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Wingard, D.W., Math, S. and Rangaraju, P.R. ABSTRACT Recently a deicer-modified mortar bar test method, revised EB-70 test method, was developed to evaluate aggregate reactivity in the presence of potassium acetate deicer. This test employs a soak solution with a composition of 3M KAc and 1N NaOH, wherein the mortar bars with the suspect aggregates are exposed over a period of 28 days, and the mortar bar expansion is periodically recorded. Previous research has shown that this test captures the interactions that occur between a concentrated deicer solution and a highly alkaline environment within the pore solution of concrete. Results from investigation of over 30 aggregates in this test method yielded positive correlation with the field performance of the aggregate. In this paper the applicability of this test method to evaluate effectiveness of typical ASR mitigation measures such as fly ashes, slag and lithium admixtures, was investigated. Findings from these studies suggest that the revised EB-70 test method can be employed to evaluate the effectiveness of ASR mitigation measures in the presence of potassium acetate deicer. Factors such as the chemical composition of the SCM and its dosage rate in the mixture appear to play a significant role in effectively mitigating ASR in the presence of deicers. 1. INTRODUCTION Recent laboratory investigations on the impact of airfield deicing chemicals on concrete durability have shown that deicers such as potassium acetate (KAc) are capable of inducing deleterious alkali-silica reaction (ASR) in concrete (1-3). Evidence from forensic field investigations suggested that while the penetration of potassium acetate into sound concrete was minimal (only to an extent of 10-15 mm from the pavement surface), its penetration into concrete with pre-existing cracks was found to be significant, particularly along the length of the crack (4-5). It is therefore conceivable that when deicers do penetrate concrete, its potential to inflict ASR distress can be significant. In order to investigate the susceptibility of aggregates to under ASR in the presence of potassium acetate deicer, a deicer-modified mortar bar test method (EB-70 test method and revised EB-70 test method) was recently developed (1,6-9). A detailed description of this test method and its comparison with the standard ASTM C 1260 test method is presented elsewhere (7). The principal difference between the deicer-modified test and the standard ASTM C1260 test is the composition of the soak solution employed in the test method. In the deicer-modified test method, a 3M KAc + 1N NaOH solution is employed as soak solution instead of the standard 1N NaOH solution. The reason for using the 3M KAc + 1N NaOH soak solution is to capture the pH jump that is observed in deicer solutions when blended with alkali hydroxide solutions. It was shown that the increase in the pH observed in the proposed soak solution (i.e. 3M KAc + 1N NaOH) was not just based on the concentration of the hydroxyl ions, but due to an increase in the activity coefficient of the hydroxyl ions (7, 10). It should be noted that in a previous version of the deicer-modified test method (EB-70 test method), where 6.4 M KAc was employed as a soak solution, the high pH observed in the soak solution was entirely TRB 2012 Annual Meeting Original paper submittal - not revised by author.
