Monday, February 15, 2010

COMPARISON OF COMPRESSIVE AND FLEXURAL STRENGTH OF CONCRETE MADE FROM DIFFERENT COARSE AGGREGATES

ABSTRACT
This research, comparison of compressive and flexural strength of concrete made from different coarse aggregates written in accordance to British standard. The different sizes of coarse aggregates used are; 10mm, 12 mm and 20mm.

These aggregates were used to produce concrete cubes (150mm x 150mm x 150mm) and beans (150 x 150mm x 150mm). The beans and cubes were compacted in three layers and cured for 7 days, 1 day and 28 days, after which they were crushed to determine their compressive and flexural strength and also comparing them. Slump test was also carried out.

The compressive strength of the 10mm aggregate ranges from 15.63 to 29.03 N/mm2, 3.97 t0 5.57N/mm2. The compressive strength of the 12mm aggregate ranges from 19.7 26.10N/mm2 while its flexural strength is from 4.05 to 5.63N/mm2 of 20mm aggregate ranges from 4.15 to 2.3.74N/mm2. The slump of the beans ranges from 1.8 to 2.05am for the different sizes of the aggregates.

TABLE OF CONTENTS
Title page- - - - -- - - - -- i
Approval page - - - - - - - -- ii
Dedication - - - - - - - - - iii
Certification - - - - - - -- - - iv
Acknowledgement - - - - -- - - - v
Abstract - - - - -- - - - -- - vi
Table of contents - - - - - - -- - vii
CHAPTER ONE
1.0 Introduction - - - - - - -
1.1 Statement of the study - - - - - -
1.2 Aims and objective of the study - - - -
1.3 Scope of the study - - - - - -- -
1.4 Limitations - - - - - - - -
CHAPTER TWO
2.0 Literature Review - - - - -- - -
2.1 Use of concrete - - - - -- - -
2.2 Concrete properties - - - - - - -
2.3 Properties of Aggregate - - - - - -
2.4 Types of Aggregates - - - - - -
2.5 Water - - - - - - - - -
2.6 Cement - - - - - - -- - -
2.7 Properties of cement - - - - - -
2.8 Concrete mix design - - - - - - -
2.9 Compaction of concrete - - - - - -
2.10 Curing of concrete - - - - - - -
CHAPTER THREE
3.0 Methodology - - - - - - - -
3.1 Concrete mix design - - - - - -
3.2 Raw materials to be used - - - - - -
3.3 Measuring and mixing of concrete - - - -
3.4 Compressive Test - - - - - - -
3.5 Flexural Test - - - - - - - -
3.6 Slump Test - - - - - - -- -
CHAPTER FOUR
Presentation of Results - - - - - - -
CHAPTER FIVE
Analysis of Results - - - - - - - -
6.0 Conclusion and Recommendation - - - -
6.1 Conclusion - - - - - - - -
6.2 Recommendation - - - - - - -
Reference - - - - - - - -- -
Appendix - - - - - - - -- -

CHAPTER ONE
1.0 INTRODUCTION
One of the characteristics of concrete that has made it to be widely used is due to its high compressibility in with standing burden.

Compressive strength of concrete can be defined as the maximum compressive load it can carry per unit area. The concrete performance test has always been referred to as the compressibility in withstanding concrete cube load with dimension of 150 x 150 x 150mm at the age of 28 days.

The flexural strength of a concrete can be defined as the maximum compressive load it can carry per unit areas. The concrete performance test has always been referred to as the compressibility in withstanding concrete cube load with dimension of 150 x 150 x 150mm at the age of 28 days.

The flexural of a concrete cab be defined as the ability of a beam to withstand a particular force before it shears. It gives a measure of tensile strength in bending. There are many techniques known to be applied order to obtain compressive and flexural strength of concrete, whether directly or indirectly non destructive test etc. In this research, the method applies shall be non destructive.

In this work also, the non destructive test which is the cube compressive strength test with a dimension 150 x 150 x 150mm for three different aggregate sizes of 10mm, 12mm and 20mm and the flexural strength test with a beam of 150 x 150 x 600mm for the same sizes of aggregates were investigated. The cubes and beams were tested at the age of 7, 14 and 28 days respectively and the compressive and flexural strength compared.
1.1 STATEMENT OF PROBLEM
When concrete is stressed, failure may originate within the concrete, or the aggregate matrix interface (the bond).The aggregates are stringer that the concrete itself. Therefore a concrete cast without an aggregate does not develop the special properties required such as weather resistant and the strength characteristics. A smooth rounded aggregate result in a weaker bond between the aggregate than an irregular or angular aggregate.
The use of poor quality material in construction works due to its affinity is wearing and abrasion.
1.2 AIMS AND OBJECTIVE OF THE PROJECT.
The aims and objectives of this project are as follows;
1. Determination of workability of concrete.
2. Determination and comparison of both flexural and compression strength.
1.3 SCOPE OF THE STUDY
The concrete strength test to be carried out will be bases on the following;
i. Concrete cube test with the dimension 150mmx 150 mmx 150mm
ii. Flexural test with beam of dimension 150mm x 150mmx 600mm.
iii. Comparison of the results
obtained in (i) and (ii) above
1.4 LIMITATION OF THE STUDY
This project is handicapped by a number of factors such as:
i. Insufficient Equipment: Most of the equipment used were borrowed from labourers working within the Engineering block. There are also limited number of beam moulds for the practical.

