Stabilization of Cinder Gravel With Clay and Cement

Stabilization of Cinder gravel with clay and cement Final year project

Addis Ababa University, Technology Faculty, Civil Engineering Department July 2008 Page 1

CHAPTER ONE

INTRODUCTION

1.1 Background

In the year 1999 e.c. the Ethiopian federal government put about 58.9 % of its

yearly budget to the construction industries. The Ethiopian road authority is going to launch a

road project that will cost the federal government about 43 billion birr and the construction will

take 5 years (200106).

Our thesis is on volcanic cinder gravel which occur extensively in Ethiopia, but in the

past they have been used for road construction only to a limited extent and the reason for the

limited use of volcanic cinder gravels up to the present is that they are generally deficient of fine

material and do not conform with the grading specifications for conventional crushed rock bases.

Another reason is that they have a reputation for being difficult to compact, even though their

use would substantially reduce road construction costs in many instances. Studies conducted on

the use of cinder gravels for road construction show the potential of using this stabilized material

by improving its gradation.

1.2 Statement of the problem

The location of the road construction can affect the material that can be used for the

construction. If the material found at the construction site can not satisfy the requirement the

material have to be stabilized. In this thesis we investigate the durability and unconfined



compressive strength of volcanic cinder gravel by stabilizing it so that it can be use as base

course material in the road construction.

1.3 Scope

First the sample was taken. The cinder gravel taken from Nazareth area was tested for

routine aggregate tests like gradation, impact test, crushing test, specific gravity. Then we tried to

find how much amount of clay needed to stabilized the volcanic cinder gravel. The clay was

taken from Addis Ababa around “Addisu Gebeya”. The test which was carried out to find

suitable clay is CBR and Proctor test. 10% 15% of clay of the total weight of cinder was taken

to be tested, and then optimum clay content chosen by CBR test results. Finally optimum

moisture content was taken for 3%, 5%, 7% and 10% of cement and mechanically stabilized

cinder gravel and find out the durability of molded mixture.

1.4 Outline

This report contains five chapters

Chapter 1 presents the objectives and scope of the research.

Chapter 2 is a literature review on cinder gravel and base course material.

On chapter 3 it was tried to give a quarry site selection, sampling, methodology and testing.

Chapter 4 is about present the results from laboratory testing.

Chapter 5 deals with: conclusion of the research and provide recommendation.



1.5 Objective

The objective of this final project is

Ø To investigate the durability of cement stabilized cinder in the laboratory.

Ø To find out the unconfined compressive strength of the stabilized cinder.



CHAPTER TWO

LITERATURE REVIEW ON CINDER GRAVEL AND BASE

COURSE MATERIALS

2.1 Introduction

Volcanic cinder gravels occur extensively in Ethiopia, but in the past they have been used

for road construction only to a limited extent, even though their use would substantially reduce

road construction costs in many instances. As part of a joint research project undertaken by the

Ethiopian Road Authority and the United Kingdom Transport and Road Research Laboratory,

research has been carried out to provide information on the occurrence and properties of volcanic

cinders with the object of encouraging their wider use in future road construction.

This thesis reports the result of laboratory tests made on specific volcanic cinder gravel

and gives detail information weather the material is good for road base course. The laboratory

investigation showed that cinder gravels, which typically have weak particles and are deficient in

fine material, are improved by blending and compaction in that some breakdown of the larger

particles occurs, producing a better grading and higher strength. Blending, addition fines,

improves the strength and density of the compacted cinder gravels.

2.2 Definition of volcanic cinders

“Volcanic cinders are pyroclastic materials associated with recent volcanic activity. They

occur in characteristically straight sided cone shaped hills which frequently have large concave

depressions in their tops or sides where mixtures of solids and gases were released during the

formation of the cone”[5]. Cinders vary in color often within the same cone and may be red,

brown, grey, or black. The cinder particles also vary in size from large irregularly shaped lumps

50cm in size, to sand and silt sizes. In some cones, however, particles may be more uniform with

the largest size not exceeding 3cm in diameter. Other characteristic features of cinders are their

light weight, their rough vesicular surface and their high porosity. Usually they are weak enough

to be crushed under the heel.



Volcanic cider gives an advantage for a road construction which is relatively easy to be

dug from the quarry: a mechanical shovel or hand tools are usually adequate for their extraction

although occasionally a bulldozer may be required to open up a working face. For our case, the

sample was taken with a hand shovel.

2.3 Field Survey

Field visits in connection with the survey were carried out within a distance 150km of

Addis Ababa by the Ethiopian Road Authority and the United Kingdom Transport and Road

Research Laboratory. They were concentrated in areas near to Debrezeit, Nazareth, Zewai,

Butajira and Gion (see fig 2.1).

Fig 2.1 cinder gravel distribution in Ethiopia



Cinder cones rarely support any vegetation other than grasses and examination of the

exposed profiles showed that the depth of soil cover was not more than a few centimeters. A

weathered cinder zone, however, usually extended down to a depth of about two meters. In some

cones deposits of calcium carbonate coated the cinder gravel: these did not persist throughout the

cones but in thin white bands parallel to and usually close to the surface. The size of cinder cones

varies but they do not normally exceed 100m in height and side slopes are generally of the order

of 1:200230. The largest cones would be expected to contain cinder deposits of about one

million cubic meters. Occasionally cones occur singly but more commonly they are found in

clusters in a linear arrangement associated with geological faults and recent lava flows.

The distinctive shape of cinder cones made them easily identifiable on aerial photographs

and photographs were used both to plan the survey and subsequently in the field work. The

examination of airphotos and print laydowns was extended to cover the whole of Ethiopia and

from these and a study of areas of recent (Quaternary) volcanic on geological map, a preliminary

map was compiled showing the occurrence of cones throughout the country (see Fig 2.1). They

were mostly concentrated in the Rift valley which extends from Tanzania and Kenya and bisects

the country in a SSWNNE direction; an identification of their frequency for each of the areas

that were identified has been given.

2.4 STABILIZED PAVEMENT MATERIAL

2.4.1 General

Natural soil is both a complex and variable material. Yet, because of its universal

availability and its low cost of winning, it offers great opportunities for skilful use as an

engineering material.

The term ‘soil stabilization’ may be defined as the alteration of the properties of an

existing soil either by blending (Mixing) two or more material and improving particle size

distribution or by the use of stabilizing additive to meet the specified engineering properties.

The chief properties of a soil with which the construction engineer is concerned are:



1. Strength: to improve the strength (stability and bearing capacity) for subgrade, subbase,

base and low cost road surfaces. A number of stabilization method are available by which

the strength or deformation resistance of soil may be increase none of these are more than

marginally effective in organic soil however. It still remains good practice to remove the

organic layer (topsoil), an increase of soil density, either by heavy compaction and/or

mechanical stabilization.

2. Volume stabilization: To improve volume stability, undesirable properties such as

swelling, shrinkage, high plasticity characteristics, and difficulty in compaction etc,

caused by change in moisture. Seasonal and long term moisture changes in an expansive

clay soil, if uncontrolled, rapidly disrupt road surfaces, tilt poles, crack buildings, break

underground service pipes and generally cause great economic loss.

Clay soil may be converted to a rigid or granular mass is by chemical or thermal

treatment. ‘Water proofing’ or ‘Sealing’ with tars or bitumen is used for short term

protection against volume change.

3. Durability: to increase the resistance to erosion weathering or traffic. Poor durability

can be a problem both for natural and stabilized soils. It is chiefly a surface problem for

road and pavement (beneath the seal), for drainage ways, for bridge and other abutments,

for the wall of pise and adobe houses, etc. poor durability is reflected in high

maintenance costs rather than in major structural failure.

4. Permeability: to improve high permeability, poor workability, dust nuisance, frost

susceptibility, etc. permeability presents engineering problem, of which the chief are

associated either with pore pressure dissipation or with seepage flow. Poor compaction of

dry soil lead to high permeability, because the hard clay lumps resist compactive effort

and thus leave large interstitial voids such voids also result from natural leaching and soil

aggregate formation processes including even some forms of stabilization problem of soil

permeability can generally be corrected by drainage, compaction and stabilization.

