Properties, structure and mechanism of high-temperature modified steel slag based on solid waste.

In this study, a composite modifier (CMCDL) containing coal gasification residue, dicyandiamide waste slag, and lake sediments was used to modify steel slag at high-temperature. Five kind of raw materials was analyzed in physicochemical properties, mineral composition and microstructure, cementitious properties and soundness, and particle size analysis, the same to steel slag after high-temperature modification (SHTM). The new mineral phases were found that tricalcium aluminate (C 3 A), gehlenite (C 2 AS), magnetite (Fe 3 O 4), spinels (MgFe 2 O 4), quartz (SiO 2), celite (C 6 AF 2) and diopside (CMS 2) formed in the SHTM when the mass fraction increase from 10% to 30% in CMCDL. The HTM with CMCDL increases the glass phase and hydrated mineral (C 3 A, C 3 S, C 2 S) and in raw steel slag, promoting the disassembled of RO phase, turning the phase from FeO into MgFe 2 O 4 and Fe 3 O 4. MgFe 2 O 4 and Fe 3 O 4 have similar crystal structures, and they form mixed spinels. When the content of CMCCL (coal gasification residue: dicyandiamide waste slag: lake sediments =7:9:4) is 20%, the temperature is 1250 °C, result showed that the mass fraction of f-CaO in SHTM using CMCCL decreases from 4.81% to 1.86%, with a decrease of 61.3%, the 28-day activity index of SHTM increases up to 17.6% compared with raw steel slag, reaching 86.2%. Therefore, the CMCDL-blended SHTM can be applied harmlessly in cement and concrete, enabling low-energy fine grinding of steel slag. [ABSTRACT FROM AUTHOR]