ii. Safety: No personal protective equipment was used during the experiment and which is very dangerous. Concrete splash for instance is vulnerable to skin corrosion.
iii. Time: The writing of this project could have been to a large extent enhanced if the researcher did have sufficient time to do the work, since it was carried, alongside with pressure of other academic commitment.
iv. Finance: The project was obviously limited by inadequate or insufficient finance.

CHAPTER TWO
LITERATURE REVIEW
2.0 DEFINITION OF CONCRETE
Concrete may be defined as mixture of cement or binder, water, and aggregates, where the water and cement or binder form the paste and the aggregate forms inert fillers. In the absolute volume, the aggregate amounts in 60-80% of the volume of concrete and is therefore the major constituent.

Concrete can also be defined as a man made composite, the major constituents of which is natural aggregate such as gravel, and sand or crushed rock. Alternatively, artificial aggregates for example, blast furnace slag, expanded clay broken bricks and steel may used where appropriate. The other principal constituent of concrete is the binding medium used to bind the aggregate together to form a hard composite. The most commonly used binding medium is the product formed by a chemical reaction between cement and water. Other binding medium is used on a much smaller scale for certain project in which the cement and water are replaced either wholly or partial by polyester resins.

In the hardened state, concrete is a rock like material with a high compressive strength.

Normally concrete is good in compression, but poor in tension. For structural applications, it is normal practice either to incorporate steel to resist any tensile forces (reinforced concrete) or to apply compressive forces to counteract these tensile forces.
2.1 USES OF CONCRETE
Concrete may be used for the following purposes:
* For decorative purpose:
Special surface finished for example exposed aggregates can be used to great effect.
* Concrete is used structurally in buildings for foundation, columns, beams and slabs, in shell structures bridges, sewages treatment work, rail way sleepers, roads, cooling to were, dams, chimneys, harbors, off shore structures, coastal production work and so on.
* It is used for a wild range of pre cast concrete products which includes concrete blocks, cladding panels, pipes and lamp standards.

2.2 PROPERTIES OF CEMENT (FRESH)
Fresh concrete is a mixture of water, cement, and aggregate. After mixing of these constituents materials, to produce a uniform blended operation such as transporting, placing compacting and finishing of fresh concrete can also affect the properties of hardened concrete. It is important that the constituent materials remain uniformly distributed within the concrete mass during the various stages of its handling in order to achieve full compaction.
2.3 WORKABILITY
Workability can be defined as the ease with which a concrete mix can be handled from the mixer to its final compacted shape. The three main characteristics of the property are consistency, ability and compatibility. In this context, the required workability of a mix depends not only on the characteristics and relative proportions of the constituent material but also on the:
* Method employed for conveyance and compaction
* Size formwork or mould.
2.4 MEASUREMENT OF WORKABILITY
Four tests widely used for measuring workability are the slump, compacting factor, and vibe time and flow tests. These are standard tests in the United Kingdom (UK). The British standard 5328 (BS 5328) requires the measurement of workability of concrete to be writing certain limited of the required value as given in table 1 below.
TABLE 1
Suitability and allowable to levance of workability test for concrete.
METHOD WORKABILITY RANGE ALLOWABLE TO LEVANCE
Slump Medium high Greater of 1mm of required value
Compacting factor Low- high -+0.03 for values > 0.90
+ 0.04 for values >0.8 &<0.8
+0.05 for values < 0.8

Vibe time Very low- low greater of + 3 req. value

Flows Very low + 50mm about the req.

2.5 SLUMP TEST
This test was developed by chap man Adams in the United States (US) in 191, and has been adopted as a check of the consistency of concrete in the construction works. A 300mm high concrete cone with the bottom and top diameter of 200mm and 100mm respectively was used for the test. It is suitable for detecting changes in workability. For example, an increase in the water content or deficiency in the proportion of fine aggregate results in an increase in slump. Although the test is suitable for quality control purposes, it should be remembered that it is generally considered to be unsuitable for mix design since concrete requiring varying amount of work for compaction can have similar numerical values of slump. The test is not suitable for very dry or wet mixes. For very dry mixes, with zero or nearly zero slump, moderate variations in workability do not result in measurable changes in slump. For very wet mixes, complete collapse of the concrete produces unreliable values of slump.

