Microstructure And Fracture Properties Of Crumb Rubber Concrete

Compared with ordinary concrete,rubber concrete has certain advantages in terms of anti-abrasion,crack resistance,impermeability,frost resistance,earthquake resistance,etc.,and can effectively reduce the use of natural aggregates and the accumulation of waste rubber.A large number of applications in actual water conservancy projects will produce huge economic and environmental benefits.However,the strength of rubber concrete is low,and the fracture mechanism is more complex,which greatly limits its application.The macroscopic performance of material properties is often closely related to its microstructure.In view of this,this paper studies the microstructure and fracture performance of rubber concrete,discusses the influence of environmental temperature and humidity on the strength and fracture performance of rubber concrete,in order to promote its application in water conservancy projects.The main research contents and achievements are as follows:(1)The formation process of rubber concrete microstructure was studied.Scanning electron microscopy and pore structure parameter analyzers of hardened concrete were used to observe the changes in microstructure of hydration products,microcracks,micropores and other interfaces in rubber concrete at different ages,and the effects of some microstructures on macro strength were discussed.The results show that the rubber particles do not participate in the hydration process of the cement.After 7 days of standard curing,the length density of micro-cracks around rubber particles in rubber concrete increases with age.The compressive strength of rubber concrete increases with the increase of curing age,and after 14 days,it has a negative correlation with the pore spacing coefficient and the average pore diameter.(2)The basic mechanical properties of rubber concrete under different temperature and humidity were studied.After simulating the complex temperature and humidity environment of the hydraulic concrete structure,the cube compression and splitting tensile tests were carried out.The results show that the compressive strength and splitting tensile strength of rubber concrete increase first and then decrease with the increase of ambient temperature.However,when the ambient temperature is lower than zero,the strength of rubber concrete will be greatly improved under low temperature.The influence of environmental humidity on the strength of rubber concrete is relatively small,and the strength increases with the increase of environmental humidity.(3)The fracture behavior and cracking process of rubber concrete were studied.Combined with digital image correlation(DIC)technology,a three-point bending beam fracture test was carried out.The results show that the fracture toughness and fracture energy of rubber concrete increase first and then decrease with the increase of ambient temperature.The influence of environmental humidity on the fracture toughness and fracture energy of rubber concrete is relatively small.The fracture toughness and fracture energy increase with the increase of environmental humidity.The main fracture mode of rubber concrete is type I fracture.The maximum width and crack width of the fracture process area are close to that of ordinary concrete.The width of the fracture process area is about half of the maximum aggregate diameter,and the crack width almost decreases linearly with the increase of the height.