Recycling the waste dolomite powder with excellent consolidation properties: Sample synthesis, mechanical evaluation, and consolidation mechanism analysis

Alkali activation has gradually become an important means to treat solid waste and produce green cementitious materials. The alkali-activated samples were successfully prepared by waste dolomite powder, whose consolidated-performance and environmental friendliness are both excellent. This work intensively investigates the preparation process and thermo-mechanical properties of alkali-activated waste dolomite powder, and emphatically analyses the consolidation mechanism, which is distinct from that of silicate alkali-activated materials. The optimal preparation parameters were found as follows: alkali concentration (1.5 wt%), compression molding pressure (125 MPa), curing temperature (could be from 22 to 150 degrees C), and holding time (2 h); under these preparation parameters, the corresponding samples' compressive strength could reach a level between 67.77 MPa and 73.75 MPa. And its heat-resistance temperature is at least 400 degrees C, which is higher than that of Ordinary Portland Cement. Via the characterization analysis including TG-DTA, FTIR, XRD, SEM, and EDS, two-part mechanisms were suggested that may support this performance: the consolidation mechanism at room temperature (22 degrees C) was considered to involve two kinds of chemical reactions that were dedolomitization and ion cross-linking, and the thermal reaction was believed to contain the decomposition of magnesite and then of calcite. These results exhibit the alkali-activated waste dolomite powder has excellent mechanical properties and heat-resistance temperature, which not only provides an efficient, green path for waste dolomite powder handing but also renders a novel idea in the alkali-activated system based on dolomite. (c) 2021 Published by Elsevier Ltd.