Mechanical properties and microscopic characterization of cemented paste backfill with electrolytic manganese residue matrix binder

With the exploitation of mineral resources, more and more mined-out areas need to be backfilled. In order to meet the needs of backfill, a new cemented paste backfill (CPB) is developed. The new material uses electrolytic manganese residue (EMR), slag and red mud as binder, tailings as aggregates, and sodium hydroxide as alkali activator. Taking the EMR content, the mass concentration and bone glue ratio as the influencing factors, the un-confined compressive strength (UCS) of 3 d, 7 d and 28 d as the target, the single factor design was carried out, and the mixture proportion recommended was obtained. According to the 28 d UCS of CPB under mixture proportion recommended, a piecewise damage constitutive model with the end of initial compaction stage as the critical point was established. The three microscopic test methods of scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the CPB at different ages under the mixture proportion recommended. The internal morphology, composition, phase composition and chemical bond combination of the CPB were analyzed. The results show: when the EMR content is 20%, the mass concentration is 81%, and the bone glue ratio is 6, the mixture proportion recommended for the developed CPB was recommended; The established constitutive model can fit the UCS curve well; At the initial stage of reaction, C-S-H and C-A-S-H gels were formed inside the CPB; With the increase of age, the amount of gel for-mation increased, the diffraction peak of the reactants weakened, the diffraction peak of the product enhanced, the pore played a filling role, so that the internal structure was dense, porosity decreased; The corresponding characteristic bands originate from the asymmetric stretching and bending vibrations of H-O-H, Si-O, Si-O-Si, C-O and O-H chemical bonds. This new type of CPB can well meet the requirements of backfill, and can reasonably use solid waste.