Comparative long term study of concrete mix design procedure for fine aggregate replacement with fly ash by minimum voids method and maximum density method

Abstract

Replacement of scarcely available natural sand with fly ash has economical and environmental advantages. However due to lack of knowledge people avoid using fly ash at construction sites, which is increasing area under land bank. The paper presents the results of experimental investigation, which indicated about 20% increase in the compressive strength and about 15% increase in flexural strength of concrete by the inclusion of fly ash as a partial replacement of sand as compared to control concrete. Sand was replaced by fly ash by Maximum density method and Minimum voids method. Addition of 0.5% super plasticizer could achieve about 30% increase in the compressive strength and about 20% increase in flexural strength of concrete by the inclusion of fly ash as a partial replacement of sand as compared to control concrete. Results indicated increase in workability for all the cases over control concrete. Concrete with fly ash was also found to be about 25% economical when cost per N/mm2 was compared. Based on experimental results correlations are developed to predict Compressive Strength, Flexural strength, cost per N/mm2, Slump and Dry Density for percentage sand replacement with fly ash.