How to Achieve a Crack-Free Finish on Your Concrete Slab

Shrinkage is a major cause of cracking in concrete slabs. As the material hardens and dries, it shrinks due to the evaporation of excess mixing water. Even if the concrete cures slowly, it is possible that a large slab, such as a patio or sidewalk, will still crack as a result of shrinkage that occurs as temperatures change and water is consumed in the hydration process. To anticipate and direct any future cracks, control joints are cut into the slab to about a quarter of its depth.

For buildings that require extra resilience, a new form of concrete has been developed that is much more resistant to cracking than normal types. To produce a given settlement, pea-gravel concrete requires more water than concrete made with larger coarse-grained aggregates, shrinks more and is more likely to crack. Concrete made with the larger aggregate and placed on an unbonded slab will also crack, but perhaps in fewer locations. If you want to prevent cracks from forming immediately, ensure the best longevity, and avoid costly repairs, follow these five simple tips to achieve a crack-free finish on your patio or driveway:

  • Understand what your contractor is doing with respect to each of the items listed above.
  • Ensure that the concrete mix has the right amount of water.
  • Determine the maximum joint spacing.
  • Keep coatings wet during the curing period.
  • Create a stable base for the concrete slab.
You can also add steel fibers to the concrete mix to reduce cracking.

Depending on the size and shape of the flat sections being placed, steel fibers can eliminate most cracks. Additionally, you can use a larger pump to deliver concrete that shrinks less. Finally, you can use rubberized concrete as a replacement for traditional concrete. This replacement gives concrete slabs a rubber-like quality, allowing them to contract and recover when subjected to impacts, rather than cracking. When noticing a crack in your concrete slab, it's important to remember that most residential work has too much water added to the concrete on the job site. To get the best results, check out this video tutorial on how to pour the perfect slab from the experts at Quikrete.