To estimate the concrete strength using the maturity method, you need to make a maturity calibration.
The aim of performing a maturity calibration is to find the relationship between time, temperature, and strength for each concrete mix design that you intend to use. This relationship is called the strength-maturity relationship and is established in a laboratory.
Once you have found the strength-maturity relationship for your specific concrete mix, you can use this to estimate the in-place strength of the concrete at your job site.
The procedure for making a proper maturity calibration is well described in the ASTM C1074 standard practice. We recommend you to read this and become familiar with all the details on how to make a successful calibration.
How to Perform a Maturity Calibration
1. Prepare the samples
Prepare at least 15 samples so that you are able to perform tests at minimum five different test ages. Three samples are needed for each test age, two for the actual tests and the third in case the difference between the two first test results is higher than 10% from their average.
The samples must be prepared according to standard procedures for making and curing concrete test samples in the laboratory or in the field.
2. Embed temperature sensors
Embed temperature sensors in at least two of the samples. The sensors must be placed within ±15 mm of the center.
3. Connect data loggers or transmitters
4. Cure the samples
Once the samples have been prepared, cure all of them according to standard procedures and under the same conditions, e.g. in a water bath or moist room.
It is important to have the same curing conditions for all the samples in order to obtain a correct correlation between the strength and maturity.
5. Perform compression tests
For the first test age, break two samples and note down the compressive strength for each of them. Also note down the date and time. Finally, calculate the average strength for the samples.
6. Determine the maturity
Find the related maturity value at the time of the compression tests. When you have determined the maturity for each of the instrumented samples, calculate the average maturity of these.
7. Determine the strength-maturity relationship
You have now determined the strength-maturity relationship for your first test age. This consists of:
- The average compressive strength found through the break testing
- The average maturity found by calculating the maturity from the temperature history up until the time of the test
Now find the strength-maturity relationship for the remaining test ages by repeating the last three steps above.
(days at 20 °C)
Once you are finished with all the test ages, gather the results in a table. Each test age shows the correlation between the average compressive strength and the average maturity.
(days at 20 °C)
8. Create the maturity curve
Plot the maturity vs. strength for each test age and create the best fitting curve.
You can now use the maturity calibration to estimate the in-place strength of the concrete at your job site.
Read our Estimate In-field Concrete Strength with the Maturity Method article to learn more.
If you want to see a step-by-step explanation about how to make a maturity calibration using Maturix: