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Yang P, Liu L, Suo Y, Qu H, Xie G, Zhang C, Deng S, Lv Y. Investigating the synergistic effects of magnesia-coal slag based solid waste cementitious materials and its basic characteristics as a backfill material. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 880:163209. [PMID: 37001664 DOI: 10.1016/j.scitotenv.2023.163209] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 03/18/2023] [Accepted: 03/28/2023] [Indexed: 05/27/2023]
Abstract
Applying solid waste resources as backfill material can reduce both the cost of backfill and the environmental problems caused by solid waste landfills. In this paper, the synergistic reaction effects of solid waste modified magnesia slag (MMS), coal gasification slag (CGS), and desulfurized gypsum (DG) as magnesium-coal slag based cementitious materials (MCC) and their preliminary feasibility as mining cementitious materials in synergy with coal gangue for the preparation of backfill materials are investigated. The results show that the order of the compressive strength of the cementitious systems is ternary system > binary system > monolithic system, which proves the existence of synergistic effect among MMS, CGS, and DG and determines the optimal dosing of each raw material in the ternary system. At early ages, the physical effect of CGS and the chemical effect of DG in the ternary system can promote the hydration reaction of MMS, but the synergistic effect between the three is weak; At later ages, a synergistic effect occurred among silica-aluminate depolymerization in CGS, dissolved sulfate from DG and hydration products from MMS, which promoted the production of more hydration products calcium-silicate(aluminum)-hydrate (C-S(A)-H) and AFt, and improved the compressive strength. In addition, the strength, fluidity and leaching of the backfill material prepared by MCC in collaboration with coal gangue can meet the preliminary feasibility for mine backfill. In the present work, the full solid waste MCC is developed to completely replace cement and use it to prepare backfill materials, which is of great importance to the comprehensive utilization of bulk solid waste, the reduction of backfill costs, and the enhancement of the economic and ecological interests of mines.
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Affiliation(s)
- Pan Yang
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
| | - Lang Liu
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China; Key Laboratory of Western Mines and Hazards Prevention, Ministry of Education of China, Xi'an 710054, China.
| | - Yonglu Suo
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China; Key Laboratory of Western Mines and Hazards Prevention, Ministry of Education of China, Xi'an 710054, China
| | - Huisheng Qu
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China
| | - Geng Xie
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China
| | - Caixin Zhang
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
| | - Shunchun Deng
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
| | - Yin Lv
- Energy School, Xi'an University of Science and Technology, Xi'an 710054, China.
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Ren Z, Zhao W, Wang J, Zhang J, Chen L, Li Y. Multi-Response Optimization of High-Performance Low-pH Grouting Materials by Using Taguchi-Based Grey Relational Analysis. MATERIALS (BASEL, SWITZERLAND) 2023; 16:ma16103891. [PMID: 37241518 DOI: 10.3390/ma16103891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/06/2023] [Accepted: 05/18/2023] [Indexed: 05/28/2023]
Abstract
The most accepted approach to sealing in high-level radioactive waste repositories (HLRWs) is to develop a low-pH grouting material with a pH of the pore solution of less than 11. Currently, the most widely used binary low-pH grouting material is MCSF64, which comprises 60% microfine cement (MC) and 40% silica fume (SF). In this study, a high-performance MCSF64-based grouting material was developed by incorporating naphthalene superplasticizer (NSP), aluminum sulfate (AS), and united expansion agent (UEA) to enhance the slurry's shear strength, compressive strength, and hydration process. Orthogonal experiments were conducted to measure the flow time, yield stress, plastic viscosity, initial setting time, shear strength, and compressive strength of the MCSF64-based slurry, and the optimal mix proportion was determined using the Taguchi-Grey relational analysis method. The pH variation of the pore solution, shrinkage/expansion, and hydration products of the optimal hardened slurry were evaluated using simplified ex-situ leaching (S-ESL), a length comparometer, and scanning electron microscopy (SEM), respectively. The results demonstrate that the Bingham model effectively predicted the rheological properties of the MCSF64-based slurry. The optimum ratio for the MCSF64-based slurry was water/binder (W/B) ratio of 1.4, and the contents of NSP, AS and UEA by mass of binder were 1.9%, 3.6% and 4.8%, respectively. The optimal mix exhibited a pH value below 11 after curing for 120 days. The addition of AS and UEA facilitated hydration, shortened the initial setting time, improved early shear strength, and enhanced the expansion ability of the optimal mix under water curing conditions.
