Thermal Performance and Workability of Concrete Containing Rice Husk Ash as a Partial Cement Replacement

Abstract

This article converts a civil engineering dissertation on rice husk ash (RHA) concrete into a journal-style research article. The study evaluated the feasibility of using RHA as a partial cement replacement and examined whether the replacement changed the thermal response and workability of concrete blocks. Five M20 concrete mixtures were considered: a control mixture with 0% RHA and four modified mixtures containing 5%, 10%, 15%, and 20% RHA by cement replacement. RHA was obtained from brick and pottery industry sources, sieved to a fine particle range, and incorporated into a 1:1.5:3 concrete mix at a constant water-cement ratio. Five 150 mm cube specimens were cast, cured for 14 days, conditioned for 24 hours, and then exposed to direct sunlight. Surface and internal temperatures were recorded for seven days, while workability was evaluated by the slump test. The results show a consistent reduction in internal temperature as RHA percentage increases. The average internal temperature decreased from 28.35 C for the control sample to 27.45 C for the 20% RHA sample, and the maximum surface-inside temperature difference increased from 1.2 C to 3.6 C. Workability, however, reduced steadily from 95 mm slump at 0% RHA to 70 mm at 20% RHA. By combining the experimental temperature data with the dissertation literature review on strength, durability, water absorption, modulus of elasticity, and density, the article identifies 15% RHA as a practical optimum for balancing improved thermal performance with acceptable concrete properties. The study supports the use of RHA concrete blocks as a sustainable, lower-cement, potentially lightweight construction material, especially where thermal comfort and environmental performance are important. Keywords: rice husk ash; concrete; cement replacement; thermal performance; workability; sustainable construction