Recycled Concrete Performance Prediction And Engineering Applications

The performance of recycled concrete directly affects the feasibility of its engineering applications.At present,there is a lack of corresponding mechanical theory prediction research for the study of the elastic modulus of recycled concrete which is an important mechanical index.In addition,the acoustic emission characteristics of the damage process of recycled concrete and the existence of the Kaiser effect have not been adequately studied.In addition,the application of recycled aggregates to road base not only consumes a large amount of construction waste but also has relatively low requirements on the performance of recycled aggregates.However,the study of waste clay brick content on the road performance of cementstabilized recycled aggregates is not sufficient due to the great proportion of waste clay brick production in construction waste.In this study,the physical and microscopic properties of recycled aggregates were first investigated.The results show that the recycled aggregate contains a large number of pores and interfacial transition zone(ITZ)making its physical properties such as apparent density,water absorption,and crushing values decrease,but its composition and content of each element indicate that it can replace natural aggregate for engineering construction.Secondly,four prediction models for the elastic modulus of recycled concrete were obtained based on four classical models in micromechanics,including the Voigt model,Reuss model,Eshelby method,and Mori-Tanaka method.The optimal prediction model was determined experimentally,and it was compared with the models predicting the elastic modulus of concrete in the literature.The results show that the Mori-Tanaka method has the best prediction performance compared with both the experimental and existing models,indicating the wide applicability of this method for the prediction of the elastic modulus of recycled concrete.In addition,the acoustic emission characteristics of the damage evolution process of recycled concrete with different replacement rates of recycled coarse aggregate(hereinafter referred to as the replacement rate)and the presence of the Kaiser effect were researched on the basis of the acoustic emission technique.The results show that the peak acoustic emission energy of recycled concrete is higher than that of ordinary concrete during uniaxial compression,and the dominant frequency decreases in the early and late loading periods,and the magnitude of the peak energy and the amount of acoustic emission energy generated in the mid-loading period increase with the substitution rate,and the magnitude of the dominant frequency and the frequency change decrease.The recycled concrete has Kaiser effect,but there is no lower-stress limit.And the upper-stress limit of recycled concrete Kaiser effect is increased compared with the ordinary concrete.Finally,the experimental study on the effect of waste clay brick(WCB)content on cementstabilized recycled aggregate(RCA)was carried out to verify its road performance by test section laying and finite element analysis.The results show that the appropriate amount of WCB fine aggregate is beneficial to the performance of cement stabilized WCB/RCA blends,while WCB coarse aggregate has a poor effect on the performance of blends.According to the test results of the test,a trial pavement section was paved and its test results meet the construction design requirements.The results of finite element analysis showed that the maximum vertical displacement and maximum von Mises stress both increased with the decrease of resilient modulus of cement stabilized WCB/RCA blends.This study takes recycled concrete as the research direction and engineering applications,providing a basis for the study of micromechanics in recycled concrete,a theoretical and practical basis for establishing a damage assessment system for recycled concrete,and promoting the application of WCB in road base.