Concrete is used today in all facets of construction and landscaping; it’s even used underwater. If you’re planning to use it for a patio, sidewalk, steps, or driveway, it’s important to know how long does it take concrete to dry, set, and cure. If you’re looking for useful information, we’re here to help.
Concrete usually begins to set within 30-minutes of pouring, the surface can be finished 2 to 4 hours after placing, and is considered set after 10 hours. It can withstand foot traffic and have forms removed within 24 hours, light vehicles in 48 hours, is 70% cured in a week and ready for heavy equipment, and is considered fully ‘cured’ and dry after 28 days.
In this guide, we’ll discuss what curing, drying, and setting means, how long concrete takes to set, dry, and cure, plus the effect of temperature, wind, and moisture on the processes. We’ll also explain different ways to accelerate setting, curing, and drying, different types of concrete mix, and what the Building Code has to say about concrete curing. Additionally, we’ll look at pouring concrete in the rain. Our goal is to provide you with all the information you need about the drying, setting, and curing times of concrete.
- What Is The Difference Between Concrete Curing, Drying, and Setting?
- How Long Does Concrete Take to Dry?
- Factors Affecting Concrete Dry and Setting Time
- How to Dry Concrete Faster
- How Long Does It Take Concrete to Fully Cure?
- Concrete Curing Time Chart
- How to Cure Concrete Faster
- How Long Does Concrete Take To Set
- What Is Fast Setting Concrete
- What Is Quick Drying Cement
- Can You Pour Concrete in the Rain?
What Is The Difference Between Concrete Curing, Drying, and Setting?
Concrete is made up of cement, sand, and different aggregates. Like most parts of the construction industry or any industry, it has terms that mean something important within that trade. Curing, drying, and setting are time-sensitive and refer to different processes that happen within concrete once it has been poured and placed.
Curing refers to the hydration process that affects the bond between the cement and the aggregate used. The longer the hydration process after the concrete is poured, the stronger the finished product. Curing is maintaining adequate moisture or humidity of 80% and temperature higher than 50°F over 3 to 14 days after the pour. Since curing is a chemical process, it will never really end if moisture is present. So, even though we say concrete is cured in 28 days, it will continue to react as long as moisture is present.
Drying is not the physical process of drying. Drying is providing the conditions necessary for concrete to cure to the moisture condition required for its planned use or the application of floor finishes. Concrete may take 24 to 48 hours to dry enough to be walked or driven on, and 28 days to be considered dry. Wood, vinyl, and linoleum flooring or epoxy finishes may not breathe, so can interfere with the curing process, which means the concrete should have a moisture vapor emission rate (MVER) of 3lb/1000sqft/24-hours or less to be considered dry.
Setting is the gradual change from fluid to rigid concrete, or its stiffening after being placed. It is the result of calcium silicate hydrate and ettringite formation. The setting period ends when concrete is no longer workable and is often affected by the amount of water in the mix. The concrete is in a weak state and needs to cure and dry to harden to its full strength after setting. Concrete begins to set within 30 minutes of placing and is considered set after 10 hours. A value of 3.43MPa or 500psi on a Penetrometer usually identifies the start of hardening, and a reading of 26.97MPa the end of hardening.
How Long Does Concrete Take to Dry?
Concrete is commonly considered dry and hardened after 28 days, although it typically takes about a month per inch of thickness for the moisture to bleed out of the concrete. Most concrete mixes are dry enough to walk on and have the forms removed within 24 hours. Concrete can be driven on by light vehicles after 48 hours and heavy equipment after 7 days. However, temperature and humidity, as well as mix density plus additives to the concrete mix can affect the initial drying times.
How Concrete Dries
Concrete dries gradually over time. After the initial pour and placing, water evaporates from the surface. Moisture within the concrete mass is drawn to the surface through capillaries to replace the evaporated water and is also evaporated. Evaporation continues until the moisture in the air equals or is greater than that in the concrete. As a result, moisture within the concrete can continue to evaporate long after the concrete is considered dry.
What Causes Concrete to Harden?
Concrete is a measured mixture of Portland cement, aggregates like sand and gravel, and water. When initially mixed with water it forms a slurry or cake batter consistency. Portland cement contains dicalcium and tricalcium silicate which contribute to the strength and hardness of concrete, plus tricalcium aluminate, tetracalcium aluminoferrite, and gypsum.
Adding water to the cement causes hydration which generates chemical reactions that form bonds between the aggregate material and the cement. Tricalcium silicate reacts more quickly to form the initial bond strength, while dicalcium silicate reacts more slowly to contribute to the strength after 7 days. The calcium silicate hydrate – a combination of the dicalcium and tricalcium silicate and water – form a crystalline matrix of fibers that harden and bind or cement the aggregate mixture together.
How Long indoors
A concrete floor, whether indoors or outdoors, has to hydrate to form the crystalline bonds that harden the concrete. The humidity and the temperature within a building may slow or accelerate the initial binding, and lighten the color of the concrete as it hardens. It may be easier to control humidity and temperature indoors, which can speed up the hardening process so it can support more weight sooner. However, the chemical reaction of hydrating shouldn’t be considered finished until 28 days have passed.
Factors Affecting Concrete Dry and Setting Time
Temperature and humidity are just two factors that affect the setting and drying time of concrete. Wind and the type of concrete mix or composition of the mix are the other two main factors that affect the drying time. It should be noted though, that while a quicker setting and initial drying time may be desirable, the chemical hardening reaction will still take 28 days, and can take even longer depending on the thickness of the pour. The shape and size of the pour is also a factor, but more in the aspect of controlling how the other four factors affect it.
Temperature can speed up or slow down the set and drying time of concrete. Warm and hot temps accelerate evaporation and speed up drying, colder temps slow it down. The faster the evaporation of moisture from the concrete, the quicker it will set up and dry. Concrete will usually set up in less than 2 hours at 100°F, 4 hours at 80°F, 8 hours at 60°F, 14 hours at 40°F, but isn’t likely to set up at 20°F. It should be noted though, that too rapid a drying can make the concrete brittle.
A warm dry wind will suck moisture out of concrete faster than a humid wind, thus accelerating set up and drying. The main concern is an accelerated surface drying speed which can cause cracking due to shrinkage. Additionally, the faster the wind movement, the greater the risk to the concrete’s strength, especially as the surface can dry faster than the inside mass. The accelerated surface drying and shrinkage can actually cause warping too.
Too much or too little water in the concrete mix affects the strength of the concrete. Too little moisture will cause fewer bonds to form, accelerate drying, and result in a weaker product. Too much moisture can weaken the top layer and result in surface flaking. The common ratio of water to cement, based on weight, is 0.5:1, or water is half the weight of the cement in the mix. The ratio may go up or down slightly depending on temperature and wind, but usually only by 0.05.
Type of the Concrete Mix
The type, composition, quality, and fineness of cement, the amount of gypsum, plus any added accelerants in the concrete mix will affect set up and drying times. Caution should be taken when using accelerants though as they can weaken the overall strength of the finished project. In most cases, the type of concrete and any additives will accelerate the set up and initial bonding, which will allow drying to begin sooner. However, concrete typically still requires 28 days to be considered fully cured and dry, even though it will continue to dry after that.
How to Dry Concrete Faster
There are additives that will accelerate the setting time of concrete and other methods that will harden concrete more quickly so it can be used sooner. Some can be applied prior to pouring and others after the concrete has been placed or finished. The type of concrete used can also affect drying speed too. Having said that though, regardless of which method or type of concrete is used, concrete will still take 28 days to achieve 99% of its strength.
Before the Pour
There are a number of ways to speed up the initial setting and drying times for concrete before it is poured. Using less water or a higher cement ratio will reduce the initial drying time. Pouring on a warm sunny day will accelerate the process. Adding calcium chloride to wet concrete prior to pouring will also speed up the hardening time. Use warm water instead of cold water when mixing the concrete helps. Placing a moisture barrier down prior to pouring will prevent ground moisture from being sucked up into the concrete, making drying easier and quicker.
After the Pour
Once the concrete has fully set up, there are several ways to speed up drying so the concrete can be used more quickly. Dry or normal curing will take longer than moist curing, and pond curing is even faster. Controlling the humidity and temperature are two other common ways to accelerate drying.
Dehumidifiers can be used to remove moisture in the air which will draw moisture from the concrete more quickly. Keeping windows and doors closed while using dehumidifiers will decrease the relative humidity inside too, and not draw moisture in from outside. Concrete will set and dry more quickly in warm temperatures than in cold, so use heaters to increase the temperature to speed up drying.
Covering the pour with a concrete blanket or black plastic sheeting will help warm the surface and trap escaping moisture, accelerating curing, and resulting in a stronger product. Troweling techniques can also help with drying too. It should be noted though, over troweling or hard troweling can close capillary pores in the concrete and slow drying.
Two other ways to dry concrete faster than air drying are moist-curing and pond curing. They both use water to accelerate the curing process and strengthen the concrete more quickly, thus drying it sooner. Wet or moist-curing is slowing the drying time by wetting the concrete surface 5 to 10 times a day for up to 7 days to keep it moist. Pond curing uses berms or other containment around the pour to hold 4” to 12” of water on top of the concrete. It has the same effect as moist-curing, but it does it in 3 days instead of 7, thus accelerating drying.
How Long Does It Take Concrete to Fully Cure?
Concrete is made up of cement and aggregate materials. The cement bonds to the aggregate when water is added, which causes an exothermic chemical reaction called hydration. The speed of the reaction affects concrete’s hardness, durability, permeability, and resistance to freeze-thaw damage and surface scarring.
Concrete normally sets up fully within 10 hours. Once set and finished, it is important to maintain adequate temperature and moisture content for a set period of time. It ensures the hydration reaction continues, forms stronger bonds with the aggregates, and results in a harder and stronger finished product.
Dry curing is allowing the concrete to dry at its own speed and is dependent on environmental conditions. Dry curing can lead to shrinkage, cracking, and a product up to 50% weaker. Wet or moist-curing slows the initial drying time but results in stronger concrete more quickly. Pond curing achieves the same strength values as moist-curing, but in 3 days instead of 7.
Strength is an indication of both curing and drying. Some types of cement will achieve approximately 20% of their strength within 24 hours, and others up to 50% in that period. You can usually walk on concrete 24 hours after it’s poured without marking it, and drive light vehicles on it after 48 hours. Within 72 hours, concrete will have achieved between 30% and 75% of its strength, and after 7 days between 45% and 85%. Once the concrete has reached 50% of its strength, it can support most heavy equipment too.
Since curing and drying are related to a chemical process, it will never really end if moisture is present. So, even though concrete has reached 99% of its strength in 28 days and is considered dry and cured, it will continue to harden long after that.
How Concrete Cures
Concrete begins to cure as soon as it is placed and finished. Maintaining an acceptable temperature and moisture content for the initial curing period (3 to 7 days) ensures hydration continues. Proper hydration improves strength, stability, and resistance to scaling, abrasion, and frost.
Concrete contains Portland cement and aggregates such as sand and gravel. The cement contains dicalcium and tricalcium silicate, tricalcium aluminate, tetracalcium aluminoferrite, and gypsum. Mixing water with the cement in the correct measure, usually 0.5:1, begins a chemical process resulting in calcium silicate hydrate, a blending of di and tricalcium silicate, and water.
The tricalcium silicate reacts faster with the water to form the initial bond strength with the aggregates. The dicalcium silicate takes longer, up to 7 days, to begin forming bonds, which contribute to the overall strength. The bond formed is a crystalline weblike matrix of fibers that hardens over the next 28 days and cements or binds the aggregates and cement mixture together.
Curing Period of Concrete as per IS Code
The International Residential Building Code (IRC), which is the foundation of many national, state, and local building codes, references the American Concrete Institute (ACI) in regards to the curing period for concrete. ACI 308.1R recommends that concrete cure for a period that allows it to attain 70% of its compressive or flexural strength, as a minimum curing period.
The type of cement can affect the speed at which concrete cures to the acceptable strength too. Regular Portland cement (Type I or GU) requires a minimum of 7 days to cure to 70%, while some blended cements (Type II or MS or MH) need a minimum of 10 days. Cements that achieve high strength early (Type III or HE) commonly cure to 70% in 3 days, and those used for low heat of hydration (Type IV or LH) up to 14 days. The curing time for different hydraulic cements varies, so check the manufacturer’s fact sheets.
Concrete Curing Time Chart
Concrete curing is important to the strength of the finished product. Although there are ways to accelerate the curing speed, it is good to know how long it usually takes common types of cement to achieve 70% of their strength. The table below identifies types based on ASTM C150, ASTM C1157, and ASTM C595.
|Concrete Curing Time for 70% Strength by Cement Type|
|Type||Description||Curing Time to Reach 70% Compressive Strength|
|Type I, ASTM C150
Type GU, ASTM C1157
|Normal cement or General Use (GU) concrete||7 days|
|Type II, ASTM C150
Type MS, ASTM C1157
Type MH, ASTM C1157
Type HS, ASTM C1157
|Moderate Sulfate (MS) Resistance for use when concrete will be in contact with soils, Moderate Heat of Hydration (MH) and High Sulfate (HS) Resistance||10 days|
|Type III, ASTM C150
Type HE, ASTM C1157
|High Early (HE) Strength cement||3 days|
|Type IV, ASTM C150
Type LH, ASTM C1157
|Low Heat (LH) of Hydration||14 days|
|Type V, ASTM C150
Type HS, ASTM C1157
|High Sulfate (HS) Resistance||14 days|
|Type IL, ASTM C595||Blended hydraulic Portland-Limestone cement,||Time varies
(Often less than 24 hours)
|Type IS, ASTM C595||Blended hydraulic Portland-Slag cement|
|Type S, ASTM C595||Blended hydraulic Slag cement|
|Type I (SM), ASTM C595||Blended hydraulic Slag-modified Portland cement|
|Type IP or Type P,
|Blended hydraulic Portland-Pozzolana cement|
|Type I (PM),
|Blended hydraulic Portland-Pozzolana modified cement|
|Type IT, ASTM C595||Blended hydraulic Ternary Blended cement|
How to Cure Concrete Faster
There are different ways to decrease the time it takes concrete to attain 70% of its compressive strength. Curing time affects the overall strength of concrete, so doing it right is best. The goal is to maintain moisture in the concrete after it has set, decrease the water loss off concrete surfaces, and thus accelerate the strength gain in the concrete.
Using Type III or HE, high early strength cement is one way, and additives like calcium chloride another way. Applying curing compounds to the concrete surface once it’s free of moisture but not dry enough to absorb it, works too – one drawback is that flooring adhesives may not stick. Supplying heat helps, as does additional moisture. Contractors use one method or another, or a combination of different strategies.
Maintaining moisture is a good way to accelerate concrete’s strength gain. There are different methods, such as covering the surface once it is set and won’t be marked with waterproof plastic or paper sheeting, sand, straw, manure, burlap, or canvas that can be kept wet to slow moisture movement out of the concrete. Some of these methods, including plastic, can discolor the concrete, so shouldn’t be used if the appearance of the concrete is important.
Concrete blankets have been developed to accelerate the curing process. They will either warm or cool the concrete depending on exterior temperatures to maximize strength development. The blankets can cure the concrete up to three times quicker than many other methods, are easier to use, and don’t require constant attention while maintaining moisture during the hydrating process.
Water curing, including spraying or fogging when temperatures are above 50°F, helps to slow evaporation and keep the moisture in the concrete, which accelerates strength gain. However, ponding, flooding, or immersion is the most effective method and can cure concrete to 70% strength in 3 days where other methods can take up to 7 days or longer. Covering the concrete with 4” to 12” of water is an effective way to prevent moisture loss and maintain a uniform temperature too.
How Long Does Concrete Take To Set
Setting refers to the change of state in concrete from a liquid to a solid. The process begins once the concrete is poured and placed, usually within 30 minutes. Concrete can initially be poured, wheeled, shoveled, pushed, leveled, and screeded as it sets up. Walking on it is like walking in mud. However, as moisture moves out of the concrete and the calcium silicate hydrate and ettringite form bonds with the aggregates, the mixture stiffens or hardens.
