Preventing, Assessing, Mitigating and Managing Alkali-Aggregate Reaction (AAR) in Concrete Infrastructure: Challenges and Research Needs

Dear Colleagues,

Alkali-aggregate reaction is one of the most harmful distress mechanisms affecting concrete infrastructure worldwide. AAR is a chemical reaction between alkali-hydroxides from the concrete pore solution and some unstable mineral phases present in the aggregates used in concrete. AAR provides a gel that swells upon moisture uptake, leading to induced swelling and deterioration of the affected concrete. AAR is normally divided into two distinct mechanisms: alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR); ASR is by far the most common deterioration mechanism.

Over the years, a number of protocols and test procedures have been developed to either prevent or mitigate AAR-induced development prior to its occurrence in the field. Although some of the procedures were observed to be more reliable than others, the vast majority of experts agree that it is now possible to design AAR-risk free concrete mixtures. Conversely, once a concrete infrastructure is affected in the field, there is no “universal” solution considered sufficiently reliable and efficient to properly cope with the issue. First, incomplete techniques are often used to assess the extent of deterioration and its potential development over time. Moreover, most of the rehabilitation procedures adopted in the past are considered either inefficient or very expensive. Finally, there is a current gap in the literature of systematic, efficient, and quantitative management protocols to better deal with affected structures in service. Therefore, the purpose of this Special Issue is to further discuss alternative, advanced, and innovative techniques/protocols able to: a) reliably and quantitatively appraise the current (i.e., diagnosis) and future (i.e., prognosis) condition of AAR-affected infrastructure, b) evaluate the current and future structural implications of the induced expansion and deterioration, c) cease or at least significantly decrease AAR-induced development rate in the field, increasing serviceability, durability, and safety of affected structures, and d) better guide infrastructure owners and engineers in the decision making of affected structures. 

Dr. Leandro F.M. Sanchez
Guest Editor

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