Masonry Magazine September 2004 Page. 24
Cold Weather
CONSTRUCTION
Masonry construction need not be disrupted by the arrival of colder weather.
That freshly mixed mortar should be in the range of 40°F to 120°F (4.4°C to 48.9°C) and kept above freezing until used in masonry. (Note: For grout, if ambient temperatures are falling below freezing, a minimum temperature of 70°F (21.1°C) is recommended at the time of placement.) See Tables 2 and 3 for specific recommendations.
Protecting Work Areas and Construction
WIND BREAKS, heated wall coverings, and plain or heated enclosures are used to maintain adequate mortar temperatures and to improve the comfort and efficiency of masons and laborers. If the need arises, entire buildings can be enclosed with scaffolding and tarps. The level of protection required will depend on the severity of weather encountered as defined by anticipated mean daily temperatures.
Reference 1 includes provisions needed during the workday while masonry is being laid, as well as protection requirements for newly constructed masonry. Mason contractors can choose from a variety of means to accomplish this. The main point is that masonry construction need not be disrupted by the arrival of colder weather.
TABLE 3. HEATING MASONRY MATERIALS
| Material | Notes | Temperature |
|---|---|---|
| Water | Water can be heated in barrels or tubs. It is the easiest material to heat and can store much more heat (per unit mass) than the other materials used in mortar. To avoid flash set, heated water should be combined with cold sand in the mixer before adding cement. | Heat water to a maximum of 140°F (60°C) |
| Sand | Sand is typically used in a damp loose condition. It may be necessary to heat sand to thaw frozen lumps when temperatures fall below freezing. Heat with electric heating pads, over a heated pipe, or by using steam heating systems. | Heat sand to 50°F (10°C) and higher as needed |
| Masonry units | Masonry units should not have any visible ice on bedding surfaces when used, and the units can't be below 20°F (-6.7°C). Heat on pallets in an enclosure or stored in a heated area. The units should be kept dry, although very high absorption fired-clay brick may need to be wetted-but not saturated-prior to use. | Heat units to at least 40°F (4.4°C) |
REFERENCES
1. Specification for Masonry Structures (ACI 530.1-02/ASCE 6-02/-95TMS 602-02)
2. Cold Weather Masonry Construction, PCA IS248
3. Hot and Cold Weather Masonry Construction, PCA LT232 (published by the Masonry Industry Council)
4. Standard Specification for Admixtures for Masonry Mortars, ASTM C 1384
In Summary
COLD WEATHER adds a few challenges for mason contractors. While materials won't be changed, modifying mortars may help prevent negative impacts of cold temperatures - keeping in mind that admixtures have to be used very cautiously, if at all. The greater the temperature drop, the more strategies you have to employ to protect newly constructed masonry or masonry under construction.
Jamie Farmy is the Program Manager of Masonry and Special Products for the Portland Cement Association, coordinating research and promotion activities regarding cements for masonry and white cement. He participates on committees on concrete, plastering, mortars, and masonry units of the American Society for Testing and Materials and the American Concrete Institute. He holds a bachelor's degree in Civil Engineering from the Illinois Institute of Technology.