This study investigated the feasibility of Raman microscopy for monitoring early surface carbonation of hardened cement pastes in real time for up to 7 days. Samples were exposed to natural carbonation (440 ppm CO₂) and accelerated carbonation (4% CO₂), and the evolution of calcium carbonate (CaCO₃) polymorphs, portlandite, ettringite, C-S-H gel and unreacted cement particles was followed. Results showed that calcite is the main polymorph formed under both natural and accelerated carbonation. Under accelerated carbonation, the formation of calcite on the sample surface completed within 1 day whereas under natural carbonation, the formation of calcite is expected to continue beyond 7 days. The contents of portlandite and ettringite decreased rapidly under accelerated carbonation but much more gradually under natural carbonation. However, calcium silicate minerals in unreacted cement particles remained unchanged throughout the carbonation processes. Overall, this study demonstrated that Raman microscopy is a valuable tool for non-destructive real-time imaging of surface carbonation in cement-based materials.

中文翻译：

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使用拉曼显微镜实时监测硬化水泥浆的碳化

本研究调查了拉曼显微镜在长达 7 天的时间内实时监测硬化水泥浆体早期表面碳化的可行性。样品暴露于自然碳酸化 (440 ppm CO ₂ ) 和加速碳酸化 (4% CO ₂ ) 以及碳酸钙 (CaCO ₃) 多晶型物、硅酸盐、钙矾石、CSH 凝胶和未反应的水泥颗粒。结果表明，方解石是自然和加速碳化作用下形成的主要多晶型物。在加速碳化下，样品表面方解石的形成在 1 天内完成，而在自然碳化下，方解石的形成预计将持续超过 7 天。在加速碳化作用下，硅酸盐和钙矾石的含量迅速下降，而在自然碳化作用下则下降得更为缓慢。然而，未反应的水泥颗粒中的硅酸钙矿物在整个碳化过程中保持不变。总体而言，这项研究表明，拉曼显微镜是一种有价值的工具，可用于对水泥基材料表面碳化进行无损实时成像。