How to Repair Cracks in Concrete Floors

Cracks are the most common problem in indoor or outdoor concrete slabs - concrete floors, concrete driveways, garage floors, patios, pool decks, parking areas, etc. If not properly repaired, the cracks will get worse, causing spalling and disintegration of the concrete: plant grows in a crack in concrete driveway

  • Rainwater gets to the reinforcing steel, makes it rust and expand, causing more cracking and pop-outs.
  • The freeze-thaw cycle of trapped water widens the cracks.
  • Seepage of water, vapor, and radon gas into buildings.
  • Trapped moisture destroys flooring materials and may cause mold infestation.
  • Water leaches out the concrete and causes efflorescence.
  • Vehicular traffic crumbles the edges of cracks.
  • The cracks will get wider and longer due to natural movement of concrete.
  • Cracks propagate into rigid flooring tiles or concrete overlays.

RadonSeal CrackWeld Concrete Floor Repair Kit "welds" the concrete slab together. It fills the full depth of the crack and quickly cures as a rigid compound that is stronger than concrete. It provides to contractors and homeowners the state-of-the-art method for permanent repair of hairline or wide cracks (up to 1/2") in concrete floors, as well as spalls or holes in concrete slabs. No need to route out the cracks!

The wrong way to repair floor cracks

Covering the crack with caulk is cheap and easy but short-term. Water wicking through the concrete or trapped water vapor will weaken its bond to concrete, which may show up as efflorescence. The caulk will not last in traffic. After a couple of years, the caulk gets loose and can be easily peeled off.

Hydraulic cement is a temporary fix only. Yes, it is waterproof but it does not bond well to concrete – that’s why you have to chisel out the crack as an inverted V-groove to hold it in place. It also is more rigid than concrete. However, concrete continually moves, shrinks and expands which loosens the stiff hydraulic cement. After a couple years, water seepage and likely also efflorescence will appear around the edges of the plug.

CrackWeld DIY floor repair kit
Click to enlarge!

Why use CrackWeld for concrete crack repairs

RadonSeal CrackWeld is a two-component compound. When ejected out of the cartridge through a mixing nozzle, it fills the crack, reacts, and quickly cures. Similar to epoxy but only 1/10 as viscous – routing is not needed. It bonds with sand into an indestructible, impermeable mass inside cracks, spalls, or holes. Water, vapor, or gases cannot penetrate. It is also a structural repair – it stops the crack from further movement.

The CrackWeld slab repair kit makes permanent crack repair quick and easy:

  • Very low viscosity to also fill hairline cracks – no need to route out cracks (unlike epoxies)
  • Fast-curing (ready in half an hour for overlays or heavy traffic)
  • High-strength bond (stronger than concrete) to prevent elongation and yawning of cracks.

Shipping and Pricing

Not sold in stores but delivered directly from the factory to your door. Orders received by 1 PM ET are normally shipped the same day and delivered by courier (UPS) within 2 to 5 workdays.

CrackWeld Concrete Floor Repair Kits
Size Price Shipping  
CrackWeld DIY Kit 2-pack
$79
$9
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CrackWeld DIY Kit 4-pack
$139
$10
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CrackWeld PRO Kit
$184
$12
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   CrackWeld PRO Consumables
$119
$10
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Based on shipping by courier to the lower 48 states. For expedited shipping or
shipping to other states and Canada, please inquire first by e-mail or telephone.

Coverage: DIY Kit 2-pack ... up to 50 ft. of a 1/16” crack, DIY 4-pack or Pro Kit... up to 100 ft.

Feedback from customers

I used your CrackWeld 4-pack to fill many hairline cracks and several 1/4 inch cracks on my driveway and garage. ... My driveway and garage are over 30 years old and some of my neighbors, in the last few years had spent thousands of dollars to have their driveway repaired because of cracks. I am glad I found your product ... I will be buying more CrackWeld to do some cracks in my basement too... Dan B., WI

I live in San Juan Capistrano, CA and a few days ago we had a small 3.6 earthquake and this is about a week after I used the CrackWeld to fill small and large cracks in my garage concrete.  I checked the cracks after I got home from work and no separation and the seal looked just like it was before the quake...Romeo F., CA

See more Testimonials

Applications for CrackWeld crack repair kits

Indoor concrete:

  • Residential – cracks in basement floor, foundation slabs, garage floors
  • Industrial – cracks or spalls in factory or warehouse floors subject to heavy traffic (allows heavy traffic to resume in half an hour)

Outdoor concrete:

  • Driveways, parking areas – a must before installing overlays to prevent propagation of cracks
  • Patios, sidewalks, pool decks – cracks, spalls or “divots”
  • Concrete roofs – cracks, spalls, holes
  • Bridges, roads, airport runways – cracks, spalls, holes

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

Color: When cured, CrackWeld has a gray color but when exposed to direct sunlight it may change hues. Broadcasting sand over CrackWeld (silica is included) before it cures will result in a lighter gray color. Sanding or better yet, grinding the repair even with the sidewalk will reduce the polymer's exposure to sun. Due to the high silica content of the repair (about 80%) the surface usually holds some stain or paint.

