Abstract
The paper focuses on the propagation of debonding along an interface between a concrete substrate and a cement-based thin-bonded overlay under fatigue loading. The investigated overlay materials were fibre reinforced and rubberised cement-based mortars. Tensile tests were performed to obtain the residual normal stress-crack opening relationship for the overlay materials. The drying shrinkage of the overlay materials was characterised by tests on prismatic specimens that showed the evolution of drying shrinkage vs. the mass loss. The substrate-overlay interface was investigated by static tensile tests to provide the relationship between debonding opening and residual normal tensile stress. Its evolution under fatigue loading was assumed to follow a cyclic bridging law for plain concrete. Three-point bending fatigue tests were then carried out on repaired substrate to obtain information on the structural behaviour of the interface. The debonding propagation was monitored by a video microscope with a magnification of 175x. Relying on the identified and quantified parameters, the above-mentioned fatigue tests were modelled by the finite element method using the CAST3M code developed in France by Atomic Energy Commission. A comparison between model and experimental results shows good agreement and proves the important role of fibre reinforcement and of rubber aggregates on the durability of the repair with respect to debonding.