scholarly journals Coupled Effect of Curing Temperature and Moisture on THM Behavior of Cemented Paste Backfill

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Wenyuan Xu ◽  
Runkang Zhao ◽  
Xiaocong Yang ◽  
Lijie Guo ◽  
Chaowu Xie ◽  
...  
Keyword(s):  
Model Simulation ◽  
Cost Effective ◽  
Curing Temperature ◽  
Underground Mines ◽  
Cemented Paste Backfill ◽  
Waste Discharge ◽  
Stress Strain Relation ◽  
Paste Backfill ◽  
Simulation And Experiment ◽  
As Stress

Cemented paste backfill (CPB), a mixture of tailings, binder, and water, is widely and continually utilized in underground mines for subsidence control and disposal of surface hazardous waste discharge. The mechanical strength of CPB, which is the key for the backfill structure to play the role of supporting overlying roof and controlling subsidence, is governed by complex factors (thermal, hydraulic, and mechanical loads), particularly strongly affected by the environmental conditions, such as ambient temperature and humidity. Thus, it is crucial to understand and assess the response of CPB subjected to the loads mentioned above, so as to better ascertain its performance and obtain a cost-effective, safe, and stable CPB structure. Accordingly, a coupled THM model is developed to describe and analyze the performance of CPB. Comparisons between model simulation and experiment data prove the capability of the developed model in predicting the evolutions of temperature and internal relative humidity, as well as stress-strain relation of CPB. The obtained results indicate that all these properties are significantly affected by ambient humidity and temperature.

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 Insight into Saturated Hydraulic Conductivity of Cemented Paste Backfill Containing Polycarboxylate Ether-Based Superplasticizer

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 93
Author(s):  
Sada Haruna ◽  
Mamadou Fall
Keyword(s):  
Hydraulic Conductivity ◽  
Environmental Performance ◽  
Mining Industry ◽  
Design Criterion ◽  
Saturated Hydraulic Conductivity ◽  
Curing Temperature ◽  
Partial Replacement ◽  
Cemented Paste Backfill ◽  
Curing Conditions ◽  
Paste Backfill

Recycling of tailings in the form of cemented paste backfill (CPB) is a widely adopted practice in the mining industry. Environmental performance is an important design criterion of CPB structures. This environmental performance of CPB is strongly influenced by its saturated hydraulic conductivity (permeability). Superplasticizers are usually added to improve flowability, but there is a limited understanding of their influence on the hydraulic properties of the CPB. This paper presents new experimental results on the variations of the hydraulic conductivity of CPB containing polycarboxylate-based superplasticizer with different compositions and curing conditions. It is found that the hydraulic conductivity of the CPB decreases with the addition of superplasticizer, which is beneficial to its environmental performance. The reduction is largely attributable to the influence of the ether-based superplasticizer on particles mobility and cement hydration. Moreover, both curing temperature and time have correlations with the hydraulic conductivity of CPB containing superplasticizer. In addition, the presence of sulfate and partial replacement of PCI with blast furnace slag reduces the hydraulic conductivity. The variations are mainly due to the changes in the pore structure of the CPB. The new results discussed in this manuscript will contribute to the design of more environmental-friendly CPBs, which is essential for sustainable mining.

scholarly journals Cost-Effective Treatment of Hemihydrate Phosphogypsum and Phosphorous Slag as Cemented Paste Backfill Material for Underground Mine

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Xilong Xue ◽  
Yuxian Ke ◽  
Qian Kang ◽  
Qinli Zhang ◽  
Chongchun Xiao ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Cost Effective ◽  
Strength Loss ◽  
Quality Standard ◽  
Cementitious Materials ◽  
Cemented Paste Backfill ◽  
Technical Requirements ◽  
Cost Effective Treatment ◽  
Paste Backfill ◽  
Phosphorous Slag

The environmental pollution caused by the discharge of phosphogypsum (PG) and phosphorous slag (PS) is a common issue for all countries. In order to fully utilize hemihydrate PG (HPG) and PS and treat goafs in mines, the HPG and PS were used as cementitious materials for cemented paste backfill (CPB). The physical and chemical properties of HPG and PS were first analyzed, and then, the characteristics of CPB were evaluated through fluidity tests, gas detection, uniaxial compressive strength (UCS) tests, bleeding tests, and scanning electron microscopy (SEM). After this, the underground environmental impact of CPB-based HPG and PS was investigated through a dynamic leachability experiment. The results show that (1) the UCS of CPB increases with the increase of the HPG content and mass fraction, and the addition of 3% quicklime can eliminate CO2, H2S, and SO2 generated from the slurry of CPB-based HPG-PS; (2) the addition of 3% quicklime and 5% cement to the HPG-PS mixtures can offset the strength loss of CPB in the late curing stage; (3) the UCS of the recommended specimen reaches 1.15–3.32 MPa after curing from 7 to 28 days, with their slump values varying from 15 mm to 26 mm, and the bleeding rates between 0.87% and 1.15%, which can meet the technical requirements of mining methods; (4) the UCS of CPB is the result of the cohydration reaction of hemihydrate gypsum (HG) in HPG and active Al2O3 and SiO2 in PS; and (5) the leaching indexes meet Category IV of the Chinese Groundwater Quality Standard (DZ/T 0290-2015). The results of this investigation provide a cost-efficient way for the efficient mining of phosphate resources and the comprehensive utilization of HPG and PS.

In situ measurements of cemented paste backfill at the Cayeli Mine

2012 ◽  
Vol 49 (7) ◽  
pp. 755-772 ◽  
Author(s):  
B.D. Thompson ◽  
W.F. Bawden ◽  
M.W. Grabinsky
Keyword(s):  
Cement Hydration ◽  
Time Pressure ◽  
Binder Content ◽  
Underground Mines ◽  
Cemented Paste Backfill ◽  
In Situ Data ◽  
Field Instrumentation ◽  
Rise Rate ◽  
Paste Backfill

Cemented paste backfill (CPB) is accepted as the optimal backfilling material for many underground mines. However, the lack of in-stope backfill pressure data poses fundamental problems from both operational and research standpoints. In response to the requirement for in situ data, a comprehensive field instrumentation project has been conducted. Results are presented here for two stopes at the Cayeli Mine, where geotechnical instruments were installed at the barricades and throughout the stopes. Measurements from a large (slow rise rate) stope with high binder content CPB demonstrated a rapid departure from hydrostatic loading, resulting in relatively low barricade pressures. Conversely, data from a smaller (fast rise rate) stope with lower binder content CPB demonstrated that when cement hydration is retarded, high barricade pressures occur. These examples illustrate the relationship between CPB rise rate and the moderating effect of cement hydration on in situ pressures, which ultimately control barricade pressures. Once CPB gains shear strength, arching of pressures occurs. In situ pressures were reduced with proximity to stope walls and further, under stope access brows, demonstrating that barricade location influences barricade loads. The application of real-time pressure monitoring of pastefill barricades has been demonstrated as an important tool in optimizing operational backfilling efficiency.

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