Tan Yaowen, Tang Kangkang
Department of Civil and Environmental Engineering, Brunel University London, Uxbridge, Middlesex, UB8 3PH, UK.
Heliyon. 2024 Sep 26;10(19):e38322. doi: 10.1016/j.heliyon.2024.e38322. eCollection 2024 Oct 15.
The early-age temperature rise in concrete, induced by cement hydration, poses a significant risk of thermal cracking. Accurate prediction of concrete hydration temperature is essential for thermal cracking prevention. Cement hydration heat obtained from isothermal calorimetry has been applied to concrete temperature modelling by previous studies. Isothermal calorimetry often excludes coarse aggregates due to the calorimeter capacity limitations, assuming mortar hydration heat can represent concrete, which may neglect the hydration delay effect of coarse aggregates. This study uses an isothermal calorimeter capable of accommodating coarse aggregates to measure the hydration heat of concrete and equivalent mortar, evaluating the validity of this assumption. Results show that the 3-day cumulative hydration heat of concrete exceeds that of mortar, especially at elevated curing temperatures. Significant differences were found in the activation energy and hydration parameters between concrete and mortar, indicating that the presence of coarse aggregates affects samples' temperature sensitivity and hydration heat development. Concrete temperature finite element modelling, validated by semi-adiabatic calorimetry, demonstrates that models based on concrete isothermal calorimetry data provide higher accuracy than those based on mortars. This study demonstrates that the hydration heat development, activation energy, and hydration parameters differ significantly between mortar and concrete. Concrete temperature models based on mortar hydration heat data can result in prediction errors exceeding 5 %. This study recommended employing micro-concrete samples in isothermal calorimetry to replicate actual concrete mixes.
水泥水化引起的混凝土早期温度上升会带来显著的热开裂风险。准确预测混凝土水化温度对于防止热开裂至关重要。以往的研究已将等温量热法测得的水泥水化热应用于混凝土温度建模。由于量热仪容量限制，等温量热法通常不包括粗骨料，假定砂浆水化热可代表混凝土，这可能会忽略粗骨料的水化延迟效应。本研究使用一种能够容纳粗骨料的等温量热仪来测量混凝土和等效砂浆的水化热，评估这一假设的有效性。结果表明，混凝土的3天累计水化热超过砂浆，尤其是在较高的养护温度下。混凝土和砂浆之间的活化能和水化参数存在显著差异，表明粗骨料的存在会影响样品的温度敏感性和水化热发展。通过半绝热量热法验证的混凝土温度有限元模型表明，基于混凝土等温量热法数据的模型比基于砂浆的模型具有更高的精度。本研究表明，砂浆和混凝土之间的水化热发展、活化能和水化参数存在显著差异。基于砂浆水化热数据的混凝土温度模型可能导致预测误差超过5%。本研究建议在等温量热法中采用微混凝土样品来模拟实际混凝土配合比。
