How to make a maturity calibration​ using Maturix In-situ

Last update: 24/11/2021
Version:Maturix In-situ
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This guide is intended for users of Maturix In-situ.
The guide for Maturix Precast can be found here.

Before undertaking any calibration, please purchase and thoroughly read the ASTM C1074 – Standard Practice for Estimating Concrete Strength by the Maturity Method. Section 8 explains the procedure to develop the strength-maturity relationship.
You might benefit from reading the general maturity calibration guide on our website.

Before the calibration

Requirements:

  • Access to the Maturix In-situ Web Portal
  • Two Maturix transmitters and type K thermocouples
    • These must be visible under the “Device Manager” in the web portal
  • Sigfox coverage at the place of calibration

Preparations in the Web Portal

Step 1: Log in to the Maturix In-situ Web Portal at insitu.maturix.com with your user account

Step 2: Create a project for calibration purposes and add devices to it

Step 3: Then you need to create a cast under the project:

  1. Open the project you just created and click on Casts in the menu
  2. Click on New cast in the top right corner.
  3. In the pop-up:
    1. Give the cast a name, e.g. “Maturity Calibration”
    2. Click on Advanced Settings and choose the maturity function and settings you want to use for the maturity calculation
    3. Click on Create

Step 4: Now you need to set up the monitorings:

  1. Click Add monitoring on the cast you just created
  2. In the pop-up:
    1. Write e.g. “Maturity 1” under the Monitoring Description
    2. If you want, you can choose the device you intend to use under Planned Device (Optional)
    3. Click on Save changes
  3. Create another monitoring by following step 4-5, but name it e.g. “Maturity 2”

Step 5: Click on Start the monitoring and select the correct device/ensure that the correct device is chosen and click on Start

Prepare and Cure Specimens

Step 1: Prepare at least 15 specimens, where you embed the type K thermocouples in at least two of the specimens. The tip of the thermocouples must be placed within ±15 mm of the centre.

  • Once the specimens have been prepared, cure them according to standard procedures (e.g. ASTM C511) and cure all the specimens 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 specimens in order to obtain a correct correlation between the strength and maturity.

Step 2: Connect the thermocouples to the Maturix transmitters as soon as possible to start recording the temperature history.

Perform Break Tests

Perform compression tests at minimum five different test ages, e.g. after 1, 3, 7, 14, and 28 days. The specimens with the thermocouples embedded should be tested last to remain for maturity monitoring.

Step 1: At the first test age, break two specimens and compute the average strength. This improves the reliability of the results. Note down the compressive strength and at what time you did the break tests.

  • If the difference between the two tests is higher than 10% from their average, break the third specimen and use the average of the three.
  • If you obtain a low test result due to an obviously defective specimen, discard the low test result and use the average of the other two specimens.

Step 2: Open the Maturix In-situ web portal to find the calculated maturity:

  1. Open the project and click on Casts
  2. Click on the cast name, e.g. “Maturity Calibration”, to open the report
  3. Read the maturity by hovering the mouse over the lines on the graph. If you performed the break tests at 12:47, find the first maturity point at or just after 12:47. Note down the maturity values.
  4. Compute the average maturity index from Maturity 1 and Maturity 2 at the time of the break test.

You should now know the strength-maturity relationship from your first test age, which is consisting of the average strength (found through break tests) and the average maturity (read in the Maturix In-situ web portal).

Step 3: Do the above two steps (determining the average strength and average maturity) for the remaining test ages.

Create Maturity Curve

You should now have at least 5 data points, where each point is the correlation between the compressive strength and the maturity index. This can now be entered into the Maturix In-situ web portal for strength prediction.

  1. Click on Concrete Database in the menu and then click on Add concrete mix in the top right corner.
  2. Fill out the pop-up box:
    1. Concrete Name: Write the name of the concrete mix
    2. Maturity Function: Choose the maturity function and change the settings in the bottom (this should be the same as the ones set during the calibration)
  3. Add the five data points that you determined by writing the results for each test age in the fields and clicking “Add to dataset”
    • The software will automatically draw the curve showing the strength-maturity relationship
  4. Click Save – and you now have added the concrete mix

Validate Test Results

To validate the calibration and maturity curve, make some specimens during the next pour/batch and compare the strength predicted by Maturix with the compressive strength results obtained from laboratory break tests.

  • If the difference is more than 10%, you should perform a re-calibration and develop a new strength-maturity relationship for the concrete mix.
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