As the bonds form in the concrete and it stiffens or hardens, moisture bleeds out of the surface and drains or evaporates off. Several hours after pouring, concrete can be walked on, troweled, and finished. Concrete is usually too hard to work after 6 to 10 hours, at which point many consider it set. Technically though, concrete is considered set when it reaches a hardness of 26.97MPa on a Penetrometer.
Temperature affects setting time, with concrete setting up more quickly the warmer the air and ground temperature. At 100°F it can take less than 2 hours to set, 4 hours at 80°F, 8 hours at 60°F, and up to 19 hours at 30°F. In colder temperatures, it will take longer for concrete to set. Depending on the type of cement, and use, concrete can set up more quickly too. It’s common for a post hole filled with quick setting concrete to set up in 15 to 40 minutes, so placing and leveling a fence post or basketball stand needs to be done quickly, and it can be used sooner too.
What Is Fast Setting Concrete
Fast setting cement is specially blended cement that accelerates hydration and bonds quickly with the sand and aggregates it is mixed with. It will set up within 10 to 30 minutes and can often be used within hours of pouring. It reaches 50% strength in 24 hours or less, and 70% to 90% within 3 days. The fast setting means bracing often isn’t necessary, and the finished concrete is strong and durable. Fast setting cement is used where high-strength concrete is needed more quickly, and still meets or exceeds ASTM C387 requirements for compressive strength.
The cement is commonly mixed with water when used for driveways, sidewalks, slabs, patios, curbs, ramps, stairs, and other structural purposes. When used to anchor post, railings, swings, and to fill holes or other items, it’s normal to pour half the water volume into the hole around the post or item, dump the dry mix in on top of the water, and then add the rest of the water measure on top. The cement and water mix together chemically without any mechanical assistance, set up quickly, and harden within hours.
What Is Quick Drying Cement
Modern cement used in concrete sets up and can be finished within hours and achieve 50% to 70% of their structural strength in 3 to 7 days. Once the concrete reaches 70% of its strength, it can normally be used for its intended purpose. Most quick-setting cements, or rapid hardening, drying, or curing cements contain finely ground cement or chemicals (or both) to accelerate the bonding and hardening process.
Hydraulic cement is rapid hardening and offers reduced shrinkage when compared with non-hydraulic cements that harden quickly. Most hydraulic cements achieve 70% to 90% of their compressive strength in a matter of hours, and can often be used in an hour. They are used in new construction and for concrete repair work and are often blended with other products for different uses.
Rapid hardening or quick-drying hydraulic cement contains similar materials to Portland cement. However, it’s primarily composed of hydraulic tetracalcium triluminate sulfate, also known as calcium sulfoaluminate. When water is added, the calcium sulfoaluminate hydrates to form strong needle-like crystals known as ettringite, which bond quickly with the aggregates. The other main component of the cement is dicalcium silicate which forms a highly durable bond.
Can You Pour Concrete in the Rain?
Concrete is a blend of aggregates, sand, cement, and water. Adding the water begins a chemical reaction that creates the bonds between the cement and the aggregates. Too much water can weaken the bond, and damage the concrete finish. However, you can pour concrete in the rain.
Pouring concrete in the rain requires extra steps to prevent the precipitation from being worked into the concrete. Remove standing water, don’t work it in, and cover the concrete with plastic or tarps to prevent damage. Avoid pouring concrete in torrential downpours, if possible, though. Check out our article Can You Pour Concrete in the Rain?
Temperature, moisture, wind, and other environmental conditions affect concrete’s setting, curing, and drying. Concrete doesn’t dry in the usual sense; it uses moisture to create bonds to harden from a liquid state to a solid. The initial change begins within 30 minutes of a pour and is usually complete within 10 hours, by which time it is considered set. It is usually ready for use within 1 to 7 days, depending on the type of cement used in the pour. However, it isn’t considered ‘dry’ until 28 days after pouring or it has reached a moisture vapor emission rate (MVER) of 3lb/1000sqft/24-hours. Hopefully, you have a better understanding of how long it takes concrete to set, cure, and dry.