Reasons Why Concrete Driveways and Paths Crack and How to Prevent It
Cracks in concrete driveways and paths can quickly ruin their appearance, and while all concrete can be prone to cracking, scaling and pitting over time, newly poured concrete that develops cracks soon after is usually a sign of an improper job. There are many different reasons why cracks form and these (as well as how to prevent cracking) are explained below.
Lack of Control Joints
All large concreted areas, particularly large areas like driveways should include control joints that are pre-planned cracks that account for changes in temperature and natural shrinkage that occurs in cement. This means that joints are cut at least 25 per cent the depth of the slab and cut in a straight line. This allows for expansion in the concrete rather than messy, uncontrolled cracks which will eventually form if there are insufficient control joints or no control joints at all. Grooving tools should be used to cut control joints between 8-12 feet apart. Ensure joints run along any inside corners, which are especially prone to cracks.
Extremes in Temperatures
Freezing and thawing in cold climates is one of the most common culprits for cracking in outdoor concrete, and unfortunately if you live in these areas, there is only so much that can be done to prevent cracking entirely as frozen moisture adds pressure to the concrete mix. Use sand to help fill any tiny gaps in the concrete pores where ice could form. Concrete sealants are used during winter but will need to be continually reapplied in freezing weather.
The Wrong Strength Concrete
If in doubt, ask your contractor about the ratio of water to cement used in their mix. Too much water can weaken concrete. For driveways and pathways mix one part of cement, three parts construction aggregate, and two parts of sand. If making the mix yourself, follow mixing charts available online that explain mixing ratios. Too much water content in a mix is the biggest reason for concrete shrinkage, which will result in cracks.
Wrong Preparation of Soil and Pouring Site
Another common reason why concrete can crack sooner rather than later is soil was too soft or not compacted adequately before pouring began. A depth of 5 inches is recommended to support the weight of a parked car (such as with driveway concrete) without causing cracking. Reinforcing the slab with steel racks about 2 inches down from the top of the slab is a recommended final step. Steel helps to hold slabs together and reduces the length of cracks, even if some cracking does occur.
Often it's not a matter of if cracks will occur, but when they'll occur. Fortunately there are a number of strategies available to repair and re-fill large and unsightly cracks in driveways and concrete paths. Speak to a concrete contractor, such as Raw Worx, for more advice about how they can repair cracks through sealing, epoxy injection, and other stabilising techniques.