Concrete Curing: Techniques for Strength and Durability

Learn the steps involved with the concrete curing process. Avoid costly repairs down the line by ensuring you know about proper concrete preparation and installation!
Jimmy Soldatos
Jimmy Soldatos
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Last Update:
January 10, 2023

If you're going to use concrete for your new driveway or patio, you should know about the curing process. In this post, we'll go over what the curing process is, why it's important, and tips for taking care of your new driveway or patio in its first week.

Concrete Curing Process: Techniques for Strength and Durability

Curing is the process of controlling the rate and extent of moisture loss from concrete during cement hydration. It may be either after it has been placed in position (or during the manufacture of concrete products), thereby providing time for the hydration of the cement to occur. 

Since the hydration of cement takes time, (days, and even weeks rather than hours) curing must be done for a reasonable period of time if the concrete is to achieve the most potential strength and durability. 

Curing is designed primarily to keep the concrete moist, by preventing the loss of moisture from the concrete during the period in which it's gaining strength. 


How does concrete curing work?

Curing may be applied in a number of ways and the most appropriate means of curing may be dictated by the site or the construction method.

However, many of these ways tend to be limited to large scale projects - road work, airports, bridges, etc. These objects need the absolute maximum care in order to achieve the highest possible concrete strength, and thus employ these expensive and tedious practices.

Residential projects, while unable to benefit from these processes, can also achieve high quality with proper care in just the first seven days after pouring. This is also where the difference between a properly reinforced slab and a poorly reinforced one lies. 

A thin slab with small, widely spaced out rebar will show severe contraction and crack much sooner than one reinforced with thicker, more tightly spaced rebar, while concrete slabs reinforced evenly with synthetic or metal fibers will fare even better. Even if the slab does not crack visibly in the first days, higher contraction rate will significantly lower its overall lifespan.

Since moisture loss is inevitable, it's of utmost importance to moisten the concrete slab as much as possible, and as consistently as possible. The less drying out in those first 7 days, the better. The industry offers many solutions for higher end projects, such as thick plastic sheets and membrane forming curing compounds, but even at the residential level, proper curing is possible when concrete is watered or moistened consistently. 


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Why is curing concrete important?

Curing concrete is essential to ensuring its durability and strength. Correct curing allows concrete to harden properly and reach its full strength potential, making it more resistant to cracking, shrinkage, and other issues that can compromise its structural integrity. Without adequate curing, concrete can weaken over time, leading to costly repairs and potential safety hazards. Additionally, curing can improve the concrete's resistance to the elements, such as freeze-thaw cycles and exposure to chemicals. By taking the time to properly cure concrete, you can ensure that their structures are strong and durable, with a longer lifespan and lower risk of structural failure.

How to Cure Concrete

Curing concrete is essential to ensure it achieves its maximum strength and life expectancy, so it's important to know how to cure concrete correctly. Here are a few ways to cure concrete.

Step 1: Maintain Moisture

Maintaining moisture during the concrete curing process is crucial to ensure the concrete sets correctly and retains its strength and durability. One of the most common methods of maintaining moisture is through water curing, where water is sprayed or ponded on the concrete surface. Alternatively, wet coverings like burlap, sand or wetted polyethylene sheets can be used to retain moisture. Another method is to use a curing compound that forms a membrane over the concrete surface to prevent moisture loss. Whichever method is chosen, it is essential to ensure that the concrete remains hydrated to avoid shrinkage and cracking, resulting in a strong and durable structure.

Step 2: Reduce Loss of Water

Reducing water loss during the concrete curing process is equally important to maintain its strength and durability. Excessive water loss through evaporation can cause shrinkage cracks, weakening the concrete's structural integrity. To reduce water loss, protective covers like plastic sheeting or temporary windbreaks can be used. This prevents moisture from evaporating and reduces the risk of cracks. Additionally, keeping the concrete surface damp and misted with water can also prevent rapid evaporation. By reducing water loss during the curing process, you can ensure that the concrete hardens properly, resulting in a strong and long-lasting structure.

