Thermal and Mechanical Properties of SiO2 Aerogel–Incorporated Geopolymer Insulation Materials

Abstract

Geopolymer-blended aerogel materials (GAMs) prepared by adding different proportions of water and SiO2 aerogel (AG) were studied with respect to stability, viscosity, segregation degree, density, thermal conductivity, compressive strength, and interfacial characteristics. These properties were tested by contact angle tester, rheometer, thermal conductivity tester, universal testing machine, and scanning electron microscope, among others. Results indicated that AG can stably exist within GAMs regardless of its high alkaline activator. With increasing AG content, the apparent viscosity of GAM slurry rose obviously and segregation degree increased slightly, then remained at around 2.6%. Due to its high porosity, an increased volume of AG generally contributed to a lowered density and thermal conductivity. The relationship between thermal conductivity and AG content conforms to a modified Maxwell-Euchen model, and the value of parameter t is determined as 1.1–1.2. However, AG generally can lead to reduced compressive strength of GAMs. Considering this disadvantage, the AG surface was further modified with epoxy resin AB adhesive and silence coupling KH550. The compressive strength of GAMs with modified AG reached 46 MPa, a 30% increase, due to enhancement of the intertransition zone between aerogel and geopolymeric matrix as witnessed via scanning electron imaging.