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Concrete Maturity Calibration
Build a maturity equation for your mix from your own cylinder breaks and EXACT temperature data.
The EXACT Portal estimates in-place concrete strength from temperature data, using a maturity equation calibrated for your mix. This guide shows how to build that equation from your own cylinder breaks.
You set up an Element to record the temperature of two cylinders with EXACT probes in them, break the rest of the cylinders at set ages, and enter the results. The Portal works out the maturity at each break and generates the equation.
Before you begin
- Access to the EXACT Portal, with permission to create Elements and Mixes
- An EXACT Logger with two free inputs, and two 0.75 m (2.5 ft) probes
- For a LoRa Logger, a working Relay within 300 m (1,000 ft) of the Logger
- Moulds and concrete for at least 17 cylinders of the mix you're calibrating
- A curing room or curing box, and a compression testing machine to break the cylinders
In the screenshots, numbered marks show where to click for each step.
Set up the calibration Element
The Element records the temperature of the two probed cylinders. Give it a project of its own, such as Calibrations, so it stays apart from your production pours.
Create the Element
Select Create Element in the top-right corner of the Portal.
On the Information tab, enter an Element Name, such as Calibration Mix followed by the date.
The Information tab of a new Element. Under Project, select Create New.
If you already have a project for calibrations, select it instead and skip the next step.
Enter a Project Name, such as Calibrations.
Set Monitor Start (pour) to the date and time you'll cast the cylinders.
Set the Duration to cover every break you plan to make. It becomes the Element's monitoring period.
Add the Logger
Select the Hardware tab.
Select Add Device.
Choose the Logger you'll use for the calibration.
Under Show, select the two inputs you'll connect the probes to.
Under Input Label, rename those two inputs Cylinder 1 and Cylinder 2.
Select Save at the bottom of the page.
Cast, monitor and break the cylinders
Two of the cylinders hold EXACT probes and record the temperature history of the mix. You break the rest at set ages and record their strength.
Plan the breaks
Plan at least five break times, centred on the age at which you expect the mix to reach its target strength. For example, if your target is 30 MPa at 24 hours, break two cylinders at each of 16, 20, 24, 28 and 32 hours.
More cylinders and more break times give a more accurate, reliable equation, so cast more than 17 and break at more than five times if you can. Whatever you cast, keep two cylinders for the probes.
Cast and monitor the cylinders
Connect two 0.75 m (2.5 ft) probes to the Logger inputs you named Cylinder 1 and Cylinder 2.
A Logger with two probes connected. Cast at least 17 cylinders.
Before you cover them, set two cylinders aside for the probes.
Embed one probe in each of those two cylinders, as close to the centre as possible.
The two probed cylinders, each with its probe lead coming out through the lid. Place the two probed cylinders, the Logger and all the other cylinders in the curing room or curing box, such as an EXACT match-curing chamber.
EXACT match-curing chambers: the EM1 (left) and the EM3 (right).
Break the cylinders
At each break time, break two cylinders.
Record the date, time and strength of each break. Record the time to the minute: the margin of error is minutes, not hours.
Work out the average strength of the two cylinders. This is the strength you enter for that break time.
Important
If the two strengths differ by more than 10% of their average, break a third cylinder and use the average of all three, as ASTM C1074 requires.
Example break record
| Cylinder 1 | Cylinder 2 | |
|---|---|---|
| Date | Jul 31/23 | Jul 31/23 |
| Time | 4:09 PM | 4:17 PM |
| Strength | 752 PSI | 814 PSI |
The two strengths are 62 PSI apart, 8% of their 783 PSI average, so no third break is needed. The strength to enter for this break time is 783 PSI.
Generate the maturity equation
Enter your break results in the Portal. It works out the maturity of the probed cylinders at each break time and generates the equation.
Create the mix
Select Concrete in the top menu.
Select Mixes.
Select Create Mix.
Create Mix sits above the list of concrete mixes. Enter a Label for the mix. A Description is optional.
The Create Concrete Mix page. Select Create.
Calibrate from your Element
Select Calibrate Maturity From an Element.
In the Select Elements window, select the checkbox next to your calibration Element.
The Select Elements window, with the calibration Element selected. Select Confirm.
Set up the equation
Enter a Label for the equation.
Under Unit Preference, select MPa or PSI.
Under Maturity Method, select Temperature-Time Factor (Nurse-Saul) or Equivalent Age (Arrhenius).
Optionally, enter a Datum temperature in °C.
Under Inputs (probes), select Cylinder 1 and Cylinder 2.
The Portal averages the inputs you select. You can select up to three.
The probe inputs, the start of the data to use, and a preview of the selected inputs. Under Use Data Starting From, enter the Start Date and Start Time when the probes went into the concrete-filled cylinders.
Enter the break results
For each break time, enter the Age in hours and the average Strength.
The Portal calculates Maturity for each row from the probe data. Leave Override empty: it's for entering your own maturity values when EXACT didn't record the cylinder temperatures. The Portal accepts as few as two results, but enter every break time.
If you need more rows, select ADD 5 ROWS or ADD 50 ROWS.
Check that the graph beside the table looks logical: strength should rise as maturity increases, with no point far off the curve.
The strength graph for the results above. The points sit close to the fitted curve.
Finish the equation
Enter a Safety Factor, or leave it at 0. The Portal subtracts it from every estimated strength.
Optionally, set a Strength Range. The Portal only displays estimated strengths inside it. You can set a minimum, a maximum, both or neither.
