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Although winter concreting is no longer viewed as a special activity it is still more costly than work performed under warmer conditions. But this extra cost can be minimized if the engineer will appraise the service performance requirements for concretes in various categories and then establish the protection necessary to meet these requirements. Four main categories exist. One, concrete that will not, at an early age, be required either to support a load or to withstand cyclic freezing and thawing. Initial curing need only be sufficient to prevent freezing damage to the fresh concrete. Second is a category which includes, like the first, concrete structures that will not be required to support an early load, but which will be exposed, prior to loading, to sufficient warmth and moisture for final strength development. Initial protection must be sufficient for the concrete to attain an adequate early resistance to freezing and thawing. The third category includes structures that are partially loaded shortly after initial curing and structures that probably will not develop additional strength between the time they are given initial curing and the time a load is applied. Initial protection need only be sufficient to produce the strength required to resist the early loading. The fourth category includes the most critical group: structures which, because of their ultimate environment, will not be exposed to warm, moist conditions after initial curing. Since strength development is so severely curtailed, additional design strength is the best solution.