The three types of slump shear slump and collapse slump. The true slump gives the correct slump. The true slump is up to 125mm, shear slump up to 150mm while the collapse slump is between 150-250mm. a true slump is observed with cohesive and rich mixes for which the slump is usually associated with very wet mixes and is generally in dilative of poor quality concrete and most frequently results in segregation of its constituent materials. Shear slump occurs more often learner mixes than in rich ones and indicates a lack of cohesion which is generally associated with harsh mixes (low mortar contents). Wherever a shear slump is obtained, the test should be repeated and if persistence, this fact should be recorded together with test results, because widely different values of slump can be obtained depending on whether is of true or shear form.

The standard slump apparatus only suitable for concrete in which the maximum aggregate size does not exceed 0mm. It should be noted that the value of slump, changes with mal hydration process and evaporation of some of the free water, and it is desirable therefore that tests are performed within a fixed period of time. It is advisable delay testing for around 10 minutes after the addition of water to allow for the absorption of water by dry aggregates.
2.6 FACTORS AFFECTING WORKABILITY
Various factors known to influence the workability of a freshly mixed concrete are shown in fig 1 from the following discussions, it will be apparent that a change in workability associated with the constituent materials is mainly affected by water content and specific surface of cement and aggregates






Fig 1: Factors affecting workability of concrete.

2.6.1. CEMENT AND WATER
Typical relationship between the water/ cement ratio by (volume) and the volume fraction of cement for different workability are shown in fig 2.

Hughes (1971) has shown that similar linear relationship exist, irrespective of the properties of the constituent materials. Workability is relatively insensitive to changes in only the cement content and for practical purposes may be considered dependent only the cement content and for practical up to 10- 22%. For a given mix, the workability of the concrete decreases as the fineness of the cement increases as a result of the increased specific surface. The effect being more marked in reach mixtures. It should be noted that finer cement improves cohesiveness of a mix.





1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5

Basic volume fraction of cement (Percentage) for different workability Fig 2: Graph showing typical relationship between the water/ cement ratio and volume fraction of cement for different workability.
2.6.2 ADMIXTURES
The principal admixtures affecting the improvement in the workability of concrete are water reducing and air entraining agents. The extent of the increase in workability is dependent on the type and amount of admixture used and the general characteristics of the fresh concrete. Water reducing admixture is used to increase workability while mix proportion are kept constant or to reduce the water content while maintaining constant workability.
2.6.3 AGGREGATES
For a given cement, water and aggregate contents, the workability of concrete is mainly influenced by the total surface area of the aggregate. The surface area is governed by the maximum size, grading and shape of the aggregate. Workability decreases as the specific surface increases, since this required a greater proportion of cement paste to wet the aggregate particles, thus leaving a smaller amount of paste for lubrication.

It therefore follows the, all other conditions being equal, the workability will be increased when the maximum size of aggregate increases.
2.6.4 AMBIENT CONDITION
The environmental factor that may cause a reduction in workability are temperature, humidity and wind velocity. For a given concrete changes in workability are government by the rate of hydration of the cement and the rate of evaporation of water. Therefore, both the time interval from the commencement of mixing to compaction and the condition of exposure influences the reduction in workability. An increase in the temperature speeds up the rate of which water is used for hydration as well as its loss through evaporation.
2.6.5 TIME
The time that elapse between mixing of concrete and its final compaction depends on the general conditions of work such as the distance between the mixer and the point of placing, site procedures and general management. The associated reduction in the workability is a direct result of loss of free water with time through evaporation, aggregate absorption and initial hydration of the cement. The rate of loss of workability is affected by certain characteristics of the constituent materials, for example, hydration and heat development characteristics of the cement, initial moisture content and porosity of the aggregate as well as the ambient conditions.

2.7 STABILITY
Apart from being workable, fresh concrete should have a composition such that its constituent material remain uniformly distributed in the concrete during both the period between mixing and compaction and the period following compaction before the concrete stiffens. Because of the differences on the particle size and specific gravity of the constituent materials, there exist a natural tendency for them to separate, concrete capable of maintain the required uniformity is said to be stable and most cohesive mixes belong to the to this category. For an unstable mix, the extent to which the constituent materials will separate depends on the methods of transportation, placing, and unstable concrete are segregation and bleeding.
2.8 PROPERTIES OF HARDENED CONCRETE
The properties of fresh concrete are important only in the first few hours of its history, whereas the properties of hardened concrete assume an important which is retained for the remainder of the life of the concrete. The important properties of hardened concrete are strength, deformation under load, durability, permeability and shrinkage.
The general strength is considered to be the most important property and the quality of concrete is often judged by strength.

There are however many occasions when other properties are more important for example, low permeability and low shrinkage are required for water retaining structures.

