Preparation of Glass–Ceramics Using Low-Pressure Sintering Method for High-Value Utilization of Blast Furnace Slag

To utilize blast furnace slag in an environment friendly, economically efficient and high value-added manner, this study successfully prepared glass–ceramics by directly using high-basicity blast furnace slag (R = 1.26) as raw material through low-pressure sintering method (80 kPa). This study examined the influences of particle size, heat treatment temperature and duration on the sintering densification and crystalline phase transformation of glass–ceramics, employing both fine and coarse glass frits of blast furnace slag. Notably, since the crystallization mode of glass–ceramics was surface crystallization, this crystallization behavior leads to microscale inhomogeneity in coarse powder-based glass–ceramics, ultimately resulting in poor mechanical properties. Furthermore, the glass–ceramic features dendritic merwinite as the transitional phase and globular gehlenite magnesian as the crystalline phase. However, due to the smaller size of the glass frits, the fine powder-based glass–ceramics exhibit a higher degree of homogeneity, and the glass–ceramic sintered at 900 °C for 3 h exhibited a porosity of 6.81%, a flexural strength of 116.6 MPa. Furthermore, after being exposed to the solutions of 1 vol.% H₂SO₄ and 1 wt.% NaOH at room temperature for 650 h, it exhibits an acid resistance of 89.83% and an alkali resistance of 99.99%.