Abstract

Sol-gel processing allows synthesis of low-energy glasses. In this work, binary magnesium silicate glasses with various MgO contents are synthesized using a modified sol-gel route. TGA and XRD analyses indicate that amorphous glasses with up to 50 mol% MgO can be obtained at 500°C. The reactivity of the glasses is evaluated to assess the use of the sol-gel technique in the large-scale synthesis of alternative cementitious materials. Reactivity tests show that, as MgO content increases, reactivity of glasses increases, reaches an optimum and then declines. This trend doesn’t agree with the theoretical one estimated by NBO/T value, which is generally used for the evaluation of glass reactivity. Mg²⁺ ions play a role as the network modifier when first introduced to silicate glasses. This leads to the depolymerization of the networks, causing an increase in reactivity. Then the magnesium partly behaves as a network former, bonding with oxygens to form MgOₓ polyhedron when there are insufficient primary glass-forming oxide SiO₂, resulting in the polymerization of networks, hence the decrease in reactivity.