Archeological slag from Glinet: An example of silicate glass altered in an anoxic iron-rich environment

• Vitreous archeological slags were studied as analogs for vitrified nuclear waste.
• We studied the effects of iron on glass alteration in anoxic and clay-type environment.
• The interfacial area between the glass and corrosion products inside cracks was deeply characterized.
• We propose an alteration scenario including four main mechanisms.
• Iron had a detrimental impact on the mean alteration rate due to Fe-silicate precipitation.

Vitreous slag wastes produced by a blast furnace working during the 16th century at the Glinet ironworks site (Normandy, France) are studied as analogs for vitrified nuclear waste. They display a specific interface between iron corrosion products and the glass matrix, which can contribute to understanding the influence of iron on glass alteration mechanisms and kinetics under anoxic conditions. Characterization of the archeological artifacts, especially of the interfacial area between the glass and corrosion products inside cracks, using micro and nanobeam techniques (micro-Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, scanning transmission X-ray microscopy) suggests that four main mechanisms have taken place: iron carbonate precipitation, glass hydration and interdiffusion, silicate network hydrolysis, and precipitation of iron silicates. Extrapolation using the results from short-term experiments and comparison with alteration thickness measurements carried out on archeological artifacts reveal that the presence of iron has a detrimental effect on glass durability. This can be attributed to the precipitation of iron silicates, consuming silicon and sustaining glass hydrolysis.

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