Durability of silica aerogel cementitious composites - freeze-thaw resistance, water resistance and drying shrinkage

Owing to its exceptional physical properties, silica aerogel is regarded as an attractive candidate material for building insulation applications; however, the widespread adoption of silica aerogel is limited by its inherently brittle nature and related sub-micrometre dust release. In this paper, the poor mechanical properties of silica aerogel were improved by combining the silica phase and cementitious materials to reach engineering strong composites and maintain relatively low thermal conductivity. The mechanical properties, durability (freeze-thaw resistance, water resistance and drying shrinkage) and thermal conductivity of the silica aerogel-cement composites were comprehensively studied. The composites show improved mechanical properties as compared to pure silica aerogel, but this decreases with the increase of silica aerogel content. With respect to the durability, surprisingly, the silica aerogel can efficiently improve the frost and water resistance of the composite, which might be benefited by the strong hydrophobicity of the silica aerogel. The optimal performance of the composite is observed at 60 vol.% aerogel loading. The thermal conductivity, compressive strength, flexural strength and bonding force are 0.065 W/(m/K), 181 MPa, 2.23 MPa and 0.27 MPa, respectively, and the drying shrinkage of the composite is only 0.12% after 90 d.