THE EFFECT OF WATER AND CEMENT RATIO ON COMPRESSIVE STRENGTH OF PALM KERNEL SHELL CONCRETE AT 1:2:4 NOMINAL MIX
CHAPTER ONE
1.0 INTRODUCTION
Concrete is a composite engineering material made from the mixtures of cement, water, fine aggregate (sand), coarse aggregates (such as crushed stones or rocks and granite) and a small amount of air in a specific proportion that hardens to a strong bony substance or become ossified. The cement always serves as a binder for the aggregate.
The uniqueness quality of concrete makes it desirable as a building material, because it can be moulded into virtually any shape or form. Concrete provides a wide latitude in surface textures, such as large buildings, bridges, dams, highways, roadways hydraulic structures, silo, farm building etc.
Concrete can be broadly classified as normal weight aggregate concrete and light weight aggregate concrete based on the density of the concrete. The density of concrete varies with the amount and density of its constituents (the coarse aggregate, fine aggregate, water cement ratio and sometimes entrapped air). A normal weight aggregate concrete has a density of approximately 2400kg/m3 while a light weight aggregate concrete contains natural or artificial aggregate unit with density usually less than 2000kg/m3. Light weight concrete has been successfully used in buildings for over 80 years. However, as report of moisture- related flooring problems have escalated in the past
decades, the drying time of light weight concrete has attracted much attention. A key issue is the volume of water in light weight concrete. It is a standard practice to pre-soak light weight aggregate before batching
Concrete has relatively high compressive strength, but much and significant lower tensile strength and such is usually reinforced with material that are strong in tension. There are different types of concrete mix design. The mix design depends on the types of structure been built, how the concrete will be mixed and delivered and how it will be placed to form this structure. As concrete matures it continues to shrink, due to the ongoing reaction taking place in the material, although the rate of shrinkage falls relatively quickly and keeps reducing over time (for all practical purpose, concrete is usually considered not to shrink due to hydration any further after thirty years). The relative shrinkage and expansion of concrete and brick work require careful accommodation when the two forms of construction interfere. Generally concrete has a very low coefficient of thermal expansion and shrinks as it mature.
Concrete mixes are usually specified in terms of dry volume ratios of cement, sand (fine aggregate) and coarse aggregate used. A 1:1:1 mixes for instance, consist of one part by volume of cement, one part of sand and one part of coarse aggregate. Depending on the applications, the proportion of the material in the concrete can be altered to produce specific changes in its properties, particularly strength and durability. The mix ratio of 1:2:4 by dry weight not by dry volume and the amount of water cement ratio added to this mixes are, 0.3, 0.4, 0.5, 0.6, and 0.7 times the weight of the cement. For high strength concrete, the water content is kept low with just enough water added to wet the entire mixture. In general, the more water in a concrete mix, the easier it is to work with, but the weaker the harden concrete becomes. (Microsoft Encarta premium, 2009)
Large amount of agricultural waste was disposed in most of tropical countries, for countries like Thailand, Philippine, Nigeria and Malaysia. If the waste is not disposed properly, it will lead to social and environmental problems. The high cost of conventional construction materials is a major factor in the delivery of construction in the country. To limit the cost of construction in Nigeria, the government has advised the use of local materials in the construction industry. This has necessitated research into alternative materials of construction. Recently the use of recycled materials as concrete ingredients has been gaining popularity because of increasingly strict environmental legislation.
The most popular way of achieving light weight concrete production is by using lightweight aggregate (LWA) (Polat et al, 2010). Lightweight aggregate concrete (LWAC) is not a new invention in concrete technology; it has been used since ancient times. LWA may be subdivided into two groups: those that occur naturally and those that are manufactured. The main natural LWAs are diatomite, pumice, scoria, volcanic cinders and tuff (Neville and Brooks, 2008). An alternative LWA in tropical region and countries that have a palm oil industry is oil palm shells (OPS), sometimes called palm kernel shells (PKS). The use of PKS as a lightweight aggregate or porous aggregate in producing lightweight concrete was researched early in 1985 by Salam and Abdullah (1985) in Malaysia. The oil palm industry is important in many countries such as Malaysia, Indonesia and Nigeria. Malaysia is one of the world leaders in the production and export of palm oil (Subramanian et al, 2008) and contributes about 57.6 percent of the total supply of palm oil in the world (Ahmed et al, 2010).
