Effects of partially replacing sand with laterite on compressive strength of hybrid OPC -activated metakaolin concrete

Abstract

This study focused on the effects of replacing sand with laterite on the compressive strength of concrete produced by hybridizing ordinary portland cement (OPC) and activated metakaolin (AMk) as binder. The AMk binder was produced by activating metakaolin with a combination of sodium hydroxide and sodium silicate alkaline solution, which was then used to substitute OPC at 10%, 20% and 30% levels. Laterite was also used to replace sand at 10%, 20% and 30%. Control specimens with 0% laterite and 100% OPC were also cast which served as control. A mix ratio of 1:2:4 binder to fine aggregate to coarse aggregate by weight was used. The resulting concrete specimens were cured for 7, 28, 56 and 91 days in water and the compressive strength determined at the maturity ages. A maximum compressive strength of 23.6 N/mm² obtained was for the control specimen at 91 days. Laterized concrete (without AMk) at 30% replacement level of sand attained a maximum compressive strength of 22.5 N/mm², which is 95.3% of the control at the same curing age of 91 days. The maximum strength obtained for OPC-AMk hybrid concrete was 19.8 N/mm² at 10% AMk and 30% laterite replacement of OPC and sand respectively, representing 84% of the compressive strength of the reference concrete. From the outcome, the optimal laterite content was 30% with 10% AMk. It was also revealed that partial replacement of sand with laterite gives better compressive strength results for hybrid OPC - AMk concrete than with just OPC concrete.