| Abstrakt: |
An unusual example of freezing of fresh concrete in floor slabs has been observed in the Platteville Elementary School Building, Platteville, Colo., built in the fall of 1957. Initial evidence of distress was numerous, closely spaced bumps in the finished surface of the floors. These protuberances are especially disturbing in areas of tiled floor, where they were first noted. Detailed examination of the floor slabs, both at the site and by microscopical examination of drilled cores, showed that the upper 1/2 to I in. of the concrete had been frozen before hardening, causing intense fracturing of the near-surface portion and producing bumps over originally frozen lumps of sand and shale incorporated in the concrete. It is concluded that the bumps formed as a result of growth of ice lenses within and adjacent to the frozen lumps. The irregularities of the floor surfaces have increased progressively with time in areas of concentrated traffic, because of disinte-gration of the highly fractured near-surface concrete beneath the floor tile under the impact of heavy foot traffic. [ABSTRACT FROM AUTHOR] |
