Mechanical properties and gas permeability of silica-gel modified hydratable magnesium carboxylate bonded refractory castables in drying process

Abstract

The hydratable magnesium carboxylate (HMC) bonded castables have a high-level gas permeability while the mechanical strength decreased sharply during drying process. Silica-gel with high activity is a porous structure after drying and can potentially increase the intermediate-temperature strength without reducing the gas permeability of the castables. In this study, the mechanism of silica-gel modified the HMC, and the effects on the properties of the castables were investigated. The surface of the hydration products of HMC is covered with a thin protective layer of siloxane network. The proportion of fine permeable pores (0.1 μm ∼1 μm) increased, optimizing the connected network channels in the castables. Compared to the pure HMC bonded castables, with the HMC/silica-gel mass ratio of 2, the cold modulus of rupture of the castables increased by 2 times after heat treatment in the range of 400 °C ∼600 °C. Especially, the permeability constants Darcian k1 and non-Darcian k2 increased by 37 times and 38 times after heat treatment at 600 °C, respectively.