture and are shown in Figure 7, 8 and 9 for BSL, WAS and BSH compactive efforts. The

cohesion was observed to reduce with increased in bagasse ash and cement contents.

The effect of cement and bagasse ash content on the angle of internal friction are shown in

Figure 10, 11 and 12 for BSL, WAS and BSH compactive effort respectively.

The angle of internal friction increased with increasing sawdust ash. The sawdust ash seemed to

reduce the cohesion while increasing the angle of internal friction as the sawdust ash content

increased. These are as a result o the reduction in clay size fraction and an increament in the

larger soil particles, which resulted from the ion exchange reaction that deposits free lime.

41

0 1 2 3 4 5 62.25

2.3

2.35

2.4

2.45

2.5

2.55

2.6

2.65

2.7

2.75

% SDA

SPEC

IFIC

GRA

VITY

Figure 4.7. Variation of angle of internal friction with sawdust ash content

42

0 1 2 3 4 5 60.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

SDA Content, %

An

gle

of in

t fr

icti

on(ø

0)

0 1 2 3 4 5 60

10

20

30

40

50

60

70

80

SDA Content,%

Coh

esio

n(C

KN

/m2)

Figure 4.8. Variation of cohesion with sawdust ash content

43

CHAPTER FIVE CONCLUSION

The following conclusions can be drawn from the result of this investigation on the Modification

of lateritic soils with Sawdust ash by british standard heavy compactive energy.

1.      The physical and chemical composition of sawdust ash (SDA) are satisfactory and confirm

to the requirements of class F pozzolanas and oxide composition.

2.      The laterite is classified to be an A - 7 - 6 soil based on AASHTO classification system. It

contains Kaolinite as the predominant glass mineral. Quartz and Attapulgite mere also identified

these are in general agreement with ferruginous tropical soils in Zaria area as identified by

[Mua’zu,2006].

3.      The optimum moisture content (OMC) increased while maximum dry density (MDD)

decreased with increasing SDA content. This compaction behaviour occurs as a result of both the

grain size distribution and specific gravities of the soil and the modifying effect of the sawdust

ash(SDA) and bagasse. The modifier initially coats the soils to form larger aggregates, which

consequently occupy larger spaces. This tendency is for the fine-grained soil to decrease in dry

44

density especially with SDA and which has specific gravity lower than that of the soil. The

increase in optimum moisture content may be due to water requirement for sawdust ash

hydration and pozzolanic reaction of the lime released during hydration of sawdust.

4.      The effect of sawdust ash content on lateritic soil on cohesion and angle of internal friction

is that, the cohesion decrease while the angle of internal friction increases. This may be due to

reduction of clay - size fraction.

5.         The liquid limit reduced while the plastic limit increased and consequently the plasticity

index reduced with increased in sawdust ash content. The reduction in plasticity was due to a

reduction in liquid limit. The effect of sawdust ash content on liquid limit, plastic limit may be

connected to pozzolanic action of sawdust ash in aiding the flocculation and aggregation of the

clay particles. This brought about increased in effective grain size due to agglomeration of the

clay particles. The agglomeration turned the clayey soil to a silty soil and this by itself decreased

the liquid limit of the soil because of the surface area, thus consequently increases the plastic

limit.

6.         With respect to particle size distribution. There was a general reduction in the percentage

of fines with the increase in sawdust ash contents. The changes in shape of curves are very

apparent to sieve 600μm and more marked at sieve 212μm down to clay particle size. The

percentage-passing sieve BS 200 was reduced to almost zero from 63%. This was due to

flocculation and agglomeration of mixture of the clay fraction to form pseudo-silt sizes.

7. The modified laterite at 1 to 5% of sawdust ash tretment could be recommended for most

engineering works, which could include rail-road embarkment filling etc

45

REFERENCES

1. Alexander L. T., Cady J. G., Genesis and Hardening of laterite in Soil, U.S. Department of Agric,

Technical Bulletin No. 1282 Washington DC USA, 1962, p. 1-10.

2. ASTM, Specification for Fly Ash and Raw Calcined Natural Pozzolana for use as a Mineral

Admixture in Portland Cement Concrete (9618 - 78), 1978.

3. ASTM, Standard Test for Classification of Soil for Engineering proposed American Association got

Test and Material ASTM, Designation D. 2487 - 1969, 1970.

4. AASHTO, Standard Specification for Transportation, Material and Method of Sampling and Testing

14th Edition. Amsterdam Association of State Highway and Transportation Official Washington D.C.,

1986.

5. BS 1377, Method of Testing Soil for Civil Engineering Proposed, British Standard Institute BSI

London England, 1990.

6. BS 1924, Method of Test for Stabilized Soils, British Standard Institute BSI London England, 1990.

7. Federal Ministry of Works, Nigerian General Specification on Road and Bridgeworks, Federal

Government of Nigeria, Lagos, Nigeria, 1970.

