Electrochemical repair Use of electrochemical migration to mitigate alkali-silica reaction in large scale concrete structures

Cement alkalis, sodium (Na+) and potassium (K+), then attack the aggregates and combine with the remaining silica to form a gel product. This gel product swells as it absorbs water from the surrounding cement paste. The expanded gel induces pressure within the concrete, which leads to cracking (Folliard, 2006). The process of concrete ASR expansion and cracking can be split into three separate periods: 1. Incubation Period-ASR gel absorbs water and

begins to expand in the concrete structure and the gel moves into available adjacent voids. The internal pressure is limited at this stage due to the freedom to expand. The chemical reaction is “incubated” at this stage while the reaction is still occurring (Fan, 1998).