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Concrete boasts incredible compressive strength, making it ideal for flat surfaces that will last for decades. However, it is more vulnerable to point loads or shear forces, making corners and edges more susceptible to damage.

From stair treads to column corners to curbs, this damage can cause serious safety concerns – not to mention aesthetic issues.

For years, these types of structures were repaired using slow-setting materials poured into forms – less than ideal for getting them back into service quickly. Today’s advanced materials make this process easier than ever, allowing you to eliminate forms and get the job done in minutes, not hours.

Project Prep

Choosing the right product for the job is the first step. If the repair is between ¼” and 2” vertically, use Sakrete Fast Setting Cement Patcher. For repairs up to 4” vertically, step up to Sakrete Pro-Mix All-Purpose Cement Mix.

  1. Estimate your repair area to choose the correct package size. Because damaged concrete corners are often oddly-shaped, it’s recommended to use the largest vertical, horizontal and width dimensions of the repair so you don’t run short.
    1. As an easy rule of thumb, consider a broken concrete step with the front edge broken off. For a common 2” vertical x 2” deep repair:
      1. 10# will be enough material to fix 3 linear feet
      2. 20# will be enough material to fix 6 linear feet
      3. 40# will be enough material to fix 12 linear feet
  1. As an example:
    1. The repair shown here has dimensions of approximately 2” x 2” x 6”, or .0138 ft3. One pound of Fast Setting Cement Patcher yields about 0.009 ft3, so this repair used approximately 1.5lbs of material.
    2. Always over-estimate when mixing by eye!
  2. Sweep the repair area to remove any dirt or debris that act as bond breakers. Consider using a pressure washer for large or heavily soiled areas.
  3. Dilute Sakrete Bonder & Fortifier 1:1 with water and to the repair area using a paint brush.
  4. Allow to dry for a few minutes until tacky – but be careful to not let the bonding agent completely dry. Usually the time it takes to mix the repair materials is sufficient drying time.

Project Tip: Always over-estimate when mixing by eye! It’s difficult if not impossible to mix another batch halfway through, especially when using fast-setting materials.

Mixing

Repair materials have a wider range of acceptable consistencies than standard concrete and are often mixed by ratio rather than volume. The most common ratio for Fast Setting Cement Patcher is 4:1 – 4 parts mix to 1 part water.

  1. Wearing respiratory protection and gloves, add pre-measured water to your mixing pail, followed by the dry mix. Start at a 4:1 ratio – 4 parts mix to 1 part water and adjust from there.
  2. A 4:1 ratio is generally perfect for Fast Setting Cement Patcher – allowing for a loose enough mix to fill irregular voids while still setting quickly.
  3. Mix for two minutes to achieve complete consolidation of the mix.
  4. Adjust water slowly to reach desired consistency, but do not exceed 3:1.

Project Tip: Mixing by hand is sometimes most convenient for small patches. Be sure to wear gloves!

Application

The biggest time savings for fast-setting materials comes at this stage. Where you would normally build a wooden form to hold the mix in place, products like Fast Setting Cement Patcher allow you to simply hold a flat trowel in place for 5 minutes to act as a form!

  1. Place and hold one flat trowel flat against the vertical edge of the repair area. This is your “form” trowel.
  2. Fill in repair area with repair mix using a margin trowel or gloved hand.
  3. Rod the material with a margin trowel or dowel to eliminate air bubbles and ensure a good bond.
  4. Fill the repair area to the top, being sure not to over-fill – Fast Setting Cement Patcher is not a feather edge material.
    1. Note: Pro-Mix All-Purpose Cement is a feather edge material, providing additional flexibility.
  5. While still holding the “form” trowel in place, use a second flat trowel to smooth the top of the patch – two or three passes should be sufficient. Be sure not to over-work!
  6. Hold the “form” trowel in place for approximately 5 minutes to allow the repair material to set.
  7. Remove the “form” trowel by sliding it down and away from the face of the patch. Be careful to not pull or lift the trowel while removing – this could cause the patch to tear.

Project Tip: Consider skim-coating the entire repair area with Sakrete Top ‘N Bond as a final step to achieve a uniform appearance.

Finish

Put the finishing touches on the job.

  1. Wait a few minutes to allow the mix to cure slightly, then make a pass over the repair using a paint brush (for small areas) or broom (for larger areas) to make the patch match the existing concrete.
  2. Make sure to only pull the broom in one direction – and only make a single pass to avoid over-working the patch.
  3. For large areas, consider immediately applying Sakrete Cure ‘N Seal to ensure proper cure. Otherwise, cover with plastic after the material has set and regularly mist to ensure a good cure.
  4. Allow to cure for 4 hours before opening to foot traffic and 24 hours for vehicular traffic.
  5. Consider applying Sakrete Cure ‘N Seal or Concrete and Paver Sealer after the entire area after 28 days to protect the new patch – and entire structure – from future damage.

Project Tip: Applying Sakrete Cure ‘N Seal is an often-overlooked best practice that will ensure the best curing behavior of all concrete – including repair materials.

Alternate Products

Pro-Mix All-Purpose Cement Mix

Pro Strength, Pro Speed