This drying process, known as hydration, begins the moment you mix water with the dry concrete mix, giving you limited time to get the wet concrete into the forms before it hardens. Hydration continues over the next few weeks, progressing through a number of stages until the concrete is completely cured.
During the drying process, rock-hard crystals develop within the concrete that bind the sand and gravel components firmly together. Read on to find out how much time you have to pour and finish the concrete slab and what you can do during each stage to make your project a success.
With most concrete mixes, such as Quikrete Ready-To-Use Concrete Mix in the yellow bag , you can expect to have about an hour of work time to get the concrete shoveled into the forms, spread out, vibrated, and leveled before the mix begins to harden. If you do have to pour in hot weather, the following tips will help extend pour time:. When pouring concrete, plan to spend half of the work time on the pouring process, and the other half on the finishing process.
If the concrete mix has an approximate one hour of work time work time is listed on the bag , plan to spend no more than 30 minutes on the actual pouring and screeding process, so you have adequate time to finish the slab. To start the finishing process, you must screed the surface. Screeding is the process of removing excess concrete by leveling the top level of the slab. Thankfully, in the case of concrete that will be driven on, we are more interested in curing than drying.
Some applications, however, such as the use of concrete as a subflooring, require it to dry to a certain level before work can continue. Let's take a closer look at the difference between curing and drying. Cement starts off as a powder-like substance that is mixed with water. Concrete adds aggregate to that mixture to serve as a filler. It is the process of curing that turns the concrete into the hard, solid substance that we want it to be rather than a paste with rocks in it.
Curing happens because mixing cement and water starts a chemical reaction. As the cement cures, some of the water mixed into it will be chemically transformed to become part of the new hard surface. Only some of the water that is added to the cement undergoes this chemical reaction. The rest of the water must evaporate away. Concrete can be fully cured and still have moisture trapped inside that has yet to fully evaporate.
The fact that it is the excess water that needs to dry is part of the reason why drying takes longer than curing does. Anything moisture-sensitive that will be placed on the concrete needs to have the remaining moisture be below a certain threshold. Concrete is a top choice for driveways because once it is properly cured, it can last for up to 50 years.
The key to getting nearly a half-century worth of use out of your concrete is being patient at first and letting it reach the hardness that it needs.
You should keep everything off of the concrete for 48 hours. After that, you can walk on it. Vehicles are heavy, so it stands to reason that it takes longer before you can drive on it than it does before you can walk on it. In fact, at this point, even skateboards and bicycles should be kept off as their wheels concentrate the weight into small areas and are more likely to damage the still curing concrete.
It is generally recommended that you wait at least a week before driving on the surface with a passenger vehicle. Even then, the slower curing areas, such as the edges, will not be as hard as they need to be. For this reason, you'll want to be careful until the concrete is fully cured. As for thickness, non-reinforced pavement four inches thick is standard for passenger car driveways. For heavier vehicles, a thickness of five inches is recommended. Do I need rebar in driveway?
Rebar is best utilized in a driveway for which inches of concrete can be poured. This is because rebar is relatively thicker than galvanized mesh reinforcement. How long should you keep fresh concrete covered with plastic? Should I wet concrete while curing? Keep Concrete Moist for Maximum Strength. Concrete hardens as a result of a chemical reaction, called hydration, between cement and water, not because it dries. Is it OK if it rains after pouring concrete?
Pouring Concrete vs Pouring Rain. If the rain occurs when the concrete is fresh about hours after mixing , the surface should be protected from the rain. If the finishing process was recently completed, rainwater may not cause damage as long as it is not worked into the surface and the slab is left untouched.
Is wire mesh necessary in concrete driveway? Fiber mesh is use in patios, sidewalks and driveways because the material is placed through and through.
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