混凝土初始损伤细观结构特性数值试验研究

Numerical experiment study of initial damage microstructural behaviors of concrete

细观结构特性是混凝土材料最重要的特性之一,细观结构参数的改变直接影响混凝土弹性模量、抗拉抗压强度等宏观力学性能变化.首先采用混凝土随机骨料模型进行混凝土细观数值试验,将混凝土看成由骨料、水泥砂浆以及两者之间的界面过渡区(ITZ)组成的三相复合材料,并在水泥砂浆中引入不同孔径、孔隙率的孔隙,使用有限元分析软件MSC.Marc,通过数值试验研究了孔径、孔隙率对混凝土抗拉抗压强度和弹性模量的影响规律.试验结果表明:混凝土弹性模量在同一孔径下随着孔隙率的增长呈线性下降,在同一孔隙率下随着孔径增大呈对数下降;混凝土抗拉抗压强度随着孔隙率和孔径增大呈对数下降.其次,将数值试验结果与经验公式进行了对比,验证数值试验结果的正确性.最后,根据数值试验结果,建立了混凝土初始损伤与孔隙率和孔径之间的关系,描绘了细观尺寸下混凝土的初始损伤面,为建立混凝土细观结构参数和宏观力学特性之间的联系,改善混凝土的力学性质打下了基础.

Microscopic structure characteristic is one of the most important behaviors of concrete.The change of microscopic structure parameters affects the macroscopic mechanical behaviors of concrete,such as the elastic modulus,the tensile and compressive strengths.Firstly,the numerical experiment of concrete is carried out with the random aggregate model.The concrete material is discretized as the three-phase composite material with aggregate,cement mortar and the interfacial transition zone（ITZ）and the void element with different porosity ratio and pore diameter is introduced to simulate the porosity of concrete.Using the finite element analysis software MSC.Marc,the specimens are simulated numerically to study the effects of porosity ratio and pore diameter on the elastic modulus,the tensile and compressive strengths of concrete.Experimental results show that the concrete elastic modulus decreases linearly with the increasing porosity ratio at the same pore diameter and decrease logarithmically with the increasing pore diameter at the same porosity ratio.The tensile and compressive strengths of concrete decrease logarithmically with the increasing porosity ratio and pore diameter.Secondly,the numerical results and the empirical formula are compared to verify the correctness of the numerical experiment results.Finally,according to the numerical experiment results,the relationship between the initial damage and the porosity ratio and the pore diameter of concrete is established and the initial damage surface of concrete is depicted on the microscale,which lays a foundation for establishing the relationship between the microstructure parameters and the macroscopic mechanical properties of concrete,and improving the mechanical properties of concrete in the future.