Preparation and properties of nanopore-rich cement-based porous materials based on colloidal silica sol

Abstract

Cement-based porous materials (CPMs) with different dry densities were successfully prepared by using silica sol as pore-forming agent. The rheological behavior of the fresh CPMs was discussed, then pore structure, pore-forming mechanism of silica sol, dry density, compressive strength and thermal conductivity of CPMs were investigated and presented. The results indicate that nanopores in cement paste were formed in-situ by adding silica sol, which led to the optimization of pore structure of CPMs, thereby improving the properties of CPMs. When the substitution of cement matrix by silica sol reached to 95 vol%, CPM with a nanopore volume of 0.675 cc/g, dry density of 488 kg/m3, thermal conductivity of 0.081 W/(m·K) and compressive strength of 0.5 MPa was successfully obtained, showing excellent insulation performance. CPMs with achieved strengths and low thermal conductivities show great potential in the application of semi-structural and structural thermal insulation systems of buildings.