Effect of fatigue load on damage and fracture properties of rubber concrete

Although rubber concrete has better properties of plasticity and fatigue, due to the incorporation of rubber, its dispersion increases under fatigue load and the damage process and the ultimate fracture mechanism are not clear. In order to study the damage and fracture performance of rubber concrete under fatigue load, the three-point bending fatigue fracture test of concrete with different rubber contents under fatigue load based on acoustic emission was carried out. The effective crack length a was calculated and the change law of the crack length a of the rubber concrete with different rubber contents under the fatigue load was analyzed. The crack length a_c and the acoustic emission cumulative energy E_AE were used to define the damage variables D_a and D_AE.The variation law of the fracture energy G_F of the rubber concrete with different rubber contents under the fatigue load and the law of the occurrence and propagation of cracks in the rubber concrete under the fatigue load were analyzed using the signal duration in the acoustic emission. The results show that the fracture energy of the concrete increases linearly with the increase of the rubber content. Under the fatigue load, both a and D_a change in an inverted S-shaped law, while D_AE shows a positive S-shaped law; The duration of the acoustic emission signal shows that the cracks in the rubber concrete always appear or expand when the load is small under the fatigue load.