Journal of Building Engineering
·
2024
·
IF 6.7
Baomin Wang,Weigao Ding,Chengcheng Fan,Fei Liu,Wenxin Lu,Haoxiang Yang
C-S-H gel is a complex cementitious system, and the properties present significant difference with various Ca/Si ratios. The immobilization mechanism of three heavy metals in C-S-H gel at various Ca/Si ratios was investigated in this work from the prospect of the physical adsorption and chemical immobilization. Results showed that higher Ca/Si ratios can result in an increase in silicon chain polymerization, and lower BET specific area, and C-S-H gel with various Ca/Si ratios showed the excellent immobilization for heavy metals. Pb(II) and Zn(II) can form hydroxyl complex polyhedra in C-S-H under strongly alkaline environments, and increase the silicon chain polymerization degree similar to the doping of C-S-H gel by Al. However, Cd(II) was immobilized in the C-S-H gel with the formation of a solid solution under the action of ion exchange with Ca(II), rather than in the form of hydroxyl complex polyhedral and cadmium hydroxide coprecipitates. The highest adsorption capacity of Pb(II) was realized in C-S-H gel with a Ca/Si molar ratio of 0.9, reaching 95.6006 mg/g. Pb(II) was mainly immobilized in C-S-H gel via physical and chemical adsorption, and the effect of chemical adsorption tended to be significant as the Ca/Si molar ratio increased. And the formation of Pb 8 Ca(Si 2 O 7 ) 3 can be detected in C-S-H gel with a higher Ca/Si molar ratio.
研究领域:
材料科学
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环境科学
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DOI
高影响因子
JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION
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2018
·Vol. 33
·期 5
·1176-1185
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IF 0.524
Lu Guosen,Deng Min,Mo Liwu
C3S pastes containing 0%, 5%, 10%, and 15% nano-SiO2 mixed with de-ionized water and alkali solutions were prepared. When C3S was completely hydrated, the pastes were ground into powders with a particle size less than 80 μm. Adsorption and desorption characteristics of alkali ions adsorbed by C 3 S-nano SiO 2 pastes mixed with de-ionized water immersed in alkali solutions and those in C 3 S-nano SiO 2 pastes mixed with alkali solutions, were investigated. Meawhile, the adsorption mechanisms of alkali ions were discussed. Results showed that the contents of alkali ions adsorbed by C 3 S-nano SiO 2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO 2 and/or the initial alkali concentrations. In C 3 S-nano SiO 2 pastes mixed with de-ionized water, each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration. No obvious difference between the adsorption capacity of a given paste for K + and Na + was observed. Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste, and charge compensation of C-S-H gel, mainly by electrostatic interactions. In C 3 S-nano SiO 2 pastes mixed with alkali solutions, alkali ions may enter the structure of C-S-H gel to replace a part of Ca 2+ in the interlayer. This assumption is supported by the structural characterization of C-S-H gel using 29 Si MAS NMR.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
COMPOSITES PART B-ENGINEERING
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2025
·
IF 14.2
Jihong Jiang,Han Wang,Junlin Lin,Zhiyong Liu,Laibo Li,Yali Li,Zongjin Li,Lingchao Lu,Yunjian Li,Zeyu Lu
Previous studies primarily considered TiO 2 as a nano-filler to accelerate cement hydration due to the nucleation site effect. However, hydroxyl free radicals (•OH), released from TiO 2 under UV irradiation, also exhibit great potential to accelerate cement hydration owing to their high nucleophilicity arising from unpaired electrons. This study is the first to reveal the accelerating mechanism of •OH generated by photoexcited nano-TiO 2 on cement hydration. Current experimental results indicated that 5.0 wt% addition of photoexcited nano-TiO 2 (under 6 h of UV irradiation during the early curing stage) improved the dissolution rate of tricalcium silicate (C 3 S) by 30 %, followed by a 35 % increase in the hydration degree of cement paste. More importantly, the polymerization degree and high-density content of C–S–H gels were also improved by 26 % and 13 %, accompanied by a 46 % reduction in porosity of the composites. All the aforementioned improvements were attributed to the presence of •OH generated by photoexcited nano-TiO 2 , which significantly accelerated cement hydration by accelerating C 3 S dissolution, facilitating faster nucleation and growth of C–S–H gels. In addition, the Density Functional Theory (DFT) calculations revealed that the accelerating effect of •OH on cement hydration may stem from the stronger interaction between •OH and the Ca ion on the C 3 S surface compared to the water molecule, and the increased surface nucleophilicity due to the dispersion of unpaired elections from •OH to all the O ions in the surface layer. These findings provide a high-efficiency approach to accelerate cement hydration by photoexcited nano-TiO 2 , thereby paving the way for the development of advanced and sustainable cement-based materials.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
