Microstructure And Mechanical Properties Of Crushed-stone-reinforced Polymer Composites

Crushed-stone-reinforced polymer(SRP),as a new type of pile material,can not only overcome the shortcomings of small application scope of bulk pile,but also solve the problem of long maintenance time of cement fly-ash gravel pile,which has broad development prospects.In order to study the relationship between the composition,structure and mechanical properties of SRP,the meso-mechanical method was used to analyze the influence of each meso component on the mechanical properties of SRP.The main contents and achievements are as follows:(1)The parameters index of polymer microstructure were determined,and the microstructure characteristics of SRP were analyzed quantitatively.The influence of crushed stone on the micro morphology of polymer was studied,and the definition and determination method of the interface transition zone(ITZ)between polymer and crushed stone were proposed.There are two types of ITZ in SRP,one’s density is lower than the matrix density,the other one’s density is higher than the matrix density.Under the same matrix polymer density,the width of ITZ increases with the increase of stone particle spacing.Under the same spacing of stone particles,the width of ITZ and the content of high-density ITZ increase with the increase of matrix density.It provides a basis for the establishment of SRP meso-numerical model and the determination of parameters.(2)The geometric representative volume element(RVE)of polymer material was determined quantitatively,and the meso-mechanical model of polymer was established.The closed cell model based on the statistical similarity of the mesostructure was constructed,and the geometric RVE of polymer was determined.The meso-mechanical simulation of the uniaxial tension and compression of the polymer material was carried out.The results show that the size of the geometric RVE of the polymer is about 13 ～23 times of the average cell diameter;The stress-strain curves obtained by numerical simulation are in good agreement with the experimental results,and the numerical simulation results of elastic modulus and strength are basically consistent with the theoretical predictions and experimental results.It provides a basis for the parameter setting of polymer materials in SRP meso-numerical model.(3)The 3-phase SRP meso-numerical model of matrix,crushed stone and ITZ was established,and the applicability of the model was verified.The generation of crushed stone in the model is based on the statistical analysis of the structural characteristics of the crushed stone on the section of the SRP specimen.The ITZ in the model can be divided into low-density ITZ(the density of ITZ is lower than that of matrix)and highdensity ITZ(the density of ITZ is higher than that of matrix).The effects of finite element mesh size and crushed stone random distribution on the mechanical properties of SRP were calculated,and the mechanical properties and failure process of SRP under axial compression were simulated.The results show that the model has high applicability and stability.It provides a basis for the meso analysis of mechanical properties of SRP.(4)The numerical simulation of SRP under axial compression was carried out,and the influence of meso components on its mechanical properties was analyzed.The results show that crushed stone can increase the elastic modulus of polymer materials,has little effect on the compressive strength,which can save polymer materials;The elastic modulus and compressive strength of SRP increase significantly with the increase of matrix polymer density,and decrease with the increase of relative content of low-density ITZ or width of ITZ;The increase of crushed-stone content can raise the elastic modulus of SRP and increase the content of low-density ITZ,resulting in a slight decrease in the compressive strength of SRP.Matrix density and low-density ITZ are the main factors affecting the crack development of SRP.