Abstract: The hydration products,microstructure and thermal stability of cement-based materials prepared by mixing with nano-SiO₂ and calcium carbonate whisker were effectively characterized by using SEM,XRD and TG-DSC.The mechanical properties and thermal conductivity of thermal-insulated cement mortar were also studied by adding 0%,1%,2%,3%,5% and 10% calcium carbonate whisker and 1% nano-SiO₂.Test results revealed that by adding materials of nano-and-millimeter level scales,C-S-H gels were generated from the secondary hydration reaction between nano-SiO₂ and Ca(OH)₂ crystal,filling the voids in cement base and refining the pores in cement base.Moreover,calcium carbonate whisker has dual-function of fibers and particles,hence producing bridging effect in the cement based,forming a dense network flocculation structure inside the cement base.The strength of cement mortar can be improved by adding nano-SiO₂ and calcium carbonate whisker.The compressive strength and flexural strength of thermal insulation cement mortar mixed with 3% calcium carbonate whisker and 1% nano-SiO₂ is 25.6 MPa and 6.19 MPa,respectively,and the thermal conductivity is 0.456 7 W/(m·K).Both the strength and thermal conductivity are taken into consideration.

Key words: nano-SiO₂, calcium carbonate whisker, microscopic analysis, mechanical properties, thermal conductivity