Abstract This paper models the instantaneous phase composition of cement pastes under elevated temperatures (up to 1200 °C). First, a hydration model was introduced. Then kinetics models for dehydration of cement hydrates, including C-S-H, CH and aluminate hydrates, and evaporation of free water were proposed. Subsequently, based on the kinetics models, the thermal decomposition model for cement pastes was proposed, which could predict the solid phase, porosity and water compositions of cement pastes under arbitrary temperature history. The thermal decomposition model was then validated by multiple experiments. Finally, a parametric study was conducted to investigate the effects of heating rate on the instantaneous phase composition of cement pastes. It was found that the phase compositions of cement pastes at the same temperature differ greatly from one another among different heating rate cases. This demonstrates the needs to consider temperature histories when analyzing real-world concrete structures under fires.

中文翻译：

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模拟高温下水泥浆的瞬时相组成

摘要 本文模拟了高温（高达 1200 °C）下水泥浆的瞬时相组成。首先，引入了水合模型。然后提出了水泥水合物（包括CSH、CH和铝酸盐水合物）脱水和游离水蒸发的动力学模型。随后，基于动力学模型，提出了水泥浆体的热分解模型，该模型可以预测任意温度历史下水泥浆体的固相、孔隙度和水组成。然后通过多次实验验证热分解模型。最后，进行了参数研究以研究加热速率对水泥浆瞬时相组成的影响。结果表明，在不同升温速率情况下，同一温度下水泥浆体的相组成存在较大差异。这表明在分析火灾下的真实混凝土结构时需要考虑温度历史。