Due to their mineralogical composition, soils may be rather complex material.

Stabilization is therefore not a straight forward application of a given stabilizing agent, a

number of aspects should be taken into account in the selection of the proper stabilization



technique the factors that should be consider include physical and chemical composition of

the soil to be stabilized, availability and economical feasibility of stabilizing agent, ease of

application, site constraint climate, curing time, and safety such factors should be taken into

account in order to select the proper type of stabilization.

Basically four techniques of soil stabilization are commonly practiced in pavement

construction. These are:

1. Mechanical Stabilization

2. Cement Stabilization

3. Lime Stabilization

4. Bitumen Stabilization

2.4.2 Mechanical Stabilization

A method by which a soil or gravel is mixed with the original soil in order to improve the

grading and mechanical characteristics of the soil. Typical material used for mechanical

stabilization include river deposited sand, natural gravel, silt sand, sand clays, silt clay,

crushed run quarry products and waste quarry products volcanic cinders and scoria, poorly

graded laterites and beach sand, etc.

The principal properties affecting the stability of compacted base or sub base material are

internal friction and cohesion. Internal friction is chiefly dependent on the characteristics of

the coarser soil particles, i.e. gravel, sand and silt sizes. The cohesion, shrinkage, swelling

and compressibility are mainly associated with the quantity and nature of the clay friction as

indicated by plastic properties.

Preliminary mix design of mechanical stabilization is based on particle size distribution

and plastic properties. It is desirable also the strength test (CBR) be carried out to verify that

the required improvement has been achieved.

Stabilized material may be assessed by strength test suitable for this purpose at density

and moisture condition prevailing in the pavement during the service life. One of the most

commonly used strength test in the laboratory CBR test.



Table 2.1. California bearing ratio limit for mechanical stabilized base material:[2]

Pavement Minimum CBR Value

High class, high traffic volume 100

Rural roads, wet areas 80

Rural roads, dry areas 60

2.4.3 Cement Stabilization

Cement effective stabilizing agent applicable to a wide range of soils and situation. It has

two important effects on soil behaviors.

Reduces the moisture susceptibility of soil: cement binds the particles greatly and

reduces moisture induced volume change (shrinkage and swell) and it also improves

strength stability under variable moisture.

Develop interparticle bond in granular materials

Increased tensile strength and elastic modulus.

The Technique of cement stabilization involves breaking up (pulverizing) the soil, adding

the cement, usually by spreading on the surface of the loose soil, mixing the cement with the soil

and then watering and compacting in the usual manner.

Soil properties progressively change with increasing cement content. For practical reason,

two categories of cement stabilized material have been identified.

• Cement modified material – cement is used to reduce plasticity, volume change, etc. and

the interparticle bonds are not significantly developed such material are evaluated in the

same manner as conventional unbound flexible pavement materials.

• Cement bound material – cement is use to sufficiently enhance modulus and tensile

strength cement bound materials have practical application in stiffening the pavement.

There are no established criteria to distinguish between modified and bound materials,

but and arbitrary limit of indirect tensile strength of 80kN or unconfined compressive

strength of 800kpa after seven days moist curing has been suggested.



Any cement may be used for stabilization, but ordinary Portland cement is the most

widely used. Some use has been made of sulphate resisting cement and special stabilizing

cement has been used.

Any soil, with the exception of highly organic material, may be treated with cement and

will exhibit and improvement in properties, increase in strength. The only practical limit to

the range of use of cement stabilization are those imposed by clean well graded gravel or

crushed rock material, where stabilization is not only unnecessary but may, in fact, create

serious problems of shrinkage cracking and those imposed by the difficulty of incorporating

a dry fine powder into a moist heavy clay. Some difficulty has been reported with saline soils

but this can be overcome in most cases by increasing the cement content.

A number of factors influence the quality of the cementsoil interaction. The most

important factors can be categorized into four groups.

1. Nature & Type of soil

This include: clay content (max. 5%), plasticity of the soil (max. LL of 45),

gradation, content of organic material (max. 2%), sulphate content (max. 0.25%

for cohesive soils & 1% for noncohesive soils) and PH content. Soil with high

clay content and high plasticity are difficult to mix and high additive content are

required for an appreciable change in properties. Pretreatment with lime however

is good method to allow the soil to be cement stabilized later on.

2. Cement Content

The cement required to stabilize soil effectively vary with the nature and type of

soils. The criteria used are the compressive strength (about 1.7 MPa) after seven

days. The quantity required for gravel soil is generally much less than the required

to silty and clayey soils. Generally a soil has a maximum grain size less than

75mm, percent passing and retained 0.075mm sieve is less than 35% and greater

than 55% respectively and liquid and plastic limit less than 50 &25 respectively.



Table 2.2. General Guidance on cement requirement to stabilize soil [3]

Amount Cement (%) Soil type

By weight By Volume

A1a 35 57

A1b 58 79

A2 59 710

A3 711 812

A4 712 813

A5 813 813

A6 915 1014

A7 1016 1014

3. Moisture Content

Moisture is required for hydration of cement to take place, to improve the workability,

and facilitate the compaction of the soilcement mixture. The soilcement mixture exhibit the

same type of moisturedensity relationship as ordinary soil for a given compaction, there is an

optimum moisture content at which the maximum density is obtained.

4. Pulverization, Mixing, Compaction and Curing Condition

Many procedures of construction are available, but can be categorized into mixing in

plant (in a travelling plant and stationary plant for dry mixing) and in place mixing. The type of

machine used the procedure of mixinplace construction involves initial preparation of the sub

grade, pulverization of the sol, spreading of the soil, dry mixing the soil and the cement, adding

water and wet mix, compact and finish, and protect and cure (place a curing membrane to keep

moist). Curing is an important factor influencing on the end result. The temperature should be



high enough and he stabilized material should be prevented from drying out in order to obtain the

best result.

2.4.4 Lime Stabilization

Stabilization of soil with hydrated lime is broadly similar to cement stabilization in that

similar criteria and testing and construction techniques are employed. It differs, however, in two

important respects: first it is applicable to far heavier, clayed soils, and is less suitable for

granular material, and second, it is used more widely as a construction expedient. That is , to

prepare a soil for further treatment or to render a sufficient improvement to support construction

traffic.

Lime is a broad term which is used to describe calcium oxide (CaO) – quick lime,

Calcium hydroxide (Ca (OH) 2), hydrated lime, and calcium carbonate (CaCO3). Lime is an

effective stabilizing agent for clay material to improve both workability & strength. Lime is not

effective with cohesion less or low cohesion materials without the addition of secondary

(pozzolanicfine materials which react with lime to form cementitious compounds) additives.

The strength of lime stabilized materials is dependent on the amount of lime, the curing

time, curing temperature and compaction. In addition, the quantity of water, type of stabilizing

lime, and uniformity of mixing are important factor affecting the quality of production as they

are cement stabilization, the tendency to form bound products is less with lime than it is with

cement. Lime has more tendencies to produce granular material and consequently their major

applications are in the modification of clays, plastic sands, and plastic gravels.



Table2.3. Suggested lime content [3]

Soil Type Content for modification

Fine Crushed Rock 24%

Well graded clay graves

13%

Sand Not recommended

Sandy clay Not recommended

Silty 13%

Heavy clay 13%

Organic soils Not recommended

2.4.5 Bituminous Stabilization

Bituminous stabilization is used with non cohesive granular materials. Where the

bitumen adds cohesive strength and with cohesive materials. Where the bitumen ‘water proofs’

the soil thus reducing loss of strength with increase in moisture content. Both effects take place

partly from the formation of bitumen film around the soil particle which bounds them together

and prevents the absorption of water and partly from simple blocking of the pores, preventing

water from entering the soil mass.

Bituminous material: the bituminous material that are used for stabilization work are

mostly penetration grade bitumen and cut back bitumen and bitumen emulsion. The

characteristics of cut back dependent on the particle size distribution of the soil, the temperature

of application and the type of mix plant.

Soil requirements – Bituminous materials are used for the stabilization of both cohesive

and noncohesive granular soils. Soils which can readily pulverized by construction equipment

are satisfactory for bituminous stabilization. Cohesive soil usually has satisfactory bearing



capacity at low moisture contents. In the noncohesive granular material, bitumen serves as a

bonding or cementing agent between particles.

