Introduction to Concrete Maturity
During a construction project, it is very important to know the strength of concrete because it will determine when it is possible to walk on the surface, remove the form-work, or continue building the structure. The problem is that concrete strength can be hard to estimate, as the strength of the concrete does not always develop at the same speed. Temperature and weather conditions will affect how fast or slow the strength of a structure develops.
Concrete Maturity is a concept that relates temperature, time and strength development. In this article, we will explain what concrete maturity is, how it is calculated, and how this can be used as a method to estimate concrete strength.
What is Concrete Maturity?
Concrete Maturity represents the combination of time and temperature. It is calculated based on the temperature history of the structure by applying one of the maturity functions. In its essence, maturity is:
Maturity = time * temperature
The main concept about concrete maturity is that a specific value of maturity can be obtained with many different combinations of time and temperature. For example, the graphs below represent the temperature history of three different pieces of concrete. All of these have reached the same maturity of 100 °C-hours, but it took a different amount of hours to do so. This is because the temperature has been different throughout that period.
If you look at the first graph (Graph 1), you will see that the temperature is 20 °C and that it has been curing for 5 hours. This gives a maturity of 100 °C-hours.
If we compare this with Graph 2, you will see that the temperature is higher. Since the concrete temperature has been at 40 °C, it only took 2,5 hours for it to reach the same maturity of 100 °C-hours.
Looking at Graph 3, the temperature is the lowest of the examples at 10 °C, and in this case it will take 10 hours to reach the maturity of 100 °C-hours.
Temperature affects how fast the maturity develops. If the temperature is high, it will take less time to reach a certain maturity, compared to if the temperature is low.
Concrete maturity can be a tricky concept to grasp.
Below is an interactive graph showing two bars. They have the same maturity of 100 °C-hours, but you can change the temperature of Bar 1 to see the influence on the curing time.
- Bar 1 (orange): You can change the temperature
- Bar 2 (grey): Constant temperature of 20 °C
Try to change the temperature of Bar 1 by changing the number in the input field below. Observe what happens to the number of hours it requires to reach a maturity of 100 °C-hours.
Temperature has a large influence on the time it takes for a concrete structure to cure. The lower the temperature, the longer it takes – and the higher the temperature, the quicker it goes.
How Can You Use It?
Concrete maturity alone does not indicate how strong the concrete is. However, by using the Maturity Method, you can determine the relationship between maturity and the strength development.
The Maturity Method is an easy way to estimate the early-age strength development of a concrete mix. The main assumption of the Maturity Method is that if two samples of the same concrete mix have the same maturity, then they will also have the same strength – even if they were cured under different temperature conditions.
To use the Maturity Method you will need to perform a maturity calibration, which includes doing tests in a laboratory to find the relationship between the concrete maturity and the concrete’s strength. Once you know this relationship, you can estimate the strength of the in-place concrete by placing temperature sensors in the structure. You can find the maturity by looking at the temperature history measured by the temperature sensors, and then determine the in-place strength using the maturity calibration.
Benefits of Using the Maturity Method
During the past decades, the maturity method has proven to be one of the most reliable methods to estimate early in-place concrete strength. The method is simple and highly adaptable for different projects and needs. Some of the benefits are:
- Strength estimation in real-time
The use of the maturity method allows you to track the strength development of concrete in real-time. This will give you valuable information about how the concrete is curing.
- Better project planning
Changes in weather or temperature can make it challenging to predict when the concrete is strong enough to proceed to the next step. By using the Maturity Method, the risk of starting too early or too late is limited to a minimum, avoiding unnecessary delays and reducing product waste.
- Automatic documentation
Many of the workers’ hours are wasted every day on manual data collection and documentation. The strength estimation can be done much smarter by using maturity systems like Maturix. This will make all the calculations and create the documentation automatically, saving time and cutting costs on these labour intensive tasks.