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The Effect Of Water/cement Ratio On Compressive Strength Of Palm Kernel Shell Concrete At 1:2:4 Nominal Mix
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CHAPTER TWO
2.0 LITERATURE REVIEW
Similarly, the department of civil engineering, University of Ilorin, carried out a research work on “effect of palm kernel shell sizes and mix ratios on lightweight concreteâ€.
This project work gives an account of the study conducted on the effects of Palm Kernel Shells (PKS) sizes and percentages in lightweight concrete. It is aimed at determining the properties of PKS that make it suitable for light weight concrete works and the effects of proportion of sizes and percentages on the strength characteristics of palm kernel shell concrete. A number of tests were conducted on the PKS and concrete produced with it. Tests conducted on PKS were sieve analysis, specific gravity, water absorption capacity and moisture content, while tests conducted on palm kernel shell concrete (PKSC) included slump test, compressive strength test, modulus of rupture and splitting tensile strength test. Concrete mixes of 1:1½:3, 1:2:4, 1:3:6 and 1:4:8 were used to produce cubes, beams and cylinders which were cured for 7, 14 and 28 days before testing. PKSC had density that was less than 2000 kg/m3 for a lightweight concrete. The results showed that concrete mix of 1:1½:3with compressive strength of 20.1N/mm2 at 28 days hydration period met the British Standard recommended minimum strength of15N/mm2 for structural lightweight concrete while other concrete mixes did not but they can also be employed as plain concrete. Results of tests on modulus of rupture and splitting tensile strength exhibited similar trend to that of compressive strength test. The nominal mix 1:1½:3 gave the highest values of modulus of rupture and splitting tensile strength.(D. O. Oyejobi1, T. S. Abdulkadir, I. T. Yusuf and M. J. Badiru) Department of Civil Engineering, University of Ilorin, Ilorin, Nigeria.
After the research work, it was concluded that the nominal mix of 1:1.5:3 at 28 days curing gave compressive strength of 20N/mm2. The British Code CP 110: 1972 lays the minimum strength of concrete for reinforced concrete with light weight aggregate as 15MPa and 20MPa for the one with normal aggregate, with mix ratio of 1:1.5:3. Sample A is adequate and satisfied the conditions of being classified as light weight aggregate based on its density and compressive strength. The other Samples (B, C and D) can be used for plain concrete because the minimum strength in those cases was 7MPa. It is worth noting that concrete made with nominal mixes of 1:3:6 and 1:4:8 generally gave poor results.
2.1 WATER/CEMENT RATIO
The Water Cement Ratio is the ratio of the weight of water to the weight of cement used in a concrete mix. A lower ratio leads to higher strength and durability, but may make the mix difficult to work with and form. Workability can be resolved with the use of plasticizers or super-plasticizers.
Often, the ratio refers to the ratio of water to cement plus pozzolan ratio, w/(c+p). The pozzolan is typically a fly ash, or blast furnace slag. It can include a number of other materials, such as silica fume, rice husk ash or natural pozzolans. Pozzolans can be added to strengthen concrete.
The notion of water–cement ratio was first developed by Duff A. Abrams and published in 1918. Refer to concrete slump test.
Concrete hardens as a result of the chemical reaction between cement and water (known as hydration, this produces heat and is called the heat of hydration). For every pound (or kilogram or any unit of weight) of cement, about 0.42 pounds (or 0.42 kg or corresponding unit) of water is needed to fully complete hydration reactions.
However, a mix with a ratio of 0.42 may not mix thoroughly, and may not flow well enough to be placed. More water is therefore used than is technically necessary to react with cement. Water-cement ratios of 0.45 to 0.60 are more typically used. For higher-strength concrete, lower ratios are used, along with a plasticizer to increase flow ability.
Too much water will result in segregation of the sand and aggregate components from the cement paste. Also, water that is not consumed by the hydration reaction may leave concrete as it hardens, resulting in microscopic pores (bleeding) that will reduce final strength of concrete. A mix with too much water will experience more shrinkage as excess water leaves, resulting in internal cracks and visible fractures (particularly around inside corners), which again will reduce the final strength.
The 1997 Uniform Building Code specifies a maximum of 0.50 ratio when concrete is exposed to freezing and thawing in a moist condition or to de-icing chemicals, and a maximum of 0.45 ratio for concrete in a severe or very severe sulfate condition.
2.2 THE IMPORTANCE OF WATER/CEMENT RATIO
Three simple ingredients can be blended and proportioned numerous ways to make concrete: aggregate, cement and water. In concrete, the single most significant influence on most or all of the properties is the amount of water used in the mix.
In concrete mix design, the ratio of the amount of water to the amount of cement used (both by weight) is called the water to cement ratio (w/c). These two ingredients are responsible for binding everything together.
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ABSRACT - [ Total Page(s): 1 ]ABSTRACT IS COMING SOON ... Continue reading---
APPENDIX A - [ Total Page(s): 2 ] ... Continue reading---
CHAPTER ONE - [ Total Page(s): 3 ]CHAPTER ONE1.0 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 ... Continue reading---
CHAPTER THREE - [ Total Page(s): 3 ]CHAPTER THREE3.0 METHODOLOGYFor better achievement of this project, the following stages are ensured:ï¶ 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.ï¶ 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. It i ... Continue reading---
CHAPTER FOUR - [ Total Page(s): 6 ]CHAPTER FOUR4.0 DISCUSSION OF RESULTS4.1 Properties of Palm Kernel Shell {PKS}Results of the study from table 4.1 and figure 4.1 shows that the sieve analysis of PKS and the trend of the percentage cumulative weight retained increases as the sieve sizes decrease. The specific gravity of PKS was found to be 1.37 [Table 4.2] which [Okpala; 1990] classified as light weight aggregate.The water absorption capacity was found to be 10% [Table 4.3]. This value was considered in the design of m ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVE5.0 CONCLUSION AND RECOMMENDATION5.1 CONCLUSIONi. The result of the physical properties obtained show that PKS can be used as partial or complete aggregate substitution for lightweight structural concrete at 1:2:4 nominal mix.ii. The compression strength increases with advancement of age but decreases with increase in water cement ratios. That is, at w/c ratio of 0.3 the compressive strength is 6.5N/mm2 at 28 days while at w/c ratio of 0.5, it is 3.99N/mm2 at ... Continue reading---
REFRENCES - [ Total Page(s): 1 ]REFERENCENeville, A.M. (1996). “Properties of Concreteâ€. Longman Group Limited, London.Okafor, F.O. (1988). “Palm Kernel Shell as Aggregate for Concreteâ€. Cement Concrete Research Vol. 18, No 6, pp. 901-910.Okpala, D.C. (1990). “Palm Kernel Shell as a Lightweight Aggregate in concreteâ€. Building and Environment 25, pp. 291-296Olanipekun, E.A., Oluola, K.O., and Ata, O. (2006). “A comparative Study of Concrete Properties Using Coconut Shell and Palm Ker ... Continue reading---
