Study on the curing mechanism of cemented backfill materials prepared from sodium sulfate modified coal gasification slag

Yang, Piaoping; Suo, Yonglu; Qu, Huisheng; Xie, Geng; Zhang, Caixin; Deng, Shunchun

doi:10.1016/j.jobe.2022.105318

Cited by 21 publications

(4 citation statements)

References 49 publications

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“…C-S-H initially adsorbs the sulfate ion. When solid sulfate is consumed, the slope of thermal evolution increases and C3A hydration leads to a new exothermic peak [55][56][57][58].…”

Section: Hydration Exothermic Analysismentioning

confidence: 99%

Experimental Study on Early Strength and Hydration Heat of Spodumene Tailings Cemented Backfill Materials

et al. 2022

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Spodumene tailing is the associated solid waste of extracting lithium from spodumene. With the increase in the global demand for lithium resources, its emissions increase yearly, which will become a key factor restricting the economic development of the mining area. Mechanical and hydration reactions, as well as the microstructure of early CSTB, are studied under different tailings–cement ratios (TCR) and solid mass concentration (SC) conditions. The results show that the uniaxial compressive strength of early CSTB has a negative exponential correlation with the decrease in TCR and a positive correlation with the increase in SC: when the age of CSTB increases to 7 days, the strength increases with the rise in SC in an exponential function, and the sensitivity of strength to TCR is higher than that of SC. Compared to other tailings cemented backfill materials, the addition of spodumene tailings reduces the sulfate ion concentration and leads to a new exothermic peak (i.e., the third exothermic peak) for the hydration exotherm of CSTB. Additionally, with the increase in TCR or decrease in SC, the height of the third exothermic peak decreases and the occurrence time is advanced. At the same time, the duration of induction phase was prolonged, the period of acceleration phase was shortened, and the total amount of heat released was significantly increased. The decrease in TCR or the increase in SC led to the rise in the number of hydration products which can effectively fill the internal pores of CSTB, enhance its structural compactness, and increase its compressive strength. The above study reveals the influence of TCR and SC on the early strength, hydration characteristics, and microstructure of CSTB and provides an essential reference for the mix design of underground backfill spodumene tailings.

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“…C-S-H initially adsorbs the sulfate ion. When solid sulfate is consumed, the slope of thermal evolution increases and C3A hydration leads to a new exothermic peak [55][56][57][58].…”

Section: Hydration Exothermic Analysismentioning

confidence: 99%

Experimental Study on Early Strength and Hydration Heat of Spodumene Tailings Cemented Backfill Materials

et al. 2022

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“…According to the results, the synthetic use of coal gasification fine slag and coarse slag had a good effect on the fluidity and strength of the cement-based materials. Meanwhile, coal gasification slag modified by sodium sulfate could be used as cemented backfill materials, and the results showed that about 4% sodium sulfate had a good activating effect on modified coal gasification slag . There is little study on one-part geopolymer synthesis by alkali fusion from coal gasification slag.…”

Section: Introductionmentioning

confidence: 99%

“…Meanwhile, coal gasification slag modified by sodium sulfate could be used as cemented backfill materials, and the results showed that about 4% sodium sulfate had a good activating effect on modified coal gasification slag. 27 There is little study on one-part geopolymer synthesis by alkali fusion from coal gasification slag.…”

Section: Introductionmentioning

confidence: 99%

Effect of Alkali Fusion Methods on the Preparation of One-Part Geopolymer From Coal Gasification Slag

Chen,

Sasaki,

Tian

et al. 2023

ACS Omega

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This study investigated the one-part geopolymer synthesis by coal gasification slag through a calcination treatment. Two preparation methods, the traditional alkali fusion method (M-I) and the alkali fusion and modification method (M-II), were compared to illustrate the more suitable way for coal gasification slag-based one-part geopolymer (CGS-based geopolymer) synthesis. The reaction products and structure of the geopolymer were tested by XRD, FTIR, TG-DTG, and SEM. The results showed that the compressive strength of geopolymers prepared by M-I was raised as the NaOH amount increased, and the maximum compressive strength of geopolymers was achieved at 8.44 MPa. The low compressive strength suggested that M-I failed to be used for CGS-based geopolymer synthesis. When solid NaOH was selected for one-part geopolymer synthesis by M-II, the geopolymer possessed a compressive strength of 25.52 MPa and exhibited a well-combined and dense matrix. More Si and Al species in F-SH could be released for geopolymerization, and the coal gasification slag additive could be partially dissolved and act as the filler in the geopolymer matrix, which enhanced the geopolymerization degree. The M-II has been proven to be more suitable for preparing CGS-based geopolymers than the M-I.

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“…As coal power generation can produce a lot of fly ash, coal gasification also produces a lot of coal gasification fine ash. With the rapid development of the coal chemical industry, the emissions of CGFA exceed 33 million tons every year [19]. At present, the treatment of CGFA is mainly based on stacking and landfilling.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Properties of Coal Gasification Fly Ash and Pulverized Coal Fly Ash as Supplementary Cementitious Materials

Luo,

Jin

2023

Sustainability

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Using industrial waste as part of the raw material to produce cement-based materials is considered to be a sustainable cement and concrete materials production method. Coal gasification fly ash (hereafter CGFA) is a solid waste produced during the coal gasification process. Similar to pulverized coal fly ash (hereafter PCFA), it is also a kind of fly ash discharged from combustion coal furnaces. With the development of coal gasification technology, more and more CGFA needs to be treated. Based on the successful experience of PCFA as a supplementary cementitious material in cement-based materials, CGFA is used as a supplementary cementitious material in this paper. A comparison of the performance of two coal-based fly ashes as a supplementary cementitious material (hereafter SCM) was conducted. The effects of two fly ashes on the fluidity and strength of cement mortar were discussed, and the mechanism was analyzed from the mineral composition and morphology of hydration products. At the same time, the properties of CGFA and ultrafine CGFA (UFCGFA) as an SCM were compared. The results show that CGFA has more negative effects on the fluidity of cement mortar than PCFA. But it has a greater contribution to the strength of cement mortar than PCFA. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the active components of CGFA participate in the hydration reaction faster, showing a stronger pozzolanic reactivity than PCFA. Ultrafine treatment of CGFA not only improves the pozzolanic activity but also reduces the negative effect on the fluidity of cement mortar. The contribution of UFCGFA to the fluidity and strength of cement mortar can be greatly improved.

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Study on the curing mechanism of cemented backfill materials prepared from sodium sulfate modified coal gasification slag

Cited by 21 publications

References 49 publications

Experimental Study on Early Strength and Hydration Heat of Spodumene Tailings Cemented Backfill Materials

Experimental Study on Early Strength and Hydration Heat of Spodumene Tailings Cemented Backfill Materials

Effect of Alkali Fusion Methods on the Preparation of One-Part Geopolymer From Coal Gasification Slag

Comparison of the Properties of Coal Gasification Fly Ash and Pulverized Coal Fly Ash as Supplementary Cementitious Materials

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