A reply to the discussion by Mingshu Tang of the paper “Laboratory assessment of alkali contribution by aggregates to concrete and application to concrete structures affected by alkali–silica reactivity”

Abstract

The determination of available alkalis from aggregates is very important for design of durable concrete. This brief article answers comments on the authors original research study in which the researchers used 0.7 M NaOH or KOH solution to extract K or Na in a variety of aggregates at a solution-to-aggregate ratio of 1; the study found that the alkalis released by the aggregates in these alkali solutions can be up to 12.7 kilograms per meter cubed Na2Oe depending on the nature of the aggregate. In the commentary, Mr. Shu contended that the alkali solution extraction procedure presented in the paper is an ion-exchange test in nature and seems incorrect to be used to evaluate the available alkalis from aggregate for alkali-aggregate reaction in concrete. In this reply, Mr. Berube et al explain why their study utilized appropriate tests that measured not only ion exchange but other chemical reactions as well. The researchers discuss the reliability of immersion tests in NAOH and KOH solutions and consider the role of solution-to-aggregate ratio.