When flooring failures occur, the initial reaction is to point the finger of blame at the installer or flooring material manufacturer. Well, look deeper as the stage often has been set for failure before the installer arrives.
The flaws often begin to occur at the base with your concrete slab. Many finishers overwork the concrete surface, usually by keeping powered trowel equipment on the concrete surface too long. We call this over-finishing. It densifies the concrete surface to the point that adhesion between the concrete slab and installed floor isn’t adequate. You can see the evidence prior to installing the flooring as the concrete appears slick, smooth and darkly colored. That’s the sign that costs are about to run up as resurfacing the newly finished slab delays the project and results in paying for the job a second time.
This is a common mistake as many finishers (with the best of intentions) try to make the concrete as smooth as possible in prepping for floor installation. Here’s how to insure the job is done right the first time. Simply add some form of the following language to your concrete specification:
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Smooth, hard, hand steel-troweled finishing is preferred. Machine-troweled finishing free of trowel ridges is accepted.
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Produce a tight float finish, the machine equivalent of hand wiping the surface with a steel trowel.
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Avoid burnished and polished concrete surfaces that may impede mechanical bonding of subsequent coatings, toppings, underlayments, absorption of flooring adhesives and floor finishes.
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Finish to specified tolerances. Do not burn or overwork concrete.
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Do not blacken or burn concrete surface with power trowel.
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Of course, the best recourse for the facility manager is to have a qualified person monitor the slab finishing process.
One way to ensure the individual is qualified is to use a technician who is certified by the International Concrete Repair Institute. These trained techs can help prevent over-finishing, and other common concrete errors — such as conducting moisture testing before the building is climate controlled. ICRI technicians are trained for, among other things, moisture testing per ASTM-F2170, The Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In-situ Probes.
Aside from reducing rework, there’s another way to save on concrete costs. Using a rapid drying concrete can reduce your overall project duration up to 30 percent. This in turn reduces the overhead costs to the general contractor and offers speed-to-market benefits to the project owner.
About the Author: James Tyrone is Aridus program director for U.S. Concrete.