CEMENT AND CONCRETE RESEARCH
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2024
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IF 10.9
Binmeng Chen,Xu Fang,Yuyang Zhao,Zongjin Li
In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the size of generated silica nanoparticles remain unknown. In this work, we developed an optimized carbonation method at high water to solid ratio to fabricate silica nanoparticles from C-S-H with different C/S ratios. The particle size of silica nanoparticles was found to gradually decrease with the increased C/S ratio of C-S-H. Since as C/S ratio increased, silicate in Q 3 state shifted to Q 1 state and the silicate chain became shorter, shifting from long-range, disordered to short-range, ordered. As the disordered self-seeding growth of long silicate chains derived from C-S-H continued, the Si-O-Si network of silica nanoparticles became chaotic, leaving more unreacted Si-OH on its surface. On the contrary, the short silicate chains displayed higher possibility of condensation, making nanoparticles with a smaller diameter.
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
CERAMICS INTERNATIONAL
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2024
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IF 5.1
Xuan Hou,Shuhua Ma,Xiaohui Wang,Ruiping Liu,Muhammad Ibrahim
In the study of hydrothermal conversion of fly ash to calcium silicate hydrates (C–S–H), the concentration of Ca and Si in the liquid phase plays a vital role in determining the hydrothermal transformation results. This paper selected a fly ash as a research object, which can leach a high Si concentration into the solution in the hydrothermal process even in a slight alkaline solution, based on a new finding when studying the alkali dissolution kinetics of different fly ashes. To explore the effects of Ca and Si concentrations in the liquid phase on the hydrothermal transformation of fly ash to tobermorite or katoite, Na 2 SiO 3 (Na 2 O·xSiO 2 ·yH 2 O) and CaSO 4 were used to change the concentration of Si and Ca in the liquid in the hydrothermal system. Characterization methods such as XRD, SEM, infrared spectroscopy, and solid-state nuclear magnetic resonance indicated that a little more concentration of Si can promote the transformation from fly ash to tobermorite and persuade the conversion of the Si–O tetrahedron in C–S–H from Q 2 to Q 3 and Q 4 . However, too high a liquid Si concentration made the hydrothermal product change to colloidal calcium silicate. On the other hand, a high Ca concentration in the liquid was found to lead to the conversion of the hydrothermal product from tobermorite to katoite. According to the above results, the deep transformation from fly ash to tobermorite under the conditions of a low temperature of 160 °C and no extra alkali addition was achieved by the induction of a small quantity of Na 2 SiO 3 .
研究领域:
材料科学
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环境科学
✓ 已验证
产品关联
DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
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2024
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IF 7.4
Kaifeng Wang,Yuxun Kan,Yunsheng Zhu,Kaihong Zhong,Jiabing Hu
Calcium silicate hydrate (C-S-H) is considered a novel early strength agent, showing immense potential in enhancing the early strength of cement-based materials. Polycarboxylate (PCE) is widely used as a dispersant in the synthesis of nano-C-S-H to prevent agglomeration during synthesis. However, a comprehensive investigation is still required to establish a stable method for preparing stable C-S-H/PCE nanocomposites using chemical co-precipitation. This study employed orthogonal experiments, range analysis, variance analysis, and multi-index matrix analysis to explore the effect of the chemical co-precipitation synthesis process on the stability of C-S-H/PCE nanocomposites. It conclusively identified the calcium-to-silicon (C/S) ratio as the sole significant influencing factor, establishing optimal synthesis parameters: a C/S ratio of 1.6, stirring at 8000 r/min, a 2-hour reaction time, and a reaction temperature of 30 °C. Additionally, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to investigate the impact of the C/S ratio on the structure and morphology of C-S-H/PCE nanocomposites. Results indicated that under the optimal synthesis parameters, the average particle size and precipitation rate of the synthesized C-S-H/PCE nanocomposites were 0.122 µm and 0.44%, respectively, exhibiting a 4.7% and 47.6% improvement over the best samples in the orthogonal test. Increasing the C/S ratio decreased the crystallinity of the C-S-H/PCE nanocomposites, resulting in the emergence of multiple crystal structures, compact and ordered morphology, and reduced sedimentation. These findings collectively underscore that C-S-H/PCE nanocomposites with higher C/S ratios exhibit enhanced dispersion and stability, validating the rationality of the optimal synthesis parameters identified in this study.
研究领域:
建筑材料学
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化学工程
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
CEMENT & CONCRETE COMPOSITES
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2023
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IF 10.5
Shujun Li,Gaofeng Chen,Yasong Zhao,Zhenhai Xu,Xu Luo,Cheng Liu,Jianming Gao
Knowing the reactivity of recycled brick powder (RBP) is fundamental for its correct and efficient utilization. In this work, the dissolution behavior of RBP in NaOH solution and the degree of reaction in cement matrix were studied to investigate the reactivity of RBP. The results revealed that the main active species of RBP, Si and Al, showed obvious lasting dissolution with a significant non-steady state dissolution stage, indicating that the reaction proceeds slowly. The dissolution mechanism controlled by the phase boundary reaction, with activation energies of 82.74 kJ/mol and 75.79 kJ/mol for Si and Al dissolution, respectively, further confirmed this finding. The strength activity index, thermogravimetric analysis , selective dissolution, BSE-IA-Mapping and MAS NMR all confirmed reactivity of RBP. Additionally, reaction rims were observed around RBP particles in cement paste . The low Ca/Si and Ca/Al ratios and their significant increases in a direction from the particle boundary to the paste demonstrate that the rim was a hybrid phase composed of the original RBP components and the reaction products.
研究领域:
材料科学
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土木工程
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）