Numerical Model for Minimizing Risk of Damage in Repair System

Abstract

New cement-based repair overlays are subject to restraint and eigenstresses that can lead to crack formation and delamination. The origin of this complex state of stresses is found in the dimensional instability of the new coating. Drying shrinkage, autogeneous shrinkage, and temperature gradients are the most important loads acting on the system. In most cases the design of such coating systems is carried out in an empirical way. In this paper a new approach based on a numerical model is proposed to determine the relevant key parameters for the design of repair systems. By means of this model time-dependent moisture distributions and crack evolution in a drying concrete repair system can be simulated in a realistic way. Crack formation and delamination is described, with the smeared and discrete crack models, applying nonlinear fracture mechanics. The relevant material parameters influencing shrinkage cracking and delamination are identified by means of a sensitivity analysis. Finally, this approach is applied to analyze in a rational way the repair measures on a concrete bridge. This study primarily aimed to decide which repair material is more suitable with respect to shrinkage-induced damage and consequently which one provides the highest durability for the rehabilitated structure.