Physical, mineralogical, thermal, and mechanical properties of aerogel-incorporated concrete exposed to elevated temperatures

Abstract

This paper investigated the physical, mineralogical, thermal, mechanical, and microstructural performances of concretes with four aerogel contents (i.e., 0, 5, 10, and 20 vol %) and after exposure to elevated temperatures (i.e., 200, 400, 600, 800, and 1000 °C). Mechanisms both of the heat-induced degradation and of the aerogel in mitigating the degradation of concrete were unveiled. Specimens after 200 °C exposure bear the same mineralogical compositions as those at 20 °C. After being exposed to 400 °C and 600 °C, portlandite disappeared. Dolomite and C–S–H still occurred after 800 °C exposure whereas disappeared after 1000 °C exposure. The residual strength of specimens decreased with an increase in the exposure temperature, except for the unexpectedly elevated ones after 400 °C exposure. Incorporating aerogel into specimens alleviated the strength loss after exposure to elevated temperatures, especially after 200–600 °C exposure. For instance, the strength losses of A0, A5, A10, and A20 after 600 °C exposure are 39.4, 39.1, 25.9, and 19.1%, respectively. Aerogel maintained its 3D nano-structure after 400 °C exposure; their thermal insulation properties remained functional. The heat flow was significantly retarded while meeting aerogel particles in the concrete. After 600 °C exposure, the gradual fusion of aerogel thickened the particle skeleton, and enhanced the stiffness and strength of the skeleton, making the aerogel-incorporated concrete resist higher loads than the control concrete. The sintering properties of aerogel play a vital role in mitigating the heat-induced degradation of concrete.