Effects of elevated temperature on rubber concrete: Fracture properties and mechanism analysis

Recycling waste tires for the production of concrete materials with good toughness is a green and economical solution, but the severe deterioration of rubber under high temperatures limits its application in engineering practice. Therefore, to examine the impact of elevated temperature on the fracture characteristics of rubber concrete (RC), three-point bending fracture tests were conducted on RC with five rubber replacement rates and five treatment temperatures. The purpose was to correlate the fracture parameters of RC with the rubber replacement rate and the temperature. Then, by employing the digital image correlation (DIC) technology and microscopic testing methods, the crack evolution trend and the potential mechanism were analyzed in detail. The results indicate that rubber particles can effectively improve the toughness, deformation capacity, and fracture energy of concrete, but have a significant weakening effect on the load and fracture performance. When the treatment temperature is below 400 ℃, rubber particles mainly affect the initiation and propagation of cracks by alleviating the stress concentration phenomenon at the crack tip and improving the crack propagation path. Rubber particles may initiate cracks earlier, but significantly delay their propagation process. When the treatment temperature is above 400 ℃, rubber particles tend to exert a weakening effect on the fracture performance. As the temperature rises, the microstructure of rubber particles gradually changes from a relatively uniform state in close contact with the cement matrix to a fragmented state filled with pores separated from the matrix. This process will lead to severe deterioration of concrete performance. It is anticipated that the findings of this study will provide a theoretical basis for predicting the performance of RC in high-temperature environments.