Mechanical Properties and Length Change of High Strength Concrete Containing Coal Bottom Ash as an Internal Curing Agent

Abstract

AbstractConstruction demand for high rise buildings is gradually increasing at several developing countries, leading to an over-exploitation of river sand which causes environmental impacts such as riverbank erosion. Coal bottom ash, which is a by-product of coal fired power plants, is considered as one of alternative materials to natural river sand for concrete production to diminish environmental impacts and conserve natural resources. Therefore, the aim of the present study was to investigate mechanical properties and length change of high strength concrete internally cured by coal bottom ash to evaluate the effectiveness of replacement of river sand by this material. In experiment, five replacements of natural river sand by coal bottom ash under saturated-surface dry condition were 0, 25, 50, 75, and 100% by volume. A water-to-cement ratio of 0.34 was employed for all concrete mixtures. Mechanical properties (including compressive strength and flexural strength), and length change (i.e., shrinkage) of high strength concretes cured under sealed condition were tested up to age of 56 days. Results showed that the replacement of natural river sand by coal bottom ash reduced compressive strength of the concretes at the age of 1 day. The 50% replacement of coal bottom ash increased compressive and flexural strengths of the concretes after aging for 7 days. The replacement reduced shrinkage of the high strength concretes up to the age of 56 days. Consequently, the coal bottom ash under saturated-surface dry condition is found to be a potential alternative to natural river sand to produce internally cured high strength concrete.KeywordsCoal bottom ashCompressive strengthFlexural strengthInternal curingShrinkage