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How to Repair Cracked Concrete

How to Repair Cracked Concrete

by Ethan Hagan (email Ethan) | | November 8, 2012 | 24 Comments »

Ever since Jocie and I purchased our home in 2006 the concrete stoop has had this long, ugly crack, and this past summer some yellow-jackets tried to take up residence within the crack. That was enough for me to bump the concrete repair to the front of my to-do list.

If you look around online, the typical repair involves filling the crack with a flexible patching compound followed by a sealant. The result is a structurally sound and visibly unattractive repair. I wanted something better because this is a repair that everyone will see when they come to our front door.

Tools & Materials

Quikrete generously sent me a bucket of FastSet Repair Mortar which is used for repairing concrete, masonry and stucco. The mortar is polymer modified, rapid setting and features a “low-sag formula” which makes it ideal for vertical and overhead repairs.

It’s important to know that this crack has not moved or expanded at all for the past 6 years. If there was any chance of movement, the appropriate product for this repair would be a flexible, polyurethane concrete crack sealant.

Temperatures
Fortunately temperatures here in Maryland are still above 32° F even at night. Otherwise the water (mixed with the dry mortar) would freeze and cause the repair to crack. If the temperatures are too low, pros often use accelerant to speed up concrete set time and insulating blankets to trap heat. During the hot summer months, pros use retarder to slow the set time.

I don’t own any concrete tools. Instead, I used an old drywall knife and a grout float. I also grabbed a wire bristle brush and hammer.

Step 1: Clean Crack

I started this repair by cleaning the crack with my wire brush and removing any small, broken pieces. I used a broom to clear away any leftover debris.

Step 2: Mix Repair Mortar

I combined a portion of the 20 lb. bucket with warm water (speed up set time) until it was thoroughly mixed and a stiff, gel-like consistency.

Step 3: Apply Mortar

Before starting, I sprinkled some water over the concrete to wet the surface. Using my drywall knife I applied mortar to the crack and skim coated the rest of the face of the concrete. Much like painting, it’s easier to spot a partially repainted wall so I used the corners as transitions.

Step 4: Tool Mortar

I continued tooling the mortar after the initial set to achieve a smooth uniform look.

As the mortar hardened, I switched to my grout float because I could apply heavy pressure and better round the corners.

Step 5: Pulverize Old Concrete and Use on Transitions

I used a hammer to pulverize a few chunks of concrete into a fine powder, and I lightly dusted the top edge where the repair meets existing concrete. My goal was to further hide the transition from new to old.

Step 6: Allow to Cure

Aside from ensuring the repair doesn’t dry too quickly during the first 24 hours, there are no special procedures to cure FastSet Repair Mortar.

Finished

Even with the warm water, the cooler temperatures slowed cure time. After 24 hours the mortar color was much lighter and it began to blend with the existing concrete. I used the wire brush again to smooth out a few places along the corner.

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24 Responses to How to Repair Cracked Concrete

  • Brady responds...
    November 8th, 2012 8:24 am

    The detail steps (dusting with concrete powder and wire brushing) make this look like a pro quality repair! Great work.

    [Reply]

    Ethan Reply:

    Thanks Brady. I got the idea for the concrete powder from thinking about how to re-point some brick. It’s next to impossible to match existing brick mortar from 20+ years ago. I haven’t actually tried it yet, but it worked well enough on the concrete.

    [Reply]

  • jeff_williams responds...
    November 8th, 2012 9:32 am

    Color me surprised. I thought it would turn out like lipstick on a pig but it looks really nice. After a little weathering no one will ever know.

    [Reply]

    Ethan Reply:

    HA! Thanks Jeff. It’s a small porch and now that I’m finished, I’m debating giving the rest of it a quick skim coat to make it look really uniform.

    [Reply]

  • Icarus responds...
    November 8th, 2012 10:08 am

    How about that. you ignored this for 6 years and it took less than 60 minutes (+ 24 dry time) to resolve, right?

    [Reply]

  • paintergal responds...
    November 8th, 2012 10:18 am

    That is a much nicer fix than the one we attempted. Definitely need to check this out.
    Thanks!

