Floors
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Floors on Grade The Striker requires the support of formwork, cold slabs, or screed rails. Floor placement often includes slabs greater than the width of the Striker. Split the slab into bays about 25 feet in width with rows of screed chairs which carry 1-1/4” screed pipe. The same screed chair is used on a blind edge, such as a wall of curtain of rebar. Pinheads are placed on top of rebar pins to provide a saddle for 1-1/4” screed pipe, then reused once the pipe slides forward. The Striker cuts slab elevation in reference to the support.
The use of friction on the surface yields a different elevation than when vibration is used. Vibratory systems often yield a grade slightly higher than the formwork or cold slab they rest upon. However, the Bunyan Striker yields a grade that is slightly lower than the formwork or cold slabs they rest upon. This is caused by the aggressive cutting action of the tube as well as slight shrinkage of the concrete itself. For this reason, we recommend operators place a steel spacer strip on the cold slab, to space the Striker slightly higher than the cold slab, so the final elevation will match perfectly. This also prevents the tube from contacting the cold slab directly.
Formwork is installed 1/8 inch above the finished elevation and finishers should seek a surface elevation of the slab rather than the formwork. Avoid the practice of filling the edges to match the formwork.
Cold slabs often have error in surface elevation and flatness. Slabs are prone to develop error in the form of curling. A screed rail resting on the cold edge provides a straight reference for elevation for the Striker Tube.
The Bunyan Striker Tube in neck configuration corrects these errors with support from an elevated screed rail. The elevated screed rail acts as a bridge, placing a flat elevation which is 1/16 below the highest points in the cold edge. The striking face of the Striker Tube does not come in contact with the cold slab.
Floors on Deck Similar method is used for floors on overhead decks. Use similar method with cold slabs and formwork.  When screed chairs are fastened to decking, the concrete placement affects a change in elevation.  Once concrete is placed, the elevation of screed chairs must be verified for accuracy.