Although in most cases, an improvement of the other properties of concrete. For example, increase in the cement content of a mix improves strength but results in higher shrinkage, which in extreme cases can adversely affect durability and permeability.
2.8.1 STRENGTH
The strength of a concrete is defined as the maximum load (stress) it can only carry. As the strength of concrete increases, its other properties usually improved and since the tests particularly in compression are relatively simple to perform concrete compressive strength are commonly used in the construction industry for the purpose of quality control, concrete is a comparatively brittle material which is relatively weak in tension.
2.8.2 COMPRESIVE STRENGHT
The compressive strength of a concrete is taken as the maximum compressive load it can carry per unit area. Compressive strength of up to 80Nm-2 or more can be achieved dependent mainly on the relative proportion of water to cement that is water / cement ratio, and the degree of compaction.

Concrete structure except for road pavements are designed on the basis that concrete is capable of resisting on compression, the tension being carried by steel reinforcement. A cube of 150mm is used to determine compressive strength and the test specimen should be cured in water at 20_+20C and crushed by loading it at a constant rate of street increase of between 12 and 24N/mm2 immediately after it has been removed from curing tank.
2.8.3 TENSILE STRENGTH
The tensile strength of concrete various from one eight of the compressive strength at early ages to about one-twentieth later, and it is not usually taken into account in the design of reinforced concrete structures. The tensile strength is however of considerable important in resisting cracking due to changes in moisture content or temperature. The test is used for concreter roads and airfields.

The measurement of the strength of concrete in direct tension is difficult and is rarely attempted. Two more practical methods of accessing tensile strength are available, the split cylinder tests and the flexural test.

The flexural strength gives a measure of tensile strength in bending. The standard size of specimen used is a beam of 150mm x 150mm x 600mm for aggregate of maximum size 40mm and 100mm x 100mm x 400mm long for 20mm size of aggregate.

After curing, the specimen is crushed by applying a load at the third point of the span until the specimen breaks and the modulus of rupture calculated. The two half of the specimen may then be crushed to determine the approximate compressive strength. The flexural strength can be calculated using the formula,
Mo.R = PL
Bd 2

Where P = maximum applied loan
L = Length of the beam
b = Beam breath
d = Beam depth

2.8.4 SHEAR STRENGTH
In practice, shearing of concrete is always accompanied by compression and tension caused by bending and even in testing, it is impossible to eliminate an element of bending.

2.8.5 FACTORS AFFRECTING STRENGTH
In practice, shearing of concrete is always accompanied by compression and tension caused by bending and even in testing, it is impossible to eliminate an element of bending.

2.8.5 FACTORS AFFECTING STRENGTH OF CONCRETE
Several factors which affect the strength of concrete are listed below; their influence is discussed with particular references to compressive strength. In general, tensile strength is affected in a similar manner.
2.8.5.1 TYPE AND QUALITY OF CONCRETE
The rate of strength gain and the ultimate strength may be affected. The influence of cement on concrete strength for a given its fineness and chemical composition through the process of hydration, the increases the strength of concrete. The gain in strength is most marked at the early stage and after 28 days, the relative gain in strength is much reduced. It is apparent that cement containing a relatively high parentage of Tricalcium silicate (C3S) gains strength much more rapidly than those rich in Dicalcium silicate (C2S).
2.8.5.2 TYPES AND TEXTURE OF AGGREGATE
The bond strength is influenced by the shape, surface texture and cleanliness of the aggregate. A smooth rounded aggregate will result in a weaker bond than an irregular or angular aggregate or an aggregate with a rough surface texture. Aggregate shape and strength. A fine coating of impurities, such as silt and clay on the aggregate surface hinders the development of a good bond. A weathered and decomposed layer on the aggregate can also result in poor bond as this layer can readily become detached from the sound aggregate beneath. The aggregate size also affects the strength. For given mix proportion, the concrete strength decreases as the maximum size of aggregate increases.
2.8.5.3 INFLUENCE OF CURING
Curing of concrete us a pre- requisite for the hydration of the cement content. For a given concrete, the amount and rate of hydration and furthermore, the physical make up of the hydrate products are dependent on the time- moisture temperature history. The greater its final strength. It is normally accepted that a concrete made with or denary Portland cement and kept in normal curing conditions will develop about 75% of its final strength in the first 28 days. This value various with the normal strength of concrete however, it increases as the nominal strength of the concrete increases.
2.8.5.4 INFLUENCE ON THE METHOD OF PREPARATION
When concrete materials are not adequately mixed into a constant homogenous mass, some poor quality concrete is inevitably the result. Even when a concrete is adequately mixed care must be taken during placing and compaction to moralize the probability of occurrence of bleeding, segregation and honey comb, all of which can result in poor quality concrete.
2.8.5.5 INFLUENCE OF WATER
A concrete mix containing a minimum amount of water required for complete hydration of its cement, if fully compact would develop the maximum attainable. Strength at any given age. A water cement ratio of approximately 0.25 (by weight) is required for fully hydration of the cement but with thus water content a normal mix would be extremely dry and virtually impossible to be compaction. A partially compacted strength will drop.
2.9 DEFINITION OF AGGREGATE
Aggregates may be defined as naturally occurring gravel, crush rock, slag, sand and other similar material, which helps to improve the volume, stability and durability of concrete. The geological process by which a deposit was formed are responsible for it size, shape and location, the type and condition at the rock, the grading, rounding and degree of uniformity. Aggregate is cheaper then cement and maximum economy is obtained by using as much aggregate as possible in concrete.
2.9.1 PROPERTIES OF AGGREGATES
The criterion for a good aggregate is that it should produce the desired properties in both the fresh and hardened state. The most important properties of aggregate are the crushing strength and the resistance to impact, other important properties are: the size and shape of the particles, which can affect the bond with cement paste. The porosity and water absorption characteristics affects the resistance to chemical attach and forest attach and the immunity from shrinkage.
2.9.2 BULK DENSITY AND VOLD
The bulk density of a material is the weight of the material held by a container of unit volume when filled on compacted under defined conditions. It is expressed in Kg/m3. The bulk density of an aggregate is affected by several factors, including to amount of comp active effort used in filling the container.
2.9.3 BULKING
When sand is moistened, films of water form on the particles and the surface tension tends to hold them apart, causing an increase in volume or bulking. Fine sand bulks more than coarse sand, aggregate retained on a 5mm sieve is scarcely affected. As the moisture content of sand increases to about 4-6% the sand rapidly bulks to the extent of 20- 30%. Further increase in moisture content results in a decrease in bulking until when the sand is completely saturated, its volume practically the same as it was in a dry condition.

