Petrography of Potentially Alkali Reactive Sandstone from Argentina

Petrographic characteristics of sandstone from the Province of Corrientes, Argentina, were studied. The rock has been classified as potentially alkali reactive in previous work using the accelerated mortar bar test method (ASTM C 1260). The average expansion was 0.337% at 16 days and 0.432% at 28 days. Moreover, the concrete prism test (ASTM C 1293) was used. The expansion measured at 1 year was 0.074%, exceeding, at 4 weeks, the limit established for 1 year (0.040%). The rock was classified as quartzose sandstone. The cement is chalcedony, cristobalite, opal and cryptocrystalline quartz, all of them potentially alkali reactive. The study made in fragments of the mortar bar, determined that particles near the surface have no cement, forming an unconsolidated aggregate. Cracks are abundant, affecting the lithological components and the mortar. Siliceous cement in the aggregate particles has been leached, and silica is deposited mainly in voids. The mortar microstructure was studied by SEM-EDS in order to evaluate the characteristics of the deleterious reaction