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Freeze-thaw resistance of high-performance concrete
Entrained air-pores reduce all mechanical properties of concrete. On the other hand, air-filled pores are required in order to secure freeze-thaw resistance. Therefore, one has to find a compromise between good mechanical properties and high durability. HPC has potential of high freeze-thaw resistance also without air-entrainment, or with very low air-entrainment. This potential is explored theoretically in the paper. Fundamental properties analysed are freezable water content, self-desiccation and permeability. It is shown that the amount of potentially freezable water in saturated HPC is always bigger than required for causing frost damage. This is also the case when the w/c-ratio is very low. Self-desiccation is a favourable factor, that might save HPC from internal frost damage. However, the self-desiccated pores may become water- filled during long time of water storage. Then, frost resistance is severely reduced. A theoretical analysis indicates that the low permeability of HPC is normally a favourable factor. If the concrete contains freezable water in aggregate or in defects, low permeability can, however, be negative. The results of salt-frost scaling tests are presented indicating that non-air-entrained HPC with w/c-ratio of the order 0.30, and lower, has high resistance to scaling. Tests of the internal frost resistance are less unambiguous; the result seems to depend on the test method. Dilation tests in air of water-stored non-air-entrained concrete indicate very high frost resistance, while traditional freeze-thaw tests of the same type of concrete, performed in water, indicate very low frost resistance.
Freeze-thaw resistance of high-performance concrete
Entrained air-pores reduce all mechanical properties of concrete. On the other hand, air-filled pores are required in order to secure freeze-thaw resistance. Therefore, one has to find a compromise between good mechanical properties and high durability. HPC has potential of high freeze-thaw resistance also without air-entrainment, or with very low air-entrainment. This potential is explored theoretically in the paper. Fundamental properties analysed are freezable water content, self-desiccation and permeability. It is shown that the amount of potentially freezable water in saturated HPC is always bigger than required for causing frost damage. This is also the case when the w/c-ratio is very low. Self-desiccation is a favourable factor, that might save HPC from internal frost damage. However, the self-desiccated pores may become water- filled during long time of water storage. Then, frost resistance is severely reduced. A theoretical analysis indicates that the low permeability of HPC is normally a favourable factor. If the concrete contains freezable water in aggregate or in defects, low permeability can, however, be negative. The results of salt-frost scaling tests are presented indicating that non-air-entrained HPC with w/c-ratio of the order 0.30, and lower, has high resistance to scaling. Tests of the internal frost resistance are less unambiguous; the result seems to depend on the test method. Dilation tests in air of water-stored non-air-entrained concrete indicate very high frost resistance, while traditional freeze-thaw tests of the same type of concrete, performed in water, indicate very low frost resistance.
Freeze-thaw resistance of high-performance concrete
Frost-Tau-Beständigkeit von Hochleistungsbeton
Fagerlund, G. (author)
2002
18 Seiten, 11 Bilder, 1 Tabelle, 31 Quellen
Conference paper
English
Freeze-Thaw Resistance of High-Performance Concrete
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