微膨胀混凝土早期收缩试验与数值分析

Early-age Shrinkage Experiment of Micro-expansive-concrete and Numerical Analysis

摘要:

通过建立微膨胀混凝土水泥浆体早期收缩以及膨胀剂膨胀效应机理参数模型，引入在混凝土材料细观模拟，实现微膨胀混凝土早期收缩行为的细观场域仿真分析。基于材料试验监测结果进行模型参数修正，校验模拟方法的准确性，并探讨材料细观变异性以及骨料颗粒类型对于材料收缩应变分布的影响。研究结果表明，微膨胀混凝土收缩细观模型能够精准便捷地描述材料应变随时间变化规律；骨料颗粒空间随机分布对材料内部收缩应变场域分布影响显著，受拉应力峰值出现于细长骨料棱角位置以及骨料间隙位置水泥浆体，该膨胀剂效应能够降低材料内部受拉应力水平至普通混凝土20%左右，有效缓解材料收缩微观开裂损伤的潜在风险，保障工程结构应用中材料内部应力储备。基于研究模拟结果，结合具体结构性能需求仍有必要对骨料颗粒种类、形状进行优化控制，以实现材料内部较低且均匀的初始收缩应力场域分布。

Abstract:

By establishing the mechanism parameter models of the early shrinkage of cement mortar and expansion effect of agent， the mesoscopic simulation analysis of micro-expansive concrete early expansion behavior was completed with mesoscopic modelling method. With parameter modification based on the measuring results of material test， the simulation accuracy was verified and the influence of material mesoscopic variability and aggregate particle types on the distribution of material shrinkage strain was discussed. The investigation results show that the mesoscopic shrinkage model of micro-expansive concrete can describe the rule of material strain time-depending distribution accurately and conveniently. The influence of aggregate random distribution on the material internal shrinkage strain distribution is remarkable. The peak tensile stress appears on in the angular position of slender aggregates and the cement mortar narrow gay between particles， and in the specified micro-expansive concrete material， the effect of expansion agent can reduce the tensile stress to about 20% of the normal concrete material， which can alleviate the potential risk of micro-scale shrinkage cracking damage and ensure the stress reserve in material for engineering structural applications. According to the discussion， it is necessary to control and optimize the aggregate types and shapes based on the detailed requirement on structural performance， and the low and uniformed initial shrinkage stress distribution in material can be realize.