Upgrade of hydraulicity of some cement phases synthesised by sol–gel method

Abstract

The sol–gel method was applied to synthesise xerogels of C₂AS and C₂S at ambient temperature. Then they were thermally treated at 600, 900, 1100 and 1250°C and the crystallisation of C₂S and C₂AS was characterised using X-ray diffraction (XRD). The evolution of the heat of hydration of these samples was investigated at 70°C using a conduction calorimeter. The microstructure of the samples, separately cured under hydrothermal conditions (7 days at 70°C), has been examined by means of SEM. Calorimetric measurements of hydration heat evolution showed that C₂AS and C₂S, synthesised via sol–gel method are much more active during hydration than their related clinker minerals synthesised by the conventional method. Furthermore, hydration activity of samples depends chiefly on calcination temperature. While C₂S calcined at 900°C has the most intense hydration rate, C₂AS has the same aspect when calcined at 1100°C. The hydration products of C₂S, heat treated at 600°C, are well crystallised as characterised by XRD analysis. Large gehlenite hydrate crystals were observed to form during the hydration C₂AS prepared via sol–gel processing.

Keywords:

• SOL-GEL METHOD
• CEMENT PHASES
• HYDRAULICITY
• GEHLENITE HYDRATE
• DICALCIUM SILICATE HYDRATE