Controllable preparation of aerogel/expanded perlite composite and its application in thermal insulation mortar

Abstract

The extremely low strength and high cost of aerogel limit its applicability in energy-efficient buildings. In this paper, the controllable preparation method of aerogel/expanded perlite (AEP) was developed, and the particle gradation effect on AEP thermal insulation mortar (AEPM) was assessed, which provided an effective way for the application of aerogel and AEP in buildings. The results showed that the acid/base catalysis two-step method was imperative for preparing AEP. It was also found that the pH of SiO2 hydrosol should be controlled within 3.2–3.5, and the corresponding gel time of SiO2 hydrosol was 30–90 min. The impregnation-adsorption process of EP adsorbing SiO2 hydrosol should be completed before the initial viscosity of 3 mPa·s changes. The amount of SiO2 hydrosol adsorbed by EP had a logarithmic relationship with the adsorption time under the adsorption of ambient pressure (AP), whereas its linear relationship with the adsorption pressure under the adsorption of vacuum pressure (VP) was found. The pores of expanded perlite (EP) were filled with well-structured aerogel due to the controlled preparation of AEP. Thus, the AEP bulk density increased by 24%-50% compared with EP. However, the thermal conductivity decreased by 14.6%-31.8%, and the particle strength of AEP was not significantly improved compared with that of EP. AEPM prepared by AEP showed typical characteristics of high strength and low thermal conductivity. The compressive strength of AEPM was 6.5% lower than that of EPM but more than twice that of AERM, while the corresponding water absorption and thermal conductivity were 27.6% and 26.6% lower than EPM. As a new nano-micron porous composite, AEP has great applicability in developing thermal insulation materials, phase change materials, and adsorption materials.