Influence of Chloride Ion in Sea Sand on Mechanical Properties of Fly Ash Concrete Exposed to Accelerated Carbonation

Abstract

This study aims to investigate the influence of chloride ion in sea sand on the compressive strength and modulus of elasticity of fly ash (FA) concrete exposed to accelerated carbonation. Non-desalted sea sand (NSS) and desalted sea sand (DSS) were used as fine aggregates. Four mixtures were prepared with a constant water-to-cementitious materials ratio of 0.50. Ordinary Portland cement (OPC) was replaced by FA at 15 mass%. After cured under sealed condition at 20 °C for 28 days, half of concrete specimens were continuously sealed, whereas the others were exposed to carbonation at 5% CO2, 20 °C and 60% relative humidity until designated ages. Compressive strength and modulus of elasticity were measured at 28, 91 and 182 days. Results showed that the chloride ion in NSS improved the compressive strength and modulus of elasticity of concrete not only under sealed condition but also under accelerated carbonation condition regardless of FA replacement. The compressive strength and modulus of elasticity of FA SS concretes were higher than those of reference concrete (OPC-DSS) under sealed condition at 182 days. Under accelerated carbonation condition, the compressive strength of FA SS concretes was nearly the same while their modulus of elasticity was slightly lower in comparison with OPC-DSS.