Thermo-economic analysis of porous building materials with admixtures

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Most buildings in many nations of the world including African countries are built with porous materials especially sandcrete blocks. It has been observed that various factors including presence of admixtures affect the engineering properties of the blocks. Recent reports show that admixtures are being introduced into these blocks to achieve different purposes including cost reduction and strength enhancement. In the process, some vital properties are traded-off. Prominent among these traded-off properties apply to the thermal characteristics of the blocks which determine the thermal comfort within the built space in addition to energy conservation and other environmental consequences. This paper reports the effects of percentage substitution of the constituents of sandcrete block with coconut husk ash, crushed glass, and granite fines on its thermophysical properties. It was observed that the presence of the admixtures slightly increases the thermal conductivity and the thermal diffusivity but decreases the specific heat capacity and the thermal effusivity. Attendant effect on air conditioning load estimated shows that the load increases with the percentage substitution of the admixtures with granite fines having the highest increase of about 10% at 25% substitution. Recommendations are also made on the techno-economical suitability of these admixture-based blocks in building applications.