Abstract The microstructural changes of paste, mortar and concrete based on Portland and fly ash containing Portland composite cements caused by carbonation have been studied. The objective was to find out why fly ash containing mortars carbonate with double rate of the neat Portland cement mortars. The reason is partly because they contain less calcium containing species prone to carbonation, but mainly because of their different hydrate assemblage: 1) Less calcium hydroxide that gives a volume increase upon carbonation. 2) More C-S-H with lower Ca/Si that might give an overall shrinkage upon carbonation. 3) More AFt and AFm phases that yield a substantial volume decrease per mole upon carbonation since their crystal water goes back to liquid form. The third microstructure difference is thought to be the dominating reason for coarser pores in the carbonated zone of CEM II/B-V compared to CEM I resulting in a faster carbonation rate.

中文翻译：

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掺粉煤灰的水化水泥碳化后微观结构变化

摘要 研究了硅酸盐基浆体、砂浆和混凝土以及含粉煤灰的硅酸盐复合水泥因碳化引起的微观结构变化。目的是找出为什么含有碳酸盐的粉煤灰砂浆的比例是纯波特兰水泥砂浆的两倍。部分原因是因为它们含有较少的易于碳酸化的含钙物质，但主要是因为它们不同的水合物组合：1) 较少的氢氧化钙会在碳酸化时增加体积。2) 更多的 CSH 和更低的 Ca/Si，可能会在碳化时产生整体收缩。3) 更多的 AFt 和 AFm 相在碳酸化时每摩尔产生显着的体积减少，因为它们的结晶水回到液体形式。