Synthesis of chemically and structurally modified dicalcium silicate

This paper describes the synthesis of cements, chemically and structurally related to Ca₂SiO₄. Silica was obtained from rice hull after heating at 600 °C. Calcium oxide and small amounts of barium chloride were mixed in order to obtain a final (Ca/Si) or (Ca+Ba)/Si ratio equal to 1.95, 1.90, and 1.80, which is lower than in the conventional cement. The solids were mixed and ultrasonically treated for 1 h with a water/solid ratio of about 20. After drying and grinding, the mixtures were heated up to 1100 °C. It was possible, in some cases, to obtain a cementitious material. These cements are structurally related to β-Ca₂SiO₄ and the lower (Ca+Ba)/Si ratio obtained was 1.95. The initial chemical compositions of these cements are: (Ca_1.83+Ba_0.12)SiO₄ and (Ca_1.79+Ba_0.16)SiO₄. A further lowering in the (Ca+Ba)/Si ratio changes the nature of the silicates.