Masonry Magazine January 1975 Page.20
Summary
Cold weather masonry construction and its quality control require some additional attention to construction practices and protection. Attention should be directed to the following details as well as those normally attended.
Construction materials should be received, stored, and protected in ways that prevent water from entering the materials.
If climatic conditions warrant, temperatures of construction materials should be measured-frozen sand and wet masonry units must be thawed. Masonry units below 20 F must be heated above 20 F without overheating.
Sufficient mortar ingredients should be heated to produce mortar temperatures between 40 F and 120 F. Every effort should be made to produce consecutive batches of mortar with the same temperatures falling within this range. The mortar temperature after mixing and before use should be above 40 F, maintainable either by auxiliary heaters under the mortar board or by more frequent mixing of mortar batches. Heated mortar on mortar boards should not become excessively hot (greater tha 120 F).
During below-normal temperatures, masonry should be placed only on sound unfrozen foundations. Masonry should never be placed on a snow or ice-covered surface, because of the danger of movement when the base thaws and the possibility of very little bond being developed between the mortar and the supporting surface.
At the end of the day, the top surface of all masonry should be protected to prevent moisture, as rain, snow or sleet, from entering the masonry. This protection must cover the top surface and should extend a minimum of 2 feet down all sides of the masonry.
| WORK DAY TEMPERATURE | CONSTRUCTION REQUIREMENT | PROTECTION REQUIREMENT |
|---|---|---|
| Above 40 F | Normal masonry procedures. | Cover walls with plastic or canvas at end of work day to prevent water entering masonry. |
| 40 F-32 F | Heat mixing water to produce mortar temperatures between 40 F-120 F. | Cover walls and materials to prevent wetting and freezing. Covers should be plastic or canvas. |
| 32 F-25 F | Heat mixing water and sand to produce mortar temperatures between 40F-120 F. | With wind velocities over 15 mph provide windbreaks during the work day and cover walls and materials at the end of the work day to prevent wetting and freezing. |
| 25 F-20 F | Mortar on boards should be maintained above 40 F. | Maintain masonry above freezing for 16 hours using auxiliary heat or insulated blankets. |
| 20 F-0 F and below | Heat mixing water and sand to produce mortar temperatures between 40 F-120 F. | Provide enclosures and supply sufficient heat to maintain masonry enclosure above 32 F for 24 hours. |
NATIONAL CONCRETE MASONRY ASSOCIATION
P.O. Box 135, McLean, Virginia 22101