briefing should stress this important point to everyone who might need to work in the form. This should include the concrete placement team. While there is a very low likelihood of breaking brick once the concrete has been placed, there is the possibility that the suction of someone removing their foot from the sticky concrete will lift brick out of their pockets. Placers and vibrator operators should only step in the concrete when absolutely necessary and then only on top of the reinforcing. Pre-wetting brick . Pre-wetting thin brick prior to casting is unnecessary and not recommended. F. Placing Concrete
1. Concrete Placement. When placing concrete, care should be taken not to create currents with the concrete that could disturb the brick. Placement should be done in such a way that there is little or no forceful impact of concrete onto the brick. Ideally the discharge hose or trough should be approx. 6 inches above the brick. It is also preferable to pour the concrete onto itself into a small ‘buffer’ pile and follow it across the brick to fill the bricked areas. This minimizes the chance of brick lifting, or tilting. Never use vibration to move the concrete over embedded brick, and be careful when screeding not to drag heavy piles of concrete. The weight of the concrete produces a sticky current over the back of the bricks that can easily dislodge them.
2. Self consolidating concrete. Self consolidating, sometimes called ‘self compacting’ or ‘self leveling’ concrete, is by far the easiest to place. It requires little or no vibration, and rarely disturbs the brick. One thing however that must be considered is that some of the same properties that give these cements their elastic properties also tend to inhibit them from attaining the ‘feather edges’ that otherwise surround each brick. To compensate for this, some mild vibration may be necessary. Producing a mock-up panel would be advisable as a way to find the method that will give you the best results. 3. Vibration. Consolidating the concrete through vibration rarely causes brick to become dislodged from the liner. Brick will not ‘float’ into the concrete under normal conditions. However, excessive vibrating that causes segregation may affect both the brick and joints. If interior vibration is used it is best to insert the vibrator into the concrete perpendicularly to the panel. Do not lay the vibrator horizontal and drag it into, or along the surface of, the concrete. When the vibrator is properly inserted the energy affects a broader area and does not induce strong concentrated currents that may tilt brick. Care should of course be taken not to touch the brick with the head of the vibrator. A tennis ball or tape on the head is handy for marking the maximum depth of insertion. When exterior vibration is used it should be done sparingly. Never use the vibration to level the concrete, instead utilize hoes or screeds. High frequency vibration is preferred to high impact shock tables. Whatever method is used it is advisable to try it on the mock-up test panel first. 4. Re-bar chairs . Adhere to rule of thumb of minimum of 1.5 times the diameter of the re-bar from the surface to the steel (surface is back of brick). 5. Slump of concrete. It is not necessary to adjust the slump from the normal setting in order to accommodate the thin brick. The same batch design that gives satisfactory results to the smooth casting surfaces will work for the thin brick in VersaLiner.
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