Effect of mixing time on the properties of phosphogypsum-based cemented backfill

Min, Chendi; Li, Xibing; He, Suya; Zhou, Shitong; Zhou, Yanan; Shan, Yang; Shi, Ying

doi:10.1016/j.conbuildmat.2019.03.187

Cited by 59 publications

(15 citation statements)

References 42 publications

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“…When fly ash content is 15% and 22.5%, both the fluidity and bearing strength are considered as the ideal material ratio for filling and mining in Shanghe coal mine after field verification [1]. Unfortunately, our experiment did not design longer curing time (such as 180 d) [45]. Some scholars studied found that with the increase of fly ash content, the workability and mechanical strength of cement paste backfill (CPB) increase, and when they reach the maximum, they decrease with the increase of fly ash content [24,46].…”

Section: Discussionmentioning

confidence: 99%

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Shao

Wang

et al. 2020

Energies

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Backfill mining is the most environmentally friendly mining method at present, which can effectively control the surface subsidence, improve the recovery rate, and has good social and economic benefits. The purpose of this study is to solve the environmental problems caused by solid waste, combined with the rich geographical advantages of aeolian sand in the Yushenfu mining area of China. The rheological properties of the aeolian sand-fly ash-based filling slurry with different fly ash content are studied by experiments, and the strength development law of the filling body under different age and fly ash content are studied from the macroscopic and microscopic points of view. The rheological experiments showed that the increase of the amount of fly ash has a significant effect on the thixotropy, plastic viscosity, and yield stress of the filling slurry. Additionally, rheological properties of aeolian sand-fly ash-based filling slurry conform to the Bingham model. With the increase of the amount of fly ash, the performance of the filling slurry has been significantly improved. Uniaxial test and scanning electron microscope observation showed that the influence of fly ash on the strength of the filling body was mainly reflected in the late stage of maintenance, but was not obvious in the middle stage. Fly ash particles mainly bear the role of “water reduction” and a physical filling effect, which makes the filling slurry thicker and the internal structure more closely spaced. The volcanic ash reaction of fly ash is lagging behind the hydration reaction of cement; the secondary product of the delayed reaction is filled in the pores of cement hydrates, which can greatly reduce the porosity of the backfill body and increase the later strength of the backfill body. It provides a guarantee for the safe replacement of coal pillars in the working face.

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Section: Discussionmentioning

confidence: 99%

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Shao

Wang

et al. 2020

Energies

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“…In the first ten cycles, the continuous recrystallization of the saline (Na2SO4 and NaCl) filled up tiny pores in specimens, probably generating the observed decrease in porosity. With the formation of secondary gypsum and ettringite, the porosity of specimens decreased more significantly in the Na2SO4 solution [41]. After ten cycles, however, the porosity increased rapidly with the extension of drying-wetting tests, as shown in Figure 6.…”

Section: Pore Structurementioning

confidence: 92%

Durability Evaluation of Phosphogypsum-Based Cemented Backfill Through Drying-Wetting Cycles

Zhou

et al. 2019

Minerals

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In this study, the durability of phosphogypsum (PG)-based cemented backfill was investigated by drying-wetting cycles to explore deterioration of its strength and the release of impurities. The leachates in this test were composed of deionized water, 5% Na2SO4 solution, 5% NaCl solution, and a range of sulfuric acid solutions with pH values of 1.5, 3, and 5. After drying-wetting cycles, unconfined compressive strength (UCS), visual deterioration, porosity, microstructure and concentrations of phosphate and fluoride in the leachates were measured. The results showed that both saline and acidic solutions could lead to strength reduction of PG-based cemented backfill under different deterioration mechanisms. The mechanical damage of salinity was caused by micro-cracking and degradation of C–S–H. However, the H+ broke the backfill by dissolving hydration products, leaving the conjunctures between PG particles weakened. Furthermore, the environmental impact was investigated by measuring the concentration of phosphate and fluoride in the leachates. In acidic solutions, the release of phosphate and fluoride was greatly enhanced by H+. Compared to the great strength deterioration in saline leachates, the concentration of phosphate and fluoride were similar to that of deionized water, indicating that saline solutions had little impact on the release of hazardous impurities.

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“…With the mixing time extended to 240 min, the apparent viscosity gradually increased because of the cohesion of the hydration products. The mechanical properties testing results indicated that the compressive strength is proportional to the mixing time in the range of 5 to 60 min, while in the range of 60 to 240 min, the mechanical properties declined with the extension of mixing time due to the break of the hydration production skeleton [49].…”

Section: Cemented Paste Backfillmentioning

confidence: 98%

Low-Carbon Sustainable Composites from Waste Phosphogypsum and Their Environmental Impacts

et al. 2021

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Phosphogypsum (PG) is an industrial waste from the production of phosphoric acid and phosphate fertilizer. Disposal and landfill of PG pose significant environmental problems due to its hazardous components. Although many researchers have explored the possibility of PG recycling, challenges still exist before it can be high-effectively reused. In particular, a great deal of recent attention has been attracted to explore using PG as raw material to manufacture sustainable composites. The impurities movement, recycling efficiency, and environmental impacts have to be further investigated. This review article summarized the state of the art of the purification process, application areas, and the environmental impacts of PG waste. The main challenges and potential application approaches were discussed. This article is focused on reviewing the details of the PG reusing which benefits the readers on learning the knowledge from previous efforts. The main challenges of reusing PG were discussed from the chemical, physical, and materials perspectives.

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Effect of mixing time on the properties of phosphogypsum-based cemented backfill

Cited by 59 publications

References 42 publications

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Study on Rheological and Mechanical Properties of Aeolian Sand-Fly Ash-Based Filling Slurry

Durability Evaluation of Phosphogypsum-Based Cemented Backfill Through Drying-Wetting Cycles

Low-Carbon Sustainable Composites from Waste Phosphogypsum and Their Environmental Impacts

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