考虑温度过程效应的MgO微膨胀热积模型

混凝土掺适量MgO后产生微膨胀，可以补偿温降引起的收缩从而改善应力状态，因此MgO微膨胀混凝土在水利工程中得到越来越广泛的应用。根据MgO微膨胀混凝土的性质，提出了热积模型，即膨胀量为龄期和所经历的温度对时间积分的函数。利用该模型和开发的仿真程序，模拟了其碾压混凝土坝掺MgO后的应力过程，并与不掺MgO的结果进行了对比。结果表明：该模型能很好地反映MgO混凝土的基本性质；掺MgO对改善约束区的应力状态效果明显，远离约束区时效果不大；MgO的微膨胀会使局部混凝土的拉应力增大。具体应用中要在仿真分析的基础上进行周密的MgO掺量与温控设计。

MgO micro-expansion thermal integral model considering temperature process effect

The concrete can produce micro-expansion after proper MgO is mixed, which can compensate its shrinkage caused by temperature drop in order to improve the stress conditions. For this reason, the MgO micro-expansion concrete has been widely applied in the water resources projects. Such concrete has following characteristics. (1) Its final expansion volume is only related to the mix proportion of concrete and its MgO admixture amount. (2) The expansion volume is only in increment and irreversible. (3) The expansion increment at some time is related to the temperature at that time and the temperature process. In accordance with the above-mentioned characteristics, this paper puts forward the thermal integral model, that is, the expansion volume is the function of the integral of its age and its undergoing temperature over the time. With the use of such model and the developed simulation program, the stress process of a RCC dam with MgO admixture was simulated and then its results were compared with those without MgO admixture. The research results showed that the model can reflect well the basic characteristics of MgO concrete and the MgO admixture can obviously improve the stress conditions in the restricted zone but few effective in other areas far away the restricted zone. The micro-expansion of MgO can increase the tensile stress in local concrete. In the practical application, the MgO admixture amount and temperature control measures should be carefully determined on the basis of simulation analysis.