Mechanical Performance of Confined Consolidation on the Strength Development of Cemented Paste Backfill

2019 ◽  
Vol 38 (2) ◽  
pp. 1097-1110
Author(s):  
Chao Yang ◽  
Peng Yang ◽  
Wen-sheng Lv ◽  
Zhi-kai Wang
Keyword(s):  
Mechanical Performance ◽  
Strength Development ◽  
Cemented Paste Backfill ◽  
Paste Backfill

scholarly journals Effects of Superplasticizer on the Hydration, Consistency, and Strength Development of Cemented Paste Backfill

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 381 ◽  
Author(s):  
Jian Zhang ◽  
Hongwei Deng ◽  
Abbas Taheri ◽  
Junren Deng ◽  
Bo Ke
Keyword(s):  
Underground Mines ◽  
Strength Development ◽  
Strength Increase ◽  
Strengthening Effect ◽  
Cemented Paste Backfill ◽  
Solid Concentration ◽  
Resonance System ◽  
Low Field ◽  
Binder Ratio ◽  
Paste Backfill

The strength and consistency of cemented paste backfill (CPB) are of key concerns in the stope stability and cost control for underground mines. It is common practice to use additives, such as superplasticizer, to improve the performance of CPB. This study mainly focuses on the effects of superplasticizer on the hydration, consistency, and strength of CPB. In this study, a polynaphtalene sulfonate was used as the superplasticizer. The binder is a mix of 33.3% ordinary Portland cement and 66.7% fly ash. The CPB specimens with a tailings-binder ratio of 3:1 and a solid concentration of 70% were then tested by a low field nuclear magnetic resonance system after different hydration times. Effects of polynaphtalene sulfonate on the hydration, fluidity, and strength were investigated. Results showed that the polynaphtalene sulfonate has a strong influence on short-duration hydration, which may contribute to the strength increase of CPB. It has been demonstrated that the polynaphtalene sulfonate improved the fluidity of the CPB mixture. With the increased dosage of polynaphtalene sulfonate, the slump increased. It was also found that the polynaphtalene sulfonate dosage has a negligible effect on the 1 day (d) strength while it has a strengthening effect on the 7 d, 14 d, and 28 d strength of CPB specimens.

scholarly journals Quicklime and Calcium Sulfoaluminate Cement Used as Mineral Accelerators to Improve the Properties of Cemented Paste Backfill with a High Volume of Fly Ash

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4018
Author(s):  
Hangxing Ding ◽  
Shiyu Zhang
Keyword(s):  
Fly Ash ◽  
Co2 Emission ◽  
Mechanical Performance ◽  
High Volume ◽  
Hydration Heat ◽  
Cemented Paste Backfill ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Paste Backfill ◽  
Different Doses

In order to reduce the CO2 emission and cost of binders used in cemented paste backfill (CPB) technology, new blended binders with a large amount of fly ash (FA) were fabricated. Different doses of quicklime and calcium sulfoaluminate cement (CṠA) were used as mineral accelerators to improve the early workability of CPB. The effects of CṠA and quicklime on flowability, compressive strength, pore structure, hydration heat, and hydration evolution were investigated experimentally. The results showed that the addition of quicklime and CṠA reduced the spread diameter of the fresh backfill and improved the mechanical performance of the hardened CPB. With increasing quicklime and CṠA, the cumulative hydration heat of the blended binder distinctly increased in the first 6 h. CṠA improved the initial hydration by increasing the reactivity, and quicklime increased the hydration rate by activating FA. The blended binder (15% quicklime + 10% CṠA) with the lowest CO2 emission and cost had potential application in filling technology.

scholarly journals Effect of Gypsum Addition on the Mechanical and Microstructural Performance of Sulphide-Rich Cemented Paste Backfill

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 283
Author(s):  
Yu Tang ◽  
Juanrong Zheng ◽  
Lijie Guo ◽  
Yue Zhao
Keyword(s):  
Mechanical Performance ◽  
Early Stage ◽  
Mineralogical Composition ◽  
Strength Loss ◽  
Cemented Paste Backfill ◽  
X Ray Diffraction ◽  
Granulated Blast Furnace Slag ◽  
Paste Backfill ◽  
Sulphide Tailings ◽  
Activated Slag

The present study investigates the effect of β-hemihydrate gypsum (HG) dosages on the mechanical and microstructural performance of cemented paste backfill (CPB) produced from sulphide-rich mine tailings using NaOH-activated slag (NAS) as the major binder. X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were carried out to elucidate the mineralogical composition and microstructure of NAS-HG-CPB samples. The results illustrate that the main hydration products of NAS-HG-CPB from sulphide-rich tailings are crystalline (CaSO4•2H2O and ettringite (AFt), 3CaO•Al2O3•3CaSO4•32H2O) and amorphous. The results also show that the 28 d unconfined compressive strength (UCS) of CPB with 30 wt. % HG replacing NAS increased by 52% compared to the UCS of CPB containing no HG, and both have stable long-stage (180 d) UCS (i.e., no strength loss). Excess HG addition (≧50 wt. %) reduced the early-stage (≦28 d) UCS of NAS-HG-CPB and led to unstable long-stage (180 d) UCS by the formation of secondary gypsum. The use of 30 wt. % HG replacing NAS in NAS-HG-CPB accelerates the hydration process of ground granulated blast furnace slag (GGBS) in the alkaline solution by forming ettringite (AFt), leading to the denser microstructure and improved mechanical performance in comparison with CPB containing no HG. The NAS-HG binder with low dosages of HG (≦30 wt. %) will be a promising binder for stabilising sulphide and non-sulphide tailings and CPB production.