CEMENT & CONCRETE COMPOSITES
·
2024
·
IF 10.8
Yamei Cai,Xiaohong Zhu,Keke Sun,Kesheng Yin,Dongxing Xuan,Chi Sun Poon
This study compared the sulphate resistance of deionized water (DI)- and seawater (SW)-mixed cementitious materials based mainly on microstructural observations. The results show that, after a 450-day exposure to 50 g/L Na 2 SO 4 solution, there was an increase in the mean chain length and polymerization degree of the remaining silicate chains in C-S-H gel for both DI- and SW-mixed pastes at a depth of 0–2 mm from the exposed surface. Notably, the Ca leaching of C-S-H gel in the SW-mixed paste at depths larger than 0.3 mm was slightly less than that in the DI-mixed one, despite the Ca leaching in both samples was comparable at a depth of 0.1 mm. For the aluminate phase, the mass loss and length change of the SW-mixed C 3 A mortar were lower than that of the DI-mixed C 3 A mortar, after immersing in 50 g/L Na 2 SO 4 solution at different times. It seemed that more expansive product can be accommodated in the SW-mixed C 3 A matrix. Consequently, fewer cracks deposited by gypsum were observed in SW-mixed paste than in DI-mixed paste. The above were responsible for relatively less compressive strength loss of the SW-mixed mortars suffering from sulphate attack for 450 d.
研究领域:
土木工程
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2016
·
IF 2.421
Zhenhai Xu,Zonghui Zhou,Peng Du,Xin Cheng
In order to evaluate the influence of nano-silica on tricalcium silicate (C 3 S) hydration, hydration rate, Ca(OH) 2 content, quantification of C–S–H, pore size distribution and micrographs of hydration products were measured. Results revealed that with the increase content of nano-silica, the hydration of C 3 S is accelerated before hydration for 3 d but slows down in the later age (7 d, 28 d and 60 d). C–S–H content increases with the increase content of nano-silica. However, an obvious reduction in C–S–H increment occurs at 7 d, 28 d and 60 d. In addition, the hydration products morphology changes from rod-shape to dense matrix at 28 d after nano-silica modification, and the Ca/Si ratio of C–S–H gel decreases. Besides, the addition of 3 wt.% nano-silica can reduce the total porosity of C 3 S by 4.04% and optimize the pore structure. Furthermore, the density of paste increases by 4.22%, which finally leads to the more compact structure of hardened paste.
研究领域:
材料科学
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土木工程
✓ 已验证
产品关联
DOI
高影响因子
CEMENT & CONCRETE COMPOSITES
·
2024
·
IF 10.8
Guangpeng He,Deyu Kong,Xiaoguang Chen,Shujing Fan,Tao Meng,Jiabin Li
In this paper, low-cost dihydrate gypsum (CaSO 4 ⋅2H 2 O) was used as calcium source together with sodium metasilicate solution to prepare calcium silicate hydrate (C-S-H) gels through a mechanochemical activation strategy by using planetary and vibrational ball-milling. The influences of the prepared C-S-H gels on hydrating and hardening properties of super-retarded cement-based materials with sucrose were investigated. The results showed that CaSO 4 ⋅2H 2 O reacted with sodium metasilicate solution under mechanochemical effect during both planetary and vibrational ball-milling, although CaSO 4 ⋅2H 2 O was just slightly dissolved in water. It was also interestingly found that the C-S-H gels can continuously form while resting for a certain time after ball-milling. Under the mechanochemical activation, the prepared C-S-H gels had complete characteristic diffusion peaks and were composed of layered, flocculent and fibrous structures. While incorporating the prepared C-S-H gels into the super-retarded cement paste with sucrose, the cement hydration was greatly accelerated and the compressive strength of the hardened cement-based materials was also effectively improved at early age as expected. Through X-ray diffraction (XRD) analysis, it was found that C-S-H gels can effectively promote the growth of CH crystals along the (001) and (101) crystal planes. The scanning electron microscopy (SEM) results supported that the C-S-H gels inhibited the refinement of ettringite (AFt) crystals in super-retarded HCP with sucrose, which was more obvious at 28 d.