    [Reply]

  • frazzled5 responds...
    November 8th, 2012 10:42 am

    Ethan, Why dont you all live in Georgia? We could use your expertise in fixing the concrete on the bottom portion of our cedar sided home:)

    [Reply]

  • Reuben responds...
    November 8th, 2012 10:47 am

    Pretty good fix. I’m also impressed with how well it turned out. The pulverized powdering is a good trick.

    [Reply]

  • poiboybf responds...
    November 8th, 2012 1:01 pm

    Turned out great! Looks so much better now than the first picture.

    [Reply]

  • WH responds...
    November 8th, 2012 2:20 pm

    Made it look easy. Better than 1 of my own recent efforts ;-)

    [Reply]

  • Jake responds...
    November 8th, 2012 4:31 pm

    Looks great. Love the blending Techniques.

    [Reply]

  • bigredmachine responds...
    November 8th, 2012 9:55 pm

    I have seen the quick fixes at big box stores that don’t work, good to see you address this issue

    [Reply]

  • John responds...
    November 9th, 2012 11:23 am

    Great job. I needed this one!

    [Reply]

  • trebor responds...
    November 11th, 2012 9:26 am

    Outcome looks great! I like the attention to detail on transitions. I wonder why the crack appeared but hasn’t expanded at all though…seems like the crack could still be suspect to expand

    [Reply]

  • Handyman Hawaii responds...
    November 30th, 2012 6:05 pm

    I also use these methods when repairing concrete structures in buildings and homes with old looks: cement is very hard to work with if you zero experience…..

    [Reply]

  • ranch-burger responds...
    December 3rd, 2012 12:57 pm

    I recently pulled up the carpet in 3 of our bedrooms and found what appear to be surface cracks on the foundation – should I fill/repair these before the new flooring goes down?

    [Reply]

    Ethan Reply:

    Hi Ranch-Burger,

    I depends on the new flooring, and the extent of the cracks. For instance, minimal cracks can easily just be covered up with new carpet / carpet pad. For tile, you may want to consider sealing it with crack-isolation membrane. I know this isn’t a definitive answer, but I hope it helps.

    Let us know what you end up doing.

    [Reply]

    jeff_williams Reply:

    Depending on your area of the country Radon may also be a concern with those cracks. If you have the floor torn up it would be a good time to test for it and if it’s high, install mitigation measures.

    [Reply]

  • supimeister responds...
    December 14th, 2012 11:51 am

    nice tricks! super helpful

    [Reply]

  • HANDYMAN51 responds...
    May 16th, 2013 1:03 pm

    Bookmarked and on my ” do soon” bucket list. O.K., I live a simple life! Thanks for making it even simpler.

    [Reply]

  • EvaS responds...
    July 13th, 2013 12:50 pm

    This is great. Do you have any tips on setting concrete in 80 degree temperature? I want to make sure it won’t crack.

    [Reply]

  • HANDYMAN51 responds...
    July 27th, 2013 9:02 pm

    Had some concrete problems on our front steps, some areas crumbling on step’s edges and a major horizontal crack on a horizontal surface. I cleaned the areas, applied a coat of a liquid bonding agent, placed some compressed ” chicken wire” in the large horizontal crack, then placed a 2×10 piece( wood surface brushed with motor oil to allow easier removal) flush against the step with the crumbling edges. The 2×10 was held in place with some concrete blocks. I filled the broken areas on the step’s edge and allowed the concrete repair to set up. I then packed the horizontal crack and placed the board against it, held in place by the blocks. I was pleased at the results, though I must admit my repair was done as aesthetically as Ethan’s!

    [Reply]

  • How to Repair Cracked Concrete - Craft Like This responds...
    November 26th, 2013 4:29 pm

    [...] How to Repair Cracked Concrete [...]

  • How To Revive Old Concrete With Decorative Leaves - responds...
    September 25th, 2014 6:41 pm

    [...] This post shares tips and tricks on resourceful ways to repair cracked concrete. With everything you will need to get going including materials and step by step instructions. Soon you’ll be repairing the concrete cracks in no time! Details at: Repairing Concrete Cracks [...]





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