Contents
- 1 The Difference between Curing and Drying
- 2 Curing Times for Concrete
- 3 Curing Concrete-Colder Temps
- 4 The Dos and Don’ts of Curing Concrete
- 4.1 Do Wet Down Your New Concrete
- 4.2 Don’t Forget to Use Control Joints
- 4.3 Do Keep Your Concrete Warm
- 4.4 Do Use a Curing Compound
- 4.5 Don’t Paint or Stain Concrete for at Least a Month
- 5 Factors That Affect Concrete Setting
- 6 Tips on Curing Concrete
- 6.1 How to Speed Up Concrete Drying Time
- 6.2 DON’T let new concrete get too cold
- 6.3 DON’T subject new concrete to excessive weight
- 7 A Business Built on Service
One of the first questions homeowners ask after having a new driveway installed is how long they should wait before using it. A new concrete path can be walked on after about a day, but cars weigh a lot more than people. Driveways also tend to be a fair bit thicker than patios, and using more concrete means more prolonged drying and curing times. Concrete begins to dry and cure as soon as it is poured, but drying and curing are not the same things.
The Difference between Curing and Drying
Curing is a chemical reaction that takes place inside concrete. This is the process you will be most interested in if you want to park on a new driveway since this is when concrete gets its strength.
While several factors can influence how long this takes, a general rule of thumb is that it takes about 30 days for an inch of concrete to cure. However, a new concrete driveway should be strong enough to support an automobile after about ten days.
Drying takes a lot longer than curing. This is because only a part of the water added to concrete during mixing is used in the curing process. The rest of the water remains inside the concrete and slowly makes its way to the surface. How long this water takes to evaporate depends on the air temperature and relative humidity.
Curing Times for Concrete
Adding or reducing the amount of water used to mix concrete will lengthen or shorten its curing time, but getting the ratios just right takes a trained eye and a careful hand.
Too much water will result in concrete that is porous and prone to chipping and cracking, but not enough water makes mixing very difficult. Using concrete mixes that contain accelerators like calcium chloride is one way to shorten curing times, but these substances can also corrode rebar.
Most concrete mixes reach 70% of their compressive strength after about seven days. They harden very quickly for the first few days, and then they continue to strengthen for another few weeks.
Curing Concrete-Colder Temps
Concrete cures the best at temperatures higher than 50 degrees Fahrenheit. Hydration slows down significantly at even slightly cooler temperatures and almost stops entirely at about 40 degrees Fahrenheit. Concrete poured in these conditions can lose as much as half of its 28-day strength.
To prevent this from happening, it is crucial to stop new concrete from freezing until it has reached a strength of approximately 500 psi. This generally takes about two days. Things that can be done to keep concrete warm during this time include:
- Using hot materials: Using hot water and aggregates to mix concrete can really take the edge off cold weather. If the temperatures are not too cold, this may be all that is needed to achieve the desired strength.
- Adding accelerators: Accelerators like calcium chloride, calcium nitrate and sodium nitrate speed up curing times, but they should be used as one step of a larger plan because they do not make concrete more resistant to freezing.
- Mixing air-entrained concrete: This special kind of concrete fills with air bubbles when it cures. These bubbles then give water a place to go when it freezes and expands. This allows air-entrained concrete to freeze and thaw without cracking.
- Covering concrete: There are now heated blankets available that can keep recently poured concrete warm enough to ensure that it cures properly. These coverings run on electricity like a heated bed blanket, and they can cure concrete about three times faster than tarps or regular blankets.
- Using a heater: Heaters can both raise the temperature and lower the humidity of the air near concrete.
The Dos and Don’ts of Curing Concrete
Time is the magic ingredient that allows something that starts with the consistency of oatmeal to harden into a substance that can hold buildings up. Of course, all of that strength is built up in just a few weeks, as long as moisture levels and temperatures remain where they should. Here are some dos and don’ts that you can use on your next concrete job.
Do Wet Down Your New Concrete
Concrete that is kept wet for a few days after being poured can be up to 50% stronger than concrete that is allowed to dry naturally. This is usually done by spraying new concrete with a garden hose up to 10 times a day. Another option is building berms around concrete and then flooding the area inside them. This method is known as pond curing, and it offers the same benefits as spraying without all of the work.
Don’t Forget to Use Control Joints
Control joints are cut into concrete less than 24 hours after it has been poured. They prevent random cracking by giving concrete a predefined area of weakness. When cracking does occur, it is in a straight line and below the surface.
Do Keep Your Concrete Warm
The temperature of your concrete should be 50 degrees Fahrenheit or hotter for at least two days. If you have to work in cooler temperatures, heat your water and aggregate before mixing and cover your concrete with a blanket or plastic sheet.
Do Use a Curing Compound
Curing compounds are solutions that can be sprayed onto concrete to form a protective film. This barrier prevents evaporation and ensures concrete cures at a consistent rate. Check the label before starting, as some curing compounds disintegrate naturally, while others must be removed by scrubbing.
Don’t Paint or Stain Concrete for at Least a Month
While your new concrete driveway will be strong enough to support a car after about a week, it will take a month before the hydration process is over. If you add a layer of paint or stain while moisture is still rising inside the concrete, it will probably not adhere very well and start peeling or flaking.
Factors That Affect Concrete Setting
The factors that affect setting times the most are the materials used to make concrete and the weather conditions it is poured in. Using hot materials, along with less water and accelerants, speed up setting times, but it will still take about a week for poured concrete to reach about 70% of its final strength.
Controlling humidity is especially important as moist air does not draw water out of concrete as well as dry air will. This problem can be avoided by using desiccants indoors and heaters or condensation dehumidifiers outdoors.
Tips on Curing Concrete
You can do a few things to reduce the amount of time it will take new concrete to cure. Here are a few final tips.
How to Speed Up Concrete Drying Time
The best way to speed up the time it takes concrete to dry is to use just enough water to make a mix that is easy to work with. Chemical admixtures like silica fume promote desiccation and speed up drying times, and putting a vapor retarder under concrete prevents ground moisture from entering the slab.
DON’T let new concrete get too cold
Pouring concrete in cold weather takes experience and skill. If a temperature of at least 50 degrees Fahrenheit is maintained for two days, the concrete will lose up to half of its strength. Fortunately, you can avoid losing concrete integrity by using hot water to mix concrete, adding accelerants to the mix and using blankets or heaters.
DON’T subject new concrete to excessive weight
The waiting is the hardest part of laying a concrete path, driveway or patio. Here is a rough timetable of how strong your new driveway will be during the various stages of the curing cycle:
- The first 24 hours: This is the time when your concrete driveway is at its most vulnerable. Cordon the area off, and do not allow anybody to walk on it or drag objects over it.
- Between one day and nine days: Concrete is tough enough to walk on after about 24 hours, but it is still curing under the surface
- After 10 days: This is the point when concrete has gained enough strength to support a car.
- After 28 days: Concrete is usually fully cured after about 28 days. After that, it is strong enough to support large trucks.
A Business Built on Service
If you would prefer to let professionals worry about aggregate, humidity and curing times, you should think about calling Nashville Concrete Contractors for your next project or repair. We always go the extra mile for our customers, which is why our business has been built on referrals and recommendations. If you would like to learn more about our concrete installation and repair services, you can fill out our online form or contact us at (615) 505-3595.
FAQs
How Long Before You Can Park on Concrete? ›
For Concrete: You may drive and park your personal vehicle on your new concrete surface after 7 days. Your new concrete is designed to reach 90% of its full strength potential after 7 days, so feel free to drive your personal vehicle on it then.
Can I drive on concrete after 3 days? ›Concrete professionals suggest waiting at least seven days after the crew is finished before parking or driving your personal vehicle(s) on your new concrete. The reason for this is because one week is the time period it takes for your new concrete to achieve 90% of its full potential strength.
How long do you have to stay off concrete? ›Concrete typically takes 24 to 48 hours to dry enough for you to walk or drive on it. However, concrete drying is a continuous and fluid event, and usually reaches its full effective strength after about 28 days.
Can you walk on concrete after 12 hours? ›After 24 hours, you can safely walk on your new concrete.
If there has been a lot of rain or you've done decorative stamping in the concrete, you should wait longer. Normal foot traffic should be fine on standard concrete at this point, but you should still be cautious about damaging the surface of the new paths.
The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic.
Can you drive on concrete after 1 week? ›Do not drive on the concrete for the first 7 days. Leave the warning tape in place to let delivery vehicles and others know that they need to stay off your concrete. After One Week – After 7 days, it's OK to drive on your new concrete with normal passenger vehicles.
What happens if you drive on concrete too early? ›You can damage your concrete driveway, both structurally and aesthetically, by driving or walking on it too soon. At a minimum, you may leave tire tracks, footprints, or scuff marks in the surface. At worst, the concrete will crack and its strength will be compromised.
When should I start watering my concrete? ›Many construction specialists recommend watering it down five to ten times per day, for the first week, starting 2-4 hours after it has been poured. The first two to four hours lets the concrete “finish”, which refers to the setting process.
How do you know when concrete is fully cured? ›Curing time of concrete is typically 24-48 hours, at which point it's safe for normal foot traffic. After one week, concrete is typically cured enough to handle continued construction including heavy machinery. Concrete is recognized to have reached full strength 28 days after placement.
How long should concrete cure before putting weight on it? ›Curing times for concrete
After 7 days, the concrete will have gained around three quarters of its compressive strength, but you should refrain from driving vehicles or heavy machinery over the surface until after the 28 day mark.