研究领域:
建筑材料学
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无机材料科学
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土木工程
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED FUNCTIONAL MATERIALS
·
2022
·Vol. 32
·期 51
·2208676
·
IF 19.924
Bo Pang,Zuquan Jin,Yunsheng Zhang,Zhiyong Liu,Wei She,Penggang Wang,Yong Yu,Xiaoying Zhang,Chuansheng Xiong,Ning Li,Guowen Sun,Peng Zhao,Guojian Liu,Xiaoyun Song,Song Gao
Cement-based sensors (CBSs) have demonstrated potential in structural health monitoring (SHM) despite rare applications due to their poor flexibility and sensing accuracy/protection with robustness. Herein, a promising strategy is reported to design a waterborne epoxy resin (WEP)-modified cement-based composite coating sensorcapable of simultaneous stable SHM and durable protection. The interpenetrating network (IPN) formed by WEP within cement paste is bionic to the toughness and crack resistance of biological muscle tissue and balances the ion permeation performance and polarization of hydration products. The polymerization-redispersion progress and mechanism of calcium silicate hydrate (C-S-H) gel modified with [3-(2-aminoethylamino)-propyl]trimethoxysilane silsesquioxane (C-POSS) are characterized and revealed. The results show that the muscle-like IPN increases the cement-based coatings’ maximum deflection angle to 30° and improves the monitoring accuracy of compressive, tensile, and fatigue microchanges of concrete structures to more than 95%. The POSS···Ca 2+ ···C-S-H interaction in C-POSS partially transferred the intra-adhesive hydrogen bonds surrounding the nanoconducer into electrostatic bridging ones to maintain an excellent electromechanical conductive dispersion.
研究领域:
土木工程
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材料科学
·
传感器技术
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DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2019
·
IF 4.046
Tao Yang,Zuhua Zhang,Huajun Zhu,Xuan Gao,Chendong Dai,Qisheng Wu
High-magnesium nickel slag (HMNS) has shown the potential as precursor in the production of alkali-activated materials (AAMs). This study re-examines the suitability of HMNS by comparatively investigating the reactivity of four different sourced HMNSs and analyzing impacts of the magnesium sources in HMNS on the reaction products of AAMs. Results show that the cooling way plays a determinant role of their mineral compositions. The air-cooled HMNSs contain only ∼30 wt% glassy phases, while the water-quenched one is dominantly amorphous. The reactivity of HMNS determined by the dissolution tests correlates well with the calculated depolymerization degree of glasses. HMNS indeed exhibits lower reactivity than the precursors commonly used for AAMs production, such as fly ash and blast furnace slag . In the HMNS samples in the sodium hydroxide solution, M-S-H, C-S-H and hydrotalcite are the main reaction products. The OH − ions in the aqueous system react with Mg 2+ to form the brucite, indicating that there is still a volume expansion risk if sodium hydroxide is used as activator. In comparison, only M-S-H and C-S-H gels are coexistent in the samples leached in the sodium silicate solution, because of the kinetic hindrance of soluble silicates for the formation of hydrotalcite and brucite.
研究领域:
材料科学
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硅酸盐化学
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无机非金属材料
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固废资源化
·
建筑材料
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）