Masonry Magazine January 1984 Page. 34
BRICK PAVERS
Mason contractors can take advantage of securing new markets through the venerable brick paving units that have withstood the rigors of time and are still adding beauty, warmth and charm to communities nationwide.
By BRUCE N. VOSS
Because of their beauty, warmth, variety of colors and sizes and ability to withstand high-volume traffic, brick pavers are being used more and more in all types of construction. Pavers help restore the charm of our older cities. Their richness and durability add quality to the image of a new home. Their ease of installation makes them essential in today's cost-conscious market.
Over the years, BAC craftsmen have devised various systems for the efficient installation of brick paving units. In this article, we will be discussing the "Two-Step" system which most frequently is used when pavers are set over concrete. The pavers will be set in cement mortar called "deck mud." The joints between the paving units which are left open in step one will be grouted full as part of step two. The basic tools used in this type of paving are a flat trowel, wood float, brick and hammer, 4 straight edges, rubber mallet, pointing trowel, masons level and water brush. In some instances, reinforcing and/or a waterproof membrane may be required in the mortar bed.
Setting Bed
Before any setting bed is laid down, the concrete surface upon which the pavers will be set should be closely inspected for cracks, grease spots or sealing agents. Cracks in the concrete, if not properly treated, will ultimately produce cracks in the pavers. Grease spots or remaining sealing agents will prevent proper bond.
In large areas the location of expansion joints should be carefully considered as well. Any control joints in the concrete slab should have paver control joints directly lined up over them, otherwise cracks will result directly at those locations.
The finish of the concrete should not be "steel trowel" smooth, but should have a float or broom finish. This will allow for a better bond between the slab and setting bed. In instances where the concrete is too smooth, it may be necessary to create a rough surface by bush hammering, sand blasting, scarifying or acid etching the surface to allow for a better bond with the setting bed. Precaution must also be taken to remove any foreign matter such as grease or remnants of a sealant.
Once the slab is determined to be satisfactory, it is swept clean, moistened and a bond coat applied. A bond coat is needed to bond the setting bed to the concrete slab.
There are three accepted methods of applying a bond coat. In the first, pure portland cement is sprinkled on the surface. After it has been wetted down, it is broomed in thoroughly. The second method is to pour a slurry on the surface and broom it in thoroughly. The slurry is prepared by adding water to a mixture of one part portland cement and one and a half parts of clean sharp sand. In the third method, a slurry of pure thin-set portland cement and water is mixed and poured into the dry surface. For this method, the surface must be dry. It is then spread evenly over the surface using a trowel.
Regardless of which of the three methods is used for laying down a bond coat, it should only be put down for an area which will be covered by the deck mud during the same day, before it glazes or becomes dry.
The setting bed, called "deck mud," is normally mixed by hand in a mortar box or wheel barrow. Commonly, it is one part portland cement and six parts sand. The sand and cement are mixed dry first. Water is added sparingly and chopped into the mixture. Properly mixed, the mortar should form a ball when squeezed between your hands, yet when released, it should hold together. When trowelled, this mixture will readily assume a smooth, slick surface.
There are several accepted methods of laying down the deck mud to form the setting bed. Two of the most commonly used methods are with mud screeds and flat strips. Mud screeds are formed of mortar.
About the author
Bruce Voss is executive director of the International Masonry Institute's Apprenticeship & Training Program, Washington, D.C.