考虑孔隙影响的混凝土有效弹性模量预测分析研究

Effect of Pores on Effective Modulus of Elasticity Prediction of Concrete

本文通过纳米压痕实验技术得到混凝土材料细观各相参数,基于渐进均匀化理论,采用蒙特卡洛方法和双向游走方法建立了含孔隙混凝土的胞元模型.分析了孔隙在冻融循环次数增加情况下对混凝土有效弹性模量的影响,同时与有限元模拟分析进行了比较.结果表明:随着冻融循环次数增加,孔隙体积分数增大,界面与砂浆压痕模量相对降低,但对骨料影响较小,导致混凝土宏观弹性模量随之降低;理论分析预测的混凝土有效弹性模量与有限元模拟结果吻合良好.应用含孔隙混凝土胞元模型能有效地预测混凝土宏观弹性模量,进而也为其在冻融作用下老化演变机理的研究评估提供了基础.

In this paper, a cell model of porous concrete is established using Monte Carlo simulation and a bidirectional walk method. By using nanoindentation technique, the microscopic mechanical properties of each phase of concrete are obtained. The asymptotic homogenization theory is then used to predict the effective modulus of elasticity of concrete and evaluate the effect of pores with increasing freeze-thaw cycles, in comparison with numerical finite element analysis. The results show that as the volume fraction of pores increases due to increased freeze-thaw cycles, the indentation moduli of the interface and mortar decrease obviously and the one of aggregate seldom changes, resulting in the decrease of macroscopic modulus of elasticity of concrete. The theoretical analysis results are in good agreement with finite element simulation. The cell model of porous concrete is effective in predicting the modulus of elasticity of concrete, and it paves the foundation for evaluating aging mechanism of concrete under freeze-thaw actions.