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

• Published in: Journal of Glaciology
• Main Authors: HAMMONDS, KEVIN, BAKER, IAN
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2016
• Subjects: Earth-Surface Processes; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/jog.2016.84; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143016000848

ABSTRACT 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 CaSO 4 -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 CaSO 4 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 CaSO 4 -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.