3D crystalline phase and pore structure evolution upon CO2 exposure in sodium sulfate-activated cement pastes

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY Cement and Concrete Research Pub Date : 2024-11-11 DOI:10.1016/j.cemconres.2024.107716

Zengliang Yue, Zixian Su, Partha P. Paul, Alastair T.M. Marsh, Alice Macente, Marco Di Michiel, John L. Provis, Philip J. Withers, Susan A. Bernal

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Abstract

The effects of CO₂ exposure on sodium sulfate-activated blast furnace slag cement paste have been characterised by X-ray (attenuation) computed tomography revealing changes in micron-scale pore structure, and X-ray diffraction computed tomography (XRD-CT) elucidating changes in the spatial distribution of crystalline and semi-crystalline phases. Accelerated carbonation reduced ettringite volumes and induced formation of hydrotalcite, demonstrating the critical role of Mg-Al-SO₄-layered double hydroxide phases in the CO₂ uptake of these cements. These changes yield a refinement of small pores and increase the overall porosity, reaching values comparable to those of blended Portland cements. Formation factor values were determined considering the pore solution electrical resistivity, calculated from thermodynamic modelling, and the porosity. A correlation between simulated tortuosity and porosity is proposed to estimate the diffusion tortuosity and formation factor of sodium sulfate-activated slag pastes. This approach represents a significant step forward for assessing carbonation resistance and CO₂ uptake capacity of cementitious pastes.

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硫酸钠活化水泥浆暴露于二氧化碳时的三维晶相和孔隙结构演变

通过 X 射线（衰减）计算机断层扫描（XRD-CT）和 X 射线衍射计算机断层扫描（XRD-CT）分析了二氧化碳暴露对硫酸钠活化高炉矿渣水泥浆的影响，前者揭示了微米级孔隙结构的变化，后者阐明了结晶和半结晶相空间分布的变化。加速碳化减少了埃特林岩的体积，并诱导形成了水滑石，证明了 Mg-Al-SO4 层状双氢氧化物相在这些水泥的二氧化碳吸收过程中起着关键作用。这些变化细化了小孔并增加了整体孔隙率，达到了与混合波特兰水泥相当的数值。根据热力学模型计算出的孔隙溶液电阻率和孔隙率确定了形成因子值。提出了模拟迂回度和孔隙率之间的相关性，以估算硫酸钠活化矿渣浆的扩散迂回度和形成系数。这种方法在评估水泥浆的碳化阻力和二氧化碳吸收能力方面迈出了重要一步。

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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.