Measurements of residual expansion rates resulting from alkali-aggregate reaction in existing concrete dams

Expansion due to alkali-aggregate reaction (AAR) has caused structural and operational problems in a large number of existing concrete dams all over t he world. However, there appears to be no laboratory test method for the be havior representative of field performance. This paper presents a laborator y test methodology to measure the residual expansion potential under differ ent stresses and the suppression pressure under uniaxial and triaxial condi tions. The effect of slot cutting (the remedial measure currently wed in da ms) on expansion is also investigated. Results of tests on samples from R. H. Saunders Dam showed that the measure d expansion rates in the laboratory are consistent with those measured by a n extensive instrumentation system in the field. It is believed that the te st methodology developed herein not only provides the necessary and inexpen sive tools for measuring the stress-dependent residual expansion potentials in concrete dams, but also will have an impact on the prediction of future performance and remedial measures because of the versatility of the test m ethod.