46

8. High way Research Board, Use of Soil - cement mixture for Base Course, Wartime Road Problems

No. 7 Nat. Res. Council Div. Engg. Indust. Res. Washington, 1943.

12. Ingles O. G., Metcalf J. A., Soil Stabilization principles and Practice, Butter worths Sydney, 1972, p.

370 - 375

13. Kedzi A., Stabilized Earth Roads, Elsevier Amsterdam, 1979.

14. Lee I. K., Soil Mechanics New Horizon, Butter worth and Co. Ltd. London, 1974, p. 1 - 43.

15. Osinubi K. J., Katte V. Y., Effect of Elapsed Time After mixing on Grain size, plasticity characteristic

Soil - lime mixes, NSE Technical transaction Vol. 32, No 4, 1997.

16. Osinubi K. J., Lime Modification of Black cotton soil, Spectrum Journal, Vol. 2, No. 1 and 2, 1995.

17. Ola S. A., Stabilization of Nigerian Laterite soil with cement, bitumen and lime, Sixth Reg. Conf. For

Africa Soil Mechanic and Foundation on Engineering Durban South Africa, Sept. 1975, p. 145 - 152.

18. Ola S.A. (1978) Geotechnical properties and Behaviour of some stabilized Nigerian Laterite Soil Q.

T. J. Engg. Geo. London Vol. III Pp. 145 - 160.

19. Osula D. O. A., Cement stabilization using hydrated lime as an admixture, Unpublished Msc. Thesis

Civil Engineering Department Ahmadu Bello University Zaria, 1984.

20. Obeahon S. O., The effect of Elapsed Time After mixing on the properties of modified laterite,

Unpublished Msc. Thesis Civil Engineering Department Ahmadu Bello University Zaria, 1993.

21. Ogbonyomi T. D., Possible uses of Bagasse Ash as an Alternative cement, A seminar paper presented

at the Department of Civil Engineering ABU Zaria, 1998.

22. O’Flaherty C. A., Highway Engineering, Vol. 2, Edward Arnold London U. K., 1974.

23. Yoder E. J., Witczak M. W., Principles of pavement Design, 2nd Ed., John Wiley and Sons. Inc. pp.

200 - 321, 1975.

47

24. Millard R. O., O’Relly M. P., Standard for road building practice in tropics, Proc. Of the 2nd Conf.

Road Res. Ed. Australia Road Research Board Melbourne, Vol. 2, 1965, pp. 330-854.

.      Osinubi K. J., Bajeh I., Bituminous stabilization of laterite, Spectrum Journal, 1994, 1(2), p.

104-112.

25.      Mustapha M. A., Effect of Bagasse Ash on Cement Stabilized Laterite. Seminar Paper

Presented in the Department of Civil Engineering, Ahmadu Bello University, Zaria, Nigeria,

2005.

26.      Neville A. M., Properties of Concrete, 4th edition. Pearson Education Asia Ltd, Malaysia,

2000.

27.      Sear L. K. A., Should you be Using More PFA, In Cement Combination for Durable

28. BRRI/Lyon Associates, Laterites and lateritic soils and other problem soils of Africa. An

engineering study for USAID. AID/csd-2164, Baltimore, Md., 1971

29. De Graft-Johnson J.W.S., Bhatia H.S., Engineering properties of lateritic soils. General

Report, Spec Session on Eng. Prop. of lateritic soils, Seventh Int. Conf. Soil Mech. and

Found. Eng., Mexico City, 1969, 1, p. 117-128.

48

0% SDA COMPACTION

1% SDA COMPACTION

49

4.006.00

8.0010.00

12.0014.00

16.0018.00

20.0022.00

24.001.400

1.500

1.600

1.700

1.800

1.900

2.000

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

5.00 10.00 15.00 20.00 25.001.4001.4501.5001.5501.6001.6501.7001.7501.8001.8501.900

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

2% SDA COMPACTION

3% SDA COMPACTION

50

5.00 10.00 15.00 20.00 25.001.4001.4501.5001.5501.6001.6501.7001.7501.8001.8501.900

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

5.00 10.00 15.00 20.00 25.001.2501.3001.3501.4001.4501.5001.5501.6001.6501.7001.7501.800

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

5.00 10.00 15.00 20.00 25.001.450

1.500

1.550

1.600

1.650

1.700

1.750

1.800

1.850

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

4% SDA COMPACTION

5% SDA COMPACTION

51

5.00 10.00 15.00 20.00 25.001.2501.3001.3501.4001.4501.5001.5501.6001.6501.7001.7501.800

Series2

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

5.00 10.00 15.00 20.00 25.00 30.001.250

1.300

1.350

1.400

1.450

1.500

1.550

1.600

1.650

1.700

1.750

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.001.250

1.300

1.350

1.400

1.450

1.500

1.550

1.600

1.650

1.700

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3

52

8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.001.250

1.300

1.350

1.400

1.450

1.500

1.550

1.600

1.650

1.700

MOISTURE CONTENT %

DRY

DEN

SITY

Mg/

m3