Bulding can be determined by filling gauge-box or other container of a known volume (A) filled with damp sand the sand is then dried and filled back into water and the damp sand poured into displace the water. The new depth of aggregate in the container gives the unbulked volumes (R). The percentage bulking can then be calculated thus:
A- B X 100
B 1

2.9.4 RELATIVE DENSITY
If a section is cut through any piece it will be seen that it is to some extent honey combed with capillarity’s and tiny air holes. The relative density of a material is therefore the ratio of its unit weight to that of water. Since aggregates in corporate pores, the value of relative density varies depending on the extent which the pores absorbed water when major constituent of concrete. Therefore its relative density is an important factor affecting the density of the resulting concrete.
2.9. 5 SHAPE AND SURFACE TEXTURE
Aggregate shape and surface texture can affect the properties of concrete in both its plastic and hardened state. These external characteristics may be assessed by observation of the aggregate particles and classification of the particle shape and texture. The particle shape can also be assessed by a direct measurement of the aggregate particles to determine the Flakiness, elongation and angularity.
2.9.6 GRADING
The grading of aggregate defines the proportions of particles of size of the aggregate particles normal used in concrete varies from 37.5 to 0.15 mm. Aggregates are placed in three categories name; fine aggregate, containing particles of which the majority are smaller than 5.0mm, Coarse aggregate containing particles the majority of which are larger than 5.0mm and all in aggregate comprising both fine and coarse aggregate. The grading of an aggregate can have a considerable effect in the workability and stability of a concrete mix design.
2. 9. 7 STRENGTH
The strength of an aggregate limits the attainable strength of concrete only when its compressive strength is less than or of the same order as the design strength of concrete. In practice the majority of rock aggregate used are usually considerably stronger than concrete. While the strength of concrete does not normally exceed 80N/mm2, the aggregate commonly used is in the range of 70-35N/mm2.
2.9.7 DEFORMATION
This is considered in assessing aggregate suitability for concrete work, although they can easily be determined from compression tests on specimens from the parent rock. The deformation characteristic of aggregate plays an important role in the creep and shrinkage properties of concrete.
2.9.8 TYPES OF AGGREGATES
The general classifications of aggregates are as follow?

2.10 HEAVY WEIGHT AGGREGATE
This provides an effective and economical used of concrete for radiation shielding by given the necessary protection against X- ray, gamma rays and Neutrons. The effectiveness of heavy weight concrete with a density from 400 to 850kg/m3 depends on the type of aggregate, the dimensions and the degree of compaction. It is frequently difficult with heavy weight aggregates to obtain a mix which is both workable and not prone to segregation.
2.10.1 NORMAL AGGREGATE
These aggregates are suitable for most purposes and produces concrete with a density in the range 2300-2500kg/m3 Rock aggregates are obtained by crushing quarried rock to the required particle size. Some sand and gravel are also obtained by dredging from sea and ricer bed.

Aggregates should be washed to remove impurities such as clay and silt. In the case of river and marine aggregates, the chloride content should be less than 1%.