Durability of soilcement mixtures has been traditionally determined using American

Society for Testing and Materials (ASTM) D 559. ASTM D 559 requires brush tests in

conjunction with wetdry cycling of compacted soilcement mixtures.

Wetdry test protocols consist of compacting two replicate specimens from the same

mixture and allowing them to cure for 7 days in a moist room. After the 7day, 14day and 28

day cure for wetdry testing, the specimens are soaked for 5 hours. Specimen 1, which is

prepared to assess volumemoisture relationships, is weighed. Both specimens are then placed in

an oven for 42 hours at 71°C to dry. Specimen 1 is weighed again, and both are allowed to thaw

for 23 hours. At this point in both testing procedures, the specimens are weighed, and specimen

2, which is prepared to assess soilcement losses, is subjected to brushing. Brushing consists of

two brush strokes on all surfaces of the specimen with a force of 1.3kg. This process is repeated

12 times.

Clearly, this test is both subjective and timeconsuming, and the test results depend to a

great degree on the consistency of the individual performing the test. Another disadvantage of

these testing methods for soilcement durability is that they do not accurately represent

mechanisms that cause deterioration in the field. Because of the tedious nature of durability

testing using ASTM D 559, the UCS has been increasingly used as the single design parameter

for cement content determination by transportation agencies and materials engineers, even

though it is a reflection of only strength.



CHAPTER THREE

QUARRY SITE SELECTION, SAMPLING, METHODOLOGY

AND TESTING

3.1 Quarry site selection [9]

When selecting the quarry site there are general rules to be followed.

These are

Ø The quarry site should be located near the project site if possible.

Ø It is preferred if there is access road to the quarry.

Ø The quality of quarry for specified project should be approved.

Ø The potential of the quarry should be big enough for the project.

Ø The over burden pressure should be as low as possible.

Ø The terrain should be suitable to plant a crusher i.e. it shouldn’t be too steep.

The above points give us general guidelines for selecting a quarry site. But we have

sampling techniques and procedure as follows.

3.2 Sampling technique and procedure [9]

Sampling is a selection for testing of a portion of a mass of materials. Portion of material

are used for economic and technical reasons, for the physical and chemical measurements of raw

materials, plant process streams, and the final products and waste produced by industry. The

reliability of any measurement depends on sample quality. But, many source of error, such as

contaminated apparatus or reagents, biased methods, or operator errors, can be controlled by

proper use of measurement, standards, and reference materials.



3.2.1 Types of samples

A. Random sample: A sample is usually collected to determine the distribution of some

characteristic among the mass. To obtain the best estimate of the distribution, random

sampling may be performed. In random sampling every part of the mass has an equal

chance of being included; regardless of the location or nature of the part.

B. Representative sample: frequently connotes a single sample of mass of material

expected to exhibit average properties of the mass. It is not possible to select such a

sample by a random process, or to verify if it is representative.

C. A composite sample: It is a special type of representative sample. Many sampling

procedures assume that only average composition is desired, such as bulk, time weighted

or flowproportional averages and specify collection or preparation of a suitable

composite elaborate crushing, grinding, mixing and blending procedures have been

developed and standardized for preparing solid composite.

Roadside production shall be understood to be the production of materials with portable

or semi portable crushing, screening, or washing plants established or reopened in the

vicinity of the work on a designated project for the purpose of supplying materials for that

project.

Samples shall be so chosen as to represent the different materials, discernible, to the

sampler, that are available in the deposit. An estimate of the quantity of the different

materials shall be made.

If the deposit is worked as an openface bank or pit, the sample shall be taken by

channeling the face vertically, bottom to top, so that it will be representative of the material

proposed to be used. Overburden and disturbed material shall not be included in the sample.

Test hole shall be excavated or drilled at numerous locations in the deposit to determine the

quality of the material and the extent of the deposit. The number and depth of these test holes

will depend on the quantity of the material, and value of the resultant product. Separate

sample shall be obtained from the face of the bank and from test holes, in the manner

described above, and if visual inspection indicates there is considerable variation in the

material, individual samples from each test location shall be obtained and reduced to the



proper size by thoroughly mixing and quartering. The size of the samples shall be such that at

least 12kg of sand and 35kg of gravel are available for tests, if both constituents are present.

If the deposit being investigated does not have an open face, samples shall be obtained

entirely from test holes as outlined herein.

In sampling material from stockpiles it is very difficult to insure representative samples,

due to the segregation which usually occurs when material is stockpiled, with the coarser

particles rolling to the outside base of the pile. When it is necessary to sample capable of

exposing the material at various levels and locations. Separate samples shall be taken from

different areas of the stockpile to represent the material in that portion. Test results of the

individual samples will indicate the extent of segregation existing in the stockpiles. In

sampling sand from stockpiles the outer layer, which may have become dry, causing

segregation, shall be removed and a representative sample of the damp sand selected.

In addition of the general information accompanying all samples the following

information shall accompany samples fro roadside productions that are not commercial

operations:

1. Name of owner or seller,

2. Location of supply,

3. Approximate quantity available,

4. Quantity and character of overburden,

5. Length of haul to proposed site of work,

6. Character of haul (kind of road, max grades, etc) and

7. Some detailed record of the extent and location of the material represented by

each sample.

The number of samples required depends on the intended use of the material, the

quantity of material involved, and the variations both in quality and size of the aggregate. A

sufficient number of samples shall be obtained to cover all variations in the material. It is



recommended that each sample of crushed stone, gravel, slag, or sand represent approximately

50tons of material.

The sample sizes and weights cited are tentative. The quantities must be predicated on the

type and number of tests to which the material is to be subjected and sufficient material obtained

to provide for the proper execution of these tests. All standard acceptance and control tests are

covered by methods of AASHO (American Association of state Highway Officials), and ASTM

(American Society for Testing Materials), and specify the quantity of sample required for each

specific test.

The size of the samples is dependent upon the number of tests required. Generally

speaking, the amounts specified in table3.1 will provide adequate material for routine grading

analysis.

Table 31: Size of Samples [5]

Nominal Max Size of Particles, passing sieve

Min of Weight of Field Samples

mm Kg

Fine Aggregate

2.00 5

4.75 5

Coarse Aggregate

9.5 5

12.5 10

19 15

25.0 25

37.5 30

50.0 40

63 45

75 60

90 65



3.2.2 Sources of aggregates

Source of aggregates for use in pavement works include:

Hard rock sources (crushed quarried rock) – hard sound bed rock exposures that need blasting

and crushing.

Naturally occurring gravels – which includes alluvial deposits, and highly weathered and

fractured residual formations (rip able or can be worked using earth moving machinery such as

dozers). These may be used as is (pitrun) or may need further processing to be suitable for use

such as crushing oversized stones and screening and/or other modifications such as mechanical

stabilization.

The principal sources of road aggregates in Ethiopia include natural sand and gravel deposits,

and crushed rock. Pulverized concrete and asphalt pavements and other recycled and waste

materials are not used, but could be further source of pavement materials.

Crushed aggregates hard rocks are important source of aggregates. There are different types of

rocks, all composed of grains of crystalline minerals held together in a variety ways. The

property of a rock depends on the properties of its constituent minerals and nature of bond

between them (i.e. composition, grain sixe and texture of the rock) which in turn depends on its

mode of origin/formation. These are igneous, sedimentary, and metamorphic rocks.

3.3 Aggregate Tests

Aggregates are obtained from different sources and consequently differ considerably in

their constitutions; inevitably, they differ also with regard to their engineering properties. The

properties of aggregate that are important for road construction include its cleanliness

(contamination with dust and other deleterious materials), particle size and shape, gradation,

toughness – resistance to crushing, abrasion, wearing, durability/soundness, specific gravity and

water absorption, surface texture, tendency to polish, bonding property with bitumen. Aggregate

tests are necessary to determine the suitability of the material for a specific use and to make sure

that the required properties are consistently within specification limits. The following will



discuss important tests of aggregates and their significance of application; and all of the

following tests are tested for the cinder aggregate.

