CONSTRUCTION AND BUILDING MATERIALS
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2021
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IF 6.141
Xiaoliang Fang,Dongxing Xuan,Baojian Zhan,Weifeng Li,Chi Sun Poon
In a previous study, a novel two-step carbonation technique was developed to convert finely crushed hardened cement paste into a calcium-rich and a silica-rich residue. This paper reports a further work on optimizing the two-step carbonation process by studying the influences of a series of experimental variables including particle size, Na 2 CO 3 concentration, reaction time and temperature, CO 2 flow-rate, and CO 2 concentration on the carbonation processes. The characteristics of the chemical and physical properties of calcium-rich (mainly calcite) and silica-rich (silica and alumina-silica gel) residues formed were analyzed by using X-ray fluorescence (XRF), powdered X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). It was found that the changes in the experimental variables of both Steps 1 and 2 mainly affected the amounts of new products formed, but only slightly changed the chemical structures of the new products. Through a series of comparative tests, the most efficient conditions for the two-step carbonation process was reported. Comparing to the previous exploratory reaction conditions of 24 h stirring and 7 h flow-through carbonation using pure CO 2 gas, the optimum conditions would be: i) in Step 1: a 5–10 wt% Na 2 CO 3 solution, a reaction duration of 5–7 h under ambient temperature, ii) in Step 2: a CO 2 gas with a concentration of>50%, and the carbonation ending with a final pH ≤ 9.8 in less than 90 mins. Meanwhile, the estimated CO 2 uptake in Step 2 was 0.136 g per gram of RCP. In addition, the supernatant of Step 2 after centrifugation can be recycled and reused as the Na 2 CO 3 solution in Step 1 for another reaction cycle after pH adjustment by NaOH.
研究领域:
材料科学
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环境工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
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2023
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IF 3
Zhigang Peng,Huan Zhang,Qian Feng,Yong Zheng
To solve the problem of high brittleness and easy cracking of cement stone, epoxy resin powder elastic particles (HEEP) were developed to improve the elasticity of cement stone. HEEP was prepared from epoxy resin and trimeric anhydride by solution polymerization. The surface wettability and particle size of HEEP were analyzed by contact angle test and laser particle size analysis respectively. Mechanical performance tests, scanning electron microscope (SEM) analysis and x-ray diffraction analysis were conducted on the cement stone containing HEEP. The results showed that HEEP was the target product, with a hydrophilic surface and a water contact angle of 75.2° on the HEEP surface. The particle size distribution of HEEP was uniform, and the median particle size was 36.5 μm. The initial decomposition temperature of HEEP was 300°C, indicating a good thermal stability. The stress–strain curve showed that when the HEEP dosage was 3%, 6%, and 9%, the elastic modulus of the cement stone was 6.382, 4.017, and 3.148 GPa, respectively. Compared with the blank cement without HEEP, the elastic modulus was reduced by 28.3%, 54.9%, and 64.6%, respectively. This showed that HEEP could effectively improve the elasticity of cement stone. In addition, the compressive strength and flexural strength of cement stone containing HEEP can meet the requirements of on-site applications. SEM analysis of cement stone showed that HEEP was well filled in cement stone. When the cement stone was subjected to complex stress, HEEP could effectively buffer and disperse the stress, thereby enhancing the resistance of cement stone to external force impact.
研究领域:
材料科学
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石油工程
✓ 已验证
产品关联
DOI
高影响因子
Case Studies in Construction Materials
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2025
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IF 6.6
Xin Tang,Weiqiang Luo,Yan Yang,Xuzeng Hu,Xiangyin Li
To enhance the interface bonding performance of cement sheaths in oil and gas wells, this study developed nano TiO 2 -modified waterborne epoxy resin (NTWER) as a cement slurry additive. The mechanical properties and microstructural characteristics of the resulting cement stones were systematically examined. Results indicate that an optimal concentration of nano TiO 2 (NT) in waterborne epoxy resin (WER) improves the stability of the cement slurry. The inclusion of NTWER notably enhanced the shear bonding strength while slightly decreasing uniaxial and triaxial compressive strength and reducing Young’s modulus. When the nano TiO 2 (NT) content in the WER reached 3 %, substantial improvements in shear bonding strength were recorded at both the casing (1st interface) and borehole wall (2nd interface) interfaces after curing for 1, 2, and 7 days, compared to plain cement. Specifically, the shear bonding strength at the 1st interface increased by 23.9 %, 33.5 %, and 31.0 %, while at the 2nd interface, it rose by 25.3 %, 42.5 %, and 37.4 %. Notably, the 2nd interface consistently exhibited higher bonding strength than the 1st. Mechanic studies suggest that NTWER facilitates improved bonding by mitigating early hydration inhibition, reducing macropores, and decreasing overall porosity within the cement matrix. This densification effect and enhanced bonding properties indicate that NTWER effectively addresses the limitations of conventional epoxy resin in oil and gas well cementing applications, offering a promising approach for achieving durable zonal isolation and increased well integrity.
研究领域:
材料科学
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石油工程
✓ 已验证
产品关联
DOI
高影响因子
COMPOSITE INTERFACES
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2022
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IF 2.839
Zhigang Liu,Yuantao Xie,Lirong Yang,Chunmei Wang,Xiaoxin Feng,Zezheng Tang,Yaxin Yu
The polypropylene (PP) fibers were modified by silane coupling agent (KH570) or synergistically modified by KH570 and nano-SiO2 in this paper. The modification effect of PP fibers was evaluated by SEM and FTIR. The reinforcing effect of PP fibers and the modified PP fibers on sulphoaluminate cement-gypsum composites (SGC) was investigated. The results show that KH570 can undergo an autohydrolysis reaction and wrap on the surface of the PP fibers, which makes the hydrophilicity of PP fibers improved. Nano-SiO2 can further improve the hydrophilicity and roughness of the PP fiber surface by polycondensation reaction with KH570. KH570 and nano-SiO2 synergistically modified PP (KH570-SiO2-PP) fibers obviously increase the compressive strength and flexural strength of the hardened SGC compared with PP fibers or KH570 modified PP (KH570-PP) fibers. The SEM images show that PP-KH570-SiO2 fibers have better adhesion with the matrix than PP fibers and KH570- PP fibers.
研究领域:
材料科学
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建筑工程
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）