Semi-dry natural carbonation at different relative humidities: Degree of carbonation and reaction kinetics of calcium hydrates in cement paste

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research Pub Date : 2024-12-30 DOI:10.1016/j.cemconres.2024.107777

Naohiko Saeki, Ryo Kurihara, Takahiro Ohkubo, Atsushi Teramoto, Yuya Suda, Ryoma Kitagaki, Ippei Maruyama

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Abstract

This study investigated semi-dry carbonation at different relative humidities (RH) under atmospheric CO₂ concentrations to determine the effect of RH on the degree of carbonation (DoC) and reaction rates. The carbonation kinetics of each calcium-containing hydrate exhibited an initial rapid chemical-reaction-limited stage, followed by a significantly slower stage. DoC values plateaued after 200 days of carbonation, reaching 78 % at 95 % RH and 34 % at 33 % RH, aligning with EN 16757 values for sheltered outdoor and indoor environments, respectively. When the samples reached a stable DoC at a given RH, further carbonation occurred upon exposure to higher RH, implying that the DoC was governed by the highest RH to which the samples had been exposed. The phase assemblage was also affected, approaching thermodynamic equilibrium at higher RH but deviating at lower RH due to the formation of local equilibria and the presence of metastable phases.

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不同相对湿度下的半干自然碳化：水泥浆中水合钙的碳化程度和反应动力学

研究了大气CO2浓度下不同相对湿度（RH）下的半干法碳酸化反应，以确定RH对碳酸化程度（DoC）和反应速率的影响。每种含钙水合物的碳酸化动力学均表现为初始快速的化学反应限制阶段，随后是一个明显缓慢的阶段。碳化200天后，DoC值趋于稳定，在95% RH下达到78%，在33% RH下达到34%，分别与EN 16757的遮荫室外和室内环境值一致。当样品在给定的相对湿度下达到稳定的DoC时，暴露在更高的相对湿度下会发生进一步的碳化，这意味着DoC受样品所暴露的最高相对湿度控制。相组合也受到影响，在较高的相对湿度下接近热力学平衡，但在较低的相对湿度下由于局部平衡的形成和亚稳相的存在而偏离热力学平衡。

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来源期刊

Cement and Concrete Research 工程技术-材料科学：综合

CiteScore

20.90

自引率

12.30%

发文量

318

审稿时长

53 days

期刊介绍： Cement and Concrete Research is dedicated to publishing top-notch research on the materials science and engineering of cement, cement composites, mortars, concrete, and related materials incorporating cement or other mineral binders. The journal prioritizes reporting significant findings in research on the properties and performance of cementitious materials. It also covers novel experimental techniques, the latest analytical and modeling methods, examination and diagnosis of actual cement and concrete structures, and the exploration of potential improvements in materials.