NUMERICAL-SIMULATION CT CONCRETE EXPANSION IN CONCRETE DAMS AFFECTED BY ALKALI-AGGREGATE REACTION - STATE-OF-THE-ART

Many concrete dams and other concrete structures in Canada, and throug hout the world, are suffering from deteriorations induced by alkali-ag gregate reaction (AAR) that impair the durability and serviceability, and might also affect, in the long term, the safety of the installatio n. Alkali-aggregate reaction produces concrete expansion, and generall y leads to a loss of strength and stiffness (cracking), and generates undesirable deformations and disturbances in the equilibrium of intern al forces. The expansion mechanisms in concrete affected by AAR are co mplex and influenced by a number of factors that are difficult to quan tify. Nevertheless, advanced numerical simulation models are generally used in close conjunction with field monitoring of displacements to a ssist in the structural evaluation and rehabilitation of dams where AA R has been identified. A review of the physical processes that control the structural behaviour of concrete dams suffering from AAR, and num erical simulation procedures to represent AAR concrete expansion by th e finite element method, is presented herein. The present state of kno wledge to simulate the AAR expansion process has been found to be limi ted and not yet satisfactorily developed. A methodology to distribute the observed concrete expansion in proportion to the compressive stres s state, temperature, moisture, and the reactivity of the concrete con stituents is proposed in this paper as a first step to rationalize the numerical modelling of the AAR concrete swelling process in concrete dams.