Improved balance between compressive strength and thermal conductivity of insulating and structural lightweight concretes for low rise construction

Abstract

In order to save energy consumption in concrete buildings, there is a demand for structural cement-based materials with low thermal conductivity and sufficient compressive strength. This paper evaluates the effect of various proportion combinations of three concrete constituents namely, coarse expanded clay (CEC), fine expanded clay (FEC) and fly ash (FA), on the thermal conductivity and compressive strength of concrete at equilibrium density. The use of FEC produced a greater reduction in thermal conductivity and a lower reduction in compressive strength than using CEC. This is due to the finer pore size distribution, smaller maximum pore size and better spatial distribution within the mixture of the FEC. FA alone presents the least significant effect on both thermal and mechanical properties, but the combination of the three constituents shows capabilities to reduce the thermal conductivity, as well as the compressive strength within acceptable limits. The study shows the constituent proportions, which can be used in concrete mixtures towards an improved balance between compressive strength and thermal conductivity for low-energy concrete building applications.