The Effect of Fly Ash as Partial Replacement of Cement on the Compressive Strength of Concrete

Abstract

The utilization of industrial wastes and a by-product of coal such as fly ash in this study was essential for environmental, economic, and performance-related reasons. It offers a sustainable alternative to traditional concrete production, reducing the environmental impact, conserving resources, and potentially improving the quality of concrete structures. This study becomes imperative to ascertain the optimum usage of fly ash as partial replacement of cement in concrete.  Grade 20 concrete was made, tested and compared in terms of the compressive strength at 7 days, 28 days and 90 days of curing life for 0 %, 10 %, 20 %, 30 % and 50 % weighted replacement of cement with Class F fly ash. The results revealed a reduction of compressive strength of fly ash concrete at 7 days comparable with that of Portland cement concrete. However, there was increase in compressive strength that was obtained at higher curing life of 28 days and 90 days respectively.  Optimum usage of 30 % of Class F fly ash as a partial weighted replacement of cement in concrete was established. These amounted to about N8,000 saving in 1m³ of concrete and translated to 18.2 % in savings of cementitious materials.