Influence of aggregate interlock on the shear resistance of reinforced concrete beams without stirrups

Aggregate interlock is known to play an essential role in the development of the shear resistance of reinforced concrete (RC) beams not containing transverse reinforcement. The term 'aggregate interlock' describes the possible shear transfer between two opposing crack surfaces, which mainly depends on crack kinematics and crack surface roughness. An extensive experimental programme has been conducted at TU Wien, which consisted of 18 push-off tests and ten shear beam tests on specimens prepared from six different concrete mixtures. Different levels of surface roughness were achieved by varying the volume of coarse aggregate and the amount of cement in the mixtures, resulting in uniaxial compressive strengths ranging from 40 to 60 MPa. The results of the individual tests (roughness, push-off, and shear tests on beams) are combined and used to develop new ways to evaluate the impact of aggregate interlock on the shear strength of RC beams.