Masonry Magazine October 1993 Page. 22
Water from the mortar and lessen the possible disruptive expansion in the mortar on first freezing. However, even with absorptive units, the temperature of masonry needs to be initially maintained at a level that assures adequate curing of the fresh mortar. Units with very low absorption capability (glass block, for example) may require extended heating of the masonry to avoid disruptive freezing of the mortar. The slow stiffening of mortar resulting from the low absorption of the unit will limit productivity during construction and could contribute to color variations in mortar joints as a result of tooling wet sorption masonry units are used. mortar joints.
Materials-At cold temperatures, Type I cement can be replaced with Type III cements which hydrates at a faster rate. You may also consider changing to a higher strength mortar than you would normally use. For example: If ASTM C270 Type N mortar is specified for normal temperatures. the typically lower water retention and higher strength gain of a Type S mortar may be more appropriate for cold weather, particularly if low ab-Sorption masonry units are used.
Admixtures-Mortar admixtures are acceptable in cold weather masonry construction, but only if they are laboratory tested at the temperature extremes at which they will be used.
REPRINTED with permission, from "Masonry Today," published by the Portland Cement Association. For more detail, see: "Recommended Practices and Guide Specifications for Cold Weather Masonry Construction." International Masonry Industry All-Weather Council, available from International Masonry Institute, Washington. DC.
MCAA AND YOU
Continued from Page 16
Limited states design work, a masonry inspectors' guide, and a Tacmar project.
Market Protection and Expansion
MCAA has worked with sister industry associations to protect the masonry markets currently enjoyed by mason contractors as well as seeking to expand the markets mason contractors have to compete in. MCAA has worked successfully in gaining back markets in the prison and retail markets when less than industry standards quality was presented to masonry customers who later switched to competitive products.
MCAA's Masonry Magazine and the MCAA Conference and Masonry Expo are both successful vehicles for promoting the masonry industry, while offering educational benefits for those who participate in these activities. The programs and exhibits that are offered at Masonry Expo and the features in Masonry Magazine keep contractors on the cutting edge of the technology and methods.
Clearing House for Information
When mason contractors have questions, problems or requests for new product information, they turn to MCAA for the answers or the direction to find the answers. MCAA serves a vital link for masonry nationally to provide information that can be shared and benefitted from the entire industry.