Hygrothermal properties and heat transfer analysis of silica aerogel incorporated cementitious composites

Silica aerogel is a nano-porous ultra-light weight aggregate, and its excellent thermal insulation performance has attracted much attention in building energy conservation. However, the hygrothermal properties parameters such as thermal conductivity, water absorption characteristics, moisture distribution, and pore structure of aerogel incorporated cementitious composites (AICs) are unclear and lack for experimental data. The effects of different aerogel contents on the microstructure and thermophysical parameters of cementitious composites were systematically studied based on traditional characterization methods (Fourier transform infrared, scanning electron microscope) and low field NMR technology was used to study the distribution and migration of water of AICs in the pore structure. The result shows that the microstructure, thermal insulation performance, and hydrophobicity of AICs are affected by aerogel content enormously. The water migration in the pore structure of AICs can be divided into four stages: rapid rise stage (0-15 min), slow growth stage (15 min - 1 h), uniform growth stage (1 - 12 h), and stable stage (12 - 24 h). The thermal conductivity decreases significantly (52.72%) with the increase in aerogel. However, the thermal conductivity of AICs increases after seven days of water absorption.