| Repair
recommendations
As mentioned earlier, contractors use various techniques
in repairing cracks and prepping the surface for a decorative
coating. As Anderson points out, often "you just have
to get out there and see what works and what doesn't."
Always wash out the crack with a pressure
washer or blow it out with compressed air. The crack needs
to be clean for good bonding with the repair materials.
If you're using a concrete stain, your
"repair material needs to match the surroundings - cementitious
is often the preferred material," observes Borum.
Manuel recommends using a bonding agent
on the sidewalls of the crack if you're using a cementitious
material for better adhesion. "Feather the patch if you're
going to coat or stain the surface," he adds.
 If
using epoxy, be sure the material completely fills the crack,
advises several contractors. If you are filling only a portion
of the crack - say the top inch or so - what you have is an
upside down control joint, and you know what will happen -
it will crack.
With epoxy, pressure-feed injection
is best, reports many. Also, using a thixotropic epoxy can
be advantageous. A thixotropic epoxy congeals as it works
its way down into the crack. This lessens the runoff of the
material out the bottom of the crack and allows the material
to fill up the crack and then cure.
With caulk-like repair materials, Darrell
Adamson, vice president of Engrave-A-Crete Inc. in Sarasota,
Fla., recommends using a backer rod if there's room. "You
need a nice bond to each side of the crack, but the center
band needs to be thin to be springy or stretchy [if there's
movement]." Adamson uses a syringe when applying
caulking to small cracks and he says,
"If you need to scrape excess away, cut it up and away.
Don't smear it down with your finger. Or you can wait for
it to cure and cut it flush.".
To prepare the top surface of the concrete
after crack repairs have been made, Anderson recommends shot
blasting to give the surface a profile, followed by an acid
wash to neutralize any alkalinity and open up the surface
pores to accept the coating.
"You can be creative in how you
repair, [but] a good repair is taking your time. Don't do
the job in a hurry," advises Wes Vollmer, owner of Alternative
Finishes in San Antonio. Take the time to talk with the engineer,
he advises. "You'll educate yourself for future jobs.
Ask how you can manage cracks and where you should put control
joints. You have to be smart about how you do your work."
Cracks
as decorative elements
Mark Donaldson, owner of Skookum Floors USA Ltd. in Seattle,
says that using cracks as decorative elements is probably
a specialty or niche area, but he and other contractors have
come up with ingenious ways to hide cracks in plain sight.
A random stone look is a natural decorative
effect that uses random cracks, observes Lee Tizard, technical
sales represen. tative with Floric Polytech Inc. of Rancho
Cucamonga, Calif. After chasing out the cracks and applying
a knockdown texture, cut additional random cracks with masonry
saw blade to create a faux flagstone effect, he says.
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