Masonry Magazine October 1994 Page. 29
HOT AND COLD
Continued from Page 18
capsulating individual particles. This characteristic of the lime particle causes the masonry mortar produced therewith to have a high water demand and desired workability. Because of the high water demand, lime containing mortars are desirable, especially during hot temperatures and while using absorptive masonry units. The water within the masonry mortar promotes water retention and allows cement hydration to continue. Thus, lime containing mortars have desired performance characteristics during hot weather conditions.
Conversely, the high water demand lime containing masonry mortars are more prone toward causing units to serve as "floaters" during cold weather masonry construction. The lime containing masonry mortars are also more prone to early freezing damage than their air-entrained, lower water content counterparts.
The performance of masonry units as affected by temperature is less well known. Of primary interest would be the absorption characteristics of masonry units at varied temperatures. It would be expected that an above normal temperature unit in contact with cool water would imbibe water more rapidly than its normal temperature counterpart.
Davison', while researching the effect of temperature on brick suction, concluded that the initial rate of absorption (IRA) values for clay and sand-lime bricks decline with lower brick temperatures, especially high IRA, extruded and dry press bricks at temperatures below 32°F. The research was limited to ASTM C 672 IRA tests; the effect of prolonged (greater than one minute) contact of brick with water was not established.
Code Provisions
The current Specifications for Masonry Structures (ACI 530-92/ASCE 6-92/TMS 40202) requires submittal of cold weather and hot weather construction procedures for meeting the requirements of the Project Specification. Additionally, the Execution portion of the Specification mandates that, when specific conditions are experienced during construction, specific implementation procedures be followed.
Temperatures triggering the implementation procedures are 40°F (ambient and unit) and 100°F or 90°F (wind 8 mph) for cold and hot weather masonry construction.
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MASONRY-SEPTEMBER/OCTOBER, 1994 29