3.3.1 Gradation test: It is the characteristic of aggregates on which perhaps the greatest stress

is placed in specifications for highway bases, cement concretes, and asphalt mixes. Hence,

gradation test, also called sieve analysis, screen analysis or mechanical analysis, is the most

common test performed on aggregates to evaluate the suitability of the aggregate materials with

respect to their grain size distribution for a specific use. Gradation is determined by separating

the aggregates into portions, which are retained on a number of sieves or screens having

specified openings, which are suitably graded from coarse to fine. The results obtained maybe

expressed either as total percentage passing or retained on each sieve or as the percentages

retained between successive sieves.

The theoretical max density of aggregates is obtained when the grain size distribution

follow the Fuller max density equation of the form

P = 100 (d/D) n

In which, p is passing sieve size “d”, “D” represents maximum aggregate size in the

material and n is a constant which varies between 0.45 and 0.5 for maximum density. The

assumption in this relationship is that the voids between the larger particles are filled with still

smaller particles, until the smallest voids are filled with a small amount of fines. Strength or

resistance to shear failure, in graded. The larger particles are in contact with each other,

developing frictional resistance to shearing failure, and tightly bound together due to the

interlocking effect of the smaller particles. When aggregate particles are to be bound together by

cement or bitumen, a variation in the grading of an aggregate will result in a change in the

amount of binder required to produce a material of given stability and quality. Proper aggregate

grading contributes to the uniformity, workability and plastics of the material as it is mixed.

Often the fines content must be limited, because they are relatively weak, and require

excessive amount of binder to cover them. If fines are present as on larger particles, they weaken

the bond between the cement and those particles. Fines in highway bases may lead to drainage

and frostheaving problems. Also excessive amount of fines may result in weak mixture, as the

large particles are not in contact with each other. The strength of the mixture would then depend



only on friction between the smaller the small particles which is much less than between large

particles. In particle, the required gradation is not found naturally, particular, if the aggregates

are pitrun materials. In such cases, combining two or more aggregates of different sources the

gradation requirement for a specific use.

3.3.2 Aggregate Crushing Value ( ACV) Test. Aggregate crushing test evaluates the resistance

of aggregate against the gradually applied load. The test is used to evaluate the crushing strength

of available supplies of rock, and in construction to make sure that minimum specified values are

maintained. The test is undertaken using a metal plunger to apply gradually a standard load of

400KN to a sample of the aggregate (1014mm) contained in a standard test mould. The amount

of material passing 2.36mm sieve in percentage of the total weight of the sample is referred to as

the a Aggregate crushing value (ACV).Over the range of normal road making aggregates, AVCs

vary from 5 percent for hard aggregates to 30 percent for weaker aggregates. For weaker

aggregates than this, the same apparatus is 2.36mm sieve. The value is obtained by interpolating

of the percentage of fines produced over a range of test loads.

3.3.3 Aggregate Impact Test: This test is a means of evaluating the resistance of aggregates to

sudden impact loading. It is carried out by filling a steel test mould with a sample of aggregate

(10 – 14mm) and then the impact load applied is by dropping hammer at a height of 380mm. The

aggregate Impact Value (AIV) is the percentage of fines passing 2.36mm sieve after 15 blows.

This test produces results that are normally about 105 percent of the ACV and it can be used for

same purposes. Both tests give results which are sufficiently repeatable and reproducible for

contract specifications.

3.3.4 Abrasion Test: Abrasion test is the test used to know how the aggregate is sufficiently

hard to resist the abrasive effect of traffic over its service life. The most widely used abrasion test

is the Los Angeles Abrasion Test which involves the use of steel drum, revolving on horizontal

axis, into which the test sample of chippings loaded together with steel balls of 46.8mm

diameter. The Los Angeles Abrasion Value (LAV) is the percentage of fines passing the 1.7 mm

sieve after a specified number of revolutions of the drum at specified speed. The drum is fitted

with internal baffles causing the aggregate and the steel balls to be lifted and then fall as the

drum revolves. The test therefore gives an indicate. For bituminous surface dressings, chippings



with an ACV less than 30 are desirable and the stronger they are the more durable will be the

dressings. With premixed bituminous materials and with crushed stone bases, high mechanical

strength, though useful, is not always of paramount importance. The repeatability and

reproducibility of this test are satisfactory and appropriate for use in contract specifications.

3.3.5 Specific Gravity and Water Absorption. The tests are likely o be used both in surveys of

aggregate resources and in design, particularly in the interpretation of compaction tests and in the

design of bituminous mixtures. They may also be used as part of quality control during

construction, particularly when the survey has indicated that aggregate from the chosen source is

subject to variations in density. The test procedure is simple and the tests are repeatable and

reproducible.

Most rocks absorb less than one per cent by weight of water and, up to this level, water

absorption is of no great consequence. However, some rocks can absorb up to 4 percent of water.

This suggests that the rock ay be of low mechanical strength and will be difficult to dry and heat

during processing to make bituminous mixtures. Inadequate drying will cause difficulty in

securing good adhesion between bitumen and stone, and in hot process mixtures, where the stone

must be heated to about 180 0 c, it causes a large waste of energy.

In the tests, a 4 kilogram sample of the crushed rock of specific nominal size chippings is

soaked in distilled water for 24 hours, weighed in water (Ww), surface dried and weighed in air

(WS). It is then oven dried at 1050c for 24 hours and weighed again in air (WD). The specific

gravity and the water absorption are then obtained as follows:

Specific gravity = Wd/(Wd Ww) Water absorption = (Ws – Wd)/Wd × 100

3.4 Unbound Base Materials (ERA Pavement Design Manual Requirements) [5]

Unbound base and sub base courses in pavement structures are granular materials from

sand or gravel deposits or crushed rock from quarries without admixtures. The required

properties of these materials vary with the type of pavement and the depth of the material in the

pavement structure.



Different standard methods of design specify materials of construction differently

considering the traffic load, locally available materials, and environmental conditions. The

following describes the requirements set for different unbound pavement materials for base

courses as specified in ERA pavement design manual (2002).

3.4.1 Graded crushed aggregate: This material is produced by crushing fresh, quarried rock

usually termed a ‘crusherrun’, or alternatively the material may be separated by screening and

recombined to produce a desired particle size distribution, as per the specifications. The rock

used for crushed aggregates should be hard and durable. Laboratory and field experiences have

shown that crushed particles have, in general, more stability than rounded materials due to

primarily to added grain interlock. In addition, crushed materials possess high coefficient of

permeability. Alternate gradation limits, depending on the local conditions for a particular

project, are shown in Table 53. After crushing, the material should be angular in shape with a

Flakiness Index of less than 35%, and preferably of less than 30%. In constructing a crushed

stone base course, the aim should be to achieve maximum impermeability compatible with good

compaction and high stability under traffic.

Table 32: Grading limits for graded crushed stone base course materials

Percentage by mass of total aggregate passing test sieve Nominal maximum particle size Test sieve

(mm) 37.5mm 28mm 20mm 50 100 37.5 95100 100 28 100 20 6080 7085 90100 10 4060 5065 6075 5 2540 3555 4060 2.36 1530 2540 3045 0.425 719 1224 1327 0.075 512 512 512

To ensure that the materials are sufficiently durable, they should satisfy the criteria given

in Table 33. These are a minimum Ten Per Cent Fines Value (TFV) and limits on the maximum

loss in strength following a period of 24 hours of soaking in water. Alternatively, if requirements



expressed in terms of the results of the Aggregate Crushing Value (ACV) are used, the ACV

should preferably be less than 25 and in any case less than 29. Other simpler tests e.g. the

Aggregate impact Test may be used in quality control testing provided a relationship between the

results of the chosen test and the TFV has been determined. Unique relationships do not exist

between the results of the various tests but good correlations can be established for individual

material types and these need to be determined locally.

The in situ dry density of the placed material should be a minimum of 98% of the

maximum dry density obtained in the Heavy Compaction. The compacted thickness of each layer

should not exceed 200 mm. Crushed stone base materials described above should have CBR

values well in excess of 100 percent, and fines passing 0.425 mm sieve should be non plastic.

