The impact of carbonation, induced at different CO2 concentrations (0.04 or 1 %), in the phase assemblages and compressive strength of Na2SO4-activated slag materials was determined. Carbonation led to Ca-bearing phases' decalcification (mainly C-(A)-S-H type gel and ettringite) forming different CaCO3 polymorphs, independent of the slag composition or carbonation conditions adopted. In specimens exposed to 0.04 % CO2, a negligible carbonation front was observed, along with a continued phase assemblage evolution and compressive strength gain after 500 days of exposure. Conversely, exposure to 1 % CO2 led to complete carbonation after 28 days, and a significant compressive strength reduction. Accelerated carbonation does not lead to the development of comparable microstructures to those observed in naturally carbonated pastes. The accelerated carbonation rates were ~ 33 times higher than those determined under natural carbonation exposure. Therefore, accelerated tests are considered unsuitable for predicting the long-term carbonation performance of Na2SO4-activated slag cements.

中文翻译：

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自然和加速碳化诱导的碱硫酸盐活化矿渣水泥浆体的结构改变


测定了不同 CO2 浓度 （0.04 或 1 %） 诱导的碳化对 Na2SO4 活化渣材料的相组合和抗压强度的影响。碳化导致含钙相脱钙（主要是 C-（A）-S-H 型凝胶和钙矾石）形成不同的 CaCO3 多晶型物，与采用的炉渣组成或碳化条件无关。在暴露于 0.04% CO2 的样品中，观察到可忽略不计的碳化前沿，以及暴露 500 天后持续的相组合演变和抗压强度增加。相反，暴露于 1% CO2 会导致 28 天后完全碳化，并且抗压强度显着降低。加速碳酸化不会导致形成与天然碳酸糊状物中观察到的微观结构相当的微观结构。加速碳酸化速率比在自然碳化暴露下测定的速率高 ~ 33 倍。因此，加速试验被认为不适合预测 Na2SO4 活性矿渣水泥的长期碳化性能。