How to Repair Cracks in Concrete Floors

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Cracks are the most common problem in concrete floors, concrete driveways, patios, pool decks, concrete roofs, airport runways, etc.

If not repaired properly in the first place, the concrete will deteriorate further and the cracks will need repeated repairs. In case of buildings, they will let in water, vapor and radon gas. 

Here is the most advanced method for repairing cracks, spalls, or pitting in concrete slabs by contractors or homeowners. (Not available in stores, shipped directly from the factory.)

RadonSeal sealer as the first step

Before repairing cracks and joints, it is a good idea to first seal the concrete with RadonSeal. The cracks help the sealer penetrate into the concrete to protect it against further deterioration.

RadonSeal penetrating concrete sealer penetrates up to 4 inches, reacts with lime and alkalis, strengthens and waterproofs the concrete. It prevents or reduces further cracking and also tends to seal hairline cracks. If the cracks are also narrow inside, you may be done with the crack repair.

By keeping out water from above or below, RadonSeal protects the concrete against deterioration, pop-outs due to rusting reinforcing steel, spalling or pitting caused by the freeze/thaw cycle, road salts, and chlorine from seawater.

Stopping water seepage and efflorescence (“white powder”) will protect overlays, self-levelers or concrete patches from separating.

CrackWeld Concrete Floor Repair

The CrackWeld repair kit makes permanent crack repair quick and easy for homeowners and contractors:

• Very low viscosity (penetrates and deep-fills even the narrowest hairline cracks)
• Eliminates the need to route out cracks (!)
• Quick-curing (allows installation of overlays in half an hour)
• High-strength bond (stronger than concrete)

CrackWeld resin bonds sand into an indestructible, impermeable mass inside the crack, which fills the full depth of the slab. Water, vapor or gases cannot penetrate. It is also a structural repair – it prevents the crack from further movement.

CrackWeld application procedure

The procedure is very quick and easy – just view the video

The concrete has to be dry, including the inside of the crack. The basic steps:

1. Inject the CrackWeld resin inside the crack to wet the surfaces and make them tacky.
2. Push dry silica sand into the crack to fill it.
3. Thoroughly saturate the sand with CrackWeld resin to fill it to the surface.
4. Scrape off the surface of the crack in about 10 minutes to make it level and use sandpaper for neat appearance.

About the traditional quick “fixes”

Caulking the cracks is cheap and easy but short-term. The caulk will not last in traffic. Water wicking through the concrete or trapped water vapor will cause efflorescence (“white powder”) and will weaken the bond to concrete. After couple years, the caulk can be easily peeled off.

For a more lasting repair, route out the crack first ½” deep with a grinder. If radon is a concern, use polyurethane caulk.

Hydraulic cement is a temporary fix only. It is fully waterproof but does not bond well to concrete – that’s why you have to chisel out an inverted V-groove. And it is much more rigid than concrete, which continuously moves, shrinks and expands. This stiff “rod” will gradually get loose and water will start seeping around it.

Applications for RadonSeal CrackWeld

Indoor concrete:

• Residential – cracks in basement slabs and slabs on grade
• Industrial – cracks in factory or warehouse slabs subject to heavy traffic, allows the traffic to resume in half an hour

Outdoor concrete:

• Driveways – a must before installing overlays
• Patios, sidewalks, pool decks – cracks, spalls, “divots”
• Concrete roofs – cracks, spalls
• Concrete runways – cracks and spalls

The repair is hard and rigid. Not suitable for joints that require flexibility – expansion control joints (“saw cuts”) or floor-to-wall joints of basement floating slabs.

Hairline crack that are too narrow for sand can be filled and repaired with two passes of the CrackWeld resin.

To repair large cracks with a void underneath, insert first a foam backer rod of appropriate diameter as available in hardware stores.

RadonSeal CrackWeld floor repair contents

CrackWeld Concrete Floor Repair Kit:

• 1 dual-cartridge gun
• 2 double-tube sets of RadonSeal CrackWeld resin
• 3 mixers
• 3 needles
• 3 cross-over restrictors
• 2 nuts
• a pair of rubber gloves
• 4 lbs. of silica
• Instructions and MSDS

Tools needed – paint scraper or trowel and sand paper (80 grit).

CrackWeld Concrete Floor Repair Materials:
In case additional materials are needed. Same as the kit except for the dual-cartridge gun and gloves.

Coverage:
For full-depth repair of a standard 3.5” slab, each kit will repair up to 100 ft. of a 1/16” crack, or 200 ft. of 1/32” crack.

If additional sand is needed, use completely dry sand without fines, such as sandblasting sand with granulation similar to table sugar (30 to 40 grit). Play or beach sand is not recommended because of too many fines and moisture.

Price and Shipping

Normally shipped the same or next business day. Delivery by courier in 3 to 5 business days. Shipping costs are valid for the lower 48 states. For shipping express, to other states or Canada, please contact us for shipping rates.

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Any questions? Please contact us by e-mail,
telephone (203) 225-0366 or toll-free 1-800-472-0603

MADE IN USA
Products not sold through retail stores. Available exclusively from:
Radon Mitigation & Waterproofing Concrete Sealer Co.
Novion Inc., 18 L'Hermitage Drive, Shelton, CT 06484 USA
RadonSeal™ is a registered trademark. Copyright © 1998-2008. All rights reserved.