Concrete is one of the most durable building materials available, making it an ideal choice for professionals and DIYers alike for creating a patio, a walkway, a concrete driveway, and other structures. Concrete may retain its excellent looks and strength for years if put correctly, but proper preparation before the concrete is poured, will lessen the likelihood of cracks in the near future. Cracks are not only ugly, but they are also vulnerable to water penetration, which can cause the crack to grow and compress continuously, causing it to worsen. Water can enter the fracture and undermine the soil beneath the concrete, worsening the situation.
A good base is everything
To prepare for crack-free concrete, you first need a stable base. If concrete is not poured on a firm, sturdy foundation, it will fracture and break. Bringing in 4 to 6 inches of a good compactable base is a reasonable rule of thumb. Still, the precise quantity of base required for a concrete driveway or pathway depends on the quality of the existing soil, the climate, and what you want to park on your driveway. You might be able to pour straight over sandy or gravelly soil without adding any base. However, if you live in a cold area, are pouring over thick clay or organic soil, or want to park large cars on the driveway, you may want to extend the base layer to 10 or 12-inches. Contacting the local concrete supplier is the easiest approach to determine how much foundation you require. If you describe your soil conditions and the intended use of the slab, the provider should be able to propose the right base depth and type to use, as well as offer contact information for a local base supplier.
Another step to a good base is to compact each layer of base. To do this you should make three or four passes with a plate compactor every time you add 2 inches of base. A vibrating plate compactor would be ideal in this case instead of the plate compactors that are more powerful like a rammer or jumping jack which are used for compacting soil when backfilling trenches.
In addition to base prep, you should dampen the base before any concrete is poured. A dry base does not compact well, and if the concrete is poured on top of it the dry base tends to be loose and results in cracks in the finished concrete. When preparing the base layer in dry conditions add some moisture by spraying down each layer with a garden hose to achieve maximum compaction. You can verify this by grabbing a handful of the moisturized base and compressing it into a ball. If the shape holds you know your base is ready to use. In the case that the ball crumbles, this is an indication that you should add more water. Keep note that an oversaturated base will not compact either, you should not see any areas in the base where water begins to pool.
While it takes 28 days for concrete to completely cure, the procedures you take in the initial few days following the pour are critical for creating a durable, crack-free surface. Cement, the binding element in concrete, cures gradually and requires moisture retention to acquire full strength. Concrete is less likely to fracture if moisture evaporates slowly, therefore spraying it with water a few times each day for the first week after pouring the project will make it considerably stronger. The more frequently you should spray the fresh concrete will be based on how hot and dry the weather is.
Keep an eye on the forecast for potential cold fronts within the same seven-day timeframe. If temperatures are expected to fall below 10 degrees Celsius, cover the new concrete with a concrete insulating blanket or at least a four-millimeter thick polyethylene sheeting to prevent the new concrete from becoming too cold, which can weaken its internal structure and contribute to future cracking. If you must cover the concrete to protect it from the elements, do not uncover the surface to rinse it down. Wait until the temperature rises over 10 degrees Celsius before exposing and spraying
Mix the proper amount of water
One of the most typical mistakes DIYers new to concrete make is adding too much water to the dry concrete mix for easier mixing. This results in weak concrete with a significant breaking risk. Even one liter more water can weaken the strength of concrete by up to 40%! Wet concrete should be totally soaked with no dry spots but not watery when properly mixed. Concrete that sloshes around in the mixer or wheelbarrow is too wet while crumbling concrete is too dry. Similar to the base, the concrete mix needs the appropriate amount of water for the best results.
Add control joints
Even if you cure your concrete slowly as mentioned above, a big slab, such as a patio, sidewalk, or driveway may break due to concrete shrinkage caused by temperature changes and water loss throughout the hydration process. Concrete slabs will ultimately break due to the natural movement of the earth beneath. That is why control joints are so important. In order to foresee and direct future fractures, these purposeful weak points are carved into the slab down to roughly a fifth of its depth. Cracks are likely to form in these weakest areas.
To get the best results, multiply the intended concrete thickness, in inches, by 2.5 to get the maximum distance between joints. For example, if you are building a 4-inch-deep patio, multiply 4 by 2.5 to get a distance of 10 feet between joints. Place them closer together for further crack prevention, and consider splitting huge concrete slabs with perpendicular joints as well.
Reinforce with rebar
While concrete is powerful on its own, a little steel reinforcing may make it much stronger. For patios, pathways, and driveways this may imply installing rebar in a grid pattern, with bars spaced roughly two feet apart and halfway through the slab. Smaller projects, such as concrete vases and other ornamental pieces, might benefit from the use of wire mesh during the pour to increase strength and decrease cracking. Generally, it is ideal to install ½ inch rebar in a 2 feet grid pattern when pouring driveways. The rebar is then tied together with pre cut rebar ties fastened with a tie-wire twister. A good amount of ties should be used so that the grid will stay together even if it is accidentally stepped on while it is hanging in the air.
Concrete is a tough material that also looks appealing when installed correctly. With proper preparation, you can ensure that your new concrete surface will last a great deal of time without developing cracks. By implementing a number of preparation techniques described before the concrete is even poured you can prevent the need for immediate repair due to a fracturing concrete surface.