Masonry Magazine June 1964 Page. 16
Problems In Specifying Mortars
(continued from page 15)
Wetting of brick. Some authorities claim that wetting of brick having high rates of absorption is a necessity. But how can this be controlled on the job, and what do you do in cold weather construction when wetting simply coats the brick with ice? Can mortar be proportioned to overcome bond deficiencies when used with masonry units having high suction rates, and what can you do with proprietary cement mortars under similar conditions?
Reconstitution of bond. Some authorities place a high value on the ability of a mortar to re-establish bond once broken. Just what is the value of this property, with respect to time and to the nature of the void or crack involved?
2. Mortar Selection
For various exposures. In inquiring into this phase of masonry mortar we must bear in mind we are discussing needs on a nation-wide basis rather than on any set of localized conditions. Therefore, the question of mortar selection covers many combinations such as:
Above-grade masonry
Hot, dry climates: rainfall less than 20 in. per year
Warm, humid or wet climates: rainfall 20 in. to 50 in. per year
Very wet and hot climates: rainfall over 50 in. per year
Temperate climates: rainfall 20 in. to 50 in. per year
Wet, cold climates: rainfall 30 in. to 60 in. per year and winter temperatures below 10° to 20° F
Very cold climates: temperatures to -50° F.
Below-grade masonry and retaining walls
Dry soils seldom exposed to frost
Dry soils exposed to deep frost
Wet soils-under the same conditions.
Based on such ranges as suggested above it would be of great assistance to the specifications writer to have at hand unbiased recommendations regarding proper mortar mixes for each situation.
Structural engineers are still specifying a straight portland cement mortar below grade. However, dampness due to capillary conduction is still high. This item needs more study. Also, in connection with capillary action, how helpful are admixtures when used to produce so-called waterproof mortar? Do they affect its strength, workability or otherwise affect the materials?
Proprietary masonry cement mortars vs. cement-lume mortars. How do these prepared masonry cement mortars measure up to job-mixed mortars used in construction? Are they consistent in their ingredients? Are prepared mortars more dependable than those measured and mixed at the job site? Does the addition of lime in so-called "high-lime" mortars contribute greatly in the prevention of leaky walls, or is a straight lime mortar better? This is not an effort to set up a defense of either type mortar, but rather to establish the honest-to-goodness facts in the matter. The ultimate decision as to which will be used is the prerogative of the specifications writer, but he must know the facts in order to make a proper judgment. A complete unbiased exposition is needed as to the components and make-up of each type of mortar, and, most important, the do's and don't in their mixing and use.
Aeroil
belt speed 400 ft. per minute... places materials up to 37 ft.... hydraulic raising mechanism... materials unload directly from truck
CONTRACTORS CONVEYOR
AEROIL PRODUCTS COMPANY
69 Wesley St., South Hackensack N.J.
MASONRY June, 196