Preparation And Properties Of Architectural Glass-ceramics Using Waste Glass And Flyash

Construction glass-ceramics exhibit superior performance including rich andchangeful color, excellent luster, little color difference, high strength and low waterabsorption rate. They can take the place of traditional stoneware to be used asdecorative materials in high-grade buildings. However, high raw material price andprocess cost in the existing production technology result in higher product prices,which impedes their market promotion. In this thesis waste glass and fly ash wereused as raw materials to replace the traditional chemicals and minerals. Instead ofthe present two-step method of melting and sintering, an one-step method of directpowder sintering was introduced to prepare high-strength construction glass-ceramics. This method not only greatly reduces raw material cost and simplify theproduction process of glass-ceramics, resulting in energy saving and emissionreduction, but also massively recycles wastes glass and flyash, and prevents therelevant environmental pollution, leading to the remarkable economic and socialbenefits.Waste glass and suitable amount of chemical agents were used as raw materialsto investigate the sintering behavior and microstructure of CaO-Al2O3-SiO2（CAS）glass-ceramics. As compared to the melting and sintering method, the direct powdersintering method has higher crystallization activation energy, lower densificationand bending strength. However, the prepared CAS glass-ceramics with bendingstrength up to64MPa is obviously superior to porcelain tiles, and can be used as theconstruction decoration materials.Based on the main raw materials of waste glass and flyash, three types ofcrystallization promoters, including CaO, MgO and clay, were added to investigatetheir effects on the sintering behavior, crystallization composition, crystallizationdegree and mechanical property of glass-ceramics. The addition of18%CaOachieves the best performance of CAS glass-ceramic sintered at1100℃for2h,with a bulk density of2.26g/cm~3, a bending strength of81.5MPa, and acrystallization degree of50.7%. The grain size of raw materials prominently affectsthe sintering behavior and mechanical property of CAS glass-ceramics. In contrastto the coarse powders with80-mesh size, the fine powders with300-mesh size present rapid sintering rate, more densification and higher degree of crystallization.The bending strength of glass-ceramics from fine powder is increased by more than55%. The addition of10%MgO achieves the best performance of augite-forsteriteglass-ceramics sintered at1000℃for2h, with a volume density of1.94g/cm~3, abending strength of78MPa, and a crystallization degree of62%. The addition of15%clay achieves the best performance of augite-anorthite glass-ceramics sinteredat1000℃for2h, with a volume density of2.3g/cm~3, a bending strength of90MPa, and a crystallization degree of48%. Hence, for the three crystallizationpromoters the addition of clay has the best effect on the densification and bendingstrength of glass-ceramics.Using waste glass, flyash and clay as raw materials, the heating rate in thesintering process was studied to clarify its effect on the structure and properties ofglass-ceramics. Compared to the conventional sintering with10℃/min, two rapidsintering processes including30℃/min and the direct insertion of samples at thesintering temperature present significantly reduced sintering activation energies. Forrapid sintering, the glass-ceramics have higher volume density, smaller pore size，more complete crystallization and higher strength. The sintering temperature isdecreased, and the maximum bending strength of107MPa is obtained when theglass-ceramic was directly inserted at950℃. Finally, several colorants were appliedto prepared colorful glass-ceramics with different decorative appearances.