Effectiveness of Fly Ash and Slag in Mitigating Alkali–Silica Reaction Induced by Deicing Chemicals

Abstract

Recent studies have shown that potassium acetate based deicers are capable of triggering deleterious expansion and cracking in concrete specimens containing alkali–silica reactive (ASR) aggregates. This paper presents the results and analysis from a research study conducted to evaluate the effectiveness of fly ash and ground granulated blast furnace slag (slag) in mitigating expansions induced by ASR in the presence of a potassium acetate based deicer. Standard and modified ASTM C 1260 and 1567 tests were conducted on mortar specimens prepared with five aggregates to study the mitigation behavior of fly ashes and slag. In this study, fly ash was evaluated at 15, 25, and 35%, and slag at 40 and 50% by mass replacement of cement. Changes in length, dynamic elastic modulus, and microstructure of the mortar bars were studied. Results from these studies indicate that low- and intermediate-lime fly ashes were more effective than high-lime fly ash at 25 and 35% cement replacement levels. High-lime fly ash was ineffective even at a replacement level of 35%. Slag at 50% cement replacement was more effective in mitigating expansions compared to 40% dosage level.