When you pour a new concrete slab, you should allow it enough time to cure. A well-cured slab improves water tightness, durability, strength, and resistance for the years it will be in use. To get the strongest foundation out of your new concrete, you should observe the timelines for the curing process.
To start framing, you should allow the poured concrete slab to cure for at least 7 days from the date of installation. At this point, the concrete has attained at least 50% of the final strength, which is adequate to begin building on the concrete. If you want to start building when the concrete is fully cured, you may have to wait for at least 28 to 60 days from the date of installation. Curing is a continuous process, and you should spray water and maintain constant temperatures of at least 50 degrees Fahrenheit during the curing process.
How Concrete Cures
The three main components of concrete include cement, aggregate, and water. When you mix cement and water, a chemical reaction occurs and this binds the two components together. The binding process is what causes the concrete slab to harden.
In the binding process, the concrete becomes porous, and as long the cement is in contact with moisture, it will continue to harden to give the structure maximum strength. This is why it is necessary to spray the concrete slab with water at least 5 times every day before you start building on the slab. As soon as the concrete is poured, the curing process starts immediately.
How Long Should a Concrete Slab Cure Before Framing
In standard industrial standards, a 4-inch concrete slab achieves full strength at 28 days. However, you don’t have to wait until the 28 days lapse to start framing. After 7 days, the concrete slab will have cured to 70% full strength, and it can support loads like the framing for a house.
Once you pour the concrete, you should keep these timeframes in mind:
Once you pour the concrete, you should wait at least 24 to 48 hours to allow movements on the slab. You can remove the forms since the slab is stable enough to hold itself together. You can allow light movements of pets and people on the surface. However, the slab is not yet strong enough to hold heavier loads such as cars and bikes.
Within a week, the concrete is at least 50% cured, and you can start framing the walls. This concrete is strong enough to hold traffic from light vehicles.
The concrete is now fully cured at this stage. If you poured the concrete on a driveway, you can drive heavy vehicles such as trucks and RVs on the concrete.
Key Factors That Determine Curing Time
When the concrete is fully cured, it provides a stable foundation for the structure that will be built on top of it. Here are key factors to consider:
When you pour concrete, it can take about one week of curing for the concrete to establish half of the final strength. Depending on the weather (and other factors), concrete can establish full strength within 28 to 60 days.
Proper curing requires warmer temperatures above 50 degrees Fahrenheit. Keep the temperature constant during the curing period for strong concrete bonding. If the temperature falls to 20 degrees Fahrenheit or lower, it can weaken the curing process, and prolong the period you have to wait to establish at least half of the final strength.
The recommended concrete procedure requires builders to apply a sealant to the concrete slab as soon as the forms are removed, and the surfaced dried up. The sealant helps trap moisture within the concrete, which is required for proper curing. An alternative to using a sealant is wrapping the concrete slab with waterproof paper or plastic sheet, both of which help retain moisture and improve the curing process.
How to Cure a New Concrete Slab (To Reduce the Waiting Time)
If you are looking to speed up the concrete curing process, here are some of the things you can do:
Once you pour concrete, you should spray water 5 to 10 times every day to help in the curing process. When the concrete has enough moisture, there will be less evaporation, and the concrete will bond quickly. If there is no sufficient water, the concrete will cure fast, and this will result in weaker overall strength.
Cover the concrete slab
You can also cover the slab to help trap moisture. You can use this option if you are not available to spray the slab with water. Before you place a cover, wet the concrete first with water to keep the surface wet and improve curing.
Use curing compounds
You can buy curing compounds from your construction supplies store or concrete providers. These compounds contain an ingredient that forms a protective film on the concrete surface, hence allowing the slab to retain moisture.
Things to Avoid When Pouring New Concrete
When pouring concrete, there are certain things that can slow down the curing process. They include:
Pouring concrete in the cold
If the temperatures are low (below 20 degrees Fahrenheit), you should wait until it is warmer to pour the concrete. Pouring concrete in cold weather could result in a building that is not structurally sound since the concrete will be improperly cured. Experts recommend pouring concrete when the temperature is 50 degrees Fahrenheit and above.
Once you pour concrete, you should allow at least 24 hours to allow foot traffic. If you allow traffic sooner than 24 hours, then the concrete will have clear marks of footsteps, and you may have to redo the work. For heavy loads such as cars, you must allow the concrete to cure for at least 7 days or 28 days for heavier vehicles such as RVs and trucks.
When does curing start?
Once you pour concrete, the curing process starts immediately. However, sometimes it can start after 6 to 24 hours depending on the cement-water ratio and prevailing temperatures. Proper curing needs warmer temperatures of at least 50 degrees Fahrenheit.
How long does a 4-inches of concrete take to cure?
A 4-inch concrete takes 7 days to establish at least half of the final strength. However, curing is a continuous process, and it can take at least 28 days in warmer temperatures to be fully cured.
How long should you let the concrete cure before building on it?
After the concrete is placed, the curing process starts and you should allow at least 7 days for the structure to be at least 50% cured. At this point, it is 50% stronger than uncured concrete, and you can start building on it. However, waiting longer for at least 28 days reduces the risk of cracking, since the concrete will have attained the maximum strength.