Effect of Rice Husk Ash (RHA) and slake-lime as partial replacement of cement in the production of concrete

This study examines the utilization of rice husk ash (RHA) and slaked lime as substitutes for a portion of the cement in manufacturing concrete. The RHA was acquired from a nearby source, subjected to calcination at temperatures ranging from 500 to 700 °C, and then passed through a sieve to obtain particles with a size of 150 microns. Concrete mixes were made using Ordinary Portland cement (OPC), fine and coarse aggregates, and water, with different amounts of RHA and slaked lime. The concrete mix design adhered to established standards, with a mix ratio of 1:1.5:3 (cement: fine aggregate: coarse aggregate). The experiment was designed using response surface methods, with RHA, slaked lime, and cement as factors, each having five levels. Concrete cubes were formed using 100 mm steel moulds and then submerged in water to assess their workability. The compressive strength was measured using universal testing equipment after 7, 28, and 90 days of cure. The flexural strength of concrete beams was assessed after 7 and 28 days. Samples were subjected to scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examination after 28 days. The compressive and flexural strengths increased as the curing period progressed, with the 10% RHA substitution showing the maximum strength. The SEM analysis showed that RHA10 exhibited the maximum concentration of silicon, which corresponds to the recommended 10% replacement level of OPC and meets the concrete specifications specified by ASTM M20 grade. Utilising RHA decreases expenses and minimises the amount of concrete that is discarded. The most effective replacement for OPC was 10% RHA, which produced long-lasting and strong concrete.