Research On Uniaxial Compression Constitutive Relationship And Damage Model Of Recycled Concrete

In order to achieve sustainable development of the construction industry,recycled concrete as a new type of green building materials has become a hot topic in academic and industrial research,and has achieved some technological achievements with application prospects.A lot of research on the mechanical properties of recycled concrete has been studied by domestic and foreign scholars.The research results are different due to the difference between recycled aggregates and test methods.At present,there are few related achievements on the failure process of recycled concrete by damage theory.The model of recycled concrete compression damage needs further study for the popularization and application of recycled concrete structures in the future.In order to study the effect of recycled aggregate types and dosages on the constitutive model of the test material,five groups of tests are designed,namely: ordinary concrete group;recycled coarse aggregate replacement group;recycled fine aggregate replacement group;recycled coarse and fine aggregate replacement group and fiber group(the replacement rates of different recycled aggregates are 30%,50% and 100% respectively,and the fiber dosage is 1.5kg per cubic meter of concrete).The uniaxial compression test of recycled concrete is carried out for each group of specimens.The effects of the type and amount of recycled aggregate on compressive strength,elastic modulus,peak strain and ultimate strain of the specimens are compared and analyzed by experimental data.The expressions of elastic modulus,peak strain and stress-strain full curve of the specimens are obtained.The results show that the amount of recycled aggregate is negatively correlated with compressive strength and elastic modulus,and positively correlated with peak strain and ultimate strain;The incorporation of fibers increases the compressive strength,peak strain and ultimate strain of recycled concrete,and the ductility is well improved.The stress-strain curves of recycled concrete are similar to those of the conventional concrete and the effect to fit the test stress-strain curve based on the model of GUO Zhenhai is better.Based on the experimental data,the recycled concrete is used as the test material with initial damage,and the initial damage is used to quantify the effect of the type and amount of recycled aggregate on the test.According to the concrete uniaxial compression damage constitutive model of concrete code,the uniaxial compression damage model of recycled concrete is established,and the effect to validate the model based on the experimental data is better.The study analyzes the uniaxial compression damage evolution process of different recycled aggregate concretes.The results show that the damage evolution process of different recycled aggregate concretes is similar.Before the peak strain is reached,the damage of the specimen is relatively large.As the strain of the specimen increases,the damage will gradually increase,and eventually it will tend to be consistent.The incorporation of recycled fine aggregate will have little effect on the damage of the specimen.The addition of fibers can significantly reduce the initial damage of the specimen.