Masonry Magazine December 1995 Page. 12
All Weather Procedures
# Submittals
Certificates of Compliance with Manufacturers literature or Laboratory Test Reports:
* Portland Cement
* Masonry Cement
* Hydrated Lime
* Mason's Sand
* Concrete Masonry Units
* Clay Masonry Units
* Mortar Conformance to Specification
* Property Specification C 270. Test report attached.
* Proportion Specification C 270. No test required.
* Reinforcement and Masonry Accessories
* Joint reinforcement type (truss, ladder, other) (gage, grade, corrosion protection)
* Masonry Anchors
* Grout Conformance to Specification
* Specification ASTM C 476
* Slump between 8 and 10 inches.
# Sample Panels
When required:
* Sample panel at least 4 square feet.
* Sample panel is standard for Work.
* Retain until Work accepted.
# Masonry Execution
* Materials to be received from suppliers in weather protected condition.
* Materials to be stored on site away from traffic pattern, high and dry.
* Provisions for covering walls at work stoppages.
* Provisions for covering wall after completion of masonry segment.
Masonry units absorb water and expand. Masonry materials involving cementitious material(s) are classed as being the most sensitive to weather conditions. Temperature effects are the most critical; moisture effects are less critical, but worthy of concern.
The Portland cement fraction of the masonry mortar has "normal" water demand, setting and hardening characteristics and rate of strength development during "normal" weather conditions. Portland cement containing mixtures in the presence of cold temperatures require lower water contents and possesses slower setting and hardening characteristics than their normal temperature counterparts. Conversely and when the temperature is above normal, the portland cement requires higher water contents and possesses faster setting and hardening characteristics than its normal temperature counterpart.
Temperature also affects the workability characteristics of the mortar containing portland cement. Mortars are classed as more workable during cold temperature and require less frequent tempering while on the mortar board. Mortars are classed as less workable during hot temperatures and require more frequent tempering while the mortar is on the board.
The hydrate lime fraction of the masonry mortar contributes an exceedingly fine (high surface area) material capable of absorbing water, encapsulating 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 re-
Cold Weather Procedures
# Code Requirements:
* Apply when ambient temperature is below 40 F
* 40 F to 25 F Heat mortar to 40 F to 120 F
* Maintain mortar above freezing.
* 25 to 20 F Heat mortar to 40 F to 120 F
* Heat both faces of masonry
* Install windbreakers when velocity is greater than 15 mph
* Cold Weather temperature included in project specification
# Master plan for cold weather masonry:
* No masonry construction
* Construct interior wythe during cold weather, await warm weather for construction of exterior wythe.
* Enclose structure and provide heat.
* Mortar production in weather protected enclosures.
* Provisions made for heating sand, water, and mixer.
* Provisions made for maintaining mortar warm on mortar board.
* Provisions made for enclosures to serve as windbrakers and allow heating masonry.