Masonry Magazine June 1992 Page. 36
Warping in Cement and Precast Concrete Tiles
Cement matrix and precast concrete tiles may warp after the pieces have been set for a few days. The characteristics are similar to the green marble when the warping occurs.
The cement or concrete based agglomerate tile and precast concrete tile appear to have a common cause for the warping or curling. In every case that I have examined the materials were cast and set within a relatively short period of time. There didn't seem to be adequate time for the materials to cure before being set. Two jobs verify the logic of this theory in that the first shipment was shipped from older inventory and the subsequent shipments were made as soon as they were ready since the tile production was running behind the project schedule. In both cases the older material was bonded with no curling and the newer material curled and lost bond at the corners. The curling is so obvious that on one exterior job the age or number of days the tile had been set could be determined by sounding the floor. After the fourth day the hollow sounds became progressively greater when checked. The 2'0"x2'0"x11/4" pieces were bonded in only about a 14" radius at the center of the tile after being set for approximately three weeks. In all cases, when removed it was obvious that a complete bond had been obtained originally at the hollow sounding areas of the tiles.
The apparent cure to the cement tile or agglomerate with a cement matrix is the "cure." Adequate time for drying or curing must elapse to prevent the warping that occurs when uncured tiles are set in water based cement bonding mortar. The problem can probably be corrected in interior installations by setting the tile in an epoxy mortar if the tile moisture content is not too great to use with an epoxy.
The other problem that I have seen in thinner cementitious agglomerate is that the warping or shrinkage pressures were great enough to cause spider cracks in the surface of the tile when the tiles were securely bonded.
The resin based agglomerates vary extensively in their tendency to warp or not warp. Tests that have been made indicate that the different colored marble chips cause different degrees of warping within the same manufacturer's resinous matrix.
As of this date it isn't possible for me to advise what bonding materials to use when the precast concrete, cementitious agglomerates are being installed, since the causes of the warping are not the same nor are we always able to identify the cause after the warping occurs. Everyone, including me, usually has a theory that may not be substantiated by the evidence.
My advice is to follow the supplier's directions and attempt to avoid the responsibility of recommending bonding materials for products that you have not successfully used previously. If you do have to make the selection, it is probable that the one-hundred percent solids epoxy would Continued on Page 38
ROBERT T. YOUNG is a leading consultant for the marble and tile industry. He has over fifty years experience beginning as a helper, serving an apprenticeship and working as a marble and tile setter before establishing his own business. He owned and operated a marble fabrication shop and a marble and tile installation company for many years. He formed Ceramic Tile and Marble Consultants in 1934 to perform jobsite inspections and analysis of installation problems. He's a speaker on installation procedures to trade organizations, architectural groups and company sales and installation personnel. He serves as special consultant to trade organizations, tile manufacturers and developers to promote qualified installations. He can be reached at Ceramic Tile and Marble Consultants, 201 East Ranchwood Circle, Oklahoma City. Oklahoma 73160, phone 405/794-3675.
36 MASONRY-MAY/JUNE, 1992
Non-Stop
SCAFFOLDING
Increase Production 20%-35%
When the wall is waist high to the bricklayer, he will produce more. Government stadies, the experience of our customers, and our own experience have proven that point most convincingly. Actually, it's basic human nature. When the bending, reaching, and stooping are eliminated, a mason will fall into a fast, confortable side-to-side thythm when laying brick and block. Hell put in more units and be less tired at the end of the day. How much more production depends on the type of work. Production increases of 20% are common, while 35% is typical for Hank walls like warehouses Our users have reported production increases as high as 47% on 12 blocks.
When you calculate the labor savings from this feature alone, you will see that Non-Stop can easily pay for itself in the first 10 to 20 weeks. Some masonry contractors say that their scaffolding puid for itself on the first job
Never Run Scaffold-High Again
Building a wall from the ground to scaffold-high and then moving your men is another unnecessary expense to elininate froes your operation. It tends to scatter your men, creates extra work for the laborers, and i wastes ten to minutes of production time getting the crew started again.
Using Non-Stop, you will set your scaffolding in place first, before any work begins. Stock it with materials and your masons start the wall right off the scaffold. Once they have reached a com fortable working height, their walk bourds can be dropped in place in about 30 seconds and they continue working uninterrupted until the wall is topped out. Non-Stop gives you the ability to put your masons walkboards as low as off the ground.
Another standard feature Non Stop provides is the ability to add an extra walkboard for the masons. In many situations, like brick veneer with block back-up. you must run the block up fint. Using Non Stop, you can run the black with 3 planks for the masons, let the scaffold down. and then run the brick with 2 planks, without moving or replumbing the scaffolding.
The Fast