It was generally recognized that water absorption into cementitious materials shows two stages, the early stage with fast water uptake and the late stage with the reduced water absorption rate. Two types of anomalous moisture transport can be classified based on the shape of the water absorption curve. To investigate the main causes of different types of anomalous moisture transport, this study carried out water and isopropanol (IPA) absorption measurements for specimens of non‑carbonated and carbonated cement-based materials made of two types of cements (CEM II B-LL and CEM II/B-M). The results showed that the microstructures of the non‑carbonated materials are sensitive to the environmental conditions, so the exposure surfaces were modified by carbonation or leaching of ions due to the variation of the external moisture, while the surface layer modification does not affect the late stage of water absorption. The numerical simulation results of moisture transport further confirm that the microstructural alteration could be one of the causes of the anomaly in the early stage of water absorption. For carbonated materials, the early stages of water and IPA absorption follow the traditional square root of time function and the intrinsic sorptivities of water and IPA in the early stages are very similar, implying that the microstructure of carbonated mortars is barely altered by water and IPA; therefore, water absorption curves of the early stage can be well predicted by the conventional moisture transport models. This study concluded that anomalous moisture transport observed in non‑carbonated cement-based materials without air entrainment may be caused by microstructural alteration, complex microstructure and the heterogeneous porosity distribution, while for carbonated materials, it is most likely only from the complex microstructure which leads to different moisture transport speeds in different sizes of pores.

中文翻译：

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碳酸和非碳酸水泥基材料两阶段吸水率的不同异常


人们普遍认为，胶凝材料的吸水表现出两个阶段，早期吸水速度快，后期吸水率降低。根据吸水曲线的形状，可以将异常水分传输分为两种类型。为了调查不同类型的异常水分传输的主要原因，本研究对由两种水泥（CEM II B-LL 和 CEM II B-LL）制成的非碳酸和碳酸水泥基材料样本进行了水和异丙醇（IPA）吸收测量。 CEM II/B-M）。结果表明，非碳化材料的微观结构对环境条件敏感，因此暴露表面会因外界水分的变化而发生碳化或离子浸出等改性，而表层改性并不影响后期的性能。吸水阶段。水分传输的数值模拟结果进一步证实，微观结构的改变可能是吸水早期异常的原因之一。对于碳酸材料，水和IPA吸收的早期阶段遵循传统的时间函数平方根，并且水和IPA在早期阶段的固有吸着率非常相似，这意味着碳酸砂浆的微观结构几乎不被水和IPA改变。 ;因此，传统的水分传输模型可以很好地预测早期的吸水曲线。 本研究得出的结论是，在没有引气的非碳酸水泥基材料中观察到的异常水分输送可能是由微观结构改变、复杂的微观结构和不均匀的孔隙率分布引起的，而对于碳酸材料来说，它很可能只是由复杂的微观结构导致的。不同孔径的水分传输速度不同。