Study On Mechanical Properties And Constitutive Relationship Of Steel Fiber Scoria Aggregate Concrete After Fire Exposure

As a new green material,scoria aggregate concrete has been gradually used in some construction projects because of its light weight,high strength,good high temperature resistance,and its ability to reduce the environmental impact of construction materials.Therefore,in this paper,based on the research results of light aggregate concrete,the mechanical properties and constitutive relationship of steel fiber scoria aggregate concrete after high temperature are studied experimentally considering the temperature,scoria aggregate replacement rate,and steel fiber volume content.Through regression analysis of the experimental results,the principal structure relationship equation of steel fiber scoria aggregate concrete after high temperature is established,which provides a reference for the fire design of steel fiber scoria aggregate concrete structures and the evaluation and repair after fire,as follows.1.Physical properties tests,as well as chemical properties tests,were carried out on scoria aggregate aggregates to obtain the material properties of scoria aggregate aggregates.High temperature tests were carried out on concrete specimens to obtain the crack development of the steel fiber scoria aggregate concrete mixed after being subjected to different high temperatures.The color change of the surface of the steel fiber scoria aggregate concrete specimens after experiencing high temperature and the effect of steel fiber volume content and scoria aggregate substitution rate on the crack development of the concrete specimens were obtained.2.The cubic compressive test and splitting tensile test were conducted on the steel fiber scoria aggregate concrete specimens after high temperature,and the changes of mechanical properties of steel fiber scoria aggregate concrete specimens with 12 different fitting ratios under different temperature effects were obtained,and the residual mechanical properties of steel fiber scoria aggregate concrete were analyzed and fitted to the test results.The results show that: the mechanical properties of the specimens of steel fiber scoria aggregate concrete begin to decrease significantly with the increase of the fire temperature;increasing the replacement rate of scoria aggregate in concrete can reduce the loss of mechanical properties of concrete specimens due to high temperature,but the increase of the replacement rate of scoria aggregate will also slightly reduce the mechanical properties of concrete specimens without fire;mixing the appropriate amount of steel fiber in the specimens of scoria aggregate concrete can improve the mechanical properties of concrete specimens.The mechanical properties of concrete specimens can be improved by incorporating appropriate amount of steel fibers into the concrete specimens,but the improvement of mechanical properties of concrete specimens will be reduced when the amount of steel fibers is greater than 1%.3,the steel fiber scoria aggregate concrete specimens were subjected to the prismatic axial compressive test,and the changes of stress-strain curves of 12 different concrete ratios under different temperatures were obtained by DIC,and the fitting equations of residual peak strain,residual modulus of elasticity and residual ultimate strain were obtained by analysis of the test results.The results show that: with the increase in temperature,the peak strain of steel fiber scoria aggregate concrete increases,the elastic modulus decreases significantly,and the ultimate strain increases: with the increase of the replacement rate of scoria aggregate,the increase of the peak strain of steel fiber scoria aggregate concrete after high temperature decreases,the discount factor of elastic modulus increases,and the discount factor of ultimate strain decreases;with the increase of the steel fiber admixture,the peak strain of steel fiber scoria aggregate concrete The peak strain of steel fiber scoria aggregate concrete increased with the increase of steel fiber admixture.4.The stress-strain curve of the post-high temperature steel fiber scoria aggregate concrete was obtained by compiling and analyzing the test data,and the constitutive relationship equation of the post-high temperature steel fiber scoria aggregate concrete was obtained by curve fitting.The simulated values of the principal structure relationship equation were compared with the experimental values and found to be in good agreement,which can predict the full stress-strain curve from the test better.