Performance of Concrete Made with Coconut Shell Ash (CSA) as an Admixture in Acidic Environment

This paper presents the findings of an investigation on the use of coconut shell ash (CSA) as admixture in concrete and its effect on durability performance. The CSA used was obtained by controlled burning of coconut shell in an incinerator to a temperature of 600–650ºC for 3 hours, air cooled, sieved through 75μm sieve and characterized by using X-ray Fluorescence (XRF) analytical method. The compressive and splitting tensile strengths of concrete were investigated at varying CSA additions of 0, 2, 4, 6, 8 and 10% respectively by weight of cement. A total of one hundred and forty-four of 100mm diameter by 200mm long cylinder CSA-concrete of 1:2:4 concrete mix and water-cement ratio of 0.55 were tested for compressive and splitting tensile strengths at 3, 7, 28 and 56 days of curing in accordance with standard procedures. Eighteen number 100mm cubes were tested for water absorption after curing for 28 days in water. The resistance of concrete specimen exposed to attack from 2.5% concentration of hydrochloric acid solution was investigated. The result of the investigations showed that CSA is of high silicon dioxide (37.97%), aluminum oxide (22.12%), magnesium oxide (16.2%), iron oxide (15.48%) and calcium oxide (4.98%). The inclusion of CSA in concrete increased compressive and splitting tensile strengths respectively. CSA addition in concrete slightly increased water absorption. The use of CSA improved the resistance of concrete exposed to acidic environment. Therefore, up to 2% addition of CSA is recommended for use as admixture in concrete to improve strength, and durability in acidic environment.