Diagnosis and Prognosis of Alkali-Aggregate Reactivity in Concrete Structures

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Title: Diagnosis and Prognosis of Alkali-Aggregate Reactivity in Concrete Structures

Author(s): V. Corinaldesi and G. Moriconi

Publication: Special Publication

Volume: 212

Issue:

Appears on pages(s): 289-298

Keywords: AAR diagnosis; AAR prognosis; accelerated laboratroy test; alkali-aggregate reactivity

Date: 6/1/2003

Abstract:
Management of concrete structures affected by alkali-aggregate reactivity is quite complex, particularly in relation to prognosis more than that of diagnosis of the damaged structures. Until now a valid method to determine the potential for further deterioration is not available. Fifteen concrete structures showing typical signs of alkali-aggregate reactivity (AAR) were studied. Cores were taken from the structures and subjected to mechanical investigations and scanning electron microscopy observations in order to identify the cause of concrete deterioration. The observation on only one of these fifteen structures is reported on in this paper as an example of the adopted methodology. Once AAR was diagnosed, part of these cores were used to carry out laboratory tests performed for prognosis purposes. The cores were immerged in 1N sodium hydroxide solution at 40°C and their change in weight and dynamic elastic modulus was monitored up to six months of exposure in order to determine the potential for further reaction. Data related to dynamic modulus fluctuations in time were suitably worked out for each element of the monitored structure. Taking into account both the degree of structural integrity at the time of coring, evaluated through mechanical characterization, and the potential for future deterioration, valuable by means of the dynamic modulus fluctuation under an accelerated laboratory test, a ranking of concrete structures could be suggested in terms of priority of intervention for restoration.