Comparative ASR Performance of Concrete at External Alkali Supply

The technical specifications for the construction of airport or road pavements usually include the requirement of the appropriate selection of non-reactive aggregate for concrete. This ensures an appropriate safety factor against the occurrence of a harmful alkali-silica reaction (ASR). However, it is difficult to predict the effects of external sources of alkalis, including alkaline deicers used for winter maintenance of pavements in wet-freeze climate zone. This study is aimed to evaluate the ASR performance of concrete using RILEM AAR-12 procedure with external alkali supply comparing it to the standard evaluation in Austria (1 molar NaOH, 38 ℃) according to ÖNORM B 3100. Tested materials included reactive and moderately reactive siliceous gravel and crushed rock aggregate. Concrete specimens were subjected to cyclic exposure to high humidity storage at 60 ℃, drying, and soaking in de-icing salt solution (sodium chloride and sodium formate). Measurements of the expansion of concrete specimens, mass changes, and changes in the dynamic elastic modulus were systematically taken. The microstructural characterization of concrete was performed to identify alkali-silica reaction products using scanning electron microscopy SEM/EDS. The ASR related damage in concrete exposed to the performance testing with external alkali supply is moderately increased when NaCl solution is replaced with HCOONa solution at the same concentration.