Table 33: Mechanical strength requirements for crushed stone base defined by TFV

Typical annual rainfall (mm)

Minimum 10% fines values (KN)

Minimum ratio wet/dry Test (%)

>500 110 75 <500 110 60

3.4.2 Requirements for natural gravels and weathered rocks: A wide range of materials

including lateritic, calcareous and quartzitic gravels, river gravels, boulders and other transported

gravels, or granular materials resulting from the weathering or rocks can be used successfully as

base course materials.

Table 34 contains three recommended particles size distributions for suitable materials

corresponding to maximum nominal sizes of 37.5 mm, 20 mm and 10 mm. When the traffic is in

excess of 1.5×10 6 ESA, only the two larger sizes should be considered.



Table 34: Recommended particle size distributions for base course material

Percentage by mass of total aggregate passing test sieve Nominal maximum particle size Test sieve

(mm) 37.5mm 20mm 10mm 50 100 37.5 80100 100 20 6080 80100 100 10 4565 5580 80100 5 3050 4060 5070 2.36 2040 3050 3550 0.425 1025 1227 1230 0.075 515 515 515

For materials whose stability decreases with breakdown, an aggregate hardness based on

a minimum soaked TFV of 50KN may be specified. The fines of these materials should

preferably be non plastic but should normally never exceed a Pl of 6. If the PI approaches the

upper limit of 6, it is desirable that the fines content be restricted to the lower end of the range.

To ensure this, a maximum Plasticity Product (PP) of 60 is recommended or alternatively a

maximum Plasticity Modulus (PM) of 90 where:

PP=PI × (percentage passing the 0.075mm sieve)

PM=PI x (percentage passing the 0.425 mm sieve)

When used as a base course, the material should be compacted to a density equal to or

grater than 98 percent of the maximum dry density achieved in the heavy compaction. When

compacted to this density in the laboratory, the material should have a minimum CBR OF 80%

after four days immersion in water.

In low rainfall areas, typically with a mean rainfall of less than 500mm and where

evaporation is high, moisture condition beneath a well sealed surface are unlikely to rise above

the optimum moisture content. In such conditions, high strengths (CBR>80%) are likely to

develop even a natural gravels containing a substantial amount of plastic fines are use. In these

situation, for traffic loading within 0.7 million equivalent standard axles, the max allowable PI

can be increased to 12 and the minimum soaked CBR criterion reduced to 60% at the expected

field density.



Rock such as basalt, dolerites, and granular material derived from their weathering,

transportation or other alteration release undesirable plastic fines during constriction or in

service. The release minerals may lead to a consequent loss in bearing capacity and this is likely

to worsen if water enter the pavement and lead to rapid and premature failure. The states of

decomposition also affect their longterm durability when stabilized with lime or cement. When

weathering is suspected, petrographic analysis to detect secondary (clay) minerals and soundness

tests are carried out.

Naturally occurring gravels which do not normally meet the normal specifications for

base course materials have occasionally been used successfully. They include lateritic,

calcareous and volcanic gravels. In general their use should be confined to the lower traffic

roads. Laterite gravels with plasticity index in the range of 612 and plasticity modulus in the

range of 150250 is recommended for use as base course material for of traffic volume up to 15

million equivalent standard axles. The values towards higher range are valid for semiarid and

arid areas of Ethiopia, i.e. with annual rainfall less than 500mm. Cinder gravels can be used as

base course materials in lightly trafficked (below 0.7x10 6 ESA) surface dressed roads.

3.5 Consistency of soils: By consistency is meant the relative ease with which soil can be

deformed. This term is mostly used for fine grained soils for which the consistency denotes the

degree of firmness of the soil which may be as soft, firm, stiff or hard. Fine grained soil may be

mixed with water to form a plastic paste which can be molded into any form of pressure. The

addition of water reduces the cohesion making the soil still easier to mold. Further addition of

water reduces the cohesion until the material no longer retains its shape under its own weight,

but flows as a liquid. Enough water may be added until the soil grains are depressed in a

suspension. If water is evaporated from such a soil suspension, the soil passes through various

stages or states of consistency.



Figure 31 Consistency of soil

LQUID LIMIT (LL): is the water content corresponding to the arbitrary limit between liquid and

plastic state of consistency of the soil. It is defined as the minimum water content at which the

soil is still in the liquid state, but has a small shearing strength against flowing which can be

measured by standard means. With reference to the standard liquid limit device, it is defined as

the minimum water content at which a part of a soil cut by a groove of a standard dimensions,

will flow together for a distance of 12mm under an impact of 25 blows in the device.

PLASTIC LIMIT (PL): Plastic limit is the water content corresponding to arbitrary limit between

the plastic and the semisolid state of consistency of a soil. It is defined as the minimum water

content at which a soil will just begin to crumble when rolled into thread approximately 3mm in

diameter.

PLASTIC INDEX (PI): The range of consistency within which a soil exhibits plastic properties

is called plastic range and is indicated by plasticity index. The plasticity index defined as the

numerical difference between the LL and PL of a soil.

PI = LL – PL

Solidstate Semisolid state Plasticstate Liquid state

LL PL

Total volum

e of so

ilmass

Moisture content increase



When plastic limit cannot be determined, the plasticity index is reported as nonplastic

(NP). When the PL is equal or greater than LL, the plasticity index reported as zero.

3.6 PROCTOR COMPACTION TEST

When aggregate is used as a base course material in pavement construction, it is essential

that the material be placed in a layer and compacted to a high density. Compaction is the process

of increasing the bulk density of a soil or aggregate by driving out air. Increasing the aggregate

density improves its strength, lowers its permeability, and reduces future settlement. For any

aggregate, for a given amount of compactive effort, the density obtained depends on the moisture

content at very high moisture contents; the maximum dry density is achieved when the aggregate

is compacted to nearly saturation, where almost all the air is driven out. At low moisture content,

the aggregate particles interfere with each other, additional of some moisture will allow greater

bulk densities, with a peak density where this effect begins to be counteracted by the saturation

of the aggregate

The proctor Compaction tests, and the related Modified Proctor Compaction Test, are

tests to determine the maximum practically achievable density of soils and aggregate. The test

consists of compacting the soil or aggregate to be tested into a standard mold using a

standardized compactive energy at several different levels of moisture content. The Maximum

Dry density and Optimum moisture content are determined from the results of the test.

Aggregate compacted in the field is tested for inplace dry bulk density, and the result is divided

by the maximum dry density to obtain a ‘relative compaction’ for the aggregate in place.

3.7 CALIFORNIA BEARING RATIO TEST

California bearing ratio test gives a relative strength of the material for pavement

structure respect to crushing rock, which is considered an excellent base course material. This

bearing strength of base course is the major criteria for road construction.

The test carried out using compacted densities range from95% to 100% of the maximum

density obtained using proctor compaction test. The compaction method in CBR test is quite

similar to that of proctor test except the number of blows, the size of the mould and the number

of layers in which the compaction takes place three layers. The compacted sample will be soaked



for about four days before penetration to represent the field condition on major rainy seasons and

ground water fluctuation which cause swelling of the base course.

3.8 WETTING AND DRYING TESTS (DURABILITY)

These methods is used for determining the soilcement loss and moisture changes

produced by repeated wetting and drying of hardened soilcement specimens. The specimens are

compacted in a mold, before cement hydration, to maximum density at optimum moisture

content using the compaction procedure described in ASTM D558 or AASHTO T134, test for

MoistureDensity Relations of SoilCement Mixtures.

The test has been carried out by allowing the mould to cure for 7 days in a relative moist

environment and the 12 cycle of wetting and drying. At the end of the storage in moist room, it

was submerged the specimens in potable water at room temperature for a period of 5hrs and it

was removed. It was weighed and measured the no1 specimen. Then both specimens were

placed in an oven at 71 o c for 42 hrs and removed. They were also weighted. But specimen no2

was brushed two firm strokes on all areas with a wire scratch brush. The above procedure

described constitute one cycle of wetting and drying (48 hr). The procedure was repeated for 12

cycles. Finally soilcement loss percent calculated.

