The Earth Are Covered With Water Construction Essay

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More than 70 of the total surface of the earth are covered with water. Earth are composed of a large part of saline water or in the other word also known as sea water. Sea water are usually partly or fully enclosed by land. When there are a lot of sea water, the volume of sea sand also would be bigger. With the large amount of sea sand that available today, some research need to be conducted in order to determine the characteristic of the sea sand and its usefulness especially in the constuction industry.

Specifically, Malaysia has a lot of sandy beaches. The coastal area in Malaysia are more than 4800 kilometers including islands such as Langkawi Island, Pangkor Island, Tioman Island and Labuan Island. Recently, there are a lot of construction activity in Malaysia. Concrete have become the most popular choice to used in the constuction industry. One of the materials used for making concrete are sand. There are many types of sand such as river sand and sea sand but usually river sand are the most preferrable to be used for making concrete.

With the large volume of sea sand that available in Malaysia, some study need to be conducted to explore the benefits of sea sand in the term of concrete mixing. Therefore sea sand can be used as one of innovation materials in construction industry replacing the river sand thus it also can reduce the cost for construction project because the price for sea sand are much lower than the price of river sand.

Objectives of the Study

The objective of this study is to discover the properties of sea sand in the term of concrete mixing. The specific objectives of this study are:

To determine the compressive strength of concrete by using sea sand.

To determine the workability of concrete by using sea sand.

To compare the compressive strength and workability of concrete between sea sand and river sand.

Problem Statement

Recently, there are a lot of constuction project that are still ungoing not only in Malaysia but also in the others place in the world. Day by days, the construction project increase numerously. The demand for sand especially river sand to be used in the construction project increases significantly. The supply of river sand in the market is not sufficient to catter the demand in the construction industry. Because of the money, the sand supplier dredged the sand 24 hours a day, 7 days a week non stop without knowing the impacts to the environment.

As it have known, Sabah is a state that does not have an adequate supply of river sand. This is because, Sabah do not have the natural resource of river sand but it has a lot of sea sand due to the surrounding that consist of a lot of beaches. In order to ensure the sustainability of the river sand in Sabah, some alternative need to be find to replace the river sand in concrete batching.

Besides that, the use of sea sand in concrete mixing by replacing the river sand might occur some changes in physical properties and also particularly in the mechanical properties of the concrete due to the saltness of the sea water. The problems that might occur to the concrete such as improper quality of materials, incorrect specification, errors in construction process and exposure to the extreme environmental condition.

Scope of Study

The sea sand samples will be taken from Pantai Merdeka at Kedah and Pantai Batu Buruk at Kuala Terengganu. The samples were taken at two different location because to test either the properties of the sand were similar or not due to the different natural surrounding. The replacing of normal sand with sea sand will be experimented with the water cement ratio is 0.5

The experiment result will be used to ensure the effectiveness of this ratio of sea sand in concrete batching to determine the compressive strength and the workability of the concrete. The sample must be completed about 27 samples of concrete cube.

Sand

Days

7

14

28

Pantai Merdeka

3

3

3

Pantai Batu Buruk

3

3

3

River

3

3

3

Table 1 Samples of Concrete Cube for Compressive Test

Limitations that are applied in this research are as follows:

Dimension, shape

Aggregates

Water

Cement

Additional variables

Significant of Study

The importance of this study is the replacing of sea sand with river sand in concrete as the sea sand is a new material but available widely and easy to find that might affect the concrete for long life structure. This is due to the presence of salt in the sea sand that concern can attack the properties of the cement.

In addition, study of concrete by using sea sand in the terms of mechanical properties such as compressive strength and workability would be done. With this information, the characteristic of the concrete produced without using river sand could be determine thus it can proved either the concrete follow the standard requirement or not.

Therefore, this study signifies to propose an alternative way in replacing river sand as fine aggregate of concrete. Furthermore, the cost for the construction project could be reduced significantly due to the cheap price of sea sand and indirectly can reduce the dredging activities of river sand if the usage of sea sand can be maximize.

CHAPTER 2

LITERATURE REVIEW

Introduction

Concrete is the most comman materials which is used in construction site. Concrete being made from the mixture of aggregates that are held together by a hardened paste of cement and water. In comman with all building materials, concrete has many properties. Some of the properties are desirable and others are not so desirable (Jones, 1982).

Concrete can withstand considerable pressure and it also can even bend, strecth and shrink. However, all of these properties of concrete have limitations which is differ significantly from those of others building materials. Most significant is the range of limitations between concretes manufactured under different standard of control, the different in materials selection and for the use in variety of circumstances (Jones, 1982).

