Study On Meso Damage Of Rubber Concrete Based On Random Aggregate Model And X-CT Test

Rubber concrete is widely used in highway engineering and railway engineering.On the one hand,adding rubber into concrete can solve the problem of "black pollution" of waste rubber and realize the recyclability of resources;On the other hand,rubber particles can improve the cracking resistance of concrete and enhance the ductility of concrete.Therefore,it is necessary to do further research on rubber concrete to meet the needs of practical engineering.At present,the research of rubber concrete is mainly on the macro scale and micro scale,and the research on the meso scale is few.In fact,the meso mechanical analysis has obvious advantages: on the one hand,the meso test can completely present the spatial damage shape that cannot be reached by the macro test,so as to provide the basis for analyzing the weak position in the concrete;On the other hand,the micro test avoids the uncertainty on the micro scale,and the research results are not affected by the sampling position,and the error is small.Therefore,this thesis attempts to study the uniaxial compressive strength,unit compression damage and pore crack morphology of rubber concrete by using two research methods on the meso scale: random aggregate numerical simulation and X-CT tomography test.The main research results are as follows:(1)A two-dimensional and three-dimensional random aggregate model of rubber concrete with repeatable operation,simple operation,low cost and high precision is established.(2)The factors affecting the uniaxial compressive strength of rubber concrete are analyzed.It is found that the lower the loading rate and the greater the rubber content,the greater the uniaxial compressive strength of rubber concrete;When the number of aggregate edges is between 6 ～ 7 and the rubber particle size is between 5.5 ～ 6.5mm,the strength of rubber concrete reaches a maximum.The influence of content and particle size on uniaxial compressive strength has an order: when the content is low,the compressive strength is mainly determined by particle size,and when the content is high,the compressive strength is mainly determined by the content.(3)It is found that the higher the loading rate,the greater the rubber content and the smaller the particle size,the greater the unit damage rate of rubber concrete;When the number of edges of aggregate is between 6 and 7,the unit damage rate of rubber concrete reaches a minimum.The distribution of aggregate will only affect the location of unit damage and the path of damage development,and will not affect the unit damage rate.(4)The difference between the two-dimensional and three-dimensional aggregate strength obtained by the two-dimensional random analysis is slightly higher than the actual aggregate strength of 724.7x = 3-dimensional random analysis,and the two-dimensional and three-dimensional aggregate strength obtained by the two-dimensional random analysis is slightly higher than the actual aggregate strength.(5)The pore morphology characteristics of rubber concrete are studied.It is found that the section porosity of rubber concrete is larger than that of ordinary concrete,the number of pores is more than that of ordinary concrete,the longitudinal distribution of pores is more uniform than that of ordinary concrete,and the fluctuation of porosity is smaller than that of ordinary concrete;In addition,the pore size distribution of rubber concrete is also more concentrated than that of ordinary concrete,and the critical pore size,pore size variance and median pore size are smaller than that of ordinary concrete.The fractal dimension of rubber concrete pores is larger than that of ordinary concrete,and the smaller the particle size is,the larger the fractal dimension is.(5)The crack morphology characteristics of rubber concrete are studied: it is found that when ordinary concrete and rubber concrete are under uniaxial compression,the cracks extend from the edges to the interior of the member,the main cracks are at an angle of 70 ° ～ 80 ° with the horizontal direction,the cracks are mainly distributed at the position of 10 ～ 20 mm outside the member,and the core tube in the middle of concrete is relatively stable.The maximum crack length,maximum crack connecting area and total crack area of rubber concrete are less than those of ordinary concrete,but the average number of cracks is higher than that of ordinary concrete,and the fractal dimension is also higher than that of ordinary concrete.This thesis has 78 figures,25 tables and 121 references.