Studies on Special Refractories of Calcium Silicate Compositions

Abstract

The authors collected some samples of disintegrated residue from calcium suicide manufacturing plants, and their main chemical component was determined to be nearly dicalcium silicate 2CaO⋅SiO₂, having main compositions SiO₂: 30-32% and CaO: 59-60%. So that, these samples and other synthesized samples of dicalcium silicate from pure chemicals were mixed with 2-5% magnesia or alumina containing compounds with or without 0.5-1% K₂O, P₂O₅ or Cr₂O₃ as the third addition agents for the purpose to prohibit the disintegration of dicalcium silicate α-2CaO⋅SiO₂→α′-2CaO⋅SiO₂→γ-2CaO⋅SiO₂, or α-2CaO⋅SiO₂→α′-2CaO⋅SiO₂→β-2CaO⋅SiO₂. These powdered materials were mixed homogeneously in the wet state, dried to the state containing about 5% water, moulded under high pressure 200kg/cm², and then fired at 1400-1500°C for 6 hours. These fired test pieces were tested on their several physical properties, e.g., firing shrinkage, water absorption, apparent and volume densities, compressive strength, refractoriness, expansion on heating, softening under load, etc.. The crushed pieces were, on the one side, further powdered, and separated by heavy liquid to several portions for X-ray analysis, and on the other side, polished and etched by several reagents for reflective microscopic test to study the mineralogical structures.