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 the world. However, there appears to be no laboratory test method for the behavior representative of field performance. This paper presents a laboratory test methodology to measure the residual expansion potential under different stresses and the suppression pressure under uniaxial and triaxial conditions. The effect of slot cutting (the remedial measure currently used in dams) on expansion is also investigated. Results of tests on samples from R. H. Saunders Dam showed that the measured expansion rates in the laboratory are consistent with those measured by an extensive instrumentation system in the field. It is believed that the test methodology developed herein not only provides the necessary and inexpensive 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 medial measures because of the versatility of the test method.