Masonry Magazine October 1997 Page. 23
Only Fast Masonry Systems Insures
Profit and Top Quality
As seen at the Chicago Masonry Fair,
New Orleans Masonry Expo and Phoenix Masonry Expo
Fast Masonry Systems will increase the use of brick by enabling buildings to be designed with artistic patterns of all kinds, which in the past has been blocked by cost, and in many cases, lack of skilled craftsmen.
With Fast Masonry Systems, our goal is to insure quality, and guarantee profit! We make it easy to build with our Universal System, any masonry design, and all without the use of a level!
We would like the opportunity to meet with your company and demonstrate our systems to you. If you are interested increasing your profits, call or fax us at our toll free number.
PHONE:
1-800-957-3643
FAX:
1-517-543-5120
(please include
convenient call
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date.)
tain hydrated lime but is often manufactured from portland cement, ground limestone, and other workability agents, including air entraining agents. Since masonry cements are not required to contain hydrated lime and produce higher strength mortars than typically desired for historic restoration, we do not recommend their use for repointing historic masonry.
Lime Mortar (preblended)
Some manufacturers are providing lime putty mortar preblended with sand in which case the portland cement is then added at the job site. In some cases custom historic mortars are available with color. If considering a preblended lime mortar with the sand, chances are the sand might not match; however, if the project calls for every joint to be pointed than it could be a consideration so long as the mortar type is compatible with the historic fabric. If the project is a "spot" repoint (repointing only deteriorated areas of building) then it would make more sense to consider a mortar analysis from which a custom preblended lime mortar with a matching sand could be provided. In either case, when considering a preblended lime mortar make certain its ingredients contain Type S or SA hydrated lime conforming to ASTM C207.
Water
Water must be clean and relatively free of salts, acids, or other dissolved material.
Historic Additives
In addition to the color of the sand, the texture of the mortar is of critical importance in duplicating historic mortar. Mortars dating from the mid-nineteenth century on are finely ground and present a uniform texture and color; earlier mortars were not as well ground and may contain lumps of partially burned lime, animal hair, sea shells or particles of clay. The visual characteristics of these additives can be duplicated through the use of similar materials in the repointing mortar. The historic mortar may have been tinted possible using carbon, lamp black or brick dust; in some cases, horizontal joints have one color while the vertical joints have another.
The above mentioned mortar ingredients can be combined and mixed in varying proportions to create the desired performance and ultimate durability of the new mortar. The actual specification of a particular mortar type should consider all of the factors effecting the life cycle including; current site conditions, present condition of masonry, the function of the new mortar, degree of weather exposure and the skill of the mason.
Joint Preparation
Old mortar should be removed to a minimum depth of 2-1/2 times the width of the joint to ensure an adequate bond and to prevent mortar "popouts." For most brick joints, this will require removal of the mortar to a depth of approximately 3/4 to 1 inch; for stones with wide joints, the mortar removal may need to be several inches. Any loose or disintegrated mortar beyond this minimum depth also should be removed.
The traditional manner of removing the mortar is through the use of hand chisels and hammers. Though labor-intensive, this method poses the least threat for damage to the masonry units. Small pneumatically powered chisels also are effective as long as the masons maintain appropriate control over the equipment.
The most common method for removing mortar, however, is through the use of power grinders. These methods can be disastrous for historic masonry. The use of power grinders on walls with thin joints, such as most brick walls, almost always will result in damage to the masonry by breaking the edges and by over cutting on the head, or vertical, joints. Damage to bricks, in particular, not only affects their visual character but also can lead to accelerated weather damage. Some success has been reported on the use of caulking cutters with diamond blades. Although slow, these caulking cutters do not rotate, but only vibrate at very high speeds minimizing any damage that may occur to masonry units. Where horizontal bed joints are uniform and fairly wide, a power grinder with a blade 1/2 the thickness of the joint may assist in the removal of mortar, by cutting down the middle of the joint; final mortar removal from the top and bottom of the joints can then be easily removed