Preparation and microstructure of fly ash geopolymer paste backfill material

Sun, Qi; Tian, Shuai; Sun, Qingwei; Li, Bing; Cai, Chunhua; Xia, Yajie; Wei, Xing; Mu, Qianwen

doi:10.1016/j.jclepro.2019.03.310

Cited by 151 publications

(45 citation statements)

References 29 publications

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“…Moreover, with the increase of fly ash particles, aeolian sand particles are gradually replaced by finer fly ash particles. The fly ash particles are evenly distributed in the basic phase of the filling slurry; because of its fine particles and large specific surface area, the particle surface easily absorbs more water [34], which plays the role of "water reducing agent", making the slurry thicker, and helps to improve the uniformity of the fresh and hardened paste [35]. At the same time, the fine fly ash particles filled in the capillary pores of the slurry, reduce the porosity and makes the structure compact.…”

Section: Resultsmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

“…The hydration products are: calcium hydroxide (C-H), water calcium aluminate (C-A-H), calcium ferric aluminate (C-S-F-H), etc. [34]. Among these hydration products, C-H is an active activator of fly ash in the cement environment, and it is in the form of flake crystals.…”

Section: Mechanical Test Resultsmentioning

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 this study, a slump test of the CPB mixture was conducted according to the International Organization for Standardization(ISO) standard: "Testing of concrete Part 2: Properties of fresh concrete(ISO 1920-2)". [24] According to the literature [16], the optimal slump of CPB mixtures is approximately 200 mm.…”

Section: Experimental Methodsmentioning

confidence: 99%

Strengthening Behavior of Cemented Paste Backfill Using Alkali-Activated Slag Binders and Bottom Ash Based on the Response Surface Method

Sun

Wei

et al. 2020

Materials

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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.

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“…The tailings slurry from plants contains a large number of fine particles and mineral processing wastewater. Mature fine particles hardly settle in suspensions to form a high-concentration underflow in the gravity thickening process [8,9]. The settlement cylinder is 10 cm in diameter and 50 cm in height, with a four-picket rake.…”

Section: Introductionmentioning

confidence: 99%

Pore Connectivity and Dewatering Mechanism of Tailings Bed in Raking Deep-Cone Thickener Process

et al. 2020

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Paste and thickened tailings (PTT) technology can improve the utilization and management of tailings from processing plants. The pore size distribution (PSD) and microstructure evolution affected by the rake shear in thickening tailings beds are essential to produce a high-density tailings underflow. Continuous thickening and computed tomography (CT) scanning tests were conducted to study the PSD with and without shear. The pore morphology was studied to reveal the shearing-dewatering performance of the tailings bed. The results show that at a flocculant solution concentration of 0.01 wt % and a feed slurry concentration of 10 wt%, the underflow concentration with and without shear can reach 58.5 wt %and 55.8 wt %, respectively. The CT image reconstruction models demonstrated that the porosity of the sheared tailings bed increased with the bed height. When the bed height increased from 2.5 to 10 cm, the porosity increased from 35.1% to 41.9%, the pore fractal dimension increased from the range 1.8–1.95 to the range 2.1–2.15, and the pore quantity decreased by 21.39%. The average pore volume increased with increasing height by 13.93%, 16.57% and 12.07%. The pore structure became more complex with the bed height, and the connectivity between pores increased to form water-flow channels, which were beneficial to the drainage of sealed water.

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Preparation and microstructure of fly ash geopolymer paste backfill material

Cited by 151 publications

References 29 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

Strengthening Behavior of Cemented Paste Backfill Using Alkali-Activated Slag Binders and Bottom Ash Based on the Response Surface Method

Pore Connectivity and Dewatering Mechanism of Tailings Bed in Raking Deep-Cone Thickener Process

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