Tuesday, May 11, 2010

After the Thaw - Repairing Damaged Concrete (Part 3 of 4)

Repairing Concrete
As with the other topics in this series of blog posts entitled “After the Thaw”, the cracking and spalling of concrete and concrete surfaces is often caused, and made worse, by the freeze/thaw cycle. 

Concrete Crack Repair
The main goal when repairing cracks in concrete is to prevent further damage by preventing water from entering the crack where it can freeze and expand increasing the size of the crack and making the damage worse and worse over time.

There are 3 basics steps to follow when repairing a crack in concrete; clean it, fill it, seal it.  Some suggestions follow on the best way to perform each of those steps.
Clean it  - Remove all broken concrete, dirt and debris and rinse out the area with water.  Be sure the let the area dry completely before moving onto the next step.

Fill it - If you are dealing with a small crack, less than 1/8” wide you can skip this step.  For wider and deeper cracks fill the area with sand or foam ‘backer rod’.  Backer rod is wonderful for large cracks on vertical surfaces.  Filling the cracks helps reduce the amount of repair material you will need to use.

Seal it -To seal cracks on horizontal surfaces like walkways, patios and driveways I use self-leveling concrete sealer.  The sealer comes in both large and small caulk tubes, is easy to use and gives a visually pleasing result on top of providing good protection against water entry.  
To seal cracks on vertical surfaces look for concrete patch material that is NOT self leveling.  This also comes in caulk tubes but is applied more like caulk.
These products are typically found in the building products area rather than the caulk and sealant aisle at your local home improvement store. 

Spalling (Scaling)
Spalling or scaling are the terms used to describe damage to the surface of your concrete.  It is most often found in areas located in colder climates where the freeze thaw cycle and the use of deicing chemicals occur.
This type of repair is a little more difficult and will take more time.

Check out this article for information that will help you to prevent further damage to you concrete by the use of deicers. http://www.cement.org/tech/pdfs/DeicerPL874.pdf

Prepare it – Surface preparation is the key to a good repair.  Here is a link to a short video that will give more detail on surface preparation and repair techniques. http://www.concretenetwork.com/fix-spalled-concrete/fixing-a-spalled-driveway.html

Clean or prime the surface – depending on the type of product you choose the surface may require a primer to ensure a good, long-lasting repair. If the surface of the concrete is not rough you may need to apply an acid wash to assure a good connection between the patch and the old concrete.

Repair it – apply the patching product and allow it to cure (usually for 24 hours) before using the area again, especially in the case of a driveway.

Things to remember

•    Buy a nice caulk gun if you don’t own one.
•    Concrete must be clean and dry and in some cases a bonding agent may need to be applied.
•    The surface temperature of the concrete must be above 45°F.
•    Don’t try to repair concrete if the temperature will be dropping below freezing in the next few weeks.
•    Wear safety glasses and gloves when working with concrete it can burn your hands.



1 comment:

  1. Backer rod really covers all the bases in terms of what a crack-filling material needs to do. Sealant won't stick to it so it's a great bond-breaker, it will expand against a crack and be able to compress as well when conditions change, and it is water-resistant so it will last.

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