Macroscopic ice lens growth in hardened concrete

Abstract

Spalling of concrete has been observed in water retaining concrete structures exposed to long periods of freezing weather. A hypothesis is that poor quality concrete, inadequate compaction or aging make hardened concrete susceptible to macroscopic ice lens growth, i.e. ice segregation. To simulate winter conditions, the top surface of concrete specimens was subjected to freezing, whereas the bottom surface was submerged in heated water. Given constant thermal conditions, ice segregation occurred in sound concrete with w/c-ratio 0.9 and higher. In concrete with internal frost damage, ice segregation occurred within a few days regardless of the w/c-ratio. Ice segregation also occurred in specimens with paper sheets cast into the concrete to form cavities. However, the period of freezing required to facilitate ice segregation increased with decreasing w/c-ratio. The risk of macroscopic ice lens growth in actual structures cannot be overlooked since unfavourable temperature and moisture conditions may exist in winter.