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What is a Super Flat Floor, how is it produced, and how is it measured?
By definition, Super flat =F min 100. In order to achieve this high degree of flatness/levelness, Super flat floors must be placed in long narrow strips. The forms for Super flat placements must be set with great precision. Specialized finishing techniques and continuous quality control measurements are also required. The services of a floor design/construction consultant are usually advisable.
For Random Traffic Floors, Super flat is often defined as FF100/FL50; but Super flat tolerances are rarely required on Random Traffic Floors. Although some of the same techniques may be used in creating better, flatter, more lever floors in general.
The finishers choice of hand tools will be saw beams, check-rods(modified straightedge) and bump cutters (modified highway straightedge) Theses tools are physically different from a bull float or a channel float in that they have a 90 degree angle on the trailing edge, while the bull float or channel float has a radius. Once the floor is initially screeded (usually with a truss screed), the first hand tool in the super flat process is the saw beam (straightedge with handles). It is used to remove any remaining laitance (cement paste) behind the screeding operation. The saw beam is supported by the side forms and is moved down the concrete surface in a sawing action four times: first at 45degrees to the forms, second perpendicular to them, third at the opposite 45 degrees to the first pass, and finally, perpendicular to the forms.
Immediately following the saw beam, you use a check-rod perpendicular to the direction of screeding. This tool is used like a bull float, but when you pull back, you keep the leading edge as low as possible without digging into the concrete. This causes cement paste to flow from high spots to low spots. As you move the tool down the slab, the tool should overlap the previous pass by 50%. Because the tool is used when the concrete is plastic, corrections are easily made.
The bump cutter is the final and most critical tool used on a high tolerance super flat project. The concrete must have slightly stiffened (attained initial set) to the point where it will support the weight of the tool. When you move the tool down the slab, you rarely lift it from the concrete surface, but advance it in 8-inch to 16 inch increments per pass. The purpose of this tool is to reduce local high spots caused by any imperfections in form setting and from power floating and troweling operations. You should use the tool as often as possible behind each machine pass. The correct use of this tool will have a major impact on the final numbers achieved on any floor installation.
Floor flatness and levelness is measured by using an electronic device called a dipstick. With the dipstick we are able to set a benchmark to work against as far as determining our flatness and levelness. The flatness is measured by the Ff number and the levelness is measured by the Fl number.
Now in their third decade, The Golden Trowel Awards are the most prestigious and sought after award in the concrete flooring industry. Presented by The Face Companies, golden Trowels recognize the flattest and most level floor slabs placed around the world in the previous contest year.
A special Golden Trowel, The “Sam” Award was established in 2002 to honor “outstanding accomplishments in and contributions to the art and science of high quality horizontal concrete construction”. These awards are certainly goals that are attainable, and ones that show true excellence in craftsmanship.
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