Masonry Magazine September 2004 Page. 20
Cold Weather
Knowing how mortar and unit properties interact in cold weather enables the mason contractor to modify construction procedures to accommodate the specified materials.
Phetes courtesy of Jeep
Change Materials with the Change in Weather?
YOU MIGHT MODIFY your masonry materials for cold weather construction, but you probably won't switch materials. The masonry units themselves are typically selected on the basis of appearance or strength, not because they are suited to cold weather construction. Mortar type is also generally determined by structural or other performance criteria. The best strategy is to know how mortar and unit properties interact in cold weather, enabling the mason contractor to modify construction procedures to accommodate the specified materials.
Another variable that can be controlled is the water content of mortar. Typically, water content is established by masons or other crewmembers in the field, which permits adjustments to suit the ambient temperature. Keep in mind that mortar has water-retentive properties that affect its rate of moisture loss and stiffening. Also, mortars having high lime content or fine sands tend to have higher water demands and higher water retentivity than higher strength mortars or mortars made using well-graded sands. Although air entrainment increases water retentivity, it also reduces initial water demand required to achieve a workable consistency and has been shown to reduce susceptibility of mortar to damage by early freezing. The use of higher fineness cements (such as ASTM C 150 Type III) or accelerators increases reaction rates. These materials can be used in mortar to augment - but not substitute for - other cold weather construction practices.
Admixtures: Truth and Fiction
ADMIXTURES SHOULD be used cautiously as part of a cold weather masonry program. While accelerators are sometimes use
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Masonry
September 2004
www.masoncontractors.org