Page 176 - Masonry and Concrete

Masonry Construction Techniques
175
MASONRY CONSTRUCTION TECHNIQUES

Type III, high-early-strength portland cement because of the greater
protection it will provide the mortar.
In addition to normal storage and protection, consideration should
be given to the method of stockpiling sand to permit heating the mate-
rials if required. As the temperature falls, the number of different
materials requiring heat will increase. Mixing water is easily heated. If
none of the other materials are frozen, mixing water may be the only
ingredient requiring artificial heat. It should be warmed enough to
produce mortar and grout temperatures between 40 and 70°F at the
time of placement. Water temperatures above 180°F can cause cement
to flash set, so sand and water should be mixed first to moderate high
temperatures before the cement is added. Masonry sand, which con-
tains a certain amount of moisture, should be thawed if frozen to
remove ice. Sand should be warmed slowly to avoid scorching, and
care should be taken to avoid contamination of the material from the
fuel source. Dry masonry units should be heated if necessary to a tem-
perature above 20°F at the time of use. Wet, frozen masonry units must
be thawed without overheating.
The degree of protection against cold weather which is provided for
the work area is an economic balance between the cost of the protection
and the cost of not being able to work. Protective apparatus may range
from a simple windbreak to a heated enclosure. Each job must be eval-
uated individually to determine needs and cost benefits, but some gen-
eral rules do apply. Characteristics such as strength, durability,
flexibility, transparency, fire resistance, and ease of installation should
be considered when selecting protective materials. Canvas, vinyl, and
polyethylene coverings are often used. In most instances, a windbreak
or unheated enclosure will reduce the chill factor sufficiently to pro-
vide the degree of protection required. Precautions must also be taken
to safeguard workers against injury, and enclosures must be adequate to
resist wind, snow, and uplift loads. Cold-weather protection measures
may be necessary when the ambient temperature or the temperature of
the units is below 40°F. Figure 5-33 summarizes heating and protection
requirements for various work temperatures.

5.7.4 Hot Weather
Although not as widely discussed as cold-weather problems, hot-
weather conditions also pose special concerns for masonry construction.

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