Influence of densified silica fume on engineering properties of concrete containing coal bottom ash aggregate.

Abstract

Coal bottom ash (CBA) is a significant waste produced by the coal manufacturing power plant, harming the environment. CBA has been used in many studies to replace sand in cementitious materials. However, few studies have investigated the use of CBA in concrete as a sand replacement with densified silica fume (DSF) as a cement replacement. DSF is a potential supplementary cementitious material (SCM) to combat the engineering properties of concrete that are typically decreased when CBA is used as a replacement for natural aggregate. Therefore, the present study aimed to evaluate the influence of DSF on the engineering properties of concrete containing different content of CBA as a partial replacement for natural sand. The mix design of the ordinary Portland cement (OPC) and binary blended concrete comprised 90% OPC and 10% DSF by total binder’s weight. The CBA as the fine aggregate replacement was used at 25%, 50%, 75%, and 100% by total aggregate volume. The mechanical, porosity, absorption performance of DSF and CBA (DSF+CBA) concrete containing CBA as partial aggregate replacement material were investigated. DSF+CBA with 50% CBA replacement showed improved mechanical strength performance than control by 15% at 28d and 5.6% at 56d of curing. However, the total porosity performance for DSF+CBA concrete decrease as CBA content increases. In conclusion, the DSF as SCM in binary blended concrete with CBA content up to 50% achieved a better performance in terms of mechanical properties even though the porosity was marginally increased.