2020 Volume 31 Pages 23-32
Past research on aging open channels made of reinforced concrete in cold regions has shown that the exposed parts of the channel sidewalls contain air voids and cracks filled with white precipitates. In this study, we took core samples from the exposed parts of open channel sidewalls, and performed microscopic observations to identify the precipitates filling the air voids and cracks. We used an electron probe micro analyzer to identify surface elements, and confirmed that precipitates had filled air voids and cracks. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction revealed that the precipitates were composed of ettringite. We surmise that the formation of the ettringite in the air voids and cracks is related to the elution of calcium ions around the cracks and the movement of sulfide ions from carbonated regions.
