Decalcification of calcium silicate hydrate (C-S-H) under aggressive solution attack

Liu, Xin; Pan, Feng; Yu, Xiaobin; Huang, Jiale

doi:10.1016/j.conbuildmat.2022.127988

Cited by 28 publications

(4 citation statements)

References 43 publications

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“…Furthermore, the decalcification of C–S–H in SGRH55 was confirmed by XRD and FTIR analyses prior to the complete consumption of portlandite. The presence of portlandite elevated the alkalinity of the pore solution, which impeded the C–S–H decalcification process. , The microenvironment with a high ion concentration, resulting from the water film on the RCP particle surfaces with insufficient water, led to a high degree of oversaturation . As a result, calcium was less likely to escape from the C–S–H.…”

Section: Results and Analysismentioning

confidence: 99%

“…During this process, increasing the amount of water tends to dilute the pore solutions by lowering the elemental concentrations. It can subsequently result in the undersaturation of calcium-bearing phases such as the CH, C–S–H, and AFt/AFm phase, accelerating their dissolution/decalcification. , Moreover, water also impacts the concentration of carbonate and calcium dissolution, leading to the control of carbonation speed by either CO 2 dissolution or the Cc precipitation stage. , For example, it was found that carbonating RCPs with a very high water content (liquid–solid ratio >50) significantly enhanced the carbonation efficiency and over 60% Cc was precipitated over 6h, reaching almost complete carbonation of the RCFs, , and all the Cc formed was calcite. The high carbonation efficiency may be attributed to the saturation of micropores by bulk water in the aqueous phase.…”

Section: Introductionmentioning

confidence: 99%

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Utilizing Waste Cement for Carbon Dioxide Sequestration and Capture: The Role of Water Content on the Growth of Calcium Carbonate

Ma,

Jiang,

Jiang

et al. 2024

ACS Sustainable Chem. Eng.

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High-alkaline waste cement possesses significant potential for effectively capturing and sequestering carbon dioxide, transforming it into calcium-rich, highly reactive, supplementary cementitious materials. Water plays a pivotal role in facilitating this reaction, yet there is a conspicuous absence of extensive research in this domain. This study elucidates the mechanisms by which water affects the growth behavior (precipitation and crystallization) of calcium carbonate (Cc) in hydrated cement paste during carbonation. The findings indicated that the presence of water dramatically affected Cc's polymorphs, morphology, and crystal properties. With an increase in water content from RH = 55% to a liquid−solid ratio of 40, the calcite grain size underwent significant enlargement from less than 200 to over 400 nm. Moreover, as the water content increased, the different Cc polymorphs evolved into mainly calcite, and the polycrystalline Cc was transformed to monocrystalline calcite. Insufficient water elevated the local pH and ion concentration, resulting in a prolonged supersaturation duration. Meanwhile, the nanosized water film restricted the Cc growth and hindered Ostwald ripening, leading to the preservation of amorphous calcium carbonate (ACC) and poor crystallization of Cc.

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Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Utilizing Waste Cement for Carbon Dioxide Sequestration and Capture: The Role of Water Content on the Growth of Calcium Carbonate

Ma,

Jiang,

Jiang

et al. 2024

ACS Sustainable Chem. Eng.

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“…It is well-known that the durability of the C–S–H matrix is greatly influenced by its decalcification behavior. , To evaluate the damage caused to the C–S–H in different environments, we observed the movement trend of calcium ions leaching over time, as depicted in Figure . The decalcification of the C–S–H matrix in the nitrate/sulfate environment is severe over time.…”

Section: Resultsmentioning

confidence: 99%

Acid Radical Tolerance of Silane Coatings on Calcium Silicate Hydrate Surfaces in Aggressive Environments: The Role of Nitrate/Sulfate Ratio

Jiang

Wang

et al. 2023

Langmuir

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Silane is known as an effective coating for enhancing the resistance of concrete to harmful acids and radicals that are usually produced by the metabolism of microorganisms. However, the mechanism of silane protection is still unclear due to its nanoscale attributes. Here, the protective behavior of silane on the calcium silicate hydrate (C–S–H) surface is examined under the attack environment of nitrate/sulfate ions using molecular dynamics simulations. The findings revealed that silane coating improved the resistance of C–S–H to nitrate/sulfate ions. This resistance is considered the origin of silane protection against harmful ion attacks. Further research on the details of molecular structures suggests that the interaction between the oxygen in the silane molecule and the calcium in C–S–H, which can prevent the coordination of sulfate and nitrate to calcium on the C–S–H surface, is the cause of the silane molecules’ strong adsorption. These results are also proved in terms of free energy, which found that the adsorption free energy on the C–S–H surface followed the order silane > sulfate > nitrate. This research confirms the excellent protection performance of silane on the nanoscale. The revealed mechanism can be further used to help the development of high-performance composite coatings.

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“…Ca leaching is one of the indicators to evaluate the durability of C-S-H under a harsh environment, for example, sulfate attack, magnesium attack, carbonation, etc. [45][46][47] The decalcification behavior of the C-S-H composite was investigated by the batch reaction in Milli-Q water under stirring, where the release of normalized calcium concentration over time is compared to the synthetic C-S-H (Figure S12, Supporting Information), as shown in Figure 5c. Synthetic C-S-H shows a rapid increase in calcium ion concentration upon immersion in the solution, reaching the plateau within 50 min.…”

Section: Resultsmentioning

confidence: 99%

High Energy Absorption Nacre‐Like Calcium Silicate Hydrate (C‐S‐H) Composite Toward Elastic Cementitious Materials

Liu,

Feng,

Agudo

et al. 2023

Adv Funct Materials

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The low toughness under the tension of cement and concrete materials has been a long‐standing issue for decades and it has become increasingly urgent to address in modern society due to the growing demand for the development of high‐performance and sustainable constructions. Manipulating calcium silicate hydrate (C‐S‐H), the main hydration product of Portland cement, which determines the mechanical properties of cementitious materials, is an attractive method for improving their toughness following a bottom‐up approach. Inspired by the microstructure of nacre, a high energy absorption C‐S‐H‐based composite with a highly ordered structure is fabricated by a designed ternary building block, in which exfoliated montmorillonite provides a template for the nucleation and growth of C‐S‐H generating the “brick”, and polyvinyl alcohol acts as a “mortar” binding all the building blocks together. With the hierarchical toughening strategy explored here, the obtained C‐S‐H composite achieves a remarkable energy absorption of 16.2 ± 2.6 MJ m−3, which surprisingly outperforms the ultra‐high toughness cementitious materials by a factor of 20–60 and is even higher than that of natural nacre and other nacre‐like composites. These findings not only provide valuable insights into enhancing the toughness of cementitious materials but also open possibilities for broadening potential applications of C‐S‐H.

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Decalcification of calcium silicate hydrate (C-S-H) under aggressive solution attack

Cited by 28 publications

References 43 publications

Utilizing Waste Cement for Carbon Dioxide Sequestration and Capture: The Role of Water Content on the Growth of Calcium Carbonate

Utilizing Waste Cement for Carbon Dioxide Sequestration and Capture: The Role of Water Content on the Growth of Calcium Carbonate

Acid Radical Tolerance of Silane Coatings on Calcium Silicate Hydrate Surfaces in Aggressive Environments: The Role of Nitrate/Sulfate Ratio

High Energy Absorption Nacre‐Like Calcium Silicate Hydrate (C‐S‐H) Composite Toward Elastic Cementitious Materials

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