Masonry Magazine January 1968 Page. 35
MCAA
All-Weather Program
Cold Weather Mortar Admixtures
By Daniel A. Guntin, Marketing Manager
Sonneborn Building Products, Inc.
The length of a man's production day was once pretty much dictated by the rising and setting of the sun; his ability to work decreased with the level of light. Torches and candles helped, but not until the invention of the electric light was man freed from the limitations imposed by darkness.
Cold weather sets similar restrictions on the freedom of operation of the masonry contractor-as temperatures decline, so does efficiency, both of his labor and his materials. The day's lift is reduced, more time and energy-and money-has to be devoted to compensating for the impact of cold: artificial heat, temporary enclosures, and so forth.
As did candles and torches in our analogy, these devices permit work to continue, but with important restrictions. Like tasks completed in poor light, masonry construction carried out in cold weather entails a higher probability of mistakes and uneven results.
More callbacks and re-do problems are noted in cold weather masonry work than in such construction completed in most other periods of the year. Faulty mortar, efflorescence, mortar joint discoloration, and similar defects tend to be more pronounced when temperatures are low than at other times. Even corrosion of metalwork abutting mortar joints typically manifests itself to a greater extent during cold weather.
Complete failure calling for replacement of an entire major section is extremely rare, but in those very few instances in which it occurs, it often stems from cold weather effects.
More usual will be callbacks for repointing, for replacement of spalled bricks, or at most, redo of a portion of the completed section. It is not uncommon for a contractor to have to redo a portion of the day's lift because of defects caused by cold weather, and while not a true callback, this is still worth avoiding.
DUPLICATING WARM WEATHER
The ideal solution would be a mortar that sets in cold weather pretty much as it does in warmer weather, much as artificial light can be made to approximate daylight.
This obvious solution accounts for interest in various types of admixtures going back decades, but like early work with the electric light, early admixtures were fairly expensive and not well enough understood to provide even results.
Water proofers, for example, were among the first admixtures used, and they did help minimize freezing, but because of the fact that they decrease strength, their use has steadily diminished except for stain resistant mortars.
Today's cold weather accelerating mortar admixtures, developed from experience with earlier mixtures much as today's modern lighting stemmed from work with recalcitrant early bulbs, give the mason contractor mortar curing cycles much closer to those obtained in warmer weather. Obviously, they won't improve human efficiency, and it may still be necessary to provide enclosure protection and artificial heat, but they will dramatically shorten cure times and substantially reduce time and effort devoted to these elements.
Enclosures that might otherwise have to stay in place for fairly long periods can be moved soon after the work is finished, permitting bricklayers to accomplish more in a given period. Admixtures also radically reduce handling and working problems encountered with untreated mortar mix in cold weather.
HOW ADMIXTURES WORK
Mortar accelerators essentially make their contribution by promoting a faster initial set. This is desirable at cooler temperatures, and critical at freezing ones, since these accelerators abet by sheltering, allow hydration to occur before the water freezes.
Accelerating admixtures also afford important side benefits-high early and ultimate strengths, improved workability, uniformity, and cohesiveness or flow characteristics but their key function is promoting that fast initial set.
Reams of sound, carefully documented and proven data is available on cold weather concrete work, and
(Continued on page 36)