Thermal performance characterization of cement-based masonry blocks incorporating rice husk ash

Owing to climate change and its effects, interest has grown in finding alternative building materials to improve the energy efficiency of building envelopes and reduce CO2 emissions and costs. This study focuses on the thermal performance of cement-based masonry blocks, which are popular in many parts of the world for masonry wall construction. Masonry blocks were incorporated with rice husks, which are agricultural wastes commonly found in tropical countries and are usually dumped in landfills. Previous research on the use of rice husk ash (RHA) for construction purposes has focused on the durability properties of the product without much consid-eration for properties such as thermal conductivity or thermal transmittance coefficient (U-value), which are important for quantifying the overall energy performance of buildings. High U-values of building elements typically result in high heat gains in tropical countries, which increases the use of mechanical cooling systems to improve occupants' thermal comfort, thereby increasing building energy consumption. The study involved an experimental investigation using the laboratory hot box and heat flow metre method for U-value measurements in accordance with BS EN ISO 8990 and 9869. Several samples were prepared by partially replacing Portland cement with 5%, 10%, and 15% RHA by weight of cement. The results reflect up to a 17% reduction in the U-values and thermal conductivities of all block samples. The lowest value of 3.04 W/m2K was obtained from RHA 15% compared to 3.67 W/m2K from the control sample. The results of this study show the prospects of improving building energy consumption, occupants' thermal comfort, and building CO2 emissions using masonry blocks incorporating RHA for external building walls in tropical countries.