How long does it take concrete to dry? Interesting question, with an equally interesting answer. That's because the concrete doesn't dry, per se. Rather, it goes through a chemical curing process calledhydrationthat sees the water evaporate and hardens the aggregate material.
One little known fact about concrete is that itnever stops curing. And the longer it cures the harder it gets. There are some rules to live by in the drying or curing process you should know before you pour and subsequently "use" your concrete. Let's take a closer look at the factors that speed up or slow down the time it takes for concrete to dry.
Types of Concrete
The type of concrete you use will be the first determining factor in how long it takes to dry or cure. There are three basic types you'll encounter, regular concrete,quick set concrete, and high strength concrete.
Quick Set Concrete
As the name suggests, quick set concrete dries, or cures, the fastest. You absolutely must be sure you have enough concrete to finish the job at hand or you'll find yourself having tofix uneven surfaces or unsightly joints and blemishes.
Quick set concrete will dry between 20 and 40 minutes. It's best suited for small jobs like setting fence posts, deck posts, andsmall repair workto walls and walkways.
The hardening or drying time on regular concrete falls between 24 and 48 hours. This is a much better concrete to use on larger projects as it gives you ample time to pour,level and shape, and screed the concrete before it becomes too thick to work with.
While the drying time is one to two days, the actual work time you have to pour, shape, andscreedthe concrete is less. Regular concrete will achieve its initial set within hours at which point it will become difficult to shape and screed.
High Strength Concrete
When working withhigh strength concreteyou have a shorter dry time but around the same working time. High strength concrete will set in 10 to 12 hours but has around the same amount of working time to pour, shape, and screed.
High strength concrete is used primarily for larger jobs that need the supporting strength it provides. You'll see it on foundation slabs, support columns, and other high load-bearing applications.
After the type of concrete you choose, the weather plays the largest role in the time it takes for concrete to dry. When the weather is too hot, too cold, too wet, or too dry it affects the curing of concrete.
Remember that we said the curing process was called hydration? Well, keeping the concrete sufficiently wet allows the chemical reaction of setting to occur. The water reacts to thePortland cementinside the concrete mixture and creates crystals that grow around the sand and gravel and eventually harden.
It is recommended to pour concrete when the temperature is between 60 and 80 degrees Fahrenheit. In really hot weather the water will evaporate quickly, not giving the crystals the chance to grow and set properly. The result is weak concrete that will crack and break.
When the weather gets below freezing you shouldn't pour concrete. If concrete is allowed to rapidly cool it will crack and break because the chemical process is suspended through the freezing of the water in the mixture.
You'll want to plan ahead if you have to pour concrete in the colder months. Make sure the temperature will not dip below the freezing point for at least two days after pouring. This will give the chemical process the time it needs to complete its initial set.
Humidity will impact your curing process. The process of hydration requires a certain amount of moisture to complete. Too much water in the mixture will slow the process down and can weaken the concrete.
Too much moisture in the air will do the same thing, slowing the hydration process and result in weaker concrete. Too little moisture in the air will have the opposite effect, hastening the process and curing before the concrete has reached its full potential strength.
Tips for Hot Weather Pouring
When the weather is really hot you should take precautionary steps to ensure your hydration process is completed correctly. Wetting the sandy surface you will pour on will help reduce the amount of water drawn out from beneath by the heat.
Using cold mixing waterwill also help slow the evaporation rate. Keeping the bags of unmixed concrete in the shade will help reduce the ambient heat of the mixture.Erecting a coverto shade the area of poured concrete will help keep the sun from evaporating the moisture too quickly.
If you can, you should plan on pouring in the early morning hours when the temperature is cooler. You'll also want plenty of people ready to pour, shape, and screed before the concrete sets.
Tips for Cold Weather Pouring
If you must pour in cold weather you can take a few steps to help offset the temperature. Keeping your forms in place for as long as possible allows whatever heat is present to remain evenly distributed. Creating a shelter or some kind of insulating barrier to the area being poured will help keep the heat in.
Tips for Humidity Issues
If the weather is too dry you might try wetting the concrete after pouring. Applying the right amount of water for several days will help slow the hydration process in hot, dry weather. It's known as moist curing and you can do this for up to seven days.
This helps the moisture within the concrete from being drawn to the surface too quickly and evaporating. Some people won't have the time to return every day to wet the concrete. In this case, you might apply acure and seal solutionto create a barrier that traps the moisture within the slab allowing it to cure without excess evaporation.
Ask a Professional How Long Does It Take Concrete To Dry
Concrete curing is a delicate process that requires a deft hand. If you have any reservations you should contact a professional for assistance. They will know how to answer the question of how long does it take concrete to dry.
Our experts are ready to help you find solutions to all of your concrete needs, from mixing to screeding, and repairs and resurfacing. On Floor Technologies is an industry leader. We manufacturerestoration toolsand planetary resurfacing equipment for all of your concrete applications.
Contact us with your questions, or toschedule a demonstrationof one of our tools. We are here to help and can take you through our extensive product line to find you the right equipment for the job at hand.