The major problem common to all building trades in winter is the inability of the worker to achieve optimum production in cold temperatures. Failure to understand the nature of this problem can result in serious damage, which may prove substantially more expensive to correct than the original cost of the proper procedures. A discussion of frost action as it applies to masonry laid up in cold weather illustrates the necessity of observing certain precautions and explains the success of procedures not as yet accepted by all building codes. When the mortar has properly cured, the masonry usually possesses adequate durability to withstand normal exposure for many years. Any problems of cold weather masonry construction occur between the placing of plastic mortar in the wall and the point at which it acquires sufficient strength to withstand the detrimental effects of freezing.
Plastic mortar contains cementitious materials, aggregate and water.
Sand is commonly used as the aggregate, and in hardened mortar the sand particles are bound together by the cementitious materials, just as the units are bound together by the mortar in the masonry wall. Cementitious materials include portland cement or lime, or one of a number of combinations of these materials. During the curing process of the cement component, strength increases, and the number and size of the voids decrease, as does the water content as it is consumed by the hydration reaction. Lime cures by a carbonation process involving carbon dioxide from the air. It is much slower than the cement hydration reaction.