关键词: 铜尾矿, 碱激发, 碳养护, 固化砖, 微观结构

Abstract: By alkali activation reaction, compression moulding and carbonated conservation, copper tailings cured bricks were prepared using fine-grained copper tailings as main raw material, sodium silicate as activator, with a small amount of cement and fly ash. The phase composition, carbonized products, pore distribution and microscopic morphology of different samples were analyzed by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), mercury intrusion porosimeter (MIP) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). Then, the synergistic mechanisms of alkali activation-carbonated conservation on the performance improvement of copper tailings cured bricks were discussed. The results show that sodium silicate can stimulate part of the gelling activity of copper tailings, and generate flocculated calcium silicate hydrate (C-S-H) gels to improve the microscopic pore structure and the compressive strength of the cured bricks. Timing of carbonated conservation is critical. If the cured brick is carbonated conservation immediately after forming, the carbonization reaction will compete with the alkali activation reaction for OH^- to generate aragonite-type and calcite-type CaCO₃, resulting in the reduction of C-S-H gel generation, and then causing increasing porosity, and compressive strength reduction. When the cured brick is cured for 84 h in airtight condition and then carbonated cured for 84 h, the 7 d compressive strength would increase by 20.9%, and the internal pores are filled with the carbonized product CaCO₃, in which the volume of harmful pores and multi-harm pores greatly reduce and the number of harmless pores increases, thus improving the overall structure density, there by solving the problem of efflorescence on the surface of the copper tailings cured brick.

Key words: copper tailing, alkali activation, carbonated conservation, cured brick, microstructure