The effects of Ca++ on the strength of polycrystalline ice

• Published in: Journal of Glaciology
• Main Authors: KEVIN HAMMONDS, IAN BAKER
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2016
• Subjects: glacier flow; glacier mechanics; ice chemistry; ice engineering; ice rheology; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2016.84; https://doaj.org/article/09be5ee5ee6a4b6e8fc5949394c4bbfc

Recent studies have suggested a physical link between Ca++ ions and an increase in the ductility or ‘softening’ of polycrystalline ice. In order to investigate the potential effects of Ca++ on deformation, we created sets of both undoped and CaSO4-doped specimens of polycrystalline ice for testing in uniaxial tension or compression. Deformation tests in tension were carried out under a constant load at an initial stress of 0.75 MPa and a temperature of −6°C. Compression tests were carried out at −10 and −20°C at constant strain rates of 1×10−4 s−1, 1 × 10−5 s−1 and 1 × 10−6 s−1 and taken to 5% strain. Our results show that CaSO4 increases the strength of polycrystalline ice at higher strain rates and lower temperatures, an effect that decreases with decreasing strain rate and higher temperatures. A microstructural analysis of the post-test compression specimens reveals mean grain diameters much larger in the CaSO4-doped specimens tested at the lowest applied strain rate of 1 × 10−6 s−1. Precipitates were found to have formed along grain boundaries in some doped specimens and evidence of intergranular fracture was observed in all specimens tested at 1 × 10−4 and 1 × 10−5 s−1. In tension-tested specimens, there was no difference in the mean grain diameter between doped and undoped specimens at 25% strain.