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.

中文翻译：

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硫酸钠活化水泥浆中 CO2 暴露后的三维晶相和孔隙结构演变


CO2 暴露对硫酸钠活化高炉矿渣水泥浆的影响已通过 X 射线（衰减）计算机断层扫描（揭示微米级孔隙结构的变化）和 X 射线衍射计算机断层扫描 （XRD-CT） 阐明结晶相和半结晶相空间分布的变化。加速碳化减少了钙石的体积并诱导了水滑石的形成，证明了 Mg-Al-SO4 层状双氢氧化物相在这些水泥的 CO2 吸收中的关键作用。这些变化产生了小孔隙的细化，并增加了整体孔隙率，达到与混合波特兰水泥相当的值。根据热力学模型计算的孔隙溶液电阻率和孔隙率确定形成因子值。提出了模拟曲折度和孔隙度之间的相关性，以估计硫酸钠活化渣浆的扩散曲折度和形成因子。这种方法代表了评估水泥基浆料的抗碳化性和 CO2 吸收能力的重要一步。