Deteriorated pavements due to the alkali-silica reaction: a petrographic study of three cases in Argentina
Deteriorated concrete pavements from three regions in Argentina were studied. The aim was to evaluate aggregate constituents, especially the presence of deleterious components, determine what reaction products had developed, and find the main causes of the deterioration based on the petrographic study of the concrete. Thin sections were analyzed with a petrographic microscope to evaluate microcracking, characteristics of the aggregate-cement interface, reaction rims, and the development of reaction products. The latter were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDAX). Pavements exhibit widespread microcracking with the development of crystalline materials at the aggregate rims, identified as zeolite-like structures by XRD. From the ED AX analysis, Si, Al, O, Ca, K, and Na were determined. Ettringite is abundant both inside cavities and on crack surfaces within concrete. Its occurrence was confirmed by XRD and ED AX. The aggregate deleterious constituents are mainly glassy vulcanites and volcanic glass, generally altered to argillaceous minerals, and strained quartz, with undulatory extinction. The deterioration of the three pavements studied was due to the development of the alkali-silica reaction (ASR), involving the strained quartz.