Meso-scale Modeling And Damage Analysis Of Epoxy Polymer Concrete Under Multiaxial Loading

Epoxy polymer concrete is manufactured by blending aggregates with epoxy resin and cured for short time.Because of its excellent mechanical properties and good weather resistance,it is favored by the engineering.So far,epoxy polymer concrete has been applied in bridge pavement,railway sleeper and mechanical foundation.During the engineering service,epoxy polymer concrete is generally subjected to complex loads,and its performance is also challenged by harsh environment.It is of great significance to fully understand the failure process and mechanism of epoxy polymer concrete and reveal the damage behavior of epoxy polymer concrete under multiaxial loading.The mesoscale simulation of concrete is an effective means to investigate the mechanical properties.However,the aggregate content of epoxy polymer concrete is extremely high.When serving as pavement,its gradation is characterized by high content of large aggregate and large amount of small aggregate.Therefore,it is very difficult to establish the mesoscale model.At the same time,different from silicate concrete,the matrix of epoxy polymer concrete is epoxy resin with high tensile strength,and the bonding property between resin and aggregate is excellent,resulting in the aggregate fracture under simple working conditions.The traditional mesoscale finite element model of concrete may not be applicable for epoxy polymer concrete.In this paper,a mesoscale modeling method suitable for epoxy polymer concrete is studied,and on this basis,the characteristics of mesoscale finite element model of epoxy polymer concrete are explored.Then a thorough study on the damage behavior of epoxy polymer concrete under biaxial/ triaxial loading was made based on the mesoscale finite element model.This paper will also study the residual mechanical properties of epoxy polymer concrete under the condition of accelerated aging,imitating the environmental condition including ultraviolet light,high temperature and high humidity.The main contents and achievements are as follows:(1)A polygonal/polyhedral aggregate database based on the statistical law of shape parameters of epoxy polymer concrete was established.Through the improved take-and-place method,the ultra-high content random polygon aggregate was achieved,and the quasi-two-dimensional mesoscale modeling of epoxy polymer concrete was realized based on the background grid method.For three-dimensional modeling,the coarse aggregates were generated by shrinking the cells of Voronoi.On this basis,the delivery of fine aggregate was realized through the take-and-place strategy with scan line-based method.Finally,a three-dimensional mesoscale model with ultra-high aggregate content and satisfing the gradation of epoxy polymer concrete aggregate was generated.(2)The four-point bending and uniaxial compression experiments of epoxy polymer concrete were carried out.Through the quasi-two-dimensional mesoscopic model and uniaxial tensile simulation,the interphase characteristics of epoxy polymer concrete were determined,and the essence of the interphase of epoxy polymer concrete was reasonably explained.The influence of the zig-zag boundary introduced by the background grid method on the simulation results was analyzed.Through the simulation study of epoxy polymer concrete under four-point bending and uniaxial compression load,the damage evolution of epoxy polymer concrete under simple working conditions was reproduced.(3)Based on mesoscale finite element simulation,the mechanical response of epoxy polymer concrete under biaxial tension,biaxial compression and tension-compression combined loading with different loading speed ratio was studied.This paper focused on the damage behavior of epoxy polymer concrete under different loading conditions,and the similarities and differences between the failure envelope curve of epoxy polymer concrete and silicate concrete under biaxial loading were compared.Moreover,the failure characteristics of epoxy polymer concrete under triaxial tension/compression load were explored.(4)An accelerated aging test scheme with reference to the climatic conditions in South China was designed to study the residual bending properties of epoxy polymer concrete after aging.A laminated beam model,considering aging damage layer,was established.The residual flexural strength of epoxy polymer concrete after different aging time was successfully predicted.