Research On Mechanical Properties Of Recycled Concrete Based On Meso Structure

Recycled concrete usually refers to the new concrete made of recycled aggregate or partly replaced by natural aggregate.Using the recycled concrete technology,the waste concrete can be maximized,and the original performance of the abandoned concrete is fully played through the crushing process,and a new green building material is formed.The application of recycled concrete technology not only reduces the waste of waste concrete but also reduces the use of natural aggregate.It is a new technology that is worth popularizing in green and environmental protection.It is generally believed that the ordinary concrete consists of three phase material,and the recycled concrete is made up of five phase materials.Because of the existence of old hardened mortar,the microstructure of recycled concrete is more complex than that of ordinary concrete.Through the selection of a reasonable calculation model,the numerical simulation can avoid the restriction of the test conditions and the influence of human factors,so as to link the microstructure of recycled concrete with the macroscopic mechanical properties.Two dimensional and three-dimensional mesoscopic structures of recycled aggregate concrete are proposed,which consist of new hardened mortar,old hardened mortar,internal interface area,external interface area and five phase material of natural aggregate.Based on the concrete damage plastic constitutive model and Monte Carlo method,the two-dimensional concrete random aggregate program is written in MATLAB language,and the three-dimensional random aggregate program is programed with Python.Through the finite element software ABAQUS,the two-dimensional and three-dimensional random aggregate calculation model of recycled concrete with double interface are established.The mechanical properties of recycled concrete under uniaxial compression and tensile load are studied,such as compressive strength,tensile strength,peak strain and so on.The damage and stress distribution of recycled concrete are investigated,and the impact of the mechanical properties of each phase material on the macro mechanical properties of recycled concrete are analyzed.The results show that two dimensional recycled concrete random aggregate model is established by using MATLAB algorithm,and a three-dimensional recycled aggregate random aggregate model is established by using Python algorithm.The two models have obtained good calculation results.Under uniaxial compression,damage and failure of recycled concrete specimens are caused by tensile stress and shear stress concentration.Under uniaxial tensile load,the damage and failure of recycled concrete specimens are caused by internal tensile stress concentration.The strength of the new hardened mortar and old hardened mortar has great influence on the mechanical properties of the recycled concrete specimen,and the strength of the inner interface zone and the outer interface area is smaller.The older hardened mortar content is more obvious to the weakening of the mechanical properties of the recycled concrete.