基于细观尺度的混凝土热膨胀性能研究

Meso-scale Study on Thermal Expansion Coefficient of Concrete

用细观力学方法对混凝土有效热膨胀系数和温度应力进行研究,提出了有效热膨胀系数理论公式.同时假定混凝土为骨料和砂浆组成的两相复合材料,用代表性体积单元(RVE)建立混凝土三维随机椭球形骨料模型,并对此模型进行有效热膨胀系数和温度应力的数值计算.将所提出的有效热膨胀系数理论公式、其他经典理论公式与数值计算结果对比后发现:对于混凝土有效热膨胀系数的预测,所提出的混凝土有效热膨胀系数理论公式预测精度最高,自洽法次之,而稀疏解法精度较低且只适用于骨料体积分数较小的情况.提出的理论解与数值计算结果吻合较好,其误差随骨料体积分数的增大而增大;当骨料与砂浆的弹模比小于1时,理论解小于数值计算结果,当弹模比大于1时,理论解大于数值计算结果.

Based on meso-mechanics method,the thermal stresses and thermal expansion coefficient of concrete were studied and the concrete was assumed as a two-phase composite material composed of mortar and aggregate. Given a representative volume element（RVE）,the numerical simulations of thermal expansion coefficient and thermal stress were performed by using a 3D random ellipsoid aggregate modeling.Analyses show that the present formula has more precision for prediction of the thermal expansion coefficient than the classical self-consistent method. The dilute distribution method has lowest precision and it is just suitable under the condition of low aggregate volume fraction.The present formula shows good agreement with the numerical simulation except for the condition of high aggregate volume fraction.In the cases in which the elastic modulus ratio between aggregate and mortar is less than 1,the values obtained by present formula are smaller than that by numerical results while the conclusion is opposite if the ratio is greater than 1.