New Full-depth Hairline Crack Injection Breaks the Rules

1006-STR Roadware Easy Injection static mixer for Roadware 10 Minute Concrete Mender 600ml Cartridge.

Roadware 10 Minute Concrete Mender™ and Easy-injection mixers make full-depth crack repairs in hairline cracks without cutting. This less evasive crack repair technique breaks the rules for concrete repair.

Broken Rule One
 Hairline cracks are not worth the trouble fixing.

Broken Rule Two
 You have to cut open a hairline crack if you want to actually repair it.

Broken Rule Three
Crack injection requires pumps, ports, slow epoxy, and lots of time.

Let’s look at these “rules” one by one. 

Broken Rule One: Hairline cracks are often dismissed as not worth fixing. However, it’s important to note that almost every concrete crack starts as a hairline crack. Some of these cracks are so tiny that they are not visible to the naked eye.

Cracking naturally occurs in concrete slabs as the concrete cures and shrinks. We use saw-cut control joints to guide the concrete to crack inside the designated joints, but sometimes the concrete cracks in unexpected places. We wish there were an efficient way to fix hairline cracks, but for now, we generally ignore them and attribute them to the nature of concrete. We might reassure customers by saying, “It will be fine; you still have aggregate interlock, and the crack is just on the surface,” or “All concrete cracks, and it’s just the nature of the product.” Unfortunately, customers who have invested in a new concrete floor are usually dissatisfied with these explanations.

The truth is, we would fix hairline cracks if there were a good and efficient way to do it.

Scoring a concrete crack with a diamond grinder.

Broken Rule Two: You have to cut open crack if you really want to repair it.  A repair material has to actually get into a crack so it will actually do some good. Anything short of that is no better than caulk. For the most part, this is true. We can’t repair what we can’t reach. Traditional cut and cover techniques us a diamond blade saw to open up a crack, forming a shallow well for Concrete Mender to accumulate and flow down into the crack. It works really well, and Roadware has been doing it for over twenty years.

What is needed is a way to actively push repair products into hairline cracks. Roadware 10 Minute Concrete Mender can do the job with simple techniques and Easy Injection Mixers. That brings us to:

Broken Rule Three: Crack injection requires pumps, ports, slow epoxy, and lots of time. 

For a successful crack injection repair you need to accomplish three things:

  • Delivery of materials to the repair area.
  • The repair material needs to set before if flows away from the repair area .
  • The repair has to be structurally effective.

The Roadware Easy Injection mixers make it easy to fill cracks as small as 20 mil (0.02 inches) with Concrete Mender. Simply drill a 3/8-inch hole into the crack and then push the almost-water-thin Concrete Mender into the cracks. You can see the Concrete Mender flow along the entire length of the hairline crack. You won’t need expensive injection pumps for this – just a cartridge of Concrete Mender and a manual application gun.

Roadware 10 Minute Concrete Mender starts to thicken and cure in about 5 minutes after application, so the material will stay where you put it. Traditional injection epoxies take hours to cure. In many cases,  at the end of the day, the epoxy all ends up under the slab and no longer in the crack.

Diagram showing Concrete Mender Soft-tip mixer injection into a concrete slab.

Roadware 10 Minute Concrete Mender™ with Microdoweling™ penetrates traditional bond lines and repairs concrete from the inside out. This structural polyurethane will not become brittle over time. Epoxy injection resins become very hard and brittle. As the concrete deflects under traffic, the brittle epoxy will start grinding away at the bond-line and the deterioration will start all over again. Roadware 10 Minute Concrete Mender is designed to restore aggregate interlock and  deflect with the concrete under heavy traffic and loading. This structural polyurethane will not become brittle over time and is designed to bring the cracked concrete back to original pre-cracked condition.

Roadware 10 Minute Concrete Mender with Easy-injection mixer repairing a hairline crack.
Concrete Mender crack injection into 24 inches of concrete.
Concrete Mender crack injection into 24 inches of concrete. Notice the material penetrating full depth.
Hairline cracks less than 20 mil across repaired using Roadware 10 Minute Concrete Mender and Easy Injection application. UV Forensic Photography. See More Here

Getting Started

80300 Roadware 10 Minute Concrete Mender 600ml Cartridge
80300 Roadware 10 Minute Concrete Mender 600ml Cartridge

80300 Roadware 10 Minute Concrete Mender 600ml Cartridge

1006-STR 24-element static mixer with Easy Injection Tip
1006-STR 24-element static mixer with Easy Injection Tip

1006-STR 24-element static mixer with Easy Injection Tip

5300C 600ml Dual Cartridge Application Tool
5300C 600ml Dual Cartridge Application Tool

600ML (300x300) dual cartridge application tool for all Roadware 600ML cartridges.

52 thoughts on “New Full-depth Hairline Crack Injection Breaks the Rules”

  1. Im interested in the hairline concrete mender. Have a small crack around my pool deck, price with shipping.



  2. I have enjoyed reading the information about concreting work. Really, entire discussion is more helpful and all the tips are more effective too. I am very glad to go through this kind of helpful article. Thanks for sharing a nice article.

