Making Belite-Rich Cement Clinkers with Industrial Inorganic Sludges

摘要

Some industrial inorganic wastes are widely used as alternative materials for cement production in recent years. Belite, namely dicalcium silicate (Ca_2SiO_4), is an important constituent of cement and contributes the later-age strength of mortar and concrete. In this study the belite-rich cement clinkers were produced with electroplating sludge and water-treatment-plant sludge. The purpose of this study was to prevent the transformation of belite to γ phase by means of ionic substitution of heavy-metal ions. X-ray powder diffractometry and the reference intensity ratio (RTR) method were used to determine the crystalline phases in clinkers. The electroplating sludge contains Cu, Zn, Cr, and Ni at 2.48-7.24%. When heavy-metal ions are absent in raw meal, there is about 25% of γ-dicalcium silicate in the produced clinker. The belite in the clinker produced with >5% of the electroplating sludge is mainly β phase. It appears that the transformation from β- to γ-dicalcium silicate is disrupted when heavy-metal ions are present.