Considerations for Homeowner Concrete Repair Pt 1

Spring has finally arrived, banishing old man winter for nicer weather! However, it is possible old man winter has left a few things behind in your driveway, patio or perhaps walkway adjacent your house. I am not talking about snow but freshly cracked concrete! Winter and subsequently its partner in crime frost or frozen ground, can be very hard on your paved surfaces when Spring rolls around causing a phenomena known as frost heave. This distress results in the movement and short term weakening of subsurface soils/aggregates reducing support to the pavements above. The most basic analogy I can provide is trying to cut a peanut butter tortilla sandwich and the peanut butter squishes out the sides. That is similar to what is going on under your sidewalks and driveway during the Spring thaw, a soft saturated layer of material trapped between an upper layer of hard pavement and bottom layer of hard frozen ground. This situation creates ideal conditions for concrete failure.

Cracking is the release of stress or force within a material body and represents the ultimate failure of that material. Take a rubber band and apply force to it, stretching it until it breaks, for example to visualize this concept. The rubber band snaps releasing this applied energy. Cracking in concrete is very similar representing the release of excessive internal and external forces, possibly resulting from frost heave where a portion of the underlying base ceases to provide adequate support.

Uncontrolled Cracking Due to Lack of Contraction Joint (Chalk Line)

That said it is an old adage that concrete will be gray, get hard, and crack is very accurate however these cracks under standard construction practices will be at the locations we specify or otherwise known as joints. A general rule of thumb is concrete will produce a majority of its cracks every 12 to 24 times its thickness during the first 72 hours of curing but this may take up to 30 days for all of the cracks to show up. Assuming the joints are spaced appropriately, 4" thick sidewalk should have a joint every 4-6' to be conservative, the cause of your cracking may be something else. Some of these factors can be resolved and unfortunately some of them cannot.

Join me in the rest of this series as we walkthrough some useful tips and tricks for performing small scale concrete repairs around your property.