scholarly journals Effect of the Initial Air Content in Fresh Slurry on the Compressive Strength of Hardened Cemented Paste Backfill

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Youzhi Zhang ◽  
Deqing Gan ◽  
Zhenlin Xue ◽  
Xun Chen ◽  
Sheng Hu
Keyword(s):  
Compressive Strength ◽  
Sodium Dodecyl ◽  
Contact Structures ◽  
Cemented Paste Backfill ◽  
Mining Method ◽  
Force Analysis ◽  
Air Content ◽  
Ground Pressure ◽  
Paste Backfill ◽  
The Mathematical Model

Filling mining method can dispose of the tailings into filling slurry, which can be transported to the stope through pipelines to manage the ground pressure and protect the environment. To improve the flowability of filling slurry, additives are used more and more widely. However, some additives can increase the air content in the slurry. The air in the slurry will become pores in the hardened cemented paste backfill (CPB). Therefore, it is necessary to explore the influence of initial air content in fresh slurry on the compressive strength of CPB. In this paper, sodium dodecyl sulfate (SDS) was used to regulate the air content in the fresh slurry. After measuring the initial air content, the slurry was made into test blocks. Then, the uniaxial compressive strength (UCS) of CPB at 28 d age was tested, and the distribution of CPB microscopic pores was observed by scanning electron microscope (SEM). The results show that as the initial air content in fresh slurry increases, the UCS of CPB first increases and then decreases. Before the initial air content in fresh slurry is 6.03%, the CPB pores distribution is relatively uniform. However, after exceeding this value, “discontinuous contact” structures, pore groups, and macropores occur in CPB. Through the CPB microscopic force analysis, the mathematical model describing the effect of initial air content on UCS of CPB should be a combination of logarithmic function and quadratic polynomial. This work can provide a supplement to the theory of CPB strength.

scholarly journals 3D Numerical Modelling of the Application of Cemented Paste Backfill on Displacements around Strip Excavations

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7750
Author(s):  
Krzysztof Skrzypkowski
Keyword(s):  
Numerical Modeling ◽  
Cement Content ◽  
Cemented Paste Backfill ◽  
Mining Method ◽  
3D Numerical Modeling ◽  
Compressibility Coefficient ◽  
3D Numerical Modelling ◽  
Paste Backfill ◽  
First Time ◽  
Cylindrical Samples

This article presents laboratory and spatial numerical modeling of cemented paste backfill. The first part of the research concerned laboratory tests of a mixture of sand, water, and variable cement content (5%, 10%, and 15%). The density and curing time of the mixture were determined. Moreover, cylindrical samples with a diameter of 46 mm and a height of 92 mm were constructed, for which compressive and tensile strength were calculated after one, two, three, and four weeks. The second part of the research concerned 3D numerical modeling with the use of RS3 software. For the exploitation field with dimensions of 65 m × 65 m, a strip-mining method was designed. The main objective of the research was to determine the changes in displacements around the haulage room and transportation roadway located in the immediate vicinity of the exploitation field. For the first time in numerical modeling, a two-sided strip method was used for the four stages of mining the ore deposit where the post-mining space was filled with a cemented paste backfill. Based on this research, the compressibility coefficient was determined.

scholarly journals Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 707 ◽  
Author(s):  
Jingping Qiu ◽  
Yingliang Zhao ◽  
Hui Long ◽  
Zhenbang Guo ◽  
Jun Xing ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Orthogonal Experiment ◽  
Solid Content ◽  
Raw Material ◽  
Cemented Paste Backfill ◽  
Low Carbon ◽  
Optimum Parameters ◽  
Paste Backfill ◽  
Activated Slag ◽  
Furnace Slag

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R2 values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill.

scholarly journals Ensemble Learning Regression for Estimating Unconfined Compressive Strength of Cemented Paste Backfill

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 72125-72133 ◽  
Author(s):  
Xiang Lu ◽  
Wei Zhou ◽  
Xiaohua Ding ◽  
Xuyang Shi ◽  
Boyu Luan ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Ensemble Learning ◽  
Unconfined Compressive Strength ◽  
Cemented Paste Backfill ◽  
Paste Backfill

scholarly journals Effects of Doping Glass Fibers on the Early Strength of Sand-Based Cemented Paste Backfill for Solid Wastes Disposal in a Coal Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Cunli Zhu ◽  
Jixiong Zhang ◽  
Zhou Nan ◽  
Meng Li ◽  
Zhiwei He
Keyword(s):  
Compressive Strength ◽  
Mechanical Strength ◽  
Glass Fibers ◽  
Critical Issue ◽  
Control Group ◽  
Cemented Paste Backfill ◽  
Blank Control Group ◽  
Paste Backfill ◽  
Research Findings ◽  
Doped Glass

The mechanical strength of cemented paste backfill (CPB), especially the early compressive strength, is crucial for controlling the overlying rock movement. Therefore, improving the early compressive strength of CPB is a critical issue. In this study, the doped glass fibers’ effect on the macroscopic mechanical strength and microstructural features of the sand-based CPB (SCPB) with different curing ages was analyzed. The macroscopic properties and the microstructure of SCPB were characterized experimentally and analyzed via scanning electron microscopy. The results showed that slump sizes of SCPB specimens without and with doped glass fibers were 269 and 209 mm. Thus, doped glass fibers inhibited the SCPB transportability and significantly improved its early compressive strength. At curing ages of 1 d and 3 d, the compressive strength of SCPB specimens doped with glass fibers was improved by 679 and 278%, respectively, compared to the blank control group. As the curing age increased, the compressive strength improvement of the SCPB doped with glass fibers was gradually saturated. Finally, the correlation between macroscopic and microscopic properties of SCPB specimens was analyzed comparatively. Thus, the mechanism of doped glass fibers’ influencing the early compressive strength of the SCPB was revealed. The research findings provide theoretical guidance for improving the SCPB early compressive strength at the mining site with the CPB mining technique.

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