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Affiliation(s)
- Zengzeng Ren
- State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resource and Hydropower Research, Beijing 100038, China
| | - Weiquan Zhao
- State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resource and Hydropower Research, Beijing 100038, China
| | - Ju Wang
- Beijing Research Institute of Uranium Geology, Beijing 100029, China
- CAEA Innovation Center for Geological Disposal of High-Level Radioactive Waste, Beijing 100029, China
| | - Jinjie Zhang
- State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resource and Hydropower Research, Beijing 100038, China
| | - Liang Chen
- Beijing Research Institute of Uranium Geology, Beijing 100029, China
- CAEA Innovation Center for Geological Disposal of High-Level Radioactive Waste, Beijing 100029, China
| | - Yonghui Li
- State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resource and Hydropower Research, Beijing 100038, China
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Liu J, Yan C, Li J, Zhang J, Liu S. Investigation on the Mechanical Properties and Strengthening Mechanism of Solid-Waste-Sulfur-Based Cementitious Composites. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1203. [PMID: 36770210 PMCID: PMC9920474 DOI: 10.3390/ma16031203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/04/2023] [Accepted: 01/20/2023] [Indexed: 06/18/2023]
Abstract
This research used waste ceramic powder (CP) to replace aggregate, fly ash (FA) as filler, and combined them with sulfur to prepare composite cementitious materials. The variations of the mechanical properties with the aggregate proportions (aggregate mass/total mass) of 65%, 70%, and 75%, and the FA contents (FA mass/aggregate and filler mass) of 0%, 10%, 20%, 30%, 40%, and 50% were studied. The correlation evaluation model of sulfur content, CP content, FA content, and mechanical properties was established using the gray correlation theory, and the comprehensive mechanical property evaluation model was established as the foundation of the entropy method. Finally, the optimum proportion of the solid-waste-sulfur-based cementitious composites was determined. Results showed that, without FA, the CP increased from 65% to 75% and the comprehensive mechanical properties of the specimen increased by 60.53%. After FA was added, the peak point of the comprehensive mechanical properties appeared in group S75F10, which was 0.9210. During the hardening of the cementitious material, sulfur was mainly used as a binder, CP played the role of skeleton and part of the filler, whereas, as a crystal nucleus, the FA promoted the transformation of the sulfur crystals. Both the CP and FA can reduce the porosity of the specimen to a certain extent and have potential defect repair ability, thus densifying the matrix and improving the strength. When the proportion of sulfur: CP: FA is 1:2.7:0.3, the flexural (FS), compressive (CS), and splitting tensile (STS) strengths of the specimen are 14.8, 86.2, and 6.8 MPa, respectively. The flexural (FCR) and tensile (TCR) compression ratios are 0.172 and 0.079, respectively.
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Affiliation(s)
- Jiaxin Liu
- School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
| | - Changwang Yan
- School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
- School of Mining, Inner Mongolia University of Technology, Hohhot 010051, China
- Engineering Research Center of Inner Mongolia Autonomous Region for Ecological Building Materials and Assembly Structure, Hohhot 010051, China
| | - Jie Li
- School of Mining, Inner Mongolia University of Technology, Hohhot 010051, China
- Engineering Research Center of Inner Mongolia Autonomous Region for Ecological Building Materials and Assembly Structure, Hohhot 010051, China
| | - Ju Zhang
- School of Mining, Inner Mongolia University of Technology, Hohhot 010051, China
- Engineering Research Center of Inner Mongolia Autonomous Region for Ecological Building Materials and Assembly Structure, Hohhot 010051, China
| | - Shuguang Liu
- School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
- School of Mining, Inner Mongolia University of Technology, Hohhot 010051, China
- Engineering Research Center of Inner Mongolia Autonomous Region for Ecological Building Materials and Assembly Structure, Hohhot 010051, China
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Liang C, Xing Y, Hou X. Mechanical Property Evaluation and Prediction of Cementing Composites Blended with MK and UFA under High-Temperature Steam Curing. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6956. [PMID: 36234298 PMCID: PMC9573449 DOI: 10.3390/ma15196956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/01/2022] [Accepted: 10/02/2022] [Indexed: 06/16/2023]
Abstract
In this paper, the influence of the substitution rate of metakaolin (MK) and ultrafine fly ash (UFA) on the hydration degree, the micromechanical properties, the pore size distribution, and the corresponding fractal dimension of composite cement-based material was investigated under high-temperature steam curing. Furthermore, Thermogravimetric, Nanoindentation, and low-field nuclear magnetic resonance tests were used to explore the influencing factors of pore size distribution and its corresponding multi-fractal dimension. Finally, the correlations among the pore size distribution, related fractal dimensions, and compression strength were analyzed. Results indicate that the MK-UFA cement ternary cementation system (TCS) can improve the compressive strength and fluidity of samples and enhance the hydration degree and micromechanical properties of the cementitious system. TCS effectively refines the pore size and increases microporosity. In addition, micropore and its fractal dimension have a stronger correlation with the compressive strength of composite cement-based materials. Furthermore, the micro-fractal dimensions can better reflect the essential characteristics of the composite cementitious system. The higher the degree of hydration of the cementitious system and the nanomechanical properties of the C-(A)-S-H gel, the lower the micro-fractal dimension. Finally, the GM (1,3) prediction model of compressive strength, micro-fractal dimension, and microporosity are established based on the grey relational theory.
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Affiliation(s)
- Chao Liang
- College of Science, Inner Mongolia University of Technology, Hohhot 010051, China
- College of Civil Engineering, Inner Mongolia Technical College of Construction, Hohhot 010070, China
| | - Yongming Xing
- College of Science, Inner Mongolia University of Technology, Hohhot 010051, China
| | - Xiaohu Hou
- College of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
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