Four key factors of influence on deleterious freeze-thaw behaviour are the porosity/permeability, aggregate characteristics, moisture state and climatic conditions. In the case of highway structures, deicing agents will also be significant and this is discussed in the next section. The maturity of concrete when it first freezes is, of course, also an issue.
In addition to the key factors discussed further in this section, it must also be noted that good curing is a given requirement for good concrete. The initial curing of concrete is vital to durability from many viewpoints. In the context of freeze-thaw performance it is important that the surface layers are well hydrated. This requires careful curing to limit the excessive loss of water from these layers. Furthermore immature concrete is vulnerable to frost damage due to its relatively high capillary pore water content and its very low tensile strength. Protection of immature concrete from any freezing cycles that occur in the days after pour is essential. Pink (1978) gives advice on protective measures until the concrete has attained a cube strength of 2 N/mm2, at which stage it is assumed to be strong enough to withstand freezing.
