COMPOSITIONS PROPERTIES OF SECONDARY MINERAL RESOURCES FOR DEVELOPING HEAT-INSULATING CEMENTLESS CONCRETE

摘要

The materials used for the investigation were fly ash and granulated slag from the Yurga thermal power plant, used molding sand from the Yurga machine building plant and the high alumina product (HAP) from the Yurga abrasion works. The bulk density, the absolute density and the surface area of the fly ash were 1150 to 1200, 2800 to 2850 kg/m~3 and 300 to 310 m~2/kg, respectively. According to its chemical analysis (31.73% free CaO, 1.87% SO_3, 1.06% LOI), the ash was a high-calcium type. It had good binding properties with the coefficient of quality more than 1. (C_q=CaO+MgO+Al_2O_3/SiO_2) Slag sand of 0.14 to 5 mm particle size from its chemical analysis met the State Standard requirements for use as an aggregate. The burnt sand incorporated 92% quartz sand, 6% bentonite clay and 2% water glass. After being used in foundry and removing of gritty scale, it had the form of black sand with the fineness modulus, bulk density and absolute density being 1.91, 1450 and 2380 kg/m_3, respectively. The burnt sand had a high content of SiO_2 in the amorphous state. No loss on ignition was observed, which increased the feasibility of chemically binding the free CaO into calcium silicates. The high alumina product was a powder containing above 88% Al_2O_3. The radionuclides contents of all the materials used was 3 to 5 times lower than allowed by the standards (370 Bq/kg). By grinding the three components (fly ash, burnt sand and HAP) in the planetary mill, a new cementless binder was obtained. In the process of grinding, the mechanochemical activation of the components as well as the interaction of the amorphous silica and HAP with free CaO took place. The study of the secondary resources permits the developing on their basis of a high-performance heat-insulating cementless concrete using the air-entraining admixture and the slag sand as an aggregate.