Cracks in concrete can be a major source of frustration for homeowners, especially when they have just paid for a new driveway, concrete slab, walkway, or garage floor. Fortunately, there are steps that can be taken to minimize the occurrence of cracks and ensure a more aesthetically pleasing concrete project. The American Concrete Institute addresses the issue of concrete cracking in its American Concrete Institute manual, ACI 302. According to this manual, concrete less than 5 inches thick is more prone to cracking due to stress loads from above and below. This is why it is important to make sure the slab is built on a well-drained, evenly compacted subgrade and that it is thick enough to withstand the type of use it will receive.
In residential concrete, 4 inches is the minimum thickness for hallways and patios, while garage slabs and driveways should be 5 to 6 inches thick if heavy truck traffic is expected. Plastic shrinkage cracks can occur anywhere on a slab or wall, but they most often occur in reentrant corners or with circular objects in the middle of a slab. These cracks are usually very narrow in width and barely visible, but they extend throughout the thickness of the slab. Excessively wet mix and hot weather are two contributing factors to shrinkage in concrete.
The American Concrete Institute has no standards or recommendations that give an affirmative or negative answer as to which cracks need repair based on width and other factors. However, if your concrete is a little older, a concrete repair professional can help you fix the cracks. To prevent plastic shrinkage cracks from occurring in the first place, make sure you use the correct amount of water in your concrete mix and take steps to protect it from hot weather. Quikrete offers a range of solutions for all types of cracks, including its new line of advanced polymeric sealants.
Consult an engineer or concrete repair professional to determine the cause of the crack and recommend the best repair solution. In conclusion, thicker concrete is less likely to crack due to stress loads from above and below. It is important to make sure the slab is built on a well-drained, evenly compacted subgrade and that it is thick enough to withstand the type of use it will receive. Additionally, take steps to prevent plastic shrinkage cracks by using the correct amount of water in your concrete mix and protecting it from hot weather.
