Enhancement of Fly Ash Concrete By Hydrated Lime and Steel Fibres

Abstract

Utilisation of fly ash as partial replacement for cement often results in low early strength of the concrete and adversely affects the popularity of fly ash concrete in the field. A theory suggests that effective pozzolanic reaction of fly ash particles is hindered due to unsatisfactory quantities of lime in most fly ash compositions, and that this is the cause of low early strength in fly ash concrete. This lack maybe overcome by addition of hydrated lime (calcium hydroxide), ie, the combination of lime (calcium oxide) and water. Steel fibres are already established enhancers of concrete and with existing studies pointing to benefits of their inclusion in fly ash concrete, the effect of these fibres in the proposed improved lime fly ash concrete mix would be of importance.This paper primarily investigates the improvements on fly ash concrete with addition of hydrated lime on properties such as compressive, tensile, flexural strengths and elasticity. The studies are carried out on two main mixes, one of Ordinary Fly ash Concrete (OFC), ie, with 30% substitution of OPC with fly ash alone, and the other mix of Lime Fly ash Concrete (LFC), ie, with 5% lime, 25% fly ash and rest OPC. Instances of study include material testing, mix design, casting and curing conditions, on fresh and hard concrete. Furthermore, drawing inspiration from ancient lime-based mortars, which utilized saline and lime water, for casting and curing purposes, the same is tested for this lime-included mix. Secondly, the above studies are repeated for additional inclusion of steel fibres to further improve the capabilities of this mix. Finally, the study is concluded by drawing inferences for results, by means of theorizing possible micro mechanics of the mix, expected chemical reaction of constituents and from SEM analysis of created concrete samples