Step 3: Accelerate Strength Gain

Accelerating strength gain during the concrete curing process is particularly useful when time is a constraint. One method is to increase the concrete's temperature by steam curing, which speeds up the curing process. Additionally, chemical admixtures such as calcium nitrite or calcium chloride can be added to the mix to promote early strength gain. However, it is essential to be cautious about using too much of these admixtures, as they may compromise the concrete's long-term durability. By accelerating strength gain, you can ensure that the concrete hardens quickly and is ready for use in a shorter amount of time.

Techniques for Curing Concrete

Working with concrete is a challenge that requires expertise and skill. Many projects involve properly curing concrete, so it's important to understand the necessary techniques for this process. 

Wet curing

Wet curing is a popular technique used to cure concrete and involves keeping the concrete surface moist for an extended period. This method is particularly useful for large concrete surfaces or in areas with high temperatures and low humidity, where water loss is rapid. Wet curing is typically done using a combination of wet coverings like burlap or sand and water curing, where water is sprayed or ponded on the surface. This technique helps retain moisture and prevents the concrete from drying out, ensuring that it sets correctly and attains its desired strength and durability. By utilizing wet curing, you can ensure that your concrete structures last longer and remain strong and stable over time.

Membrane Curing

Membrane curing is another popular technique used to cure concrete, particularly for smaller surfaces or in areas with lower temperatures. This method involves applying a liquid membrane-forming compound to the concrete surface, which acts as a barrier to moisture loss. The membrane prevents the concrete from drying out and allows it to cure in a controlled environment. This technique is particularly useful for projects where water curing or wet coverings are impractical, such as in high-traffic areas or in areas with limited access. Membrane curing is an efficient method that helps ensure that the concrete sets correctly and achieves its maximum strength and durability.

Chemical Curing

Chemical curing is a popular technique used to accelerate the concrete curing process by adding chemical admixtures to the mix. These admixtures can improve the concrete's strength, durability, and early strength gain. Calcium chloride is a common admixture used for this purpose, as it accelerates the concrete's early strength gain. However, it is important to be cautious while using chemical admixtures as overuse can lead to a decrease in the concrete's long-term durability. Chemical curing is particularly useful in cold weather conditions, where the concrete curing process slows down, and builders need to ensure that the structure attains its desired strength and durability in a shorter time.

Factors Affecting Concrete Curing

Concrete curing is a process that must be carefully controlled to ensure the best results. Many factors can affect concrete curing, such as temperature, humidity, air content, and the type of cement used. When these conditions are not met correctly, the resulting product may not meet industry standards or your specifications. Here are top three factors that affect concrete durability. 

Temperature

Temperature plays a significant role in the concrete curing process, and extreme temperature variations can negatively impact the concrete's strength and durability. High temperatures can cause the concrete to dry out too quickly, leading to shrinkage and cracking, while low temperatures can slow down the curing process and prevent the concrete from achieving its maximum strength. Builders need to maintain the concrete temperature between 50-90°F for proper curing. When temperatures are too high, water curing or wet coverings can be used to retain moisture and prevent evaporation. Similarly, when temperatures are too low, insulation or heating can be used to keep the concrete temperature within the required range.

Moisture

Moisture is crucial to the concrete curing process and plays a vital role in the concrete's strength and durability. When the concrete is poured, it needs to be properly cured to allow it to attain its desired strength. However, if the concrete dries out too quickly, it can lead to shrinkage and cracking, compromising the structure's long-term durability. On the other hand, if the concrete is too wet, it can lead to weaker concrete and poor surface quality. Maintaining the correct moisture levels during curing is essential to ensure that the concrete sets correctly and attains its maximum strength and durability.

Time

The time taken for concrete to cure plays a significant role in its strength and durability. According to the American Concrete Institute, concrete gains 90% of its strength within the first 28 days of curing. However, the concrete continues to gain strength over time, with some concrete structures becoming stronger even after 50-100 years. Builders need to allow the appropriate curing time to ensure that the concrete attains its maximum strength and durability. Rushing the curing process or placing heavy loads on the concrete before it is fully cured can weaken the structure and lead to cracking. Proper curing is essential for ensuring long-lasting and durable concrete structures.

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