scholarly journals Mechanical Transformation of Fly Ash toward Its Utilization in Cemented Paste Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Haijun Wang ◽  
Yun Duan
Keyword(s):  
Fly Ash ◽  
Strength Development ◽  
Sustainable Utilization ◽  
Cemented Paste Backfill ◽  
Efficient Technology ◽  
Pozzolanic Reactivity ◽  
Wet Grinding ◽  
Paste Backfill ◽  
Mechanical Transformation ◽  
Wet Ground

Fly ash (FA) showed low reactivity when being used to prepare the binder for cemented paste backfill (CPB). In the present work, wet-grinding treatment was used to increase the pozzolanic reactivity of FA and promote its sustainable utilization. The results showed that wet-grinding could be a suitable and efficient technology for FA pretreatment. Wet-grinding strongly modified the structure of FA by decreasing the crystalline phase content and the binding energy of Si 2p and Al 2p, contributing to the increase in pozzolanic reactivity of FA. The performance of CPB samples prepared by wet-ground FA was then optimized. This was reflected by the acceleration in the sample setting and increase in the strength development. The compressive strength of the CPB samples prepared by wet-ground FA for 120 min was increased by around 40% after curing for 28 d compared with the control samples.

scholarly journals Application of Slag–Cement and Fly Ash for Strength Development in Cemented Paste Backfills

Minerals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 22 ◽  
Author(s):  
Yue Zhao ◽  
Amin Soltani ◽  
Abbas Taheri ◽  
Murat Karakus ◽  
An Deng
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Blended Cement ◽  
Dry Mass ◽  
Strength Development ◽  
Unconfined Compression ◽  
Strength Criteria ◽  
Copper Gold ◽  
Paste Backfill ◽  
Solids Content

The present study investigates the combined capacity of a newly developed slag-blended cement (MC) and fly ash (FA) as a sustainable solution towards improving the mechanical performance of the cemented paste backfill (CPB) system of a copper-gold underground mine. A total of thirteen mix designs consisting of three MC-treated and ten MC + FA-treated blends were examined. Samples were prepared with a solids content of 77% (by total mass), and were allowed to cure for 7, 14, 28, 56 and 128 days prior unconfined compression testing. Scanning electron microscopy (SEM) studies were also carried out to observe the evolution of fabric in response to MC and MC + FA amendments. The greater the MC content and/or the longer the curing period, the higher the developed strength, toughness and stiffness. The exhibited improvements, however, were only notable up to 56 days of curing, beyond of which the effect of curing was marginal. The performance of 4% Portland cement or PC (by total dry mass) was found to be similar to that of 1.5% MC, while the higher MC inclusions of 2.5% and 3%, though lower in terms of binder content, unanimously outperformed 4% PC. The use of FA alongside MC improved the bonding/connection interface generated between the tailings aggregates, and thus led to improved mechanical performance compared with similar MC inclusions containing no FA. Common strength criteria for CPBs were considered to assess the applicability of the newly introduced MC and MC + FA mix designs. The mix designs “3% MC” and “2.5% MC + 2–2.5% FA” satisfied the 700 kPa strength threshold required for stope stability, and thus were deemed as optimum design choices.

Effect of specimen composition on the strength development in cemented paste backfill

2006 ◽  
Vol 43 (3) ◽  
pp. 310-324 ◽  
Author(s):  
Katherine Klein ◽  
Dragana Simon
Keyword(s):  
Compressive Strength ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Unconfined Compressive Strength ◽  
Pore Fluid ◽  
Strength Development ◽  
Cemented Paste Backfill ◽  
Pore Fluid Chemistry ◽  
Paste Backfill

This paper focuses on monitoring setting and strength development in cemented paste backfill (CPB). The composition of the paste is altered to study the effects of binder type and content, selected chemical admixtures (superplasticizers), mineral additives (e.g., fly ash), and pore fluid chemistry (e.g., ionic concentration and pH) on these properties. The three main techniques utilized are shear wave velocity measurements, penetration tests (e.g., Vicat needle tests), and unconfined compressive strength tests. All of these tests are sensitive to changes in the paste composition. The effect of the pore fluid chemistry and the chemical additives on the CPB properties depends on the ion type and concentration and the chemical composition of the superplasticizers. The shear wave velocity in both uncemented and cemented pastes increases with time as a result of self-weight consolidation, capillary forces, and cementation (the precipitation of ions in uncemented tailings pastes or cement hydration in cemented tailings pastes).Key words: cemented paste backfill, shear wave velocity, setting, unconfined compressive strength.

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