An investigation of mortars affected by alkali-silica reaction by X-ray synchrotron microtomography: a preliminary study

A first attempt to investigate samples affected by alkali-silica reaction (ASR) by synchrotron X-ray microtomography has been made. The setup available at the SYRMEP beamline, at the third generation synchrotron Elettra (Trieste, Italy), allowed collecting phase-contrast enhanced images, with a detectability approaching that of optical microscopy (a few microns). In this study, mortar cylinders were prepared and immersed in a 1-M NaOH solution at 80 °C for 14 days to enhance the ASR. The weathered samples were studied using the traditional 2D techniques such as optical microscopy and scanning electron microscopy as well as using the 3D micro-CT. Over the aged samples, the 3D imaging allows the ASR weathering to be studied, showing the reactive aggregate progressive dissolution with subsequent deposition of gel and microcracks development. This technique has proven to be a valuable, non-destructive, method which allows the rendering of the microstructural features in specimen affected by ASR.