Masonry Magazine November 1965 Page. 25
Old & Hot Weather Aspects of Mortar
(continued from page 23)
are drops of 10, 15, or 20 degrees. For temperature drops of this type we cannot put in a sufficient quantity anti-freeze to regard this as a feasible means of protecting our masonry mortar. It was also mentioned earlier that calcium chloride can cause corrosion or can accelerate the corrosion process that takes place when reinforcement and aluminum conduit are present in a wall.
A very adequate method for accelerating the set of our mortar is to add an additional quantity of portland cement if a masonry cement mortar is being used. Oftentimes one bag of portland cement to one bag of masonry cement produces a mortar that has a sufficiently earlier set to make it equivalent to a conventional mortar mix with an accelerator added.
When the announcements for this program were mailed out, all references were made to an All-Weather Conference. The speakers today confined their remarks mainly to cold-weather construction. I have a few additional points that I would like to bring up regarding hot-weather construction.
The temperature of the room today with the air-conditioning unit off for the season makes us feel that it is very appropriate to discuss hot-weather construction. In hot weather one precaution that should be taken is that mortar tubs, mixers, other handling equipment such as wheelbarrows and so forth that the mortar is going to be handled in should be cooled off by dousing with water.
A mixer, mortar tub or a wheelbarrow that is sitting out in the hot sun can be too hot to comfortably touch with the hand but yet many times we'll take this same piece of equipment and drop our fresh mortar right on the hot surface like dropping an egg in a frying pan. This does not do the mortar any good. A rapid increase in temperature of the mortar helps drive off some of our mixing water, helps reduce the plasticity in the mortar, and the resulting material is not only harder for the men to work with but provides poorer bonds. We recommend that equipment should be shaded whenever possible. If the equipment has been setting out in the sun, as I said earlier it should be doused with water before using. Dry, absorptive mortar boards can also absorb mixing water from the mortar and cause early stiffening that we do not want to have occur.
Another recommendation is that mortar should be mixed only as it is needed. Particularly in hot weather we should avoid mixing mortar too far in advance, and frequently in hot weather we may find it advantageous to add a little more mixing water than we usually do. The rapid rate of evaporation of mixing water to the will remove this excess quantity of water. The use of cool or cold water is also recommended in extremely hot weather. Water, with its high specific heat, is the most efficient material in affecting the temperature of the mortar.
ASONRY November, 1965
Another recommendation that should be followed is the mason should not lay out extremely long bed joints as some masons have the habit of doing. In ordinary construction, in ordinary temperatures, this may be entirely permissible but on extremely hot days with hot dry winds blowing, a long bed joint can stiffen before the units are placed in this bed joint. Consequently, bond will be affected.
Again a point that I mentioned earlier is that all materials should be mixed in the mixer for a full five minutes to obtain full benefit of air-entrainment. This is particularly important in extremely hot weather because adequate air-entrainment will help improve water retention and this, of course, is extremely important in hot weather. It is important not only from the aspect of retaining the water from evaporation to the hot wind but also helping to retain the water from excessively absorptive hot dry units.
In hot weather, providing windbreaks and covers to avoid rapid drying is very important. Cold weather is not the only time we should protect our fresh masonry. A hot dry wind can oftentimes do as much damage or more damage than we sometimes occasion in cold weather.
It has been a pleasure for me to be with you gentlemen this afternoon and if any of you would like to obtain further information on some of the points that I have discussed, we have literature available that we would be happy to send to you.
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METUCHEN, N. J.
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