About CrackWeld application

The inside of the crack must be clean and dry. (Some contractors first place duct tape on both sides of the crack to make cleanup easier, particularly on rough surfaces.) The basic steps:

  1. Inject the CrackWeld resin into 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. In 10 to 15 minutes, scrape off the surface to make it level and use sandpaper for neat appearance.

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

To repair wide cracks or cracks with a void underneath, first fill the crack partially with sand to prevent the CrackWeld resin from running out.

CrackWeld DIY floor repair kit
Click to enlarge!

If additional sand is needed, use a DRY graded sand (no fines) or ideally, sandblasting sand with granulation like table sugar (30 to 40 grit).

CrackWeld sets up quickly! Maintain an steady flow of CrackWeld through the mixing nozzle or it may become plugged after a minute or two! After a stoppage, purge the mixer into a disposable cup. To minimize stoppages, repair small sections of the crack at a time say, 5-10 ft. or use up the whole cartridge. Fill the crack with sand in 2 to 3 minutes after priming while CrackWeld is still tacky. On larger jobs, try to get a helper to do the scraping.

Do-It-Yourself CrackWeld Kits

The CrackWeld DIY Concrete Floor Repair Kits are designed for a quick and easy do-it-yourself application by homeowners. Each kit includes either two (2-pack) or four (4-pack) two-component CrackWeld cartridges, as well as mixing nozzles, a bag of silica sand, and other accessories.

Coverage:
For full-depth repair of a standard 4” slab, each CrackWeld kit will repair:
        2-pack ... up to 50 ft. of a 1/16” crack or 25 ft. of a 1/8" crack
        4-pack ... up to 100 ft. of a 1/16” crack or 50 ft. of a 1/8" crack

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

CrackWeld do-it-yourself slab repair instructions Contents and Installation Instructions for do-it-yourself concrete floor crack repair

CrackWeld floor repair kit
Click to enlarge!

Professional CrackWeld Kits

The CrackWeld PRO Concrete Floor Repair Kits are for contractors or homeowners with extensive slab cracks. The two-component CrackWeld compound is packaged in dual-tube cartridges. Each kit is complete and "ready to go." It includes a professional dual-cartridge gun, as well as mixing nozzles, a bag of silica sand, and other accessories.

CrackWeld Concrete Floor Repair Kit contents:

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

The procedure is quick and easy – view the CrackWeld PRO Concrete Floor Repair video!

Coverage: For full-depth repair of a standard 4” slab, each CrackWeld Pro kit will repair up to 100 ft. of a 1/16” crack or 50 ft. of a 1/8" crack.

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

CrackWeld Pro slab repair instructions Installation Instructions for CrackWeld Pro Repair Kit, CrackWeld PRO Kit MSDS

The best first step – RadonSeal concrete sealer

Before repairing cracks, seal the concrete with RadonSeal deep-penetrating concrete sealer. Any cracks will help the sealer penetrate into the concrete, which preserves and strengthens concrete against further cracking.

RadonSeal concrete sealer penetrates up to 4 inches into concrete, reacts with alkalis, expands inside the pores, and waterproofs the concrete. It also tends to seal fine hairline cracks in slabs. It just might do the crack repair job.

By keeping out water from above or below, RadonSeal protects indoor and outdoor concrete against deterioration, spalling or pitting caused by the freeze/thaw cycle, road salts, and chlorine from seawater.

By stopping water seepage and efflorescence (whitish salt deposits), RadonSeal protects concrete overlays, self-levelers, or patches from separating.

MADE IN USA
Products not sold through retail stores. Available exclusively from:
Radon Mitigation & Concrete Waterproofing Co., Novion Inc.,
18 L'Hermitage Drive, Shelton, CT 06484 USA
RadonSeal™ is a registered trademark. Copyright © 1998-2012. All rights reserved.