| Mactaquac Generating station was constructed in the mid 1960's and is located in the province of New Brunswick in Eastern Canada. Approximately 10 years after construction the concrete structures showed signs of distress which were later attributed to alkali-silica reaction (ASR). The concrete structures are scheduled to be reconstructed around 2025 and NB Power would prefer to use the same reactive aggregate that was used in the initial construction. Therefore this project was aimed at finding a way to prevent damaging ASR using supplementary cementing materials (SCMs). The most obvious choice would be to use Class F fly ash, but other solutions were also investigated; these were: slag, high volume Class C fly ash, reclaimed fly ash, ternary blends (including silica fume), and limiting the alkali content of the cement. Tests that were completed in this project include the accelerated mortar bar test (ASTM C1567), and the concrete prism test (ASTM C1293). Additional testing included casting large concrete blocks which are stored on the UNB exposure site and massive concrete monoliths which are located at Mactaquac. Definitive results should be available for the larger specimens within 10 to 20 years.;This study found that the use of high volume Class F fly ash with replacement levels of at least 30% was successful in controlling ASR, while, high volume Class C fly ash, slag, and ternary blends were not successful in controlling ASR at the levels tested. The reclaimed fly ash alternative was found to be successful in controlling ASR with replacement levels of 40% and above, but other problems were found with the fresh properties of the concrete containing the reclaimed fly ash. |
