Why aren't brick units tested for freeze/thaw resistance? In northern climates, this would seem to be an important property of the brick. I have worked on hundreds of projects over the past 20 years, but have not seen this test required by the architect. Why is this?
The test for saturation coefficient generally is a good indication of freeze/thaw resistance. Saturation coefficient is the ratio between the amount of water a brick absorbs after soaking 24 hours in cold water and the amount of water it absorbs after it has been in boiling water for 5 hours. If the saturation coefficient is low, the brick generally have good freeze/thaw resistance, because they contain enough void spaces that provide relief for freezing water. Water is driven into these void spaces only by boiling water or by freezing water. Type SW (severe weathering) brick must have an average saturation coefficient less than 0.78. Some masonry units with saturation coefficients greater than 0.78 still may be freeze/thaw resistant. This often is true of units with very low absorption rates. In such a unit, so little water enters the clay body that it generally causes no damage. Units with higher absorption rates also may perform satisfactorily. If these units are to be classified as severe weathering brick, they must be subjected to 50 cycles of freeze/thaw testing per ASTM C 67. Occasionally, units produced with saturation coefficients less than 0.78 also have problems in severe exposures. The brick manufacturer may have information about units that have had freeze/ thaw problems in the past. If the units will be used in an unusually harsh freeze/thaw environment, ask the brick manufacturer for examples of buildings with similar exposures where they have performed successfully. In these instances, I recommend specifying freeze/thaw tests.