Development of reduced thermal conductivity ductile cement-based composite material by using silica aerogel and silane

Multi-function cement-based materials will show stronger competitive than traditional single-function building materials. Aerogels have attracted widespread attention in cement-based insulation materials because of their extremely low thermal conductivities. However, neither the compatibility between aerogels and matrix matrices nor the strength degradation of cement-based materials with aerogels has been effectively resolved. Therefore, this work aimed to improve aerogels' application prospects in cement-based materials and realize the functional diversity of cement-based composite materials. In this study, high-ductility cement-based composite materials served as the matrix while using aerogel as a lightweight aggregate to replace an equal portion of sand from the original cement. A reduced thermal conductivity ductile cement-based composite (RTCDCC) material was prepared by directly mixing silane into the cement-based material. The effects of the aerogel and silane on the fluidity, strength development, bending performance, thermal conductivity, and density of the slurry under the combined action of the aerogel and silane were systematically studied. In addition, the specimens were tested by nitrogen adsorption, X-ray diffraction, and scanning electron microscopy to investigate the pore characteristics, chemical compositions, and microstructures of the hydration products. The results demonstrated that direct mixing of silane into cement-based materials could improve the degree of bonding between the aerogels and cement-based materials, reducing the adverse effects of mixing these materials and optimizing the pore structure. In addition, when the aerogel content reached 20% with a silane content of 0.8%, the specimen exhibited favorable mechanical properties and ductility with a significantly decreased thermal conductivity.