Soilcement loss, percent = A/B × 100

Where: A = original calculated oven dry – final corrected oven dry weight

B = original calculated ovendry weight

Corrected ovendry weight = ovendry weight/(percent of water retained + 100)

3.9 UNCONFINED COMPRESSIVE STRENGTH

The compressive strength of a soilcement mould is done by similar procedure of wetting

and drying but after the 12 cycle the specimen subjected to load applied continuously

1mm/minute. Then the maximum load recorded and the stress found by dividing the maximum

load by the area of the specimen.



3.10 Methodology

The red cinder gravel sample which is brought from a quarry site near Nazareth, 99 Km

from Addis Ababa and situated 1 Km right of DerezitNazrate road is brought to the lab. Basic

material characteristics like grading, plastic testes, free swell, classification test, CBR test on

mechanical stabilization mechanical strength tests such as Losangels abrasion, aggregate impact

value and specific gravity was determined with laboratory testes. Based on preliminary (prelude)

test results and literature review other testes were made in stabilization of the cinder with clay

and cement and the stabilized cinder was tested to determine unconfined compressive strength,

moisture content and durability, the values found from the tests were evaluated and analysis was

made on the test results and some use full conclusions were drawn and recommendations

forwarded.

Steps followed

A field survey to locate and identify cinder gravels and to obtain samples for laboratory testing

Laboratory investigation to determine their physical and engineering properties.

An experiment to examine the behavior of the cinder gravel under controlled conditions in

relation to weather change (durability) and compressive strength.

Standards

From AASHTO

T8470, sieve analysis

T8470, specific gravity and absorption of fine aggregate

T8570, specific gravity and absorption of course aggregate

T9670, los angles machine

T8968, liquid limit of soil

T9070, plastic limit and plastic index of soil

T 19363, California bearing ration



From ASTM

ASTM D559 and T134, durability (wet and dry test)

ASTM D1633, unconfined compressive strength

CHAPTER FOUR

LABORATORY TEST RESULT

4.1GRADATION OF CINDER

Table 4.1 shows that the gradations of cinder gravel. It is clear that it losses fine

materials. From pan to 4.75mm sieve size, the cinder has deficiency which is below the

minimum value. At 9.5mm sieve size the cinder is out of the max value. From 25mm to 50mm

sieve size the cinder needs more course materials. The figure (fig. 41) below is clarifying the

above statement. So we need some amount of fine materials like clay.

Table 41: gradation of cinder gravel

ERA Specification

sieve size (mm)

Wt. Retained (g)

Weight retained (%)

comm. Passing (%)

Max value (%)

Min value (%)

50 0.948 6.06 93.94 100 100 37.5 1.103 7.06 86.88 97100 95 25 1.012 6.47 80.41 76 19 1.115 7.13 73.28 80 60 12.5 2.056 13.15 60.13 60 40 9.5 1.676 10.72 49.41 40 25 4.75 4.366 27.93 21.48 35 20 2.36 2.634 16.85 4.63 30 15 1.18 0.599 3.83 0.8 26.4 13 0.6 0.071 0.45 0.35 22.8 11 0.3 0.015 0.096 0.254 19.2 9 0.15 0.009 0.06 0.194 15.6 7 0.075 0.010 0.06 0.114 12 5 pan 0.018 0.115 0



Fig 41: gradation of cinder gravel graph

4.2 CBR VALUES

Before we go to stabilization we tried to find the general characteristics of cinder gravel.

Here we have CBR value for modified test. The CBR is 42% which is very small compare to the

ERA standard. ERA states that for high traffic, high class minimum CBR=100%. But for wet

Percentage passing

Sieve size (mm)



area of rural roads minimum value is 80%. So these values indicate that stabilization needed.

Table 42 and fig 42 shows the modified CBR test results.

Table 42: cinder gravel modified CBR value

penetration dial read

dial factor Load area stress CBR

(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 32 25.707 822.624 1935 0.42512868 1.27 84 25.707 2159.388 1935 1.11596279 1.91 151 25.707 3881.757 1935 2.00607597 2.54 218.5 25.707 5616.9795 1935 2.90283178 42 3.81 346 25.707 8894.622 1935 4.59670388 5.08 439 25.707 11285.373 1935 5.83223411 57 7.62 570.5 25.707 14665.8435 1935 7.57924729 10.16 648.5 25.707 16670.9895 1935 8.61549845 12.07 700 25.707 17994.9 1935 9.29968992



Fig 42: Modified CBR value of cinder gravel chart

4.3 SPECIFIC GRAVITY OF CINDER GRAVEL

Specific gravity of cinder is given for fine aggregate and course aggregate are given below in Table

43 and 44. Generally for normal road surfacing aggregates specific gravity ranges from 2.5 to 3.0, which

an average value of 2.68. Here it gives the value of specific gravity of 2.335.



A. Fine aggregate (< 4.75mm)

Table 43: Specific gravity for fine aggregate less than 4.75mm

Test no.

Weight of flask

Wt. flask + water

Wt. of sample

Wt. flask + water + sample

Bulk specific gravity

(g) (g) (g) (g)

1 161.3 658 200 772.2 2.33

2 163.3 659.5 200 774.1 2.34

Bulk specific gravity

2.335

B. Course aggregate (> 4.75mm)

Table 44: Specific gravity for course aggregate greater than 4.75mm

Weight of Surface saturate dry

In water Ovendry Bulk specific gravity

Test no. (Kg) (Kg) (Kg)

1 9.893 4.879 9.19 1.833

2 9.85 4.864 9.103 1.826

Bulk specific gravity 1.83

4.4 IMPACT TEST

Table 45 shows the impact test values. For quartzite gravel used for basecourse material, the

impact value is between 11 and 33. Since cinder is quartzite gravel it should be in the above range. Here

also we need stabilization to improve the impact value.



Table 45: Impact tests result

Sample Weight of sample Weight passing 2.36mm sieve AIV

Test no. (g) (g) (%)

1 207.8 99.7 47.98

2 204.6 93.6 45.75

3 200.1 101.4 50.67

Impact value 48.14

4.5 CRUSHING TEST RESULT

Crushing test is an important test for the road construction material. In table 46, the aggregate

crushing value is given. For normal road construction, the average crushing value is 9 to 29. But cinder

give about 50 %. Also here we need stabilization.

Table 46: Crushing value of cinder

Samples Weight of sample Weight passing 2.36mm sieve ACV

Test no. (g) (g) (%)

1 1705 815 47.8

2 1704 889 52.14

Aggregate crushing value 49.97

4.6 ABRASION TEST

Abrasion test was carried out for both aggregate types B and C. Type B contains 50% of 19mm

passing and 12.5 retained and 50% of 12.5mm sieve size passing and 9.5mm retained. The majority of the

cinder gravel is in type C. Type C 50% contains 9.5mm passing and 6.3mm retained and 50% of 6.3mm

passing 4.75mm sieve size retained.



Table 47: Abrasion test values of cinder

Aggregate type

Weight of sample Weight passing 2.36mm sieve Abrasion value

(g) (g) (%)

Type B 5000 1.492 29.84

Type C 5000 2.637 52.74

4.7 CLAY TESTS

We discussed about stabilization in the above. Mechanical stabilization is carried out by using

clay and the cinder. There are three tests that have been tested for the clay only. The clay is come from in

Addis Ababa, around Addisu Gebeya.

4.7.1 GRADIATION ANALYSIS

The cinder gravel is lack of fine materials which is less than 2.36mm size and the gradation of the

material of clay is shown in table 48 and fig 43. It is clear that it is good amount of clay for stabilized

cinder.

Table 48: gradation of clay

sieve size weight retained

percentage retained

percentage passing

(mm) (g) (%) (%) 4.75 0 0 100 2.36 61 6.1 93.9 1.18 158 15.8 78.1 0.6 216 21.6 56.5 0.3 216 21.6 34.9 0.15 153 15.3 19.6 0.075 105 10.5 9.1 pan 91 9.1 0



Fig 43: Gradation of mechanical stablizer clay

4.7.2 ATERBERG LIMIT OF THE CLAY

The plastic index of clay is a major factor for the strength and durability of the stabilized cinder.

Therefore we tried to find the PI of the soil. Table 49 shows the three tests for liquid limit and two tests

for plastic index. Fig 44 shows the liquid limit result.

