Preparation and performance study of lithium slag-based sintered bricks

Lithium slag bricks were fabricated using lithium slag and furnace slag as primary raw materials via a gas–solid reaction sintering process at 1100 °C under an air atmosphere. Benefiting from the high Al 2 O 3 content in lithium slag and the CaO supplied by furnace slag, mullite and calcium feldspar were formed under the coupled effects of carbothermal reduction and re-oxidation. High-temperature sintering facilitated the thorough carbothermal reduction of SiO 2 in lithium slag, generating a three-dimensional interconnected framework. This framework was subsequently dissolved by the calcium-rich liquid phase and contributed to the formation of the calcium feldspar crystalline phase. When the mass ratio of lithium slag to furnace slag was 73:27, the material exhibited the optimal comprehensive performance: a compressive strength of approximately 41 MPa, an apparent density of about 2.5 g/cm 3 , a porosity of around 12%, a linear shrinkage of roughly 5%, a flexural strength of 11.02 MPa, and a water absorption rate of 6.2%. After 50 freeze-thaw cycles, the compressive strength of all test specimens remained ≥ 10 MPa, meeting the threshold requirements for wall materials in cold regions. Moreover, there are significant differences in the strength retention rates of samples with different proportions. Mechanism studies showed that the low-melting components of lithium slag and furnace slag melted together to form a liquid phase, driving particle rearrangement-dissolution-re-deposition, and the crystal boundaries precipitated calcium feldspar/mullite frameworks, ultimately constructing a crystal phase-glass composite dense structure, achieving isolated refinement of pores and strength jump. This work realizes the large-scale and high-value collaborative utilization of lithium slag and furnace slag, providing a new strategy for the comprehensive valorization of mine solid wastes and metallurgical slags.