Sol–gel preparation of 2CaO·SiO2

Di-calcium silicate or belite (β-Ca2SiO4) is one of the major compounds in Portland cement clinker. Conventionally, belite is produced by long lasting sintering of limestone and quartz at temperatures exceeding 1400 °C. The subject of this paper is the sol–gel synthesis of belite. Both aqueous and non-aqueous sol–gel routes were applied. The preparation of the precursor mixture and the formation of the ceramic product were monitored using TG/DTG, XRD, FT-IR and SEM. The combination of these techniques led to the recording of all the transformations occurring during the processing of the precursors and the formation of the final products. As it was concluded, both routes can be successfully applied for the preparation of di-calcium silicate. The final products consist of very fine spherical crystallites in the range 1–3 μm. Their formation requires a 3-h sintering at 1000 °C. In both cases, β-2CaO·SiO2 is obtained without the use of any chemical stabilizers.