Masonry Magazine June 2002 Page. 32
Beating The HEAT
provide for normal strength development of the mortar. Available methods of achieving these goals include scheduling construction to avoid hot, mid-day periods, optimizing selection and preparation of masonry materials, protecting constructed masonry from sun and wind, damp curing masonry by covering with wet burlap, or fog spraying with water.
Materials
THE MATERIALS USED in hot weather masonry construction are no different than those for any other weather. All materials should conform to the appropriate ASTM material standards. Commonly in hot weather, retarders are used to delay the set time of mortar. They do not, however, reduce evaporation rates. Though this is common, it is not recommended. Any admixtures or retarders should only be used when specified and only when its compatibility with other ingredients has been confirmed by laboratory tests.
Cool water should be used to mix mortar and grout. Ideally, the water should be stored in the shade in a light-colored, open barrel to maximize cooling from surface evaporation. Water from long hoses exposed to the sun should not be used. When exposed to sunlight, long hoses act as water heaters. When practical, ice may be added to the mix water. Complete melting of the ice must take place before the water comes into contact with the other mortar or grout ingredients.
Equipment used to mix, transport and store mortar and grout needs to be flushed thoroughly with cool water immediately before use. Mortar can absorb heat from metal mixers, wheelbarrows or mortar pans, and lose water to wooden mortarboards.
Protection
THE USE OF WINDSCREENS has been shown to be effective in protecting against the drying effects of wind during extremely hot weather. Materials commonly used for windscreen protection are canvas and synthetic coverings (reinforced polyethylene and vinyl). Under severe drying conditions, research has shown that the daily application of a fog spray to the surface of the walls for a period of about three days, covering of the walls with polyethylene plastic, or both, dramatically improves flexural bond strength over walls not similarly protected. The tops of all walls not otherwise protected should be covered with a weather resistive membrane extending a minimum of two feet (0.6m) down on both sides to prevent water from entering the masonry.
Workers responsible for installing protection should have full knowledge of the type of windscreen being used, and how to properly erect, adjust, brace, anchor and dismantle the complete assemblage. Windscreens must be properly erected.
strapex USA
www.strapex.com
2601 Westinghouse Blvd.
Charlotte NC 28273
Phone: (800) 446-4347 Fax: (704) 588-8795
OR-T 241-C4F Vertical
Fully automatic vertical
and horizontal strapping
systems using plastic
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Strapex sets the standard
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• Orgapack
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30 Masonry
June 2002
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