Mechanical Properties of Lightweight Concrete Using Class F Fly Ash as a Partial Replacement for Ordinary Portland Cement

Abstract

This study shows the mechanical properties of lightweight concrete (LWC) made by partially replacing ordinary Portland cement (OPC) with class F fly ash (FFA). Natural sand and pumice were used as the fine aggregate and coarse aggregate, respectively. Five LWC mixtures, M1, M2, M3, M4, and M5, were made by replacing, by weight, of 0%, 10%, 20%, 30 %, and 40% OPC with FFA, respectively. The mix proportion of LWC, by weight, was 1.00 binder: 3.24 fine aggregate: 1.19 coarse aggregate, and the water-binder ratio was 0.32. Tests of the LWC mechanical properties were conducted at the hydration time of 28 and 56 days using 150 by 300 mm cylindrical specimens. The results indicate that the use of FFA as a partial replacement for OPC improved the development of the mechanical properties of LWC. The compressive strength and the modulus of elasticity of the LWC increased in all the mixtures during the hydration time. The optimal proportion of FFA for replacing OPC in LWC is about 20%. With this optimal proportion and after 56 days of hydration, the compressive strength and the modulus of elasticity are, respectively, about 113% and 105% of those produced by LWC made with 100% OPC.