A Guide To Concrete Curing Times
Concrete curing simply refers to concrete drying and gaining strength and durability. The material must be given the appropriate time to cure as it will impact the properties, namely strength, once hardened. But, concrete curing times can vary depending on several factors.
Factors such as the concrete design mix, weather conditions, thickness and size of the pour can all impact the curing time.
At 2 Brothers Concrete & Pumping, we have a combined 25 years of experience in the industry. We are experts at what we do, providing efficient concrete production and pumping to domestic and commercial projects across the South Coast. Our knowledge of concrete and its curing times is unparalleled, and we bring this expertise to each project we work on. In this blog, we explain the factors that will impact curing time.
What is Concrete Curing?
Concrete curing is the hardening of the liquid concrete that has been poured. During this process, the material strengthens ready for use.
The process is a chemical reaction between water and cement particles. This is essential for the strengthening process, so there must be enough moisture in the mixture to facilitate this.
Curing is an exothermic process, meaning it releases heat. Therefore, it is imperative to manage the heat of hydration to prevent cracking.
Concrete curing typically has two stages: initial curing and strengthening, which can take between 24 and 48 hours, and long-term curing which will take an average of 28 days. However, these can be influenced by many factors.
Factors Affecting Concrete Curing Times
Concrete curing times are influenced by several factors, and each of these elements must be right for your concrete to cure with the needed strength and durability.
Concrete Mix Design
There are various concrete design mixes available, each with its own benefits and uses.
The difference between each type of mix is the ingredients used, more specifically, the ratio of ingredients.
As curing is the process of hydration, the amount of water in a mix will impact the curing time. If there is a lot of water, the curing time will be longer, as there is more water to evaporate.
Meanwhile, if there is less water in the mixture, there will be less moisture to evaporate. Therefore, the mixture will have a quicker curing time.
There are options to add additional ingredients, such as additives or admixtures. Of course, these will impact the curing time.
Accelerators, such as calcium chloride, can be added to speed up the hydration process, speeding up curing time. This is often used in colder weather when the environmental temperatures are low, which slows the curing time.
Additionally, you can add retarders, such as Lignosulfonates, which slow the hydration process down. These are often used in hot weather to prevent the concrete from curing too fast and cracking.
Weather Conditions
Temperatures and humidity will have an impact on the curing time.
If it is very hot, the moisture will evaporate quicker from the mixture, which might not allow enough time for the hydration process.
On the other hand, cold weather can slow the evaporation down, which can sometimes delay construction progress as the early strength gained is slower.
It isn't just temperature that affects concrete curing times. Wind and direct sunlight also influence it.
Wind can increase the speed of curing as it accelerates the rate at which water evaporates from the concrete surface. It can also have the opposite effect, as wind can cause a drop in temperature, potentially slowing down the hydration process.
As we all know, direct sunlight can feel warm, so when it hits the surface of concrete, it can significantly raise the temperature. This will accelerate the hydration process, making the curing time faster. This can cause a few issues as a faster process increases the risk of cracking. Also, the quicker evaporation disrupts the hydration process, which can cause weaker concrete.
Thickness and Size of Pour
As with anything that needs to dry, the thickness and size of the concrete layer will impact the concrete curing time.
Thicker concrete slabs will regenerate and retain more heat during the curing process. This helps maintain the necessary temperature for hydration, promoting faster strength gains.
Additionally, because of their mass, thicker slabs will cool down more slowly, which reduces the risk of cracking.
If you are pouring large amounts of concrete into one area, there are a few considerations that will need to be made.
As the mass of concrete will generate more heat, you will need to ensure cooling measures are in place to control the curing process - if it heats up too much and cures too quickly, the concrete could crack.
You will also need to ensure there is enough moisture in the mixture to deal with the higher temperatures and will need to allow for longer curing times.
Type of Cement
The type of cement used in your concrete design will also impact the concrete curing time.
This means you can somewhat control the curing process through the materials used within the concrete mix.
For example, you could use Rapid Hardening Cement, which contains tricalcium silicate, causing faster hydration and strength gain and speeding up curing time.
Alternatively, you could opt to use Low Heat Cement, which contains less tricalcium silicate and, therefore, produces less heat during the hydration process and slows the curing time down.
Best Practices for Concrete Curing
For optimal curing times that allow the concrete to gain the strength required for a project, you should follow several best practices.
Moisture Retention
The concrete curing process needs moisture, meaning it is important that you put measures in place to ensure the mixture retains water throughout the curing time.
You can do this by using wet coverings or curing compounds.
This is important because a lack of moisture will lead to cracking and weak concrete.
Temperature Control
Temperature control is critical during the curing process as it directly impacts the strength, durability and overall quality of the material.
When cold, you must retain heat and protect the moisture in the mixture from freezing. This can be done using insulating blankets, covers, heaters or heated enclosures.
If pouring concrete in hot weather, you need to ensure the mixture is kept cool. It is recommended that you use shade coverings and reflective coverings to protect the concrete from direct sunlight.
Let Our Experts Help
The concrete curing times can be complicated as there are a lot of factors to consider.
Our team members are experts when it comes to pouring and curing concrete, so can offer helpful advice for your project.
With years of experience and a range of projects under our belts, we will know what might impact the concrete curing time for your project and can work with you to find solutions to ensure a controlled process for a strong and durable process.
We understand the importance of the curing process and how it can impact the rest of your project, so when you enquire about our concrete and pumping process, we will take time to fully understand your project so that we can consider all influencing factors on the curing time and the desired strength and durability for your concrete. We will also take into consideration the project timeframe, as this will dictate the use of specialised aggregates or cement for faster or slower curing times.
Still not sure about concrete curing times? Don't worry! We know it can be confusing, so don't hesitate to get in touch with our concrete specialists today to get answers to your queries. Call us on 01489 552737 or complete our online contact form to request a callback.
Don't forget to check out our concrete jargon buster too!