In order to produced finished concrete structure which will carry out the service for which it has been designed, the person that responsible for manufactured of the concrete needs to understand its properties and all the factors affecting the concrete. In order to understand the basic behaviors of the concrete, all properties must be studied separately. Before studying the properties it is necessary to examine the compositions of the concrete (Jones, 1982).

Properties of Fresh Concrete

Fresh concrete does not posses any strength eventhough more than 70% of its volume consist of particles that have good compressive strength. As the hydration proceed, the strength of the concrete would increase as the rate of hydration increases and eventually, the concrete is able to withstand the service loads (Somayaji, 2001).

2.1.1 Workability

Workability of the fresh concrete depends on several factors that is the poportions of ingredients, the physical characteristic of the cement and aggregates, the equipment for mixing, transporting and compacting, the size and spacing of the reinforcement and also the size and the shape of the structure. High proportion of cement, adequate quantity of fine materials, low coarse aggregate content and high water content would result to good workability (Somayaji, 2001).

Angular and elongated grains of crushed stone would produce poor workability concrete but if the coarse aggregate from crushed stone are properly graded, it can contribute to good workability. Besides that, air entraining admixtures can improve the workability and reduce the tendency for bleeding and segregation but at the same time, they lower the density and the strength of hardened concrete (Somayaji, 2001).

2.1.2 Consistency and Slump

Consistency is the measure of concrete's wetness or fluidity and its depend on the properties of ingredient and the mix proportion of the concrete. Wet mix is generally more workable compared to the dry mix but mixture of the same consistency may vary in workability. Slump test are generally used in order to measured the consistency but it is also indirectly used to measure characteristic of workability (Somayaji, 2001).

A mix with low water content would produce a near zero slump while mix with higher water content will result in increases of the slump. Concrete with properly proportioned will slump gradually and retain its original shape while a poor mix will separate, crumble and fall apart (Somayaji, 2001).

2.1.3 Factors Affecting Workability

Workability is relatively related to the proportion of cement but it is heavily dependent on the water content. This means, the increase in amount of cement without corresponding increase in water content will decrease the workability but by using some admixtures such as superplasticizers and air entraining adimixtures would help to improve the workability of the mix (Somayaji, 2001).

The increase in surface area of the aggregate will also decrease the workabiltiy of the mix. The surface area depend on the shape, grading and maximum size of the aggregate. As the maximum size of the coarse aggregate is increased and as the particles becomes round, the surface area will decrease thus improved the workability. In other words, the amount of coarse aggregate should be lowered if the maximum size of the aggregate is decreased (Somayaji, 2001).

The rate of hydration and the loss of water through evaporation also can influenced the workability. The hydration rate will speed up when the temperature is increased which increased the rate of water used for hydration. In addition, the rate of evaporation will increase with the rise of temperature. The greater evaporation loss in fresh concrete will reduce the workability thus the concrete will hardened quickly and cannot be placed, compacted or finished effectively that will result unworkable concrete (Somayaji, 2001).

2.1.4 Segregation

Segregation is the tendency for seperation between large and fine particles of fresh concrete. Some defect related to segregation that may occur when the concrete is hardened suach as honeycombing and surface scaling. Generally, high slump concrete are tend to segregation compared to low slump concrete. Segregation can occur when the concrete is moving over long distances as it is being placed within the forms. Segregation can affect the strength and durability of hardened concrete. In order to prevent segregation, fresh concrete must be dropped vertically and not at an angle (Somayaji, 2001).

2.1.5 Bleeding

Bleeding happen when the concrete mix does not posses proper consistency is unable to hold the mix water which slowly get displaced and then rises to the top of the form. This water will eventually be lost either through evaporation or by leakage between the forms. In other words, bleeding is a process of separation of water from the mix (Somayaji, 2001).

Excess bleeding will results in the movement of a high amount of water and finer particles to the top of the concrete. This situation will contribute to weaker concrete and cause the formation of fines cracks below the larger particles of the coarse aggregate. Overvibration and lean mix increase the potential for bleeding. There are some methods that can control bleeding that is by increase the fineness of cement and decrease the water cement ratio (Somayaji, 2001).

2.2 Properties of Hardening Concrete

2.2.1 Compressive Strength

One of the most attractive features of high performance concrete (HPC) is a rapid strength development after an extended dormant period. As an example, the fluid mixtures that giving compressive strength in excess of 30 Mpa at 16 hours could be design nowadays. An early tensile strength can be specified for some structures such as concrete pavement. Table 2 gives some figures for comman values adopted in various sector.

