The flexural strength of bonded ice

The flexural strength of ice surfaces bonded by freezing, termed freeze bond, was studied by performing four-point bending tests of bonded freshwater S2 columnar-grained ice samples in the laboratory. The samples were prepared by milling the surfaces of two ice pieces, wetting two of the surfaces with water of varying salinity, bringing these surfaces together, and then letting them freeze under a compressive stress of about 4 kPa. The salinity of the water used for wetting the surfaces to generate the bond varied from 0 to 35 ppt (parts per thousand). Freezing occurred in air under temperatures varying from −25 to −3 ∘C over periods that varied from 0.5 to ∼ 100 h. Results show that an increase in bond salinity or temperature leads to a decrease in bond strength. The trend for the bond strength as a function of salinity is similar to that presented in Timco and O'Brien (1994) for saline ice. No freezing occurs at −3 ∘C once the salinity of the water used to generate the bond exceeds ∼ 25 ppt. The strength of the saline ice bonds levels off (i.e., saturates) within 6–12 h of freezing; bonds formed from freshwater reach strengths that are comparable or higher than that of the parent material in less than 0.5 h.