2.10.2 LIGHT WEIGHT AGGREGATE
This is applied in a wide variety of concrete producers ranging from insulating screeds to reinforce or priestesses concrete. Although their greatest use been in the pre-cast concrete block. Examples of light weight aggregate are expanded day, sintered pulverized fuel ash, Aglitter etc. They are highly porous and absorb considerably greater quantities of water than normal aggregate.

For this reason, they should normally be batched by volume owing to larger variation that can occur in their moisture content. Their bulk density normally ranges from 350 to 850 kh/m3 for coarse aggregate and 750 to 11ookg/m3 for fine aggregates.
2.10.3 WATER
Water used in concrete in addition to reacting with cement and thus causing it to set and harden, and also facilitate mixing, placing, and compaction of the fresh concrete. It is also used for washing aggregates and for curing purposes. The effect of water content on the properties of fresh and hardened concrete has already been discussed.
In general, water fit for drinking such as tap water is acceptable for mixing concrete. The use of sea water does not appear to have adverse effect in the strength and durability of Portland cement concrete but it is known to cause surface dampness, efflorescence and staining and should be avoided where concrete with a good appearance is required. Sea water also increases the risk of corrosion if steel and its uses in reinforced concrete is not recommended. The use of impure water for washing aggregate can adversely affect the strength. In general, the presence of impurities in curing water does not have any harmful effect although it may spoil the appearance of concrete.
2.11 CEMENT
The different cement used for making concrete are finely ground powders and all have the important property that when mixed with water a chemical reaction (Hydration) takes place which in time produces a very hard strong binding medium for the aggregate particles. In the early stage of hydration, while in plastic state, cement mortar gives to the fresh concrete its cohesive properties.
2.11.1 TYPES OF CEMENT
The different types of cement are Portland cement, slog cement. Others are used where concretes with special properties are required.
11.1.1 PORTLAND CEMENT
Portland cement was developed in 1824 and relives its name from Portland limestone in Dorset because of its close resemblance to this rock after hydration has taken place. The basic raw materials used in the manufacture of Portland cements are calcium carbonate, fund in cal covetous rocks such as limestone as clay or shale, Marl, which is a mixture of calcareous and argillaceous materials can also be used.
2.11.1.2 BASIC CHARACTERISTICS OF PORTLAND CEMENT
Differences in the behaviour of the various Portland cements are determined by their chemical composition and fineness. The effects of cement mortars and concrete are considered here and the chemical compositions are summarized in the take below:


TABLE 3: CHEMICAL COMPOUDS OF PROTLAND CEMENT
NAME OF COMPOUND CHEMICAL COMPOSITION SYMBOL
Tribalism silicate 3C0. S102 C 3 S
Dicalcium silicate 2 C0.S102 C3A
Trucalcium Aluminates 3C0. Al203 C3 A
Tricalcium Aluminates oferrite 40. Al2 0 3 Fe203 C4AF

The two silicate C3S and C2 S which are the most stable of these compounds together form 70 to 80 percent of the constituents in cement and contributes most to the physical properties of concrete when cement comes into contact with water, C3S begins to hydrate rapidly, generating heat, which helps to develop early strength mainly at the first 14 days. C2S, which hydrates slowly, is mainly responsible for the development of strength after about 7days. The hydration of C3A is extremely exothermic and takes place very quickly producing little increase in strength after 12 hours. C3 A is the least stable and cement containing more than 10% of this compound produces concrete, which are particularly susceptible to soleplate attack.
2.11.2 BATCHING AGGREGATAES, CEMENT AND WATER
Batching has to do with a method of proportioning concrete constituents required for a particular mix. Batching can either be done by weight or by volume.
2.11.2.1 BATCHING OF CEMENT
Cement can be batched either by bag (normally 50kg), which ever method of batching is used, precautions should be taken to see that the cement is not high. Volume batching of cement should not be permitted because Portland cement can weight from 1200- 1520kg/m3 depending upon its fineness and the method of filling the measure.
2. 11.2.1 BATCHING BY BAGS OF CEMENT
Provided whole bags of cement are used, the only error lies in a variation in the weight in each bag as supplied by the cement works. This is not likely to be serious, although variations from 45kg to 54kg in single bags have been recorded under the A S T M Specification.
2.12COMPACTION OF CONCRETE
The objective of compaction of concrete is to eradicate air hole and to achieve maximum density, it is necessary to use a mix which is of adequate workability to enable the operator to place it in position without difficulty. During compaction ears must be taken to ensure that concrete is worked thoroughly in the neighborhood of the formwork so that the finished surface will be dense and free from honey comb.
2.12.1 HAND COMPACTION
Ordinary hand method of compaction consist Roding, tamping and spreading with suitable tools. Hand method of Roding and tamping necessitate the use if fairly workable mix. A slump of 175mm may be necessary.
2.12.2 COMPACTION BY VIBRATORS
Although the use of vibrators has extended into almost every class of concrete works, compaction by hand, properly done givens satisfactory results for many purposes, variation makes it possible to use less workable mixes resulting in increased strength and lower drying shrinkage for a given mix proportion. Since vibrators can give 3000 vibration per minute and the acceleration of 4m/S2 more in concrete is satisfactory, it is advisable to limit the time for which the vibration is applied to avoid segregation.
2.12 CURING
Curing has to do with emersing the concrete into a tank of water 24hrs after casting. The essence of this is to improve the hydration of cement and strength of concrete. Generally speaking, the longer the period during which concrete is kept in water, the greater its final strength. It is normally accepted that a concrete made with ordinary Portland cement and kept in normal curing conditions will develop about 75 percent at 28 days of which the value increases as the concrete strength increases.

