Concrete curing is the practice of keeping fresh concrete moist and within a suitable temperature range long enough for the cement to hydrate and develop its designed strength. Curing does not add strength, it protects the strength the mix was designed to reach, and concrete that dries out early can lose a significant part of its potential compressive strength permanently. In practice that means starting curing as soon as the surface will not be damaged and continuing for at least seven days, or until the concrete reaches 70 percent of its specified compressive strength, whichever comes first. The three families of curing methods are keeping water on the concrete, sealing water into the concrete, and adding heat to accelerate strength gain in cold conditions.
What Is Concrete Curing?
Concrete curing is the process of maintaining adequate moisture in concrete within a proper temperature range in order to aid cement hydration at early ages. Hydration is the chemical reaction between cement and water that results in the formation of various chemicals contributing to setting and hardening. Some of the factors that affect the hydration process are the initial concrete temperature, the ambient air temperature, the dimensions of the concrete, and the mix design. Therefore, for the success of this process, in-situ concrete must have sufficient moisture and a temperature that favours this chemical reaction at a rapid and continuous rate.
The American Concrete Institute (ACI) recommends a minimum curing period corresponding to attaining 70% of the compressive strength of concrete. The specifications say that this can happen after seven days of curing. However, 70% strength can be reached quickly when concrete cures at higher temperatures, or when certain admixtures are used in the concrete mix. Similarly, more time may be needed for curing when concrete or ambient temperatures are lower. Typically, the ideal curing temperature is around 68°F (20°C).
Why Is Concrete Curing Important?
Careful control of moisture and temperature of your in-situ concrete during curing is an essential part of quality control and quality assurance of your concrete structure. Proper curing techniques will prevent in-situ concrete from drying, shrinking, and/or cracking. This ultimately affects the performance of your structure, particularly at the cover zone. Curing of concrete should occur as soon as it has been placed. It is also essential that monitoring of concrete curing conditions take place continuously for seven days. If the water evaporates from the concrete before it has attained its maximum strength, there will not be enough remaining to fully hydrate the cement and achieve the maximum compressive strength of concrete. This is especially true during extreme weather conditions because various environmental factors can affect the concrete slab. Thus, the strength development of your concrete can be compromised.
3 Techniques for Efficient Concrete Curing
Curing methods at a glance:
| Curing method | How it works | Best suited to | Watch out for |
|---|---|---|---|
| Ponding and immersion | Standing water held on the surface keeps the concrete saturated and at an even temperature | Flat work: slabs on grade, pavements, floors, lab test specimens | Needs a level surface and a water supply, not practical on vertical elements |
| Fogging and spraying | Fine mist raises humidity above the surface and slows evaporation | Flatwork in hot, dry or windy conditions, where plastic shrinkage cracking is the risk | Wetting and drying cycles can craze the surface, keep it continuous |
| Saturated wet coverings | Burlap, cotton mats or similar fabrics held wet against the surface | Slabs, decks and formed surfaces once the concrete will not mark | Must stay wet the whole period, a dried out covering does nothing |
| Impervious sheeting | Polyethylene film or curing paper seals moisture in | Most elements, including work that cannot be re-wetted | Can discolour exposed surfaces, lap and seal edges properly |
| Membrane-forming curing compound | A sprayed liquid forms a film that slows evaporation | Large areas, remote sites, work where wet curing is impractical | Must meet ASTM C309 or ASTM C1315, and must not be applied where a bonded topping will follow |
| Left-in-place forms | Formwork holds moisture against vertical and formed surfaces | Walls, columns, beams | Only cures the formed face, tops still need separate curing |
| Insulating blankets | Trap the concrete’s own heat of hydration | Cold weather placements, thin sections | Do not place until the surface will not be damaged, monitor for overheating in thicker sections |
| Steam curing and heated forms | Adds heat and moisture to accelerate early strength gain | Precast production, cold weather work on a schedule | High curing temperatures reduce long term strength, keep within the limits in your spec |
Many factors affect the rate at which water evaporates from freshly placed concrete. This includes air temperature, humidity, concrete temperature, and wind speed. As a result, there are many techniques to help concrete retain moisture at early ages. These methods can:
- Maintain the presence of water in the concrete during the early hardening period,
- Reduce the loss of water from the surface of the concrete, and
- Accelerate concrete strength gain by supplying heat and additional moisture.
