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 degreesC. 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 degreesC. It was possible, in some cases, to obtain a cementitious material. These cements are structurally related to beta-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. (C) 2002 Elsevier Science Ltd. All rights reserved.