How to Avoid Cracks in Concrete
Cracks in concrete occur for a number of reasons, from frequent freeze-and-thaw cycles to shifting soil beneath the slab. Whatever the reason, though, a crack in your concrete can develop into a serious problem. Over time, the crack can grow, extending across the surface of your slab or down through the slab to the ground beneath, eventually breaking the slab into sections. While it's impossible to completely prevent cracking, you can avoid most frequent cracks in concrete by proper installation methods. Does this Spark an idea?
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Things You'll Need
- Plate compactor
- Trowel
- Steel rebar
- Concrete blocks
- Metal ties
- Garden hose
- Concrete sealer
Instructions
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Create a strong bed for your concrete. Compact the soil beneath the slab with a plate compactor to prevent the soil from shifting after pouring the concrete. Shifting soil creates voids and rises beneath the slab. These surface changes can cause slab flexing when you apply weight to the slab surface, resulting in cracks.
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Minimize the amount of water used in creating your concrete mix. Add just enough water to the concrete mix to make it workable in order to reduce shrinkage. The more shrinkage that occurs as the concrete dries, the greater the chance the concrete will crack during the drying process.
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Place control joints throughout your concrete to allow for movement in the slab without the creation of cracks. Use the edge of a trowel to cut the joints into freshly poured concrete, or cut joints into hardened concrete with a diamond saw. Create the joints with a depth that's at least one-quarter the thickness of the slab and spaced at intervals of two times the thickness of the slab in feet. The joints encourage cracking at joint points rather than other areas of the slab.
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Pour thicker slabs for areas where you expect heavy weight applications such as house foundations or driveways. For example, while a two-inch thick slab will suffice for a patio, a five-inch slab is better suited for pouring a driveway.
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Reinforce your concrete slab with a grid of steel rebar. The rebar helps to hold the slab together while distributing weight among a wider area of the slab than the precise location of the weight. Place the rebar in a grid in the center of the slab spaced two feet apart, supported by cut concrete blocks. Connect the grid at cross points with metal ties to keep them in place during the concrete pour.
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Keep the surface of the concrete moist during curing times to prevent the concrete from drying out. If you allow the concrete to dry too quickly, it will become brittle during the curing process, losing much of its possible strength. This will make your concrete more susceptible to cracks with use.
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Seal the surface of smaller slabs to add moisture resistance. Moisture can cause cracks in the slab during freeze-and-thaw cycles. As such, you should prevent it from soaking into the porous concrete surface. Spray a layer of sealant onto the concrete and wait 36 hours for the sealer to penetrate the concrete surface and dry before use.
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References
Resources
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