Experimental study on the capillary water absorptivity of an aerogel-based coating mortar under subsequent drying and wetting cycles

Abstract

Aerogel-based coating mortars with thermal conductivities ranging from 30 to 50 mW/(m·K) are an emerging type of thermal insulation coating mortar. They are intended for retrofitting uninsulated building envelopes due to their thermal performance which is comparable to conventional thermal insulation materials such as mineral wool. Meanwhile, their long-term hygrothermal performance and the reliability of the material properties are not fully demonstrated since these normally are declared based on single-cycle laboratory measurements. This paper presents laboratory measurements to determine the capillary water absorptivity of a commercial aerogel-based coating mortar after three consecutive wetting and drying cycles. The effect of the chosen drying (elevated versus room temperature) and sealing condition (sealed versus unsealed samples) on the measurement results were also assessed. The results show that the capillary water absorptivity of the samples increased after each repeated wetting and drying cycle regardless of the drying and sealing conditions. After three cycles, the measured capillary water absorption was more than five times higher than the initial measurement. Future research should investigate the causes of the observation and whether it applies to other aerogel-based coating mortars.