Bloating mechanism of the mixture of thin-film transistor liquid-crystal display waste glass and basic oxygen furnace slag

摘要

This study produced a synthetic lightweight aggregate (LWA) of waste glass from thin-film transistor liquid crystal displays (TFT-LCD) combined with slag from blast oxygen furnaces (BOF). We investigated the bloating mechanism of the mixtures as well as the influence of the heat-treatment conditions (temperature and duration) on the properties of the LWA (bulk density, water absorption and compressive strength). Our results indicate that the proposed mixtures bloat when the content of BOF slag is in the range of 20-40 wt%, resulting from the release of CO_2 through a reduction (2Fe_2O_3 + 3C → 4Fe + 3CO_2) of the Fe_2O_3 contained within the BOF slag. The bulk density and compressive strength of the resulting LWA decreased with an increase in heat-treatment temperature and duration within the bloating temperature range. The water absorption of the resulting LWA was affected by the pore type (open or isolated), which depended on the viscosity at the surface of the material. Variations in water absorption characteristics can be divided into three distinct stages progressing with an increase in temperature: (1) water absorption increased from the onset of bloating and the specimens formed a number of open pores on the surface of the LWA due to the release of CO_2; (2) following the formation of the glazing phase, bloating proceeded and water absorption decreased due to the sealing of open pores, transforming them into isolated pores; (3) water absorption again increased through the continuous release of CO_2 from isolated pores, resulting in significant increasing of pore size which resulted the connecting of isolated internal pores.