Incidence of Alkali Release in Concrete Dams. Evaluation of Alkalis Releasable by Feldspars

Abstract

Alkali release from aggregates can constitute a source of alkalis in concrete exposed to wet environments for long periods of time. Feldspars are one of the minerals that can release alkalis to the concrete with time. The formation of reaction products in the interface with the paste due to the alkali release from sodium and potassium feldspars has been observed in a concrete with granite aggregates. This has been observed after more than 25 years of exposure. It is necessary to evaluate the amount of alkalis releasable to define the formulation of concrete before manufacturing. Different test methods have been used to evaluate the potential alkali release from the granite extracted from the same quarry as that used in the dam. The test solutions have different composition and concentration, and different temperatures were used. Finally, the results of potential extraction are evaluated to determine the most realistic with respect to the field behavior.