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Concrete answers to concrete problems

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It doesn't take long for a freshly poured concrete driveway to start to look weathered.

“There are two things we can guarantee: that it’s gonna crack and get hard. But what we try to do to avoid the cracking of it is place what we call stress joints accordingly to the pattern of the driveway to allow it to move, and the stress joints basically prevent the cracking,” explained concrete professional Tony Johnson.

Small shrinkage cracks don’t necessarily need attention, but structural or settlement cracks that span the width of the concrete should be filled with a structural epoxy to prevent water from getting in and doing more damage.

“That’s where your problem comes a lot of times. The water sits in there and saturates and it heaves and thaws. So you want to try to close it up as soon as possible,” said Johnson.

Then there’s the off-set structural crack where the concrete has raised on either side and involves the most work.

“If you have a spot where your concrete is unlevel, it can not only be unattractive but it also can be a tripping hazard for you or your guests. When you’re considering having it replaced, you might also consider having it repaired. You can actually have it leveled and that can be less expensive and last just as long,” explained Angie Hicks, founder of Angie's List.

Leveling concrete, also known as mudjacking,  is about one-third the cost of replacement and allows you to keep the same uniform, weathered appearance. It can be done for as little as $60 for one square of a sidewalk and can be walked on within an hour of completion, but consider the overall condition of the concrete.

Leveling is a way to raise sunken concrete that may be unsightly or cause a tripping hazard. The process involves drilling 1-inch holes into an adjoining concrete section and pumping limestone underneath until the sunken section is level again. This should only be considered when the concrete is not otherwise damaged. If it has fairly significant damage, Angie's List says replacement is the better option.


3 Types of Concrete Cracks:

  • “Check crack" or shrinkage crack – Shrinkage cracks are easily identified and recognizable as they usually appear to be discontinuous and are typically in the surface of the concrete only. Most shrinkage cracks are approximately one sixteenth of an inch wide and are not typically considered to be a defect in the concrete, as all concrete shrinks a bit during the initial hydration period. Repairing of this type of crack prior to the installation of an overlay is typically not required, although it is recommended to have an anti-fracture membrane installed as a safety precaution to protect the overlay from potential reflective transfer through the overlay. 
  • “Structural crack" – Structural cracks are also known as settlement cracks, shift cracks and load cracks. The cause of settlement cracks can vary but are typically related to pour grade preparation or shifting soil. They are typically continuous and travel from one side of the concrete to the other. It is very important to note that though the result is not guaranteed, this type of crack typically requires injection of a structural epoxy. The epoxy (when hardened) acts as a liquid shim which binds or prevents the inward movement of the crack, effectively preventing the crack to close due to any additional movement. After the crack has been injected, an anti-fracture membrane should be installed over the repair area to prevent reflective energy transfer. 
  • “Off-set structural crack" – An off-set structural crack is when the crack exhibits a raised area on either side of the crack itself. Also referred to as a twisted crack, the off-set crack does not move only in and out, but also moves up and down. In this case, shimming of the crack will not work due to the up and down movement and shear load caused by the movement, thereby rendering the use of an anti-fracture membrane useless. Instead, local removal and replacement of the affected area may be the best option.