China's Refractories

Abstract: To enhance the mechanical properties of lightweight insulating materials, this work adopted expanded vermiculite as the aggregates and systematically investigated the effects of the expanded vermiculite addition, ratio of silica fume to fumed silica, and fiber dosage on the cold compressive strength and thermal conductivity of the composites. The bulk density and cold compressive strength of the samples were tested, and their microstructure was observed. The results show that: (1) as the expanded vermiculite addition increases, the required molding pressure increases and the bulk density of the samples increases; (2) when the ratio of silica fume to fumed silica is 1:2, the cold compressive strength of the composites is the highest; (3) an increase in the fiber dosage intensifies the tendency of fiber agglomeration, which is not conducive to the uniform dispersion of fibers; (4) when the expanded vermiculite addition is 40%, the ratio of silica fume to fumed silica is 1:2, and the fiber dosage is 2%, the comprehensive performance of the composite is relatively good, with bulk density of 0.51 g·cm^-3, cold compressive strength of 0.618 MPa, and thermal conductivity of 0.057 W·m^-1·K^-1 at 200 °C.

Key words: expanded vermiculite, lightweight thermal insulation material, high silica fiber, silica fume, fumed silica