Under Testing, enter a value in TTF (Temperature-Time Factor) and check the Estimated Concrete Strength it gives.
For example, the equation shown gives 783.43 PSI at a TTF of 200, close to the 789 PSI measured at a maturity of 202.5.
Test the equation, then save it. Select Save.
Done. The maturity equation is saved with the mix.
Troubleshooting
The calibration Element shows no temperature data
Check that the probes are connected to the Logger inputs you named Cylinder 1 and Cylinder 2 on the Element's Hardware tab. For a LoRa Logger, check that a working Relay is within 300 m (1,000 ft). A LoRa Logger that shows offline is usually out of a Relay's range.
My last break is after the end of the Element's monitoring period
Extend the Element's Duration. The Logger keeps recording after an Element ends, so no readings are lost.
The two cylinders from one break time don't agree
If their strengths differ by more than 10% of their average, break a third cylinder and use the average of all three (ASTM C1074).
A point on the strength graph sits far from the curve
This is usually a typing error, or a break time recorded to the hour instead of the minute. Check the Age and Strength in that row against your break record.
Getting help
Contact EXACT Technology support with the mix label and the name of your calibration Element.
Concrete Maturity Calibration
Build a maturity equation for your mix from your own cylinder breaks and EXACT temperature data.
The EXACT Portal estimates in-place concrete strength from temperature data, using a maturity equation calibrated for your mix. This guide shows how to build that equation from your own cylinder breaks.
You set up an Element to record the temperature of two cylinders with EXACT probes in them, break the rest of the cylinders at set ages, and enter the results. The Portal works out the maturity at each break and generates the equation.
Before you begin
- Access to the EXACT Portal, with permission to create Elements and Mixes
- An EXACT Logger with two free inputs, and two 0.75 m (2.5 ft) probes
- For a LoRa Logger, a working Relay within 300 m (1,000 ft) of the Logger
- Moulds and concrete for at least 17 cylinders of the mix you're calibrating
- A curing room or curing box, and a compression testing machine to break the cylinders
In the screenshots, numbered marks show where to click for each step.
Set up the calibration Element
The Element records the temperature of the two probed cylinders. Give it a project of its own, such as Calibrations, so it stays apart from your production pours.
Create the Element
Select Create Element in the top-right corner of the Portal.
On the Information tab, enter an Element Name, such as Calibration Mix followed by the date.
The Information tab of a new Element. Under Project, select Create New.
If you already have a project for calibrations, select it instead and skip the next step.
Enter a Project Name, such as Calibrations.
Set Monitor Start (pour) to the date and time you'll cast the cylinders.
Set the Duration to cover every break you plan to make. It becomes the Element's monitoring period.
Add the Logger
Select the Hardware tab.
Select Add Device.
Choose the Logger you'll use for the calibration.
Under Show, select the two inputs you'll connect the probes to.
Under Input Label, rename those two inputs Cylinder 1 and Cylinder 2.
Select Save at the bottom of the page.
Cast, monitor and break the cylinders
Two of the cylinders hold EXACT probes and record the temperature history of the mix. You break the rest at set ages and record their strength.
Plan the breaks
Plan at least five break times, centred on the age at which you expect the mix to reach its target strength. For example, if your target is 30 MPa at 24 hours, break two cylinders at each of 16, 20, 24, 28 and 32 hours.
More cylinders and more break times give a more accurate, reliable equation, so cast more than 17 and break at more than five times if you can. Whatever you cast, keep two cylinders for the probes.
Cast and monitor the cylinders
Connect two 0.75 m (2.5 ft) probes to the Logger inputs you named Cylinder 1 and Cylinder 2.
A Logger with two probes connected. Cast at least 17 cylinders.
Before you cover them, set two cylinders aside for the probes.
Embed one probe in each of those two cylinders, as close to the centre as possible.
The two probed cylinders, each with its probe lead coming out through the lid. Place the two probed cylinders, the Logger and all the other cylinders in the curing room or curing box, such as an EXACT match-curing chamber.
EXACT match-curing chambers: the EM1 (left) and the EM3 (right).
Break the cylinders
At each break time, break two cylinders.
Record the date, time and strength of each break. Record the time to the minute: the margin of error is minutes, not hours.
Work out the average strength of the two cylinders. This is the strength you enter for that break time.
Important
If the two strengths differ by more than 10% of their average, break a third cylinder and use the average of all three, as ASTM C1074 requires.
Example break record
| Cylinder 1 | Cylinder 2 | |
|---|---|---|
| Date | Jul 31/23 | Jul 31/23 |
| Time | 4:09 PM | 4:17 PM |
| Strength | 752 PSI | 814 PSI |
The two strengths are 62 PSI apart, 8% of their 783 PSI average, so no third break is needed. The strength to enter for this break time is 783 PSI.
Generate the maturity equation
Enter your break results in the Portal. It works out the maturity of the probed cylinders at each break time and generates the equation.
Create the mix
Select Concrete in the top menu.
Select Mixes.
Select Create Mix.
Create Mix sits above the list of concrete mixes. Enter a Label for the mix. A Description is optional.
The Create Concrete Mix page. Select Create.
Calibrate from your Element
Select Calibrate Maturity From an Element.
In the Select Elements window, select the checkbox next to your calibration Element.
The Select Elements window, with the calibration Element selected. Select Confirm.
Set up the equation
Enter a Label for the equation.
Under Unit Preference, select MPa or PSI.
Under