Analysis Of Concrete’s Mechanical Parameters With Influence Of ITZ Based On Asymptotic Homogenization Method

Concrete can be considered as a multi-scale material.On a mesoscale scale,it is generally considered as a three-phase composite consisting of aggregate,a grout matrix,and an interfacial transition zone(ITZ).material.The relative positions,interactions,material properties,and mix ratios of the components all affect the mechanical properties of the concrete,resulting in a very complex mechanical properties of the concrete.Therefore,it is necessary to grasp the macroscopic mechanical properties of concrete from a mesoscopic perspective.The asymptotic homogenization method(AHM)is a multiscale method with a strict mathematical basis.This paper uses AHM to calculate the elastic constants of the concrete considering the interfacial transition zone and the influence of aggregate grading from a mesoscopic point of view.The main work and conclusions are as follows:1.Representative volume elements(RVE)was setted up the diameter of single particle aggregate,to calculating the bulk modulus of the model of each single particle by AHM,The result is quite close to the one computed by generalized consistent method.In order to overcome the aggregate overflow boundary when modeling representative volume elements of the higher aggregate volume fraction,The wider range of cubic reinforcements does not affect the calculation accuracy when the cubic reinforcements were used instead of spherical reinforcements,then the weighted average method and the in-line method are respectively applied in calculate the bulk modulus Poisson’s ratio of the concrete when concerning about particle grading,the results of different aggregate volume fractions are very close to the experimental results.Finally,the effects of aggregate grading and ITZ thickness on the Young’s modulus of concrete were analyzed.The results show:(1)The Young’s modulus calculated by AHM is close to the test result,especially when the volume fraction of the aggregate is within the commonly used range.(2)With the increase of the aggregate gradation parameter M,the Young’s modulus of concrete gradually increases.(3)The thickness of ITZ also has a great influence on the Young’s modulus of concrete.As the thickness of ITZ increases,the Young’s modulus decreases gradually.(4)When the ITZ is not considered,the Young’s modulus of the concrete is not influenced by the aggregate gradation,and is only related to the volume fraction of the aggregate.2.A Monte Carlo method was proposed to establish a three-phase random concrete aggregate model,and the corresponding APDL program was written.Then using the homogenization method,a random aggregate model of mortar and concrete was established,and the mechanical parameters of mortar and concrete were calculated using AHM.The calculated Young’s modulus of the concrete is compared with the test results,and there is a large difference between the two.Finally,the reasons for the large deviation between the calculation results and the test results are analyzed.