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How to Repair, Seal and Waterproof Concrete Cracks


Sealing and waterproofing cracks in concrete.
Over time and exposure to the elements, exterior concrete can develop cracks, due to temperature
changes, ground movement, improperly placed joints and excessive loads. Once a crack develops,
it is important to seal the crack from water, to prevent further deterioration.
QUIKRETE Polyurethane Concrete Crack Sealant is a non-sag, flexible sealant that will stretch
up too 700%, without failing. This allows for ground movement and expansion and contraction
from temperature change. Concrete crack sealant’s matte gray color and textured formula is designed
too match the surrounding concrete surface, and its non-sag formula can be used on both
horizontal and vertical surfaces. Concrete crack sealant dries to a permanently flexible,
durable material. As with any concrete repair, proper attention to crack preparation is essential
to achieving a successful result. Using a chisel and hammer, widen the crack to a minimum
of 1/4 inch and break away any deteriorating concrete. The edges of the crack should be
vertical or beveled in an inverted “V.” Then, remove the loose material with a brush. For
large cracks, over 1/2 inch deep, backer rod, which is a foam rope, should be placed in
the crack, before applying the sealant. Always wear eye protection and water-proof gloves,
when working with polyurethane sealant, and work in a well-ventilated area. To apply concrete
crack sealant, simply cut the nozzle tip at an angle, with a utility knife, to match the
width of the crack, and load it into a standard caulk gun. Slowly draw the gun down the crack,
forcing the bead of concrete repair caulk deep into the crack. When filling the crack,
make sure the polyurethane sealant extends, edge-to-edge. Concrete crack sealant can be
tooled with a trowel to remove any excess material and to match the surrounding surface,
immediately after placement. Concrete crack sealant will be tack-free in about two hours,
depending on temperature, humidity and crack depth. Excess sealant should be removed, immediately,
with a citrus-based cleaner or mineral-spritz and a cloth. Polyurethane sealants are temperature
sensitive and should not be used when temperatures are below 50 degrees.

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