Hygric, thermal and durability properties of autoclaved aerated concrete

Abstract

The hygric and thermal properties of autoclaved aerated concrete (AAC) given in the manufacturers’ lists include mostly just the thermal conductivity in dry state and generic data for the specific heat capacity and water vapor diffusion resistance factor. Durability characteristics are not listed at all. This greatly limits any service life assessment studies of AAC-based building envelope systems. In this paper, complete sets of hygric and thermal properties of three commercially produced AAC with different bulk density and compressive strength are measured, together with the basic physical characteristics and durability properties. Experimental results show that the thermal conductivity can be as much as six times higher in capillary water saturation state than in dry conditions. Thermal conductivity is also found to increase up to 50% when temperature is increased from 2°C to 40°C. The dependence of moisture diffusivity on moisture content is remarkable; the differences as high as one order of magnitude are observed if its values obtained for low and high moisture contents are compared. The freeze/thaw resistance of capillary saturated samples is found satisfactory up to 25cycles and increases with compressive strength. For the moisture content lower than 10% by volume AAC in the range of compressive strength of 1.8–4MPa can successfully resist to 50cycles.