Some New Perspective on the Reaction Mechanism of MgO–SiO₂–H₂O System

Abstract

The application of MgO–SiO2–H2O system, one of the most popular basic refractories, is greatly limited because of the hydration of MgO. In this work, the phase and morphological development of MgO–SiO2–H2O system during aging were analyzed using various techniques. It is found that Mg(OH)2 initially appears and the amount increases after 10 days aging at room temperature. At elevated temperature, the heat treatment can facilitate the hydration reaction. Mg(OH)2 covers the surface of silica fume particles. The combination product connects with each other and distributes homogeneously around MgO particles to produce M–S–H gels, which inhibit the further hydration.

Effect of MgO calcination temperature on the reaction products and kinetics of MgO–SiO2–H2O system

“…Based on the reaction between light‐burned MgO and siliceous materials (eg silica gel, silicic acid, or amorphous silica), the MgO–SiO 2 –H 2 O system has been proposed as novel cementitious materials for buildings and constructions . It is also used in thermal insulation walls, encapsulation of nuclear or metal‐containing wastes, and refractory castables . Magnesium silicate hydrate (M–S–H) gel and Mg(OH) 2 are two main reaction products formed in the MgO–SiO 2 –H 2 O system …”

“…It is also used in thermal insulation walls, encapsulation of nuclear or metal‐containing wastes, and refractory castables . Magnesium silicate hydrate (M–S–H) gel and Mg(OH) 2 are two main reaction products formed in the MgO–SiO 2 –H 2 O system …”

“…Generally, M–S–H gel is an important product in the MgO–SiO 2 –H 2 O system . Wei et al prepared the MgO–SiO 2 –H 2 O system by mixing reactive MgO, microsilica, and water at different temperatures.…”

“…Li et al simulated the pH sensitivity of the reactive MgO and microsilica mixture and found that M–S–H gels formed more easily at an appropriate pH range (9.5‐10.5). Wei et al and Zhang et al found that MgO and SF pastes can be prepared at low water‐to‐solid ratio using sodium hexametaphosphate (SHMP) as a dispersant. In our previous studies, the reaction processes and products of the MgO–SiO 2 –H 2 O system were characterized and the thermodynamic parameters were calculated.…”

“…Wei et al and Zhang et al found that MgO and SF pastes can be prepared at low water‐to‐solid ratio using sodium hexametaphosphate (SHMP) as a dispersant. In our previous studies, the reaction processes and products of the MgO–SiO 2 –H 2 O system were characterized and the thermodynamic parameters were calculated. The results indicated that the formation of M–S–H gel and Mg(OH) 2 occur simultaneously.…”