Effects of Blended Portland-Fly Ash Cement on Compressive Strength of Seawater Mixed and Cured Lateritic Concrete

Abstract

The use of cement in the construction industry is accompanied by the release of greenhouse gases (GHGs) into the ecosystem, and freshwater usage is on the rise globally, putting the world in a potential freshwater scarcity. This study investigated the effects of blended Portland-fly ash cement on the compressive strength of seawater-mixed and cured lateritic concrete by partially replacing the concrete materials: cement with fly ash at 0%, 5%, 10%, 15%, and 25%; fine aggregate, with laterite at 0%, 10%, 20%, and 30%. A concrete mix ratio of 1:1.5:3 was used in the production of concrete cubes with an expected target compressive strength of 20 N/mm2. The compressive strength of the cubes was measured at 7, 28, and 56 days using standard testing procedures. Cubes cast with and cured in seawater (SW-SW) had strength values relatively higher than those cast with and cured in freshwater (FW-FW) at 28 days of curing. At 28 days, SW-SW cubes gave 22.44 N/mm2 while FW-FW cubes gave 21.80 N/mm2 as the highest strength values at 10% Lat and 10% FA. However, the FW-FW cubes had strength values higher than those of seawater mixed and cured concrete (SW-SW) at 56 days. FW-FW cubes gave 26.82 N/mm2 while SW-SW cubes gave 26.34 N/mm2 as their highest strength values at 10% Lat and 10% FA. Generally, an increase in fly ash and laterite content significantly reduces the compressive strength of concrete. Overall, seawater is recommended for curing and mixing, especially in non-reinforcing concrete. 10% fly ash and 10% laterite are also recommended for use in blended Portland cement-fly ash concrete as they give the highest strength values. Keywords: Concrete, Fly Ash, Laterite, Seawater, Compressive strength