Breaking Down the Maturity Calibration
How to Calibrate Your Concrete Maturity in 5 Easy Steps
Simply put, maturity can be described as the area below the temperature curve. The goal of the maturity calibration is to determine a relationship between maturity and strength for a specific mix. This calibration can be used to determine the in-place strength of the concrete and untimely eliminate the use of field cured cylinders. In order to perform a maturity calibration, the ASTM C1074 standard must be followed.
The maturity calibration can be done in 5 easy steps:
- Make a minimum of 17 cylinders; 2 will be used for temperature monitoring while the other specimens will be used for compressive strength breaks. All cylinders must be cured together in a moist environment (ASTM C511).
- Select a minimum of 5 break times, for example 1, 3, 7, 14, 28 days. For each day, obtain the compressive strength of two cylinders, break a third cylinder if the results vary more than 10% from the average. Note the time of the breaks.
- At the time of the break, obtain the maturity value from the two cylinders that were used for temperature monitoring and make an average of the maturity.
- You now have a set of at least 5 data points each with a strength associated to a maturity value. Plotting those data points allows you to obtain a curve with a logarithm equation. Here is the formula for calculating the maturity of concrete:
- Validate your calibration curve by making a couple of additional cylinders on your next poor, compare the calculated strength obtained from maturity to the compressive strength obtained in the lab. Up to a 10% difference is acceptable.
There are multiple approaches to calculating maturity. In North America, the most popular method is the Nurse-Saul equation due to its simplicity. Keep in mind that the same principal can be applicable for tensile strength. For detailed information about each step consult the ASTM C1074 and for more information on maturity and its advantages, see the video below: