Find out how long concrete takes to dry for your favorite DIY projects. Read this post to discover dry times during any condition and ways to make concrete dry faster
Renowned for being one of the most durable and strongest construction materials available, concrete needs to dry gradually to reach its peak strength. However, dry concrete is somewhat of a misnomer because concrete doesn’t actually “dry” in the traditional sense as water never completely evaporates from it.
The terms drying and curing are often used interchangeably when referring to pouring concrete, but they mean two different things. Curing refers to providing adequate temperature, moisture, and time to permit the concrete to achieve the desired properties for its intended use. Drying refers to the process of evaporating the excess water leftover from the pouring process. Concrete continues to dry for its entire life. The longer it dries, the stronger the concrete, which is why it remains a highly desirable material for construction projects both large and small.
As a general rule, concrete takes 24-48 hours to dry enough to walk on and 7 days to drive on depending on weather conditions and the size of the project. To be considered dried to full-strength, the curing process must be completed in a span of about 28 days.
Read on to discover the proper conditions for concrete to dry and cure, how to make concrete dry faster, length of the curing process, drying times for varying weather conditions and quick dry cement.
Why is Concrete Never “Fully Dried”?
To understand what is meant by dried concrete, we need to provide some background on the process. The drying process, also called “hydration,” is where enough water is evaporated that the concrete will not change shape and is set enough to walk or drive on without sinking into it. Hydration begins the second you combine water with dry concrete mix which gives you a limited time frame (approximately one hour, weather and mixture depending) to get concrete into your desired form before it hardens.
The drying process will continue over the next couple of weeks and go through multiple stages before the concrete is considered fully cured, which is a process that occurs over a 28 day period. Concrete is never fully dried because the water never leaves it entirely due to the chemical reaction that occurs where tough crystals develop inside of the concrete binding the gravel and sand materials firmly together. However, we can consider it completely dried because it reaches full-strength after 28 days (per 1 inch of thickness).
When waiting for concrete to dry and cure, remember these timeframes:
- 24 to 48 hours – concrete is dried to approximately 50% of its full strength and people can walk on the surface
- 7 days – traffic from vehicles and equipment is alright, wait a few more days if you have a large vehicle such as a 1-ton pickup truck
- 28 days – at this time, the concrete would be fully cured
How Can I Make Concrete Dry Faster?
Drying concrete requires the right conditions: a consistent warm temperature, about 50-90 degrees Fahrenheit, and a low ambient relative humidity. In an ideal world the temperature of freshly mixed concrete should be above 50 degrees F and maintained and cured at 50 degrees F as maintaining a temperature between 50 and 90 degrees F will still result in strong and durable concrete. Though not always possible, pouring cement at night can make maintaining proper conditions easier.
Steps can be taken before and after pouring concrete to assist in faster drying times. Here are proven things you can do before and after you pour the concrete to make the drying process faster:
Before The Pour
· Use warm water in the mixture and ensure you are using the correct amount of water. Too much water will cause more water being left over after the curing process resulting in a longer drying time.
· Use an HVAC system if possible, this will help maintain desired temperatures.
· Avoiding using lightweight concrete, these mixtures absorb a lot more water which also increases drying times. Opt for synthetic concrete that won’t absorb water.
· Use a high cement content mix to shorten drying time. This may result in shrinkage which can cause cracks in the cement.
· Limit the use of sealing or curing agents as they can prevent evaporation from the concrete’s surface causing a longer dry time.
After The Pour
· After the concrete has cured, enclose the space immediately to prevent the slab from absorbing any additional moisture.
· Place heaters near the newly poured concrete to speed up the drying process.
· Use plastic tarps to keep moisture from escaping the concrete.
· Gently trowel the concrete as hard finishing can result in the surface losing its ability to allow moisture to pass through which is mandatory for drying.
How Long Does 4 Inches of Concrete Take to Cure?
Since curing and drying are two very different processes, they have individual time frames. On average, a one inch thick slab of concrete should be cured to approximately 70% of its full strength within one week so a four inch slab of concrete is only cured to about 17% in that time. Since fully curing takes about 28 days per one inch piece of concrete, a four inch piece of concrete will take about 112 days to cure completely. At this point the concrete can be safely used.
How Long Does Concrete Take to Dry in Cold Weather?
The process of drying and curing concrete is more complicated and prolonged in cold weather, or temperature below 50 degrees Fahrenheit. According to the American Concrete Institute (ACI), cold-weather concreting is a period when for more than three consecutive days the daily air temperature drops below 40 degrees F on average and remains below 50 degrees F for more than 12 hours in a 24-hour period. When temperatures are this low, different techniques need to be employed.
Hardening or drying times vary by temperature, at 40 degrees F it will take about 14 hours to set enough to retain its shape, at 30 degrees F it will take 19 hours and at temperatures 25 degrees F or below the cement will not set. In comparison, for temperatures between 90-50 degrees F, concrete will set in about 2-11 hours respectively. Generally, your set time doubles per 20% drop in temperature.
Under cold weather conditions plastic tarps or insulated blankets should be used to protect the concrete so it doesn’t freeze as proper curing is required to make the concrete strong. In temperatures below 50 degrees F, the curing process can take up to 20 days to be partially cured enough for traffic. Once it has partially cured, gradually remove the sheets or blankets used because rapid cooling can cause cracking and ruin your project.
How Long Does Quick Dry Cement Take to Dry?
Don’t have the time two wait months for your cement to dry? Using quick dry cement, such as Quikrete Fast-Setting Concrete Mix, will drastically shorten drying time but should only be used for smaller projects because it may harden before your project is completed. In ideal conditions this type of cement will set in about 20-40 minutes.
Fast setting cement is dry enough to walk on after 2 hours. It will have cured enough to drive a small vehicle over it after approximately 4 hours. After 24 hours, the quick dry concrete can be considered completely cured to its full-strength.
What factors affect how long concrete takes to dry?
Concrete drying times are not always consistent for every situation and can depend upon the project. Here are some key factors that can affect drying and curing time:
- Mixture: Different types of concrete, whether quick dry or high quality, have different drying and curing rates. To make concrete cure faster you can add an accelerant such as calcium chloride to the mix. Although this will speed up drying time your concrete may not be as strong as full strength concrete allowed to cure under normal conditions.
- Moisture: Since the interaction that occurs when cement is mixed with water causes the curing process, if there is less water in the mixture the concrete will dry faster. This happens because there are fewer chemical bonds to make which also means that your full-strength concrete may not be as strong as expected or needed. Using too much water in the concrete mixture will result in a longer curing process and may cause flaking in the exterior/outtermost layer of concrete.
- Temperature: Moisture evaporates faster in hotter temperatures which means that your concrete will dry faster. In cold weather conditions, anywhere below 50 degrees, you can cover your concrete with a specialized blanket.
The time it takes for concrete to dry relies on many factors. Depending on the project type alone, as well as weather conditions, the requirements of the concrete’s intended use will dictate drying and curing times. Weather and humidity conditions also alter the time concrete takes to dry to full-strength since chemical reactions are constantly occurring via the interactions between the water and cement mixture.
For non-quick drying concrete, adhering to the general drying time frames can help ensure your concrete maintains the strength needed for your intended project. Proper curing is essential to achieve the concrete’s adequate strength so do shorten or neglect that process. Using the right techniques will maintain the durability and integrity of your project for decades to come.