Combined salt and frost attack is a major durability problem in concrete highway pavements in the state of Michigan, USA, where road-salts are used extensively for ice melting purposes. Previous studies have shown that continuous measurement of length-change during a freeze-thaw cycle is an effective tool in indentifying frost mechanisms. In this study the focus was to evaluate the cryogenic suction effect on frost expansion. The net frost expansion (linear dilation) was determined by monitoring the change in length of air-entrained concrete specimens undergoing a freeze-thaw cycle between 20 °C and -20 °C. Two dilation processes were found during freezing, an initial dilation at the freezing point (independent of surface exposure liquid), and a subsequent dilation, which is only found when a salt solution is present on the surface. Specimen expansion continues during the entire freezing period, including a 3 hour ramp at constant temperature (-20 °C). This secondary dilation dominates when the surface is exposed to a deicer solution. At constant temperature below initial freezing point, cryogenic suction of surface liquid (i.e., 3% salt solution) was found to be a major factor in sub-zero liquid transport that causes frost expansion in concrete. During this process, air voids are being filled as well and air is being displaced. Some air near the surface can escape. This was observed at -20 °C where escaping air was trapped in the liquid surface layer.
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