Alkali Activity of Granite Aggregates and Control in the Concrete of the Three Gorges Project

On the basis of the existing standardized test methods of concrete aggregates alkali activity, the alkali activity of the granite aggregates is studied by extending the observation time. The results showed that the alkali reaction expansion ratio of the fresh granite broke through the 0.1% criterion limit after a decade of time. The reactant microstructure characteristic is similar to the structure of the alkali-silica reaction, the thickness of reaction layer is about 2~4 µm. Controlling the total alkali content of the dam concrete and replacing cement by mixing a certain proportion of fly ash can effectively prevent the occurrence of the AAR in the Three Gorges Project.