Frost resistance

Weak permeable concrete is particularly vulnerable to the absorption of water into capillary pores and cracks. On freezing, the ice formed will expand causing frost damage. The use of air-entraining agents, which produce discontinuous pores within concrete, reduces the risk of surface frost damage. Concrete is particularly vulnerable to frost damage during the first two days of early hardening. Where new concrete is at risk, frost precautions are necessary to ensure that the mix temperature does not fall below 5°C until a strength of 2 MPa is achieved. Eurocode 2 (BS EN 1992-1-1: 2004) refers to four levels of exposure class (XF1 to XF4) with respect to freeze/thaw deterioration (Table 3.15).

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