CHAPTER THREE
RESEARCH METHODOLOGY
3.1 RAW MATERIALS USED
i. Aggregates used were gratuity rock of 10mm, 12mm and 20mm, graded, crushed angular in appearance.
ii. In preparation of the concrete mix, tap water was used.
iii. Sand measuring less than 5mm was used, the sand was air dried.
iv. The cement used was ordinary Portland cement.
3.2 SOURCES AND SAMPLING OF MATERIAL
Sample A - 10mm coarse aggregate
Sample B - 12MM coarse aggregate
Sample C - 20mm coarse aggregate

All aggregates used was bought at Austine agents along Owerri Aba road. The cement was also bought at Owerri main town. The water was gotten from the school tap.
3.3 EXPERIMENT 1
Sieve Analysis of aggregate
Apparatus used are:
i. Sieve shaker
ii. Brush
iii Weighing balance
PROCEDURE: The sample was oven dried and make free from deleterious materials. The sieves and pan was weighed empty and their masses recorded as (M1). The sieves were arranged starting from that of the largest aperture to that of smallest aperture with the pan fixed not the base. 500g, of the sample was weighted and poured into the larges sieve which was on top.

The set of sieve was then covered, fixed into the electric shaker and sieved for 15 minutes. The mass of sample + container was weighted and recorded as (M2). The mass of sample retrained was calculated as (M3) = M2 – M1. Percentage passing the sieves was also determined.

After sieving simply A, the brush was used to clean the sieves and other samples were sieved as well.
3.3 EXPERIMENT IT COMPRESSION TEST APPARATUS USED
* Cube mould of dimension 150x150
* 16mm diameter rod 600mm high
* Cleaning rag
* Head pans
* Steel Plate / pan
* Shovel
* Trowel and Scoop
* Weighing balance and weights
PROCEDURE: The first sample was sieved with 10mm sieve in order to make sure that the exact size used for the experiment is 10mm.
The moulds lubricated with engine oil. The quantities of material for 3 cubes were measured thus; 3.44kg of cement, 1.62kg of water, 5.1kg of fine aggregate and 14.04kg of coarse aggregates.
The cement, fine and coarse aggregate was mixed thoroughly before pouring the water. The mixture was turned continuously in order to obtain a homogenous mix. The moulds was then placed on a smooth and flat surface and filled to one-third of its height with the concrete which was then tamped with the 16mm rod using 150 strokes. The filling is then completed by two more layers similar in height to the first, and the top leveled with a trowel.
The cube of 150mm x150mm was cast using the 10mm aggregate. Following the same sizes, and number of cubes was cast using other size of aggregates. The cubes were left in the mould to set for 24hrs.
They were remolded the next day and immersed into a tank of water for curing. The experiment was continued until 15 cubes were cast using each of the aggregates which implies that the total number of cubes cast was 45 in number. At the age of 7days, 14 dates and 28 days of curing.
At the end of each curing period, the cubes were crushed to determine their compressive strengths
3.4 EXPERIMENT 111 –FLEXURAL TEST
Apparatus used
 Beam moulds of size 150x150x600mm.
 All other apparatus use in experiment 1 above was also
Used here, excluding the cube moulds
Procedure: The procedure also remains the same but the quantities of material vary. The size of beam cast was 150x150x600mm, the quantity of cement used was 13.6kg of cement, 6.48kg of water, 20.77kg of fine aggregates and 56.173kg of coarse aggregates. The beams were also crushed and the results obtained.
3.5 SLUMP TEST
This test was carried out immediately the concrete mix attains a homogeneous mix before the cubes or beams were cast. The test was carried out with metal cone 300mm high, having a bottom diameter of 200mm and a top diameter of 100mm.
The procedure being as follows;
The slump cone was first inspected to make sure the internal surfaces is clean, dry and free fro set concrete. The cone was then placed on a steel plate and the mould was held firmly in place while it was being filled.
The mould was filled to about one-third of its height with the concrete, which was then tamped using 25 strokes of 16mm rod, 600mm long, rounded at the lower edge. The filling was then completed by two further layers similar in height to the first. The mould was then removed by raising it vertically immediately after filling the moulded concrete was finally allowed to subside and the height of the specimen.

