A backfill material without cementitious material: Carbonation curing magnesium slag based full solid waste backfill material

Abstract

In view of the two major problems of the rapid growth of global CO₂ emissions and the high cost of mine backfill materials (cement). In this study, a new method of mixing coal gangue (CG), magnesium slag (MS) and fly ash (FA) and preparing a backfill material without cementitious material through carbonation curing was proposed, and two kinds of magnesium slag based full-solid waste backfill materials (CM and CMF) with high strength, low cost and carbon fixation were prepared. Uniaxial compressive strength (UCS), X-ray diffraction (XRD), thermogravimetric differential thermal analysis (TG-DTG), mercury injection (MIP) and other test methods were used to investigate the effects of different curing ages, MS and FA contents on the carbonation properties of CM and CMF. The results showed that carbonation curing significantly improved the early strength of CM and CMF, and the fracture surface became colorless under phenolphthalein indicator at 7 d, reaching the degree of complete carbonation. After 7 d of carbonation curing, the compressive strength of CM and CMF reached 7.048 MPa and 8.939 MPa, which increased 25.2 times and 29.4 times compared with the standard curing, and the compressive strength of CM increased with the increase of MS content, and the compressive strength of CMF first increased and then decreased with the increase of FA content. The backfill effect of carbonized products makes the microstructure of CM and CMF denser, improves the pore size distribution, reduces the cumulative pore volume and total porosity, and promotes the improvement of strength properties. In addition, CM and CMF can absorb up to 16.34% of CO₂ through this carbonation curing method. Therefore, this study confirms that the method can not only prepare a CM and CMF without using gelling materials, but also provide a new path for the combination of solid waste disposal, low-cost backfill and CO₂ storage.

Keywords

carbonation curing / mine backfill / magnesium slag / compressive strength / microstructure / CO₂ storage

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