How often should I water new concrete? ›
If water evaporates too quickly, it will weaken the finished product with stresses and cracking. To put it simply, the goal is to keep the concrete saturated during the first 28 days. The first 7 days after installation you should spray the slab with water 5-10 times per day, or as often as possible.
Does wetting new concrete make it stronger? ›Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
Is it okay if it rains on fresh concrete? ›How Long Should Concrete Dry Before it Rains. If rain is in the forecast for the days or hours after you expect to finish the job, you shouldn't have to worry. As long as the concrete is given 4 to 8 hours after mixing and finishing to set up, rainwater won't affect it nearly as badly as it could.
What happens if you don't water new concrete? ›Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
What is the best temperature for concrete to cure? ›Upon pouring and throughout curing, the concrete must be kept at 40 degrees if more than 72 inches thick, 45 degrees if 36 to 72 inches thick, 50 degrees if 12 to 36 inches thick, or 55 degrees if less than 12 inches.
Does concrete take 100 years to cure? ›Does concrete take 100 years to cure? No, this is a bit of a myth with the concrete industry. While concrete does continue to harden indefinitely, pore moisture has to drop below a certain level at some point and this isn't typically 100 years.
How thick should a concrete driveway be? ›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. To eliminate standing water, the driveway should be sloped towards the street a minimum of one percent, or 1/8 inch per foot, for proper drainage.
How strong is concrete after 2 weeks? ›Viewing the table, you can discover that concrete gains 16 percent strength in one day, 40 percent in 3 days, 65 percent in 7 days, 90 percent in 14 days and 99 percent strength in 28 days. Therefore, concrete gains strength rapidly in the first two weeks after casting (90% in just 14 days).
How strong is concrete after 1 week? ›Concrete achieves about 70% of its compressive strength at the age of seven days. After one week from the initial concrete placement and under normal weather conditions, the concrete element can withstand construction loads of labor and machinery used for construction works.
Does concrete cure faster in hot weather? ›High temperatures mean faster curing, but fast curing equates to weaker strength in the end.
HOW MUCH CAN 4 inches of concrete hold? ›
Concrete driveways are typically poured four inches thick, giving the concrete driveway enough strength to withstand loads of regular vehicles (up to approximately 8,000lbs).
Can I walk on concrete after 4 hours? ›Although concrete will harden soon after pouring, it's still susceptible to damage from weight during the first four weeks. Wait at least 24 hours before allowing foot traffic, including pets, on a newly poured sidewalk or slab, and don't drive a vehicle on a new driveway for at least 10 days.
Can you overwater concrete? ›The issue of adding too much water
Too much water added to the mix means that excess water is retained inside the concrete after the curing process has finished. This will often result in the formation of small cracks as the water eventually evaporates over time, which reduces the compressive strength of the concrete.
Please keep vehicles, children, pets, and yourself off of your newly poured concrete for the next 24 hours. After 24 hours, you can walk on your newly poured concrete, but avoid dragging your feet, 'doing the twist', or allowing your pets to walk on it as their claws can scuff the concrete.
How long should concrete cure before removing forms? ›After pouring and finishing the slab, you should wait 24-48 hours before removing concrete forms. You can remove the formwork once the concrete has enough strength to keep it from cracking. Concrete naturally contracts as it cures, so it should pull away from the forms and make them easier to remove.
Should concrete be covered when curing? ›The most efficient way to cure concrete is to use a plastic cover. The covers are placed on freshly poured concrete until the concrete has a chance to dry. Plastic concrete curing covers seal off concrete and prevents water from evaporating.
How long does it take for 5000 psi concrete to cure? ›Curing should be started as soon as possible and should continue for a period of 5 days in warm weather at 70 degrees F (21 degrees C) or higher or 7 days in cooler weather at 50 – 70 degrees (10 – 21 degrees C). Protect concrete from freezing for at least 48 hours.
Is there a difference between concrete and cement? ›What is the difference between cement and concrete? Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement.
When can I put furniture on new concrete? ›After a reseal, wait 24 hours before walking on the concrete and then wait another 2 days before adding furniture, flower pots, etc. The caution tape and stakes can be removed after 24 hours and added to your household waste.
How do you keep concrete from cracking when drying? ›- Keep an eye on the temperature. ...
- Prevent excess water. ...
- Look into using synthetic micro fibers. ...
- Brace formwork. ...
- Use formed joints. ...
- Explore pre-curing options. ...
- Provide sufficient concrete cover. ...
- Start curing the concrete as quickly as possible.
What makes concrete set up faster? ›
- Weather is a factor. If your concrete is exposed to the elements, you won't be surprised to learn that the concrete will dry faster in warmer, sunnier conditions. ...
- Using a heater. ...
- Using warm water. ...
- Reducing the amount of water. ...
