Failure mechanisms and tensile relaxation of bonded concrete overlays subjected to differential shrinkage

Restraint of shrinkage deformations is the main factor influencing the serviceability and durability of bonded concrete overlays. Failure mechanisms associated with differential shrinkage stresses are cracking and debonding. Tensile overlay relaxation may release a considerable amount of the imposed stresses and is therefore of major importance for the performance of the overlay. Composite specimens were used for the identification of fundamental characteristics of strain development of bonded concrete overlays, with regard to different interface textures and overlay materials. The development of overlay strains and material parameters in relation to the observed mechanisms of overlay failure allowed an estimation of the magnitude of tensile relaxation. A simplified approach to tensile stress relaxation in bonded overlays is introduced.