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

The sol - gel method was applied to synthesise xerogels of C(2)AS and C2S at ambient temperature. Then they were thermally treated at 600, 900, 1100 and 1250 degrees C and the crystallisation of C2S and C(2)AS was characterised using X-ray diffraction (XRD). The evolution of the heat of hydration of these samples was investigated at 70 degrees C using a conduction calorimeter. The microstructure of the samples, separately cured under hydrothermal conditions ( 7 days at 70 degrees 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 degrees C has the most intense hydration rate, C(2)AS has the same aspect when calcined at 1100 degrees C. The hydration products of C2S, heat treated at 600 degrees C, are well crystallised as characterised by XRD analysis. Large gehlenite hydrate crystals were observed to form during the hydration C(2)AS prepared via sol - gel processing.