In-service 80-year-old arch-gravity dam (Córdoba, Argentina): State of concrete conservation and potential development of the alkali-silica reaction

Abstract

In this work the state of conservation of the San Jerónimo arch-gravity dam (Córdoba, Argentina) was investigated, mainly focusing on the potential development of the alkali-silica reaction (ASR). The structure was the first of its kind in Argentina and one of the oldest in South America. It was built between 1939 and 1941, 6 km east of La Cumbre city (province of Córdoba, Argentina). First, a site inspection involving visual observation, photographic documentation and in-situ evaluation (sclerometry and air permeability) was performed. Then, cores were extracted and studied by physical–mechanical test methods (compressive strength, capillary suction, density, absorption and volume of voids) and measurement of soluble alkalis by the hot-water extraction method. Finally, petrographic-mineralogical and microchemical studies were performed on concrete samples by stereomicroscopy, polarizing microscopy, X-ray diffraction and scanning electron microscopy-energy dispersive X-ray spectrometry. Considering the age of the structure, the dam is well preserved, although some cracks developed in different sectors, but mainly in the pavement at the crest. Exuded material (calcium carbonate) was observed in the downstream walls, possibly associated with leaching of calcium-rich phases in the concrete. The quality of near surface and inner concrete varies, but in general is low, according to physical and durability indicators. Major durability problems are related to the local development of the ASR, mainly in the upstream concrete wall in the dam body, and the numerous cracks in the pavement at the dam crest, which can act as pathways for the ingress of water and CO2 into the structure.