ISSN: 0149-6123
Page Count: 9

Why the Accelerated Mortar Bar Method ASTM C 1260 is Reliable for Evaluating the Effectiveness of Supplementary Cementing Materials in Suppressing Expansion Due to Alkali-Silica Reactivity
Bérubé, M-A
Professor of geological engineering and M.Sc. student, Université Laval, Québec

Duchesne, J
Postdoctoral fellow, University of Waterloo, Ontario

Chouinard, D
Professor of geological engineering and M.Sc. student, Université Laval, Québec

Abstract

The Accelerated Mortar Bar Method (AMBM) ASTM C 1260 (or CSA A23.2-25A) is used with success for evaluating the effectiveness of supplementary cementing materials (SCMs) in suppressing expansion due to alkali-silica reactivity in concrete (ASR). This study attempts to answer the question of why this method gives good results with SCMs. The most beneficial effects of SCMs against ASR is thought to be alkali decrease in the pore solution while the bars are immersed in 1N NaOH at 80°C. Mortar bars made with different SCMs were tested in normal conditions as well as in pure water and in air at 100% RH. The expansion results were compared with the chemistry of the mortar pore solution expressed under high pressure. The results confirmed that in the presence of an SCM, the alkali decrease in the pore solution remains the most critical mechanism involved in the AMBM. The results also confirmed that alkali equilibrium between the pore solution and the NaOH immersion solution is not achieved in the presence of an SCM at the end of the testing period of 14 days.

Keywords:
accelerated testing methods, alkali-aggregate reactions, ASTM C 1260, cement, condensed silica fume, Canadian Standard CSA A23.2-25A, expansion, pulverized fly ash, mortar, supplementary cementing materials

Paper ID: CCA10333J
DOI: 10.1520/CCA10333J
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