Author(s) :

Mustapha Jama'a Garba, Egbe Ngu-Ntui Ogork, Aaron Aboshio, Smith A, S. J.

Volume/Issue :

Abstract :

ABSTRACT This paper presents the findings of an investigation on coconut shell ash (CSA) as admixture in cement paste and concrete. The CSA used was obtained by controlled burning of coconut shell in an incinerator to a temperature of between 600–650ºC for 3 hours, air cooled, sieved through 75µm sieve and characterized based on its oxides composition determined using X-ray Fluorescence (XRF) analytical method. The effects of CSA on cement paste were investigated with addition of 0, 2, 4, 6, 8 and 10% respectively by weight of cement. The workability of fresh prescribed 1:2:4 concrete mixes with 0.55 water-cement ratio and CSA content in the order above was determined. Harden properties of the concrete were also assessed using 100mm diameter by 200mm long cylinders mould where the concrete mixes were cast and tested for compressive and splitting tensile strengths at 3, 7, 28 and 56 days of curing in accordance with BS procedures. The result of the investigations showed that CSA is of high silicon dioxide (37.97%), aluminium oxide (22.12%), magnesium oxide (16.2%), iron oxide (15.48%) and calcium oxide (4.98%). The inclusion of CSA in cement decreased linear drying shrinkage but increased consistency, initial and final setting times and could be used as a retarder. The use of CSA in concrete showed a decrease in workability but increase in compressive and splitting tensile strengths respectively with addition of CSA up to 2%. Therefore, up to 2% addition of CSA is recommended for use as a retarding admixture and strength improver in concrete in normal environment. Keywords: admixture, coconut shell ash, cement paste, concrete, compressive strength

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