ALKALI-REACTIVITY OF DOLOMITIC ROCKS FROM ARGENTINA

This paper describes a series of studies conducted with the aim of evaluating the deleterious alkali susceptibility of carbonate rocks used in portland cement concrete manufacture. These studies have shown the existence of argillaceous dolomitic rocks in our country which can react with the alkalis present in concrete causing an alkali-carbonate reaction. The petrographic characteristics of the samples studied are, however, different from those described in the literature for typical carbonate expansive rocks. Experimental results indicate that the expansion mechanisms involved in this reaction, not fully understood yet, are different from those of the ASR (absence of gels, no pessimum phenomenon, increase in expansion with the increase in the maximum aggregate size, ineffectiveness of widely known chemical and pozzolan inhibitors, etc.). This paper summarizes the results obtained by using current characterization techniques (ASTM C 586, ASTM C 227, NBRI, CSA A23.2-14A, etc.) as well as X-ray diffraction analysis, optical microscopy and SEM microstructural observations.