Investigation on thermal properties of rice husk ash-blended palm kernel shell concrete

Abstract

The contribution of buildings to climate change as a result of energy consumption and greenhouse gas emissions necessitates the use of agro-industrial by-products as alternative construction materials. The present study examines the thermal properties of Rice husk ash-blended Palm Kernel Shell Concrete (RHA-blended PKSC). Three control concrete mixes with mix ratios of 1:1½:3, 1:2:4 and 1:3:6 using water-to-cement (w/c) ratios of 0.5, 0.6 and 0.7, respectively were made with cement, river sand and granite. For each mix ratio with the respective w/c ratio, five concrete mixes containing RHA fixed at 15% as replacement for cement and PKS at 20, 40, 60, 80 and 100% as replacement for crushed granite were produced. The oven-dry density, compressive strength and thermal properties (thermal conductivity, thermal diffusivity, volumetric heat capacity and thermal resistivity) were determined. The results showed that the oven-dry density and compressive strength of concrete declined with increasing PKS content. Nevertheless, the compressive strength increased with curing age and the gain in strength of RHA-blended PKSC were higher than the control at the later age. The thermal conductivity and diffusivity decreased with increasing PKS contents but increase with curing age while volumetric heat capacity and thermal resistivity increased as PKS content increases but decreased with curing age. In addition, concrete with 1:3:6 mix ratio exhibited the lowest thermal conductivity and diffusivity but higher volumetric heat capacity and thermal resistivity than those with 1:1½:3, 1:2:4 mix ratios. RHA-blended PKSC with 40% PKS and 15% RHA for 1:1½:3 mix ratio attained the compressive strength and thermal conductivity values recommended for lightweight aggregate concrete which is suitable for structural and insulation purposes. It was concluded that the combined use of PKS and RHA as raw materials in concrete is effective in improving concrete's thermal and insulation properties.