Research On Mechanical Properties And Micro Mechanism Of Basalt Fiber Reinforced Recycled Aggregate Concrete After High Temperature

The method of basalt fiber(BF)modification can improve the mechanical properties of recycled aggregate concrete(RAC),and can effectively promote the recycling of construction waste,which has become a research hotspot.However,compared with high-temperature performance,the research content is more focused on room temperature performance,and mainly focused on the research of basic mechanical properties.Based on this,a series of experimental studies of basalt fiber reinforced recycled aggregate concrete(BFRRC)high temperature test and uniaxial compression,conventional triaxial compression,and micro-electron microscopy of BFRRC after high temperature had been carried out successively.The main work and results are as follows:(1)The physical and mechanical properties of BFRRC were tested after high temperature,the influence of variable parameters on the basic mechanical properties such as cube compression,axial compression and so on were discussed,and axial compression stress-strain curve of the test blocks after high temperature were measured.The results show that: the basic mechanical properties of BFRRC gradually decrease with the increase of temperature and replacement ratio,and gradually increase with the increase of BF dosages.Finally,By introducing the influence factors such as replacement ratio,BF dosages and temperature,the equation of stress-strain curve under uniaxial compression is established.(2)To study the influence of variable parameters on the conventional triaxial compression performance and failure criterion of BFRRC,a conventional triaxial compressive test of BFRRC was carried out.the axial stress-strain relationship curve was measured.By introducing the influence factors such as replacement ratio,BF dosages,temperature and confining pressure,the whole process curve equation of axial stress-strain under triaxial compression was established.The influence of variable parameters on the peak stress and other indicators is revealed.Based on Mohr-Coulomb theory,the influence of different variable parameters on the failure criterion of BFRRC was discussed,and the envelope curve equation was established.The results show that the peak stress,elastic modulus and energy dissipation capacity decrease with the increase of temperature and replacement ratio,and increase with the increase of lateral confining pressure and fiber dosages.The peak strain of the specimen increases with the increase of temperature and confining pressure,and increases and decreases with the increase of replacement ratio.The fiber has no obvious effect on the peak strain.The ductility of test blocks increases with the increase of lateral confining pressure,fiber dosages and replacement ratio,and decreases with the increase of temperature.According to the Mohr-Coulomb theory,it is found that the shear strength of BFRRC decreases with the increase of replacement ratio and temperature,and increases with the increase of fiber dosage.The calculated value of the established envelope curve is in good agreement with the measured value.(3)The morphology of BFRRC was observed by scanning electron microscope.The influence of temperature,recycled aggregate and fiber on the mortar matrix and interfacial transition zone(ITZ)was explored,and the modification mechanism of BF on RAC was explored,which revealed the reasons for the changes of macro mechanical properties under different influencing factors from the micro level.