Sieve size (mm)

Percentage passing (%

)



Table 49: Atterberg limit of mechanically stabilizer clay

test liquid limit Column1 Column2 plastic limit Column3

can no. D18 A14 H3 T9 A34 can wt. 22.05 22.11 20.29 21.79 22.00

can+wet specimen wt.(g) 31.52 37.25 33.92 29.44 30.11

can+dry specimen wt.(g) 28.32 31.81 28.96 27.70 28.29

no. of blows 68 26 18 wt. of water(g) 3.19 5.43 4.96 1.74 1.82

wt. ofdry speciemen(g) 6.28 9.70 8.66 5.91 6.29

moisture content(%) 51 56 57 29 29

liquid limit 56 PI 27 plastic

limit 29

Fig 44 graph of liquid limit for clay



4.7.3 FREE SWELL TEST

The free swell test implies the swelling of the clay when exposed to water. It is recommended that

the value should be less than 20%. But our result shows 25%. If when we mix it with the cinder it will

decrease the swelling.

Table 4.10 Free swell test result

Test sample

No.

Initial volume

(ml)

Final volume

(ml)

Free swell value

(%)

1 100 120 20

2 100 130 30

Free swell value 25

4.8 Proctor Test for stabilized cinder with clay

Before we go to the selection of optimum clay by using CBR tests, we did proctor test to

find optimum moisture content by adding from 10% to 15% clay to the cinder gravel. Fig 45 &

46 shows the general overview of the proctor test result. All the test results of the proctor will

show in appendix.



Figure 45 graph of clay content vs. optimum moisture content

Optimum

moisture content (%)



Figure 46 graph of dry density vs. clay content

4.9 CBR of the cinder gravel stabilized with clay

The CBR values are used to find the optimum clay content by using the optimum

moisture content of the proctor test. Here we take two tests. The first is done by using the OMC

and the second one is done only by its dry state. That means without moisture on the stabilized

clay. In both cases 13% of clay is an optimum content. Fig 47 & 48 shows the above

description.



Figure 47 graph of CBR vs. clay content for wet condition



Figure 48 graph of CBR vs. clay content

4.10 MECHANICALLY STABILAIZED CINDER WITH CLAY

4.10.1 Gradation of stabilized cinder with clay

The gradation of stabilized cinder with cinder is given in table 410 and fig 49. It is easy

to see that the fine material is almost in the range. So the gradation shows fine material is

increased. We took 13% clay as optimum content.



Table 411: Gradation of cinder and clay

sieve size (mm)

Wt. Retained (g)

Weight retained (%)

comm. Passing (%)

Specification (%)

min value (%)

50 0.948 5.39 94.61 100 100

37.5 1.103 6.27 88.34 97100 95

25 1.012 5.76 82.58 76

19 1.115 6.34 76.24 80 60

12.5 2.056 11.7 64.54 60 40

9.5 1.676 9.53 55.01 40 25

4.75 4.366 24.84 30.17 35 20

2.36 2.753 15.66 14.51 30 15

1.18 0.907 5.16 9.35 26.4 13

0.6 0.492 2.7 6.55 22.8 11

0.3 0.436 2.48 4.07 19.2 9

0.15 0.307 1.75 2.32 15.6 7

0.075 0.215 1.22 1.1 12 5 pan 0.195 1.11 0



Fig 49: Gradation graph of cinder with clay

4.10.2 ATTERBERG LIMIT

As it is done in the above, the atterberg limit is done. The test gave a good result for

cement stabilization. The PI is 10 which is applicable for cement stabilization. It is shown in

table 412 and fig 410.

Sieve size (mm)

Weight Passing (%

)



Table 412: test result of cinder and clay for atterberg limit

Column1 Column2 Column3 Column4 Column5 Column6

can no. D67 A33 D31 D26 A97 can wt. 21.79 22.18 21.88 22.19 22.17

can+wet specimen wt.(g) 38.31 39.705 33.48 28.25 25.79

can+dry specimen wt.(g) 34.07 35.129 30.37 27.07 25.07

no. of blows 27 21 16 wt. of water(g) 4.24 4.58 3.11 1.18 0.71

wt. ofdry speciemen(g) 12.28 12.95 8.49 4.88 2.90

moisture content(%) 35 35 37 24 25 liquid limit 35 PI 10 plastic limit 24

Fig 410: graph values of liquid limit for cinder and clay



4.11 Proctor test for stabilized cinder with 13% of clay and cement

This test is done by using the same way as the above compaction test. We take the 13%

clay and the cinder and stabilized with 3%, 5%, 7% and 10% of cement to find the optimum

moisture content for each percentage of cement given above. All the data are given in the

appendix. But summarized graph is shown below in fig 411 and 412.

Figure 411 graph of OMC vs. cement percentage



Figure 412 graph of maximum dry density vs. cement percentage



4.12 Durability (Wetting and Drying)

After 12 cycles of wetting and drying, there are tow tests to be tested. In this, durability

of the molded sample due to brushing. It is recommended that more than 14% of the mold

shouldn’t be lost due to brushing. Fig 414 table 413 shows the graph of the UCS.

4.13 Unconfined Compressive Strength

The UCS of the mould is done according to ASTM D1633. It goes through the same 12

cycles of wetting and drying with out the brushing. Then the compressive strength of the mold

will be tested. Fig 415 table 414 shows the graph of the UCS.

Table 413 UCS after 7 days of curing and 12 cycle of wetting and drying

7 days curing and 12 cycle wetting and drying cement test 1 test 2 average value % Load(KN) Stress(Mpa) Load(KN) Stress(Mpa) Load(KN) Stress(Mpa) 3 8.2 0.4 7.9 0.4 8.05 0.4 5 13.3 0.6 13.3 0.6 13.3 0.6 7 65.9 2.9 70.3 3.1 68.1 3 10 125.5 5.6 111.2 4.9 118.35 5.25



Figure 415 graph of the compressive strength vs. cement percentage



4.14 Conclusion

To achieve desirable capacity and material durability we use a stabilizing agent commonly used for

this purpose is Portland pozzolana cement. Cementtreated material will exhibit adequate longterm

improvements in strength and durability compared to untreated soil but we have to avoid

unnecessary expense in the construction. Based on the 12 cycles of wetting and drying results that

we compare 3%, 5 %, 7% and 10% cement stabilized cinders. For final conclusion we excluding

3% cement because of its small values in the durability and unconfined compression strength

tests. And we also exclude 10% from the point of construction cost. The optimum value is

between 5% and 7%.

A cinder gravel stabilized with 7% cement stabilized cinder is selected for its 3.0MPa

unconfined compression strength and 17.80% wet and dry loss as compare to 0.6MPa

compressive strength and 20.65% wet and dry loss of 5% cement stabilized cinder.

4.15 Recommendation

The main disadvantage of using cement to stabilize a soil is that compaction must be

completed within a relatively short time and the increase in the cement content of the stabilized

cinder gravel can increase the strength but it can cause problems with durability due to primarily

shrinkage cracking, which will occurs during cement hydration. Further testing should also

necessary to validate this finding.



