CoatingsPro Magazine

MAR 2015

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 74 of 90

68 MARCH 2015 COATINGSPROMAG.COM important to keep in mind that w ith my clients, I seldom discuss any possi- ble ideas before I see the property — I just don't. So she and I had no prelim- inar y discussions about what could possibly have been going on w ith this librar y f loor. With ever ybody ready for discus- sion, I started the inter pretive phase of my obser vations. T he underly ing cause of the appearance of the grid is related to slab deformation. T he deformation is referred to as slab curl in the case of a moisture-induced problem, or as slab war ping in the case of a temperature-induced problem. T he slab showed signs that it had curled prior to the installation of the new f loor covering (i.e., the epox y and vinyl), and that after the f loor cover- ings were installed, the slab rela xed. Compression Tension Compression Tension Slab at time of installation Wet Dry Control Joint flled with cementitious fller Once an impervious floor coating or a floor covering is applied to the surface of a curled concrete slab, the moisture within the slab redistributes within the body of the slab to a near equal distribution from top to bottom. This moisture redistribution relaxes the tension/ compression strain and the slab relaxes to an uncurled condition. As the slab returns to flat, the cementitious filler material cracks due to movement stresses - the filler is now anchored to the bottom of the floor coating or the floor covering but is separated from slab. The result is visible lines outlining the location of the control joints and cracks. Condition of slab prior to the start of the installation. Top of slab is dry, bottom is considerably wetter, creating a tension/compression strain whereby the slab curls at the edges. Slab curl will be most pronounced at control joints and at cracks within the concrete. Prior to any installation, these cracks and control joints are filled with a cementitious filler material. Slab after moisture redistribution Cementitious fller cracks and pushes up beneath the foor coating or covering Impervious foor coating or covering Never Again

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