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.

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 Hydrochloric Acid Pretreatment of Different Types of Rice Husk Ash Influence on the Properties of Cement Paste

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1524 ◽  
Author(s):  
Jing Liu ◽  
Chunyan Xie ◽  
Chao Fu ◽  
Xiuli Wei ◽  
Dake Wu
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Cement Paste ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Control Sample ◽  
Control Group ◽  
Rice Husks ◽  
Acid Pretreatment ◽  
Blank Control Group

When properly processed, rice husk ash (RHA) comprises a large amount of SiO2, which exhibits a high pozzolanic activity and acts as a good building filler. In this paper, the effects of rice husk ash content, acid pretreatment, and production regions on the compressive and flexural properties and water absorption of a cement paste were studied. The experimental results showed that the compressive strength of the rice husk ash was the highest with a 10% content level, which was about 16.22% higher than that of the control sample. The rice husk after acid pretreatment displayed a higher strength than that of the sample without the acid treatment, and the rice husk from the Inner Mongolia region indicated a higher strength than that from the Guangdong province. However, the flexural strength of each group was not significantly different from that of the blank control group. The trend observed for the water absorption was similar to that of the compressive strength. The variation in the RHA proportions had the greatest influence on the properties of the paste specimens, followed by the acid pretreatments of the rice husks. The production regions of the rice husks indicated the least influence.

scholarly journals Effect of Doped Glass Fibers on Tensile and Shear Strengths and Microstructure of the Modified Shotcrete Material: An Experimental Study and a Simplified 2D Model

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1053
Author(s):  
Cunli Zhu ◽  
Nan Zhou ◽  
Yaben Guo ◽  
Meng Li ◽  
Qiangqiang Cheng
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Glass Fibers ◽  
Testing Machine ◽  
Mechanical Analysis ◽  
Sand Fly ◽  
Tensile Testing Machine ◽  
Cross Sectional ◽  
Research Findings ◽  
Doped Glass

Shotcrete material has found extensive applications as a reinforcing material in the engineering sector. This study examined the effect of doped glass fibers on the mechanical performance of the modified shotcrete material composed of aeolian sand, fly ash, cement, quicklime, and doped glass fibers. Its tensile and shear strengths values were experimentally determined via a WAW-1000D computerized hydraulic universal tensile testing machine. Its microstructure was analyzed via a size analyzer, scanning electron microscope (SEM), and X-ray diffractometer (XRD). A 2D simplified mechanical model was elaborated to reflect the influence mechanism of the doped glass fibers on the mechanical performance of the modified shotcrete material. The experimental and mechanical analysis results indicated that, at the macroscopic scale, the experimental tensile and shear strengths of the shotcrete material doped with glass fibers were significantly higher than those of the undoped shotcrete material (by up to 310% and 596%, respectively). These results were in concert with the proposed model predictions, where the compound stresses in the shotcrete material were derived as the sum of the stress borne by the shotcrete material itself and the bridging stress exerted by the glass fibers. At the microscopic scale, SEM observations also revealed that the glass fibers were intertwined with each other and tightly enveloped by the shotcrete material particles within the modified shotcrete specimens, connecting the particles of different components into a whole and improving the overall mechanical strength. In addition, the relationships of the compound stress of the shotcrete material vs. embedment length, embedment angle, and cross-sectional area of the glass fibers were established. The research findings are considered instrumental in clarifying the mechanism by which the glass fibers influence the mechanical performance of shotcrete materials and optimize their solid waste (fly ash and quicklime) utilization.

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 Prediction of Mechanical Strength Based on Deep Learning Using the Scanning Electron Image of Microscopic Cemented Paste Backfill

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Xuebin Qin ◽  
Shifu Cui ◽  
Lang Liu ◽  
Pai Wang ◽  
Mei Wang ◽  
...  
Keyword(s):  
Deep Learning ◽  
Mechanical Strength ◽  
Mechanical Response ◽  
Cemented Paste Backfill ◽  
Sem Images ◽  
Important Indicator ◽  
Sem Image ◽  
Paste Backfill ◽  
The Difference ◽  
Scanning Electron

The mechanical strength of cemented backfill is an important indicator in mining filling. To study the nonlinear relationship between cemented paste backfill (CPB) and mechanical response, a deep learning technique is employed to establish the end-to-end mapping relationship between the scanning electron microscope (SEM) images and mechanical strength. A seven-layer convolution neural network is set up in the experiment, and the relationship between the SEM image and mechanical strength is established. In addition, the difference between the measured and predicted values is calculated and the mean and variance of the error are analyzed. The average accuracy of the mechanical strength prediction is found to be 8.28%. Thus, the proposed method provides a new technique for the quantitative analysis of mechanical strength of microscale CPB.

Sign in / Sign up

Export Citation Format

Share Document