Types of utilization

Purpose

Concrete age (h)

Specified compressive strength (MPa)

Structural concrete for building

Form stripping

Withdrawal of scaffolding

14 - 16

20 - 36

5

10

Prestressed concrete in a bridge built by the cantilever method

Form stripping

Tension of the first prestressing cables

14 - 16

10 - 36

10

15 - 20

Table 2 Orders of magnitude for specified compressive strength at early stage

2.2.2 Autogenous Shrinkage

Another feature of importance in the cracking behaviour of concrete at early stage is autogenous shrinkage. This spontaneous deformation takes place with the progress of cement hydration and then accelerated by temperature rises. Autogenous shrinkage usually appeared during the first week and is superimposed by thermal shrinkage when the structure cools down (de Larrard, 1999).

Compared with drying shrinkage, autogenous shrinkage generally less than 50% of the total shrinkage. However, autogenous shrinkage will create retraining effects between severels parts of a structure cast at different stages (de Larrard, 1999).

2.3 Properties of Hardened Concrete

2.3.1 Compressive Strength

There are no inferior limit on specified compressive strength but in some application, concrete may only become a filling material. Generally, compressive strength for the ordinary building is between 20 to 30 Mpa but in the prefabrication industry especially for prestressed structural element would need a higher compressive strength. According to present regulations of various development country, the specified compressive strength for bridges at 28 days ranges from 30 to 80 Mpa (de Larrard, 1999).

2.3.2 Tensile Strength

Tensile strength may be specified where concrete is no reinforced or when a superior resistance to cracking is aimed for. The tensile strength of concrete should be higher enough in order to resist cracking from shrinkage and temperature changes. There are many methods that can be used to measured the tensile strength of the concrete such as direct tension test and flexural test (Somayaji, 2001).

2.3.3 Elastic Modulus

The elastic modulus for hardened concrete may range from 25 to 55 GPa (de Larrard, 1999 ). High elastic modulus is very important because to limit the deflection of a structure. This parameter can increase by increasing the specified strength, optimizing the aggregate grading and replacing the original aggregate by a stiffer one if the previous attemp failed to reaching desired level (Somayaji, 2001).

2.4 Aggregate for Concrete

Aggregate can be defined as rocklike material of various sizes and shapes that use in the manufacture of portland cement concrete, bituminous concrete, plaster, grout, filter beds, railroad ballast, base course, foundation fill, subgrade and so on. Aggregate are primarily from rock or stones of various type (Somayaji, 2001).

There are many reasons why aggregate have been used in concrete. Some of the reasons are because they greatly reduce cost for concrete batching, help to reduce shrinkage of the concrete and help to produce concrete with satisfactory plastic properties (de Larrard, 1999).

2.4.1 Maximum Aggregate Size

As a general rule, the maximum size of an aggregate should be as large as possible consistent with minimum section size and reinforcing bar spacings. Larger aggregates will result in a lower sand requirement. This is because the specific surface of the aggregate will be reduced thus reducing the water and cement requirement. Therefore, the resulting concrete will be more economical and exhibit lower shrinkage for a given strength (Taylor, 2000).

Besides that, there also some constraints on the maximum size of aggregate that can be used. Some of the constraints are the maximum size for the aggregate should not exceed one-fifth of the minimum dimension of the structure and the aggregate size that will be used need to be a size that is readily available (Taylor, 2000).

Nominal Max. Size (mm)

Application

40

Mass concrete, road construction

20

General concrete work

10

Thin section, screed over 50 mm thickness

5

Screed of 50 mm thickness or less

Table 2.1 Concrete aggregate sizes and typical application

2.4.2 Grading of Aggregate

Aggregate which are retained on a 5 mm mesh sieve a described as coarse aggregate. Coarse aggregate may consist of uncrushed natural gravel. In the other hand, aggregate that pass through 5 mm sieve a referred to as sands or also known as fined aggregate. Sand may comprise from natural sand resulting from natural disintergration of rock or crushed stones (Taylor, 2000).

Aggregate for concrete are usually graded continuosly from their maximum size down to the size of the cement grains to ensure that all voids between larger particles are filled without excess of fine material that can increase water and cement requirement (Taylor, 2000).

Sieve size

Mass retained (g)

Cumulative mass retained (g)

Mass passing (g)

Percentage passing

10 mm

0

0

287

100

5

6

6

281

98

2.36

17

23

264

92

1.18

32

55

232

81

600 µm

48

103

184

64

300

81

184

103

36

150

86

270

17

6

Passing 150

17

287

-

-

Table 2.2 Example sieve analysis of a sand used for concreting

2.5 Aggregate Density

2.5.1 Relative and Solid Density

Most of the aggregate comprises a mass of solid material containing air pores which may accessible or not accessible by water. The density of solid material are described as relative density or also known as specific gravity. The most important of these is relative density in the saturated surface dry (SSD) state that is when all accessible pores are full of water but the aggregate surface is dry (Taylor, 2000).

