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Scandinavian researchers have identified reduction of moisture content to 6 percent and sufficient prehardening as conditions under which mortar in masonry walls will withstand early freezing without damage. This paper reports the results of a study in which volume changes due to freezing were measured in mortars to assess these conclusions for Canadian masonry materials. Volume changes in mortar samples encased in a rubber balloon immersed in alcohol in a cylinder connected to a calibrated capillary were measured as the temperature was lowered through the freezing zone. The effect of variable moisture contents and setting times for a 1:1:6 cement-lime mortar and a 1:3 masonry-cement mortar were studied. It was found that freezing expansions of the order of 2 percent for cement-lime mortar control samples dropped sharply after a setting time of 4 h and virtually disappeared at 16 h. Expansions of 1.25 percent in masonry-cement control mortars decreased to negligible values after a setting time of 4 h. Reductions to 6 percent moisture content reduced freezing expansions to negligible values for both mortars, although problems were encountered in bringing moisture contents down to 6 percent. The possible application of the results to field conditions is discussed.
volume change, freezing, expansion, cold weather masonry, masonry mortar, moisture content, setting time, curing, durability, air content, brick suction
Research Officer, Division of Building Research, National Research Council of Canada, Halifax, Nova Scotia