The palm tree is found or grown in tropical climate of the world in countries like Malaysia, Indonesia and Nigerian. The palm kernel is found on the palm tree, a tree which is economically valuable, tree grown in the rain forest region close to the coastal area and adjacent to some inland water waste (Ondo State, Imo State Enugu State etc.).palm kernel shells are processed and gotten from palm fruit being processed in large quantities by oil mills for example in Nigeria, Malaysia, it was discovered that over 1.5 million and 4 million tons of palm kernel shell solid waste are produced annually, only a fraction which is used as a domestic fuels. (Peter Ndoke; 2006 ).
Palm kernel shell is light and ideal for substitution as aggregate in the production of light weight concrete. Olutoge (1995) in his investigation into the physical property of palm kernel shell found that it has density to be 740kg/m3. He concluded that this material have properties which resembled those light weight concrete materials. This study will adopt a “waste to wealth” policy in the use of material presently considered as having no economic value with disposal problems. This study will also ascertain their suitability as replacement for coarse aggregate in production of concrete and hence enhance their economic value.
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FIGURE 1.1 PALM TREE
1.1 STATEMENT OF THE PROBLEM
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The increase in construction activities and the consequent increase in the consumption of the available reserve of materials for these activities have led to shortage of natural aggregate in some region of the world. These shortages of conventional aggregate can only be remedied by importation of aggregate from other areas at an increase cost due to high transport charges. Construction industries, therefore, need to consider the possibility of utilizing the vast; un-sighting the idle accumulation of waste namely the palm kernel shell of the palm oil fruit, partially or totally replacing the stone aggregate in concrete will solve problems in managing waste and utilizing the waste as raw material (Bitrus, 2010).
1.2 AIM AND OBJECTIVES OF THE STUDY
The aim of this project is to determine the effect of water/cement ratio on compressive strength of palm kernel shell concrete at 1:2:4 nominal mix. The objectives of the study therefore include the following:
1. To determine the physical properties of palm kernel shell that make it suitable for concrete work in placed of natural aggregate.
2. To produce palm kernel shell concrete at mix ratio 1:2:4 and with water/cement ratios.
3. To characterize palm kernel shell concrete as light weight coarse aggregate for concrete.
4. To determine the 7th, 14th and 21st and 28th day compressive strength of palm kernel shell concrete of 1:2:4 mix ratio at varying water/ cement ratio.
5. To develop compressive strength-age relationship of palm kernel shell concrete for the water/ cement.
1.3 JUSTIFICATION
1. To make palm kernel shell have an economic value
2. To turn a waste to a re-usable and useful material
3. To reduce pollution
4. To explore an alternative material to the conventional coarse aggregate in order to reducethe high cost of construction
5. To reduce the dead load of a concrete structure
1.4 SCOPE OF THE STUDY
This project work is limited to the procedures involved in determining the effect of water / cement ratio [0.3, 0.4, 0.5, 0.6 and 0.7] on compressive strength of palm kernel shell concrete at 1:2:4 nominal mix, bearing in mind the short comings of the existing natural coarse aggregate as well as comparing and aiming at a reasonable conclusion of replacing the former (Natural coarse aggregate) with the latter [palm kernel shell (PKS)].
1.5METHODOLOGY
For better achievement of this project, the following stages was ensured:
1.5.1 COLLECTION OF MATERIALS
The materials comprises of cement, sand, palm kernel shell and water. Palm kernel shell was obtained from a local palm kernel producing village Oko, Irepodun LGA, Kwara State Nigeria.
1.5.2 PREPARATION OF PALM KERNEL SHELL (PKS)
⦁ Due to high water absorption of palm kernel shells, it is mandatory to soak the aggregate for about 30 minutes
⦁ Palm kernel shell is properly washed to remove dust, oil and other mud particles which may be present and stuck to the surface of the palm kernel shells
⦁ Palm kernel shells are then air dried for about 24 hours and ready for use
1.5.3 Laboratory Test
a. Sieve analysis
b. Specific gravity
c. Water absorption capacity
d. aggregate impact value
e. slump test
f. compressive strength test at 7th, 14th, 21st, and 28th, day for mix ratio 1:2:4
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