Experimental Study On The Fracture Behaviors Of Crumb Rubber Reinforced Recycled Aggregate Concrete After Exposure To Elevated Temperatures

Compared with natural aggregate,recycled aggregate has the disadvantages of loose structure and many internal defects,which causes the mechanical properties of recycled concrete to be worse than that of ordinary concrete.The modification of concrete by rubber can reduce the brittleness of concrete and enhance its high temperature resistance.This paper studies the change law,mass loss,fracture performance and internal microstructure of rubber recycled concrete after high temperature.The main research contents in this thesis include:(1)The crumb rubber content was at levels of 0%?2%?4% and 6% by volume substitution of sand,and the recycled aggregate replacement rate was at levels of 0%?50% and 100%.High temperatures(200??400??600?)exposure treatments were carried out for 108 notched beams(Width(9)height(9)length =100mm(9)100mm(9)515mm)in 36 groups.Experimental phenomena at different target temperatures and variation law of appearance of rubber recycled concrete incision beam specimens with different parameters were observed.And mass loss of each specimen was also measured.The results indicate that the color and crack of the specimen surface are obviously changed after different target temperature treatment,and the mass loss rate is also different.(2)Through the implementation of three-point bending test on the rubber recycled concrete notched beams specimen after high temperature,the load-deplacement curve,load-CMOD curve and load-strain curve are measure after measuring the test data.On this basis,the fracture energy,fracture toughness and double-k fracture parameters of rubber recycled concrete are calculated by formula,and the influence law of target temperature,amount of added rubber and recycled aggregate substitution rate on fracture performance is discussed.Rubber can obviously improve the fracture performance of recycled concrete at room temperature,but it has no obvious effect on the fracture performance of recycled concrete after high temperature.(3)The internal microstructure variation of rubber recycled concrete matrix after different target temperature treatment was observed by using field emission scanning electron microscope.Then the mechanism of rubber to improve the anti-bursting performance of recycled concrete and the change of hydration products in rubber recycled concrete were discussed.