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An expansive dolostone from Argentina - the common Dilemma: ACR or another variant of ASR?

Autores: Carlos A. Milanesi, Silvina Marfil, Pedro J. Maiza, Oscar R. Batic

lkali-carbonate reaction is a known harmful reaction that affects concrete durability and constitutes an issue of much controversy between researchers and concrete technologists. Since 1991, the authors have been working in this field to evaluate the possibility of the occurrence of this reaction in Argentina. The studies have shown the existence of a fine-grained dolostone that reacts deleteriously with concrete alkalis following a mechanism similar to ACR. This dolostone has two distinctive characteristics. First of all, the rock shows a clear dedolomitization reaction producing calcite and brucite (no siliceous gel was observed in thin sections). Secondly, the use of known mineral admixtures (fly ash, silica fume, ground granulated blast-furnace slag, natural pozzolan) or lithium compounds does not mitigate concrete expansion. This paper summarizes the results obtained with this dolomitic rock using current characterization techniques (ASTM C 586, ASTM C 227, NBRI, concrete prism expansion test, and polarization microscopy).