Page 177 - Masonry and Concrete

Masonry Construction Techniques
176 CHAPTER FIVE

Workday Protection
Temperature Construction Requirement Requirement

Above 40°F Normal masonry procedures Cover walls with plastic or canvas
at end of workday to prevent water
entering masonry
40–32°F Heat mixing water to produce Cover walls and materials with
mortar temperatures between plastic or canvas to prevent
40–100°F wetting and freezing
32–25°F Heat mixing water and sand to With wind velocities over 15 mph
produce mortar temperatures provide windbreaks during workday
between 40–100°F and cover walls and materials at
end of workday to prevent wetting
and freezing; maintain masonry
above 32°F for 16 hours using
auxiliary heat or insulated blankets
25–20°F Mortar on boards should be Provide enclosures and supply
maintained above 40°F sufficient heat to maintain
masonry enclosure above 32°F for
24 hours
20–0°F and below Heat mixing water and sand to
produce mortar temperatures
between 40–120°F

FIGURE 5-33
Cold weather construction requirements.

High temperatures, low humidity, and wind can adversely affect perfor-
mance of the masonry.
Rapid evaporation and the high suction of hot, dry units can
quickly reduce the water content of mortar and grout mixes so that
cement hydration actually stops. Mortar workability and grout flow
are inhibited and set occurs faster. High-temperature mortars have
lower air contents, and air-entraining agents are less effective. Board
life of mortars is shorter, and joints must be tooled sooner than normal.
Evaporation at the exterior face of joints decreases durability and
strength at the surface. When ambient temperatures are above 100°F,
or above 90°F with wind velocities greater than 8 mph, protective

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