APPENDIX



PROCTER TEST FOR CINDER AND CLAY

CINDER + 10% CLAY

MC DD 5.25 15.13

6.6 15.58 11.8 16.45

14.29 16.08 14.59 15.72

OMC = 12

MDD = 16.44



CINDER + 11% CLAY

MC DD 6.38 16.7 9.41 17.01

13.09 17.54 15.97 17.27 16.9 16.88 17.1 16.46

OMC = 13

MDD = 17.54



CINDER + 12% CLAY

MC DD 6.8 17.08 13.36 17.99 16.8 17.28 20.47 16.44

OMC = 14

MDD = 18



CINDER + 13% CLAY

MC DD 7.01 16.73 11.61 17.22 14.74 18.57 18.55 17.24 23.28 16.54



CINDER + 14% CLAY

MC DD 16.53 16.7 17.23 17.05 18.55 16.91 19.58 16.41 22.46 16.28

OMC = 17

MDD = 17.06



CINDER + 15% CLAY

MC DD 12.09 15.76 14.94 16.19 15.74 16.61 16.55 16.83 20.81 16.07

OMC = 18

MDD = 16.82



CALIFORNIA BEARING RATIO (CBR) FOR CINDER + CLAY

SOAKED

CINDER + 10% CLAY

Column1 Column2 Column3 Column4 Column5 Column6 Column7


dial factor load area stress CBR

(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 1.27 34 25.707 874.038 1935 0.451699 1.91 61 25.707 1568.127 1935 0.810402 2.54 98 25.707 2519.286 1935 1.301957 19 3.81 183 25.707 4704.381 1935 2.431205 5.08 279 25.707 7172.253 1935 3.706591 36 7.62 464 25.707 11928.05 1935 6.164366 10.16 609 25.707 15655.56 1935 8.09073 12.07 692.5 25.707 17802.1 1935 9.20005

Corrected CBR

CBR @ 2.54mm=28.5%

[email protected]=60.2%



CINDER + 11% CLAY




(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 6.5 25.707 167.0955 1935 0.086354 1.27 14 25.707 359.898 1935 0.185994 1.91 25 25.707 642.675 1935 0.332132 2.54 43 25.707 1105.401 1935 0.571267 8 3.81 94 25.707 2416.458 1935 1.248816 5.08 162 25.707 4164.534 1935 2.152214 21 7.62 347 25.707 8920.329 1935 4.609989 10.16 547 25.707 14061.73 1935 7.267043 12.07 698 25.707 17943.49 1935 9.273119

Corrected CBR

CBR@ 2.54mm=31.5%

[email protected]=41.2%



CINDER + 12% CLAY




(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 63 25.707 1619.541 1935 0.836972 1.27 166 25.707 4267.362 1935 2.205355 1.91 280 25.707 7197.96 1935 3.719876 2.54 361 25.707 9280.227 1935 4.795983 70 3.81 489 25.707 12570.72 1935 6.496498 5.08 578 25.707 14858.65 1935 7.678887 75 7.62 703 25.707 18072.02 1935 9.339546 10.16 823 25.707 21156.86 1935 10.93378 12.07 899 25.707 23110.59 1935 11.94346



CINDER + 13% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 68 25.707 1748.076 1935 0.903398 1.27 196 25.707 5038.572 1935 2.603913 1.91 305 25.707 7840.635 1935 4.052008 2.54 394 25.707 10128.56 1935 5.234397 76 3.81 520 25.707 13367.64 1935 6.908341 5.08 615 25.707 15809.81 1935 8.170442 79 7.62 757 25.707 19460.2 1935 10.05695 10.16 870 25.707 22365.09 1935 11.55819 12.07 961 25.707 24704.43 1935 12.76715

Corrected CBR

CBR @ 2.54mm=82.4%

CBR@ 5.08mm=80.3%



CINDER + 14% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 56 25.707 1439.592 1935 0.743975 1.27 90 25.707 2313.63 1935 1.195674 1.91 163 25.707 4190.241 1935 2.165499 2.54 229 25.707 5886.903 1935 3.042327 44 3.81 412 25.707 10591.28 1935 5.473532 5.08 588 25.707 15115.72 1935 7.81174 76 7.62 939 25.707 24138.87 1935 12.47487 10.16 1136 25.707 29203.15 1935 15.09207 12.07 1213 25.707 31182.59 1935 16.11503



CINDER + 15% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 13 25.707 334.191 1935 0.172709 1.27 34 25.707 874.038 1935 0.451699 1.91 61 25.707 1568.127 1935 0.810402 2.54 99 25.707 2544.993 1935 1.315242 19 3.81 200.5 25.707 5154.254 1935 2.663697 5.08 300 25.707 7712.1 1935 3.985581 39 7.62 466 25.707 11979.46 1935 6.190936 10.16 596.5 25.707 15334.23 1935 7.924664 12.07 671 25.707 17249.4 1935 8.914417

Corrected CBR

CBR @ 2.54mm=30%

CBR @ 5.08mm=50.2%



DRY STATE

CINDER + 11% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 36 25.707 925.452 1935 0.47827 1.27 110 25.707 2827.77 1935 1.46138 1.91 181 25.707 4652.967 1935 2.404634 2.54 260 25.707 6683.82 1935 3.454171 50 3.81 414 25.707 10642.7 1935 5.500102 5.08 557 25.707 14318.8 1935 7.399896 72 7.62 788 25.707 20257.12 1935 10.46879 10.16 963 25.707 24755.84 1935 12.79372 12.07 1025 25.707 26349.68 1935 13.6174

Corrected CBR

CBR @ 2.54mm=59.9%

CBR @ 5.08mm=75.3%



CINDER + 12% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 39 25.707 1002.573 1935 0.518126 1.27 114 25.707 2930.598 1935 1.514521 1.91 197 25.707 5064.279 1935 2.617198 2.54 273 25.707 7018.011 1935 3.626879 53 3.81 430 25.707 11054.01 1935 5.712667 5.08 561 25.707 14421.63 1935 7.453037 72 7.62 814 25.707 20925.5 1935 10.81421 10.16 1042 25.707 26786.69 1935 13.84325

Corrected CBR

CBR @ 2.54mm=61.2%

CBR @ 5.08mm=77.6%



CINDER + 13% CLAY



(mm) (N) mm 2 (N/mm 2 ) (%) 0 0 25.707 0 1935 0 0.64 46 25.707 1182.522 1935 0.611122 1.27 138 25.707 3547.566 1935 1.833367 1.91 273 25.707 7018.011 1935 3.626879 2.54 372 25.707 9563.004 1935 4.942121 72 3.81 530.5 25.707 13637.56 1935 7.047836 5.08 661 25.707 16992.33 1935 8.781564 85 7.62 849 25.707 21825.24 1935 11.2792 10.16 981 25.707 25218.57 1935 13.03285 12.07 1050 25.707 26992.35 1935 13.94953

Corrected CBR

CBR @ 2.54mm=82.4%

CBR @ 5.08mm=90.3%



PROCTOR TEST FOR 13% OF CLAY AND CEMENTS CINDER + 13% CLAY + 3% CEMENT

MC DD 7.01 16.54 11.55 18.32 14.89 18.16 17 17.42 20.9 16.82



CINDER + 13% CLAY + 5% CEMENT

MC DD 6.67 14.92 11.62 17.96 16.42 17.47 19.78 16.76 26.61 15.62

OMC = 13

MDD = 18.4




MC DD 10.5 17.75

14.78 18.77 20.36 17.99 22.8 16.92

OMC = 15

MDD = 18.78




MC DD 9.96 17.91

16.33 18.89 20.19 17.88 23.6 17.39

OMC=16

MDD=18.86



REFERENCES

1. Robinson, D. Newill. R and Aklilu, Kassaye, Experimental use of cinder gravels on roads

in Ethiopia by TRL, published Crowthorne Berkshire United Kingdom, June 1980

2. Adaska, Wayne S. Chairman, StateoftheArt Report on Soil cement reported by ACI

Committee 230 by, ACI material Journal, Committee Report

3. INGLES, O.G. and METCALF, J.B. Soil Stabilization Principles and Practice,

butterworths publication, 1972, reprinted 1977

4. Berhanu, Girma (Dr) Highway2 Handout, 2007

5. Robinson, D. Newill. R and Aklilu, Kassaye, The location and Engineering Properties of

Volcanic Cinder Gravels in Ethiopia by TRL, published Crowthorne Berkshire United

Kingdom, June 1980

6. Wright, Paul H. Highway Engineering, sixth edition, John Wiley and Sons, inc, 1996

7. ERA (Ethiopian Road Authority) draft manual, 2002

8. AACRA (Addis Ababa City Road Authority) draft manual, Pavement Design and

Rehabilitation, February 2003

9. AASHTO(American Association of State Highway Officials) Standard Specification for

Highway Materials and Method of Sampling and testing Part I and II adopted, 10 th

edition, 1970

10. Annual Book of ASTM(American Society For Testing and Materials) Standards, Part 11,

1972

11. Punmia, B.C. A (Dr) Soil Mechanics and Foundation, A Saurabh and Co. publication,

11 th edition, April 1988

Documents

Stabilization of Cinder Gravel With Clay and Cement