- Avoid hard trowelling.
HOW DOES RAIN AFFECT CONCRETE? Rain falling on top of freshly laid concrete can damage the surface and compromise a level and floated finish.
Does concrete need sun to dry? ›While Curing
When curing freshly-poured concrete, you must take precautions to prevent water evaporation caused by direct sunlight. For the duration of the curing process, which is typically 28 to 30 days, keep your concrete watered, covered, and sheltered from wind and sunlight.
If the rain begins after 2-4 hours from concrete placement, the surface needs to be covered; otherwise, the concrete surface will suffer damages. If rains pound on concrete 12 hours after placement, the likeliness of any damage is negligible.
Can you pour concrete over concrete? ›Yes, you can pour fresh concrete over existing concrete. As long as your concrete is in mint condition, this task is doable. If you decide to pour a new mixture over an old slab, be sure it is at least 2 inches thick.
How do you protect freshly poured concrete from rain? ›If rain is forecast on the day you are pouring concrete, make sure the site is well covered with plastic sheets and tarpaulin to keep the ground as dry as possible. If it starts to rain during the pour, make sure you are prepared with plastic sheets and timber to construct a shelter over the fresh concrete.
Does concrete cure faster in cold weather? ›Concrete poured and placed in cold weather has a much slower setting and curing time, so bleeding will also start later than expected. Be prepared to handle more bleed water than is typical in regular concrete placement.
Will concrete cure in 30 degree weather? ›Concrete sets and forms best between 50 and 60 degrees Fahrenheit. Concrete will cure at 30 degrees, and if the air temperature is between 30 and 40 degrees, you'll want to make sure your mixed concrete maintains a temperature of between 55 and 60 degrees.
How long does it take concrete to cure in 70 degree weather? ›| Temperature | Approximate Setting Time (hours) |
|---|---|
| 100oF (38oC) | 1-2/3 |
| 90oF (32oC) | 2-2/3 |
| 80oF (27oC) | 4 |
| 70oF (21oC) | 6 |
The Hoover Dam concrete would cure in 125 years by conventional or natural methods. Crews, however, used some innovative engineering methods to hasten the process. Nearly 600 miles of steel pipes woven through the concrete blocks significantly reduced the chemical heat from the setting for the concrete.
Is the concrete in Hoover Dam still curing? ›
Also intriguingly, it keeps on curing long after it's apparently set. The Hoover dam is still curing nearly a century after being built! But the upshot of the chemical reaction is to create a kind of stone you can pour into a mould.
Can concrete last 10,000 years? ›For large scale projects like buildings, concrete should last up to 100 years if it's properly cared for. Concrete projects that experience more wear-and-tear like sidewalks and driveways have an expected lifespan of about half that—50 years.
How hard is concrete after 3 days? ›Viewing the table, you can discover that concrete gains 16 percent strength in one day, 40 percent in 3 days, 65 percent in 7 days, 90 percent in 14 days and 99 percent strength in 28 days. Therefore, concrete gains strength rapidly in the first two weeks after casting (90% in just 14 days).
How strong is concrete after 5 days? ›After concrete is placed, the concrete increases in strength very quickly for a period of 3-7 days. Concrete which is moist cured for 7 days is about 50% stronger than uncured concrete.
What happens if it rains 2 days after pouring concrete? ›Concrete typically needs 24 to 48 hours to dry.
If the rain comes before the 24-hour mark, you may risk your concrete getting damaged. The time it takes to dry depends on the thickness and size of the concrete project you are attempting to take on.
How Long Does Concrete Take to Cure? Concrete never stops curing, with its strength only growing through time. It becomes safe to walk on 2-3 days after pouring, but shouldn't be considered “set” until it has set for at least a week.
Is it OK if it rains 5 hours after pouring concrete? ›As long as the concrete is given 4 to 8 hours after mixing and finishing to set up, rainwater won't affect it nearly as badly as it could. Some concrete mixes will actually benefit from rainwater on the surface because it's beneficial in aiding the hydration and curing process.
Is it OK if it rains after pouring concrete? ›Freshly placed concrete should be protected from rain for at least 12 hours from its placement. After that, the rainfall rarely influences concrete properties.
How long does it take for 4000 psi concrete to cure? ›Curing should be continued for a period of five days in warm weather of 70 degrees F (21 degrees C) or higher, or seven days in cold weather of 50 degrees F to 70 degrees F (10 degrees C to 20 degrees C). Protect concrete from freezing for at least 48 hours.
Does rain help concrete cure? ›Rain can weaken the concrete surface and compromise its strength since it can wash off the cement in the mix. This can lead to issues like cracks in the concrete and delays in the curing process, both of which can lead to a poorly finished surface.
What is the difference between cement and concrete? ›
What is the difference between cement and concrete? Although the terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and portland cement.