  3. For CMU walls and columns that have hairline cracks possibly due to rebar expansion/corrosion. Does Roadware 10 minute Concrete Mender help with deep penetration and inhibiting such expansion? Any info would be greatly appreciated. Thanks in advance.

    1. Hello,

      Concrete Mender could help seal the cracks and help prevent future water intrusion. It will likely slow down further expansion of the rebar. I do not know of any practical process that can stop rebar from expansion completely.

      Kelton Glewwe

    1. Hello,

      Yes, Roadware 10 Minute Concrete Mender is compatible with most types of floor coatings, primers, stains and paints including epoxy.

      Thank you for asking.

      Kelton Glewwe

  4. How to use Roadware to fits ceiling cracks lines?. Can it be done?. Is Roadware waterproof when cured?. I am interested to test your product for ceiling crack repair and promote your product if its effective on ceiling repairs.

    1. Hello,

      I do not recommend Concrete Mender for repairing overhead cracks. It would be difficult to hold this water-thin polyurethane in place while it cures.

  5. This really does break the rules, what a game changer! I have been hearing about this through word of mouth, have been in the industry for some years now. Will definitely be giving this a “crack”! Haha.
    Thanks for the thorough write up!
    – Dan

  6. Your website recommends these products to be installed by trained professionals. I am in the concrete repair business. Where can I access Roadware-approved training in proper crack repair techniques?

    1. Your local Roadware distributor can give you some quick training and get you set up with the product. Where are you located?

  7. I love a product that breaks the rules! And it’s so true, most concrete cracks start as itty-bitty hairlines. Thanks for the great write-up.

  8. are in Portugal. We liked this. So were or Who we van buy this products? We are constroction distributor.
    Thanksernando Fernandes

    1. Hairline cracks in new work are common. There are many underlying causes so I don’t believe cracking will be going away anytime soon. It is the nature of concrete to shrink as it cures. Cracking is part of the process.

  9. I have a crack in my shop that goes full width – 30′. Would you recommend chasing the crack full length and apply material along the crack or do a static injection every so many feet?


    1. Hello, If the crack is fairly clean and free is dirt and grease, I would us Easy Injection with a hole drilled into the crack equal to the depth of the concrete. So if your slab is 6″ deep, drill a 1″ deep hole every 6 inches. If the crack is full of dirt and grease, you will need to cut open the crack and get it as clean as possible before making the repair using Concrete Mender™ and sand.

  10. My condominium property has several cracks in the concrete of the surface lot located above our underground parking garage. During periods of heavy rain water leaks through these cracks and into the garage below. Would your product be a good option for sealing these cracks? If so, who in my area could give me an estimate of the cost?

  11. What is the best concrete crack repair product?

    Hello! That is a good question. I think a better question is what is the best crack repair product for a specific type of crack under specific conditions? Our Roadware 10 Minute Concrete Mender is great for many types of dormant cracks and structural repairs. It is very versatile and can be used in a wide range of conditions. Cracks that continue to move due to external forces my be better off with a softer caulking material. For a structural high-penetrating repair of cracks, micro-fractures and micro cracking, Roadware 10 Minute Concrete Mender is the best material and system we know of.

  12. I have a concrete slab (5 inches think) veranda with a cold cellar below it. I had tiled over the veranda several years ago. I lined my cold cellar ceiling with 2 in white styrofoam.

    I noticed the styrofoam got water stained and droppings on the floor. on the exterior I notice in almost the same place (I did not measure it) that the tiles cracked from the front towards the house . I removed the tile and sure enough this is a hairline crack under the tile…..

    Any suggestions on to repair this barely visible but there crack???

  13. Is this product compatible with water based pool deck stain? I have hair line cracks I would like to fix.

    1. The Concrete Mender itself would not allow the stain to penetrate the surface. Any sand added to the Concrete Mender repair would accept some of the stain.

  14. Hi! How much does the concrete mender cost? In Orlando, we’ve got an auto detailing shop that needs some concrete repairs. Unfortunately, we don’t enjoy working on luxurious cars with large concrete cracks present… it just doesn’t display the same level of professionalism as we strive for.

    Thanks in advance!

  15. Thanks for posting an awesome article about Roadware 10 Minute Concrete Mender. I’m a huge nail-biter and have been looking for a solution to my problem! Your post was really helpful 🙂

  16. How does this differ or work different with stained concrete used matchcrete prior on floor
    working on suspended concrete floor with radiant heat with stained concrete used matchcrete prior to staining, but over time floor has developed cracks at joists and some untreated cracks have grown slightly, largest crack is not over 1/16th

    Property owner would like to stay with stained floors but not sure how much discoloration we can expect with this or match Crete , matchcrete highlighted the crack and had to be ground flat since it exspands

    Dualpurpose Construction

  17. Thanks for the great post on repairing hairline cracks in concrete! I’m a big fan of your blog. Thanks again for all the great work you do!

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