CHAPTER FOUR
PRESENTATION OF RESULTS
Table 4: result of compressive strength test (N/mm2
Aggregates sizes (mm) 7 days 14 days 28 days
10mm 15.62 17.30 29.03
12mm 19.47 21.71 26.10
20mm 17.84 19.52 23.74

TABLE 5: Result of flexural strength test (N/mm2)
Aggregates sizes(mm) 7 days 14 days 28 days
10mm 3.97 5.53 5.57
12mm 4.05 5.63 5.63
20mm 4.15 5.54 5.,58

Table 6: Result of sieve Analysis of fine Aggregate
Sieve size Weight of empty sieve W1 (kg) Weight of sieve soil W2(kg) Mass retained (W2- W1 Mass passing % passing

2.00mm 413 414.00 1.00 49.9 99.8
1.18mm 376.2 405.80 28.80 470.20 94.6
600mm 335.00 473.70 138.70 331.50 66.34
425mm 300.00 434.70 134.70 196.80 39.20
300mm 326.4 393.67 67.01 129.20 25.94
212mm 281.10 349.29 67.59 62.20 12.44
150mm 300.6 314.70 13.40 48.80 9.76
63mm 263.30 295.70 32.00 16.02 3.20
Pan 245.10 260.80 16.00 0.01 0.02
500

CHAPTER FIVE
ANALYSIS OF DATA
Analysis of compressive strength
(C.S) = Load (N)
Area (mm2)

For 10mm Aggregate at 7 days for cube 1,
C.S = 350X103 = 15.50N/mm2
150 X 150

= Crushing load (N)
Area of cube (mm2)

C.S of cube 2: 330x103 = 14.60N/mm2
150 x 150

C.S of cube 3 = 380x103 = 16.80N/mm2
150 x 150

At 14 days

C.S of cube 1 = 460 x 163 = 17.7N/mm2
150x 150

C.S of cube 2 = 380x 103 = 16. 82N/mm2
150 x 150

C.S of cube 3= 373x103 = 16.58N/mm2
150 x 150

At 28 day curing

C.S of cube 2= 664x103 = 29.50N/mm2
150 x 150

C.S of cube 2 = 664x103 = 29.50 N/mm2
150 x 150

For 12mm Aggregate at 7 days for cube 1

C.S of cube 1 = 420x103 = 18.66 N/mm2
150 x 150

C.S of cube 2 = 460x103 = 20.44 N/mm2
150x 150

At 14 days

C.S of cube 2 = 500.8 x 103 = 22.25N/mm2
5x 150

C.S of cube 2 = 460x103 = 20.22N/mm2
150 x 150

C.S of cube 3= 510x103 = 22.66N/mm2
150 x 150

At 28 days

C.S of cube 1 = 664x103 = 24.5N/mm2
150 x 150

C.S of cube 2 = 552x 103 = 24.5N/mm2
150x 150

C.S of cube 3= 550x 103 24.44N/mm2
150 x 150

For 20mm aggregate at 7 days

C.S of cube 1 = 428x103 = 19.04N/mm2
150 x 150

C.S of cube 2 = 460 x 103 = 20.44 N/mm2
150 x 150

C. S of cube 3 = 425x 103 = 18.69N/mm2
150 x 150
At 14 days

C.S of cube 1 = 370 x 103 = 16.4N/mm2
150 x 150

C.S of cube 2= 420x103 = 18.69N/mm2
150 x 150

C.S of cube 3 = 500 x 103 =18.69 N/mm2
150 x 150
At 28 days
C.S of cube 1 = 500 x 103 = 24. 40 N/mm2
150 x150

Analysis of flexural strength (F.S) using the formula PL
bd2
Where L = length of bean (mm)
B =width of beam (mm)
D= depth of beam (mm)
For 10mm aggregate size at 7 days

F.S of beam 1 = 24.2x103 x600 =4.30N/mm2
150x 150 x 150
F.S of beam 3 = 24x103 x 600 = 4.23N/mm2
150 x150 x 150
At 14 day curing,
F.S of beam 1 = 31.25x103 x600
150 x 150 x150
= 5. 565N/mm2
F.S of beam 2 = 30.10x103x600 = 5.35 N/mm2
150x 150 x150

F.S beam 3 = 32.20x103 x600 = 5.72N/mm2
150 x 150 x150
At 28 days
F.S of beam 1 = 32.40 x 103 x 600
150 x 150 x 150
= 5076N/mm2

F.S of beam 2 = 30x 103 x 600 = 542N/mm2
150 x 150 x 150

F.S of beam 3 = 31.20x600 = 5.55N/mm2
150 x 150

For 12mm aggregate at 7 days

F.S of beam 1 = 22.20x103 x 600
150 x150x150
= 3.95N/mm2

F.S of beam 2 = 24 x 103 x 600
150 x 150 x 150
= 4.27N/mm2

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