2.5.2 Bulking and Bulk Density

Large volumes of air are trapped between particles when the aggregate are loosely packed together are referred to as bulking and for coarse aggregate it amount to between 30 to 50 per cent of the total space occupied. The moisture content is the main parameter for the extent of bulking of sand. The void contain of dry sand may be small but it can increasing when the moisture is present, thereafter decreasing as further moisture tends to assist particles to consolidate. The bulking at intermediate moisture contents is the result of thin water films increasing friction between sand particles (Taylor, 2000).

2.6 Water for Concrete

2.6.1 Fresh Water

Water that is good for drinking is usually fit for making concrete. The water that is drawn from the main must not be stored in dirty container or allowed it to become contaminated prior to be used for manufacturing concrete. Sometimes, it may be necessary to make concrete by using water from streams or river. These water must be sure not polluted which may contains animal and vegetable life together with fallen and decomposed leaves, silt and so on (Jones, 1982)

2.6.2 Sea water

Concrete can be made with sea water in certain conditions. Same with the fresh water, the presence of organic and vegetable matter in the sea water should be avoided. By using sea water, the strength of the concrete is gained more rapidly and less curing is required compared when using fresh water. Sea water should not be used if the finishing of the final structure is important because efflorescence may occur and the salt present attract moisture causing damp patches. Besides that, sea water should not be used in pre-stressed work due to the chloride salt that can corrode the steel (Jones, 1982).

2.7 Cement for Concrete

Cement is one of the essential component of concrete which it will bind the aggregate together to form the hard, strong ang monolithic whole when it hydrated. Portland cement is the commonly used in concrete throughout the world. Although cement is a simple material, but it have significant impact on the properties and behaviour of concrete from mixing through the end of its life (Peter et al, 2010).

2.7.1 Fineness

Fineness of the cement relates to the size of the cement grains. It has significantly influence on the behavior of cement during its hydration. Fineness of cement can be measured from the percentage of particles that pass 75 µm sieve. Fineness is commonly established by measuring the specific surface or surface per unit mass ( m2/kg ). Primarily, the hydration of cement is affected by fineness. The rate of hydration would increase with increasing fineness which will increase the rate of strength development and evolution of heat (Somayaji, 2001).

2.7.2 Setting

Setting are referred to when cement is mixed with sufficient water the resulting paste loses its plasticity and then slowly forms into a hard rock. In a favorable environment, within one or two hours after the mixing of cement and water the sticky paste loses its fluidity. The time lapse from the addition of water to the mix to the initial set is called initial setting time and similarly to the final set that called final setting time. The rate of setting is also a mesure of the ate of release of heat of hydration. When a concrete mixture reaches a state in which its form cannot be changed without producing rapture, it is said to have set. Mixture with higher water content will take a longer time to set (Somayaji, 2001).

2.7.3 Hardening

Hardening can be defined as the development of strength of the concrete over an extended period of time. Hardening of concrete is the net outcome of hydration. Hydration is the key for strength development in concrete but not all component in concrete hydrate at the same time. The rate of hydration of cement depends on the relative proportions of silicates and aluminates, the fineness of the cement and also the humidity and the temperature of the surrounding (Somayaji, 2001).

2.8 Gap of Research

The are some gaps between this research and the others research. Some of the gaps are as follows:

Author

Title of the research

Objective

Michael A. Taylor, 1978

Effect of oceans salt on the compressive strength of concrete.

This research were conducted in order to determine the effect of sea salt upon 28 days compressive strength of plain concrete.

W.P.S. Dias et al, 2007

Offshore sand for reinforced concrete.

This reseach were conducted in order to measure the properties of offshore sand and to study the corrosion properties of reinforced concrete containing offshore sand.

J. Limeira et al, 2011

Mechanical and durability properties of concrete made with dredged marine sand.

This research is aimed to determine the physical, mechanical and durability of concrete made with dredged marine sand.

Muhamad Nizan, 2012

Study of workability and compressive strength of concrete using sea sand.

The objective of this research is to determine the workability and compressive strength of the concrete by using sea sand.

Table 2.3 Gap of Research

2.9 Theoretical Background

2.9.1 Water Cement Ratio

Free water/cement ratio is the most important ratio since it can affect the strength and durability of concrete. A lower water-cement ratio will result to higher strength and durability concrete but may take the mix more difficult to place.

