Experimental investigation on mode I fracture characteristics of rock-concrete interface at different ages

Abstract

Listen

Translate article

• The mode I fracture toughness of rock-concrete interface at different ages was obtained. • The fracture energy of rock-concrete interface was calculated. • The acoustic emission (AE) signal of the fracture process of rock-concrete interface was recorded. • The failure characteristics of the interface between different types of rocks and different ages of concrete were analyzed. To investigate the mode I fracture mechanical properties and failure characteristics of rock-concrete interface at different ages, tests of notched semi-circular bending (NSCB) were conducted on rock-concrete specimens using a servo-controlled material testing machine (MTS Insight). For the tests, granite, limestone, sandstone and marble were used to form bi-material semi disc specimens with concrete of different ages. The uniaxial compressive strengths of granite, limestone, sandstone and marble are 139.79, 121.91, 71.67 and 105.42 MPa, respectively. And the uniaxial compressive strengths of concrete at 1, 3, 7 and 28 d are 5.9, 19.58, 22.60 and 27.40 MPa, respectively. Experimental results indicate that the fracture energy and fracture toughness of granite-concrete interface, limestone-concrete interface and marble-concrete interface increase with the age of concrete, and the growth rate is the fastest at [2d, 3d], but the growth rate decreases significantly at [4d, 7d]. For the sandstone-concrete interface, the fracture toughness also increases with the increase of concrete age, but the fracture energy at 28 d is significantly lower than that at 7 d. Interestingly, when the age of concrete is 1 d, the fracture toughness and fracture energy of rock-concrete interface are negatively correlated with the density of rock material. During the fracture process of rock-concrete interface, the intensity of acoustic emission signal at 28 d age is significantly higher than that at 1 d age. In addition, the failure characteristics of the rock-concrete interface are obviously different at different ages. At the same time, the rock type has a great influence on the failure characteristics of the interface.