Modeling of Stresses and Strains in Bonded Concrete Overlays Subject to Differential Volume Changes

Most materials used in concrete overlays undergo volume changes due to thermal and moisture movements, while the dimension of substrate concrete is relatively stable. As a result, normal and shear stresses are induced. These stresses can lead to cracking in repair material and interface delamination. Then harmful substances can penetrate into concrete through these cracks and accelerate further deterioration of concrete and reinforcement. Finally the concrete overlay fails. Various analytical models have been developed to calculate stresses and strains in bonded concrete overlays subject to differential volume changes. Most of these models are based on the linear elasticity and the Bernoulli’s hypothesis of plane remaining plane. However, it have been argued that the linear elasticity and the Bernoulli’s hypothesis do not apply for the case of bonded concrete overlay subject to differential shrinkage, and the restraint of the shrinkage of repair material is localized at interface. In this paper, new an analytical model is developed based on the classical plate theory and the assumption of the linear relation between shear stress and slip at the interface. With this model, the influence of the shear stiffness of the interface, the dimension of concrete overlays, and the elastic moduli of two materials on the stresses will be discussed. The high shear stiffness increases the potential of cracking in the repair material. Both too large and too small shear stiffness have a negative effect on the performance of the interface. In the concrete overlay with a long and thin repair material, the repair material is more likely to crack. The long and thick repair material results in high normal and shear stresses at the interface. The repair material with higher elastic modulus has a better resistance to cracking. The elastic modulus has a small effect on the interface delamination.