The method (or combination of methods) chosen depends on factors such as availability of curing materials, size, shape, age of concrete, production facilities (in place or in a plant), aesthetic appearance, and economics. As a result, curing often involves a series of procedures used at a particular time as the concrete ages. The degree of concrete hardening will determine the timing of the procedure in order to avoid damaging the concrete surface.
1) Maintaining Moisture
Ponding and immersion
Typically, ponding cures flat surfaces like pavements and floors because the earth and sand surrounding the concrete surface can retain a pond of water. Ponding is an ideal method for preventing loss of moisture from the concrete; it is also effective for maintaining a uniform temperature throughout the concrete. Immersion of a finished concrete element is commonly used for curing test specimens.
Spraying and fogging
Spraying and fogging are useful when the ambient temperatures are well above freezing, and the humidity is low. Fog mist is applied through nozzles or sprayers to raise the relative humidity of the air over flatwork, thus slowing evaporation from the surface. Fogging works to minimize plastic shrinkage cracking. If sprinkling occurs at intervals, burlap or similar materials could prevent the drying of concrete between applications of water. Otherwise, alternate cycles of wetting and drying can cause surface cracking.
Saturated wet coverings
For the curing process, it is common to use wet coverings saturated with water such as burlap, cotton mats, rugs, or other moisture-retaining fabrics. The materials should be placed as soon as the concrete has hardened enough to prevent surface damage. They should remain constantly wet so that a film of water stays on the concrete surface throughout the curing period.
Left-in-place forms
Left-in-place forms usually provide satisfactory protection against moisture loss for formed concrete surfaces. The forms usually remain in place as long as the construction schedule allows. If the forms are wooden, they should retain moisture, especially during hot and dry weather.
2) Prevent Concrete Drying: Techniques to Reduce Moisture Loss
Covering concrete with impervious paper or plastic sheets
Impervious paper and plastic sheets can be applied on thoroughly wet concrete to reduce concrete drying, such as polyethylene film. This material is a lightweight, effective moisture retarder that is easy to apply. During placement, the concrete surface should be hard enough to prevent surface damage.
Applying membrane-forming curing compounds
Membrane-forming curing compounds function to retard or reduce the evaporation of moisture from concrete to prevent concrete drying. They can be clear or translucent and white-pigmented. White-pigmented compounds are recommended for hot and sunny weather conditions to reflect solar radiation. Curing compounds should be applied immediately after final finishing and must comply with ASTM C309 or ASTM C1315.
3) Accelerating Concrete Strength Gain
Live steam
Live steam and high-pressure steam are the two methods of steam curing. Accelerated curing should keep the internal concrete temperature below 158°F (70°C).
Heating coils
Heating coils usually work as embedded elements near the surface of concrete elements. Their purpose is to protect concrete from freezing during cold-weather concreting.
Electrical heated forms or pads
Precast concrete producers use electrical heated forms or pads primarily.
Concrete blankets
Concrete insulation blankets serve to cover and insulate concrete surfaces subjected to freezing temperatures during the curing period. When using concrete blankets, we must make sure that the concrete is hard enough to prevent surface damage.
Everything you need to know about cold weather concreting here
Curing for Compressive Strength of Concrete
Freshly mixed concrete normally contains more water than the requirement for cement hydration. However, excessive loss of water by evaporation can delay or prevent adequate hydration, especially on the surface of the slab. These techniques for retaining the moisture of in-situ concrete are therefore important for proper hydration so that concrete can gain sufficient compressive strength.
Curing directly influences the quality of your overall structure. Strength gain is rapid at early ages but continues more slowly for an indefinite period. Proper curing will increase durability, strength, water-tightness, abrasion resistance, volume stability, and resistance to freezing and thawing.
