Experimental Study On Basic Mechanical Properties And Damage Damping Capacity Of Polypropylene Fiber Concrete Modified By Rubber Powder

In practical engineering,high-rise and super-high-rise buildings will inevitably be subjected to extreme loads,such as typhoons and earthquakes.The action of extreme load will lead to the damage of the members and even the failure of the structure.Therefore,in the practical engineering,the vibration of the structure is controlled in a reasonable range by means of dampers or isolation.However,the improvement of damping capacity of concrete is neglected.Therefore,in order to improve the damping capacity of concrete,a new type of concrete material mixed with rubber powder and polypropylene fiber was prepared.The basic mechanical properties and damage damping capacity of composite concrete were calculated by axial compression test,free attenuated vibration test and microstructure test.The specific research contents are as follows.(1).Basic mechanical properties: Ten groups of concrete with different mix proportion were designed,and three prism specimens were prepared for each group.Based on the axial compression test of prismatic specimens,the basic mechanical properties such as compressive strength,stress-strain curve,Poisson’s ratio and elastic modulus of prismatic specimens are studied.The test results show that the addition of polypropylene fiber concrete increases the peak strain of concrete,but has no obvious effect on the peak stress;When 4.5% rubber powder is added into polypropylene fiber concrete,the peak stress is reduced by about 18%,the peak stress is reduced by about17%,and the Poisson’s ratio is between 0.18-0.22.(2).Damage damping capacity: through the low cycle repeated damage test and free vibration attenuation test of the cantilever,the bending performance and damping characteristics of the cantilever are studied.The test results show that the damping capacity of polypropylene fiber reinforced concrete increases with the increase of polypropylene fiber content,but the working performance will decrease if the content of polypropylene fiber is too much;The addition of 4.5% rubber powder enhances the damping capacity of concrete and reduces the compressive strength of concrete;With the increase of the content of polypropylene fiber reinforced concrete,the degradation rate of the dynamic bending stiffness of the cantilever beam slows down,while the rubber powder accelerates the degradation rate;the nonlinear relationship between the damage index of the cantilever beam and the displacement angle is established.(3).Monitoring means: combining with digital image correlation(DIC)technology,the surface crack development and full field strain distribution of prism specimen during loading are tracked;By using scanning electron microscope(SEM)to observe the micro properties of the specimen surface,it is found that the existence of harmful holes formed by rubber powder falling off is the main reason for the deterioration of concrete performance.