Abstract
A new type of cemented paste backfill (CPB) was prepared by using the bottom ash (BA) from a thermal power plant as an aggregate, alkali-activated slag as a binder, and an air-entraining agent as an admixture. Based on the central composite design (CCD) response surface method, the mix ratio was optimized, and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was performed on the optimal mix ratio. ImageJ software was utilized to determine the porosity of the experimental samples at various curing ages. The results indicate that the optimal mix ratio of the aggregate-binder ratio is 3.28, the alkali dosage is 3%, the solid content is 67.44%, and the air-entraining agent dosage is 0.1%. As the curing age increases, the porosity of CPB gradually decreases. A calcium aluminosilicate hydrate (C-A-S-H) gel is the main hydration product of alkali-activated slag. At the beginning of the hydration reaction, the slag gradually dissolves, and the C-A-S-H product binds the BA together. At 14 d, complete calcium hydroxide (CH) crystals appeared in the hydration product. Finally, the degree of C-A-S-H crystallization increased further to form a dense structure.
Highlights
Coal-fired thermal power plants produce a large amount of bottom ash (BA) [1,2,3,4,5,6]
Paste backfill technology is important for converting solid waste into cemented paste backfill (CPB) for goaf filling, which can control mining subsidence and make full use of solid waste and mineral resources [7]
To obtain CPB with good workability, good mechanical properties, and low cost, mix ratio optimization can be performed through a response surface method
Summary
Coal-fired thermal power plants produce a large amount of bottom ash (BA) [1,2,3,4,5,6]. BA accumulates in the soil and ponds near power plants. BA must be treated and utilized, and it is useful to prepare BA as a cemented paste backfill (CPB) material for goaf filling. CPB is composed of aggregates, binders, water, and additives. Paste backfill technology is important for converting solid waste into CPB for goaf filling, which can control mining subsidence and make full use of solid waste and mineral resources [7]. To obtain CPB with good workability, good mechanical properties, and low cost, mix ratio optimization can be performed through a response surface method
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