What Is Concrete Maturity?
Maturity is a non-destructive approach that lets you estimate the in-place compressive strength of concrete continuously, from its recorded temperature history. Adopting the maturity approach in your jobsite reduces reliance on cylinder break tests for schedule decisions such as formwork removal, allowing you to greatly optimize your schedule.
ASTMC1074, the standard practice for maturity, defines the method as “a technique for estimating concrete strength that is based on the assumption that samples of a given concrete mixture attain equal strengths if they attain equal values of the maturity index.”
In other words, maturity is a value that represents the progression of concrete curing. The maturity index value considers concrete temperature and curing time. As a result, mix calibration is required to implement this concept in a project. The goal of the calibration is to determine a relationship between maturity and strength for a specific mix.
A Sensor for Temperature and Maturity-Based Strength Estimates
The process of placing and curing concrete on-site requires precise temperatures to avoid damage to the structural integrity of the concrete. With SmartRock®, a wireless concrete temperature sensor, you no longer have to work from ambiguous wait times. SmartRock logs the in-place temperature history and sends it to your mobile device every 15 minutes through the free SmartRock app, which uses that history to estimate in-place strength with the maturity method (ASTM C1074) once a strength-maturity relationship has been established for the mix.
This wireless sensor allows team members to work efficiently without worrying about protruding wires or searching for them under heating blankets when relying on external data loggers. The sensor is fully embedded in the concrete and secured on the rebar within the formwork. SmartRock continuously monitors the effect of ambient temperatures and the external environment on your in-situ concrete. This makes it easier to control concrete curing and ensure optimal conditions for the gain of compressive strength of concrete. In addition, real-time results allow contractors to optimize the heating process, decrease energy costs, and save time in their project schedule. This is possible by knowing when concrete has gained sufficient strength for subsequent construction operations, such as formwork removal or post-tensioning.
Read how S&F Concrete Contractors’ used SmartRock to monitor concrete curing
Concrete Curing FAQ
How long does concrete need to cure?
Seven days is the common minimum for concrete made with ordinary portland cement in moderate conditions. The requirement most specifications actually set is 70 percent of the specified compressive strength, and seven days is the rule of thumb for reaching it. Cold weather, high supplementary cementitious material contents and thin sections all push the period longer, while warm conditions and accelerating admixtures shorten it, which is why measuring the in-place temperature history is more reliable than counting days.
What is the best temperature for curing concrete?
Concrete hydrates well when the in-place temperature stays roughly between 50°F and 75°F (10°C and 24°C). Below about 40°F (5°C) hydration slows sharply and can effectively stop, so strength gain stalls. Above roughly 90°F (32°C) the concrete gains early strength quickly but ends up weaker and less durable at 28 days and beyond, so hot weather curing is about holding the temperature down, not just keeping the surface wet.
Does curing concrete longer make it stronger?
Curing longer does not push concrete past its design strength, but stopping too early permanently caps what it can reach. Once the concrete has dried out, the unhydrated cement in it cannot react again simply by getting wet later, so the strength that was lost during the dry period is not recovered. The practical answer is that extra curing days buy durability and surface quality more than headline strength.
What happens if concrete is not cured properly?
Poorly cured concrete loses compressive strength, cracks from plastic and drying shrinkage, and ends up with a weak, dusty, permeable surface layer. The damage concentrates in the cover zone, which is the part of the element that protects the reinforcement, so poor curing shortens service life as well as reducing strength.
How do you cure concrete in cold weather?
Protect the placement so the concrete’s own heat of hydration is retained, using insulating blankets, heated enclosures or heated forms, and keep the concrete above the minimum temperature in your specification for the required protection period. Never place concrete on frozen ground, snow or ice, and monitor the in-place temperature rather than the air temperature, because the two diverge quickly under blankets.
**Editor’s Note: This post was updated for accuracy and comprehensiveness in October 2026.
