Why did the new stamped overlay that was recently installed over the old concrete developed spider web hairline cracks in surface?
As a client that paid good hard earned money to have their home's concrete resurfaced, seeing hairline cracks may be disturbing at first, and panic may set in, the mind begins to wonder if the new installation wont last and fall apart. The short answer is it's not as bad as you think.
Unlike many other resurfacing materials, concrete overlay mixes require proper curring time and often the curring takes place in not so ideal conditions that cannot be easily controled during the installation process especially in extreme hot sunny and or hummid days. So why does this happen?, And what can be done?
Typicall these are shrinkage cracks caused by pushing imprinting stamp tools into the concrete after the surface has become a little too hard. Although these hairline cracks do not compromise the strenght of the overlay, this surface hardening, is known as "crusting," usually caused by rapid exposure to sun and wind, overfinishing the concrete mix design, and even the concrete colour (darker colours more readily absorb heat from the sun) causing top surface to cure faster the bottom.
A good analogy is what happens when you cook pudding. When the pudding comes off the stove, it's a viscous liquid, similar to concrete when it comes out of the truck. The pudding then goes into the fridge to cool. If it cools too quickly, the rapid temperature drop causes a skin to form on the surface. The pudding then thickens and hardens from the top down. The same thing occurs when concrete dries too fast from the top down. Remedies for reducing surface crusting include using admixtures to slow the concrete set time, using surface evaporation retarders, avoiding darker colors, and scheduling the concrete pour for the coolest time of the day. Using stamping tools with deep grout lines, such as random stone and large slate patterns, can aggravate the cracking problem.
One way to repair these small cracks is to use a colored cement paste, or color patch. Some color hardener manufacturers offer these patches in their standard color palette for use in filling and repairing these types of cracks and small popouts. Some contractors will sift the sand out of the color hardener they are using on the project and use this to make a color patching material. I recommend wetting color patch materials with a 50:50 blend of concrete bonding polymer and water. Use a wooden tongue depressor or gloved finger to smear the color patch into the cracks. Soften the edges with a damp rag or sponge to blend the patch and color into the slab. Let the repairs cure for 24 hours. If you are located in the GTA area of Ontario, and would like to get a an estimate on resurfacing or repairing your existing concrete, contact the author at http://www.concreteartfx.com/.
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It would be interesting if Concrete Art-FX mentioned the type of warranty they carry or how the behave once a problem is encountered.
ReplyDeleteI engage this company to do a very straight forward job of applying an acid stain concrete + 2 coats of urethane on an office space of 600 sqf. I was very clear about our walls and ceiling being already finished. Nonetheless, the company didn't cover properly the walls and decided to grind without water without our consent (dust everywhere that was impossible to take off). The worst was that at the end, they didn't clean properly the surface, therefore the stain and sealer was poured over dusty areas.It's already being not more than 1 week and it already started to peel off. There were imperfections all around,uneven areas and brush marks all over the place. At the end, the owner from this questionable company, decided not to show up and not to be responsible for any of his faulty job. Worst experience ever... Stay away!