Numerical simulation of concrete expansion in concrete dams affected by alkali–aggregate reaction: state-of-the-art

Abstract

Many concrete dams and other concrete structures in Canada, and throughout the world, are suffering from deteriorations induced by alkali–aggregate reaction (AAR) that impair the durability and serviceability, and might also affect, in the long term, the safety of the installation. Alkali–aggregate reaction produces concrete expansion, and generally leads to a loss of strength and stiffness (cracking), and generates undesirable deformations and disturbances in the equilibrium of internal forces. The expansion mechanisms in concrete affected by AAR are complex and influenced by a number of factors that are difficult to quantify. Nevertheless, advanced numerical simulation models are generally used in close conjunction with field monitoring of displacements to assist in the structural evaluation and rehabilitation of dams where AAR has been identified. A review of the physical processes that control the structural behaviour of concrete dams suffering from AAR, and numerical simulation procedures to represent AAR concrete expansion by the finite element method, is presented herein. The present state of knowledge to simulate the AAR expansion process has been found to be limited and not yet satisfactorily developed. A methodology to distribute the observed concrete expansion in proportion to the compressive stress state, temperature, moisture, and the reactivity of the concrete constituents is proposed in this paper as a first step to rationalize the numerical modelling of the AAR concrete swelling process in concrete dams. Key words: alkali–aggregate reaction, concrete dams, finite element method, dam safety.