Effect of SiO2 Aerogel on the Properties of Inorganic Cementing Materials

SiO2 aerogel powder has ultralow weight and thermal conductivity, and it cannot be easily dispersed in inorganic cementing materials (i.e., it is incompatible with inorganic cementing materials). In this study, the properties of inorganic cementing materials with hemihydrate gypsum and α-hemihydrate gypsum as main cementing materials were investigated. Moreover, the property changes resulting from the addition of SiO2 aerogel to inorganic cementing materials were examined. Based on the obtained results, the composites of SiO2 aerogel and inorganic cementing materials with optimal properties were prepared and investigated. The results revealed that when the composition mass ratio of the inorganic cementing material was 1:3:9:0.8 (fly ash:cement:hemihydrate gypsum:lime), the compressive strength of the cementing material was largest, reaching 7.71 MPa after 28 days of curing. Moreover, when the composition mass ratio of the inorganic cementing material was 1:3:9:0.4/0.6 (fly ash:cement:hemihydrate gypsum:lime), its softening coefficient was highest, reaching 0.97. Under the same mass ratio, the 28-day compressive strength of the α-hemihydrate gypsum-based cementing material was 2.4 times that of the plaster-based cementing material. When the SiO2 aerogel was added to the gypsum-based composite cementing material, the compressive strength and softening coefficient decreased with increasing SiO2 aerogel’s content.