Water/cement ratio =

2.9.2 Density of Concrete

It is only from an accurate knowledge of concrete density that batch masses of cement and aggregate for a given volume of concrete can be reliably predicted. The density of the concrete can influence the dead load of the structure. Density of the concrete can be calculated as follow:

Density of concrete =

2.9.3 Compressive Strength of Concrete

Compressive strength is the most important property of hardened concrete, and generally considered in the design of oncrete mix. Compressive strength of concrete is the capacity of a material or structure to withstand axially loaded pushing forces. Compressive force can be calculated by using formula below:

Compressive strength =

CHAPTER 3

METHODOLOGY

3.0 Formulate Research Objectives

The objective of this research is to study the workability and compression strength of concrete by using sea sand. This research would determine either the mechanical properties of concrete would be different if the normal sand or also known as river sand being replaced by sea sand.

3.1 Literature Review Studies

An intensive study need to be done in order to collect information regarding the topic of the research. The main sources for this research comes from the journals that can be found in the internet. Most of the journals are related to the topic of the rsearch that is sea sand but there are also journals that related to concrete mixing and concrete testing. Others than that, the sources from anonymous that can be easily found in the internet also have been used in this research because of the similarity and suitable with the topic.

3.2 Finding Research Materials

The materials for this research will be taken from 2 different location. This is because in order to observe either the samples from different locations can affect the properties of the concrete due to the different composition of the sand. The samples will be taken at Kedah situated at north of Malaysia and also at Kuala Terengganu located at east of Malaysia.

3.3 Concrete Testing

The reason for testing concrete and concrete materials is to produce data from which unbiased estimates of certain characteristics of the material can be derived. The reliability of

these estimates improves as the number of test results increases. Also, although depending somewhat on the purpose for which the estimates will be used, the reliability tends to increase as the quantity of material undergoing test increases. There were two test that will be conducted that is:

3.3.1 Slump Test

 This test is performed to check the consistency of freshly made concrete. Consistency is a term very closely related to workability. It is a term which describes the state of fresh concrete. It refers to the ease with which the concrete flows. It is used to indicate the degree of wetness. Workability of concrete is mainly affected by consistency for example wetter mixes will be more workable than drier mixes but concrete of the same consistency may vary in workability.

3.3.1.1 Equipment

Slump rod

Steel rule

Small scoop

Slump cone

Rigid metal plate

Damp cloth

3.3.1.2 Procedures

The slump cone and base plate are cleaned and damp.

The base plate is placed at flat surface and then the slump cone is placed on the plate.

The cone is filled with three equal layer and each layer is compacted 25 times by using steel rod.

The concrete spillage from sides and base plate are cleaned

The cone is then lifted straigth up and clear to a count of between 2 to 5 second.

The distance between the underside of the cone and the highest point of true slump are being recorded.

3.3.2 Cube Test

This test is used to determine the compressive strength of a concrete cube which has usually been made from fresh concrete cast in a standard test mould. The value of compression strength can then be used to assess whether the batch of that concrete cube represent meets the required compressive strength. Following the cube manufacture and curing, the cube is then crushed at a constant speed until it can sustain no further increase in load. The strength is then derived by calculation using the maximum load and cube dimension.

3.3.2.1 Equipments

Small scoop

Damp cloth

Brush and mould oil

Cube moulds

Tamping bar

Hammer

3.3.2.2 Procedures

The mould are cleaned and oiled with all bolts are tightened to ensure there are no leakage occur.

The mould are filled with 3 equal layer and then compacted by using tamping bar not fewer than 35 tamps.

The side of the mould is then tapped with hammer until large bubbles of air cease appeared on the concrete surface.

The mould edges are cleaned and then the mould are stored overnight.

The bolts are slacken and the mould are lifted off carefully.

The cubes then placed in the curing tank.

The moulds are reassemble and cleaned.

CHAPTER 4

EXPECTED OUTCOME

4.0 Introduction

Hopefully in this research, the workability and compressive strength of concrete by using sea sand can be understand and analyzed thoroughly which will result in accurate and dependable data. In general,i am hoping to obtain an accurate result from the slump test and cube test which will be compared to the data of the river sand which should have a small difference between them.

4.1 Compressive Strength of Concrete

Sea sand

Compressive

strength

River sand

Time

Figure 4 Concrete strength development with time

4.2 Workability of Concrete

River sand

Sea sand

Slump value

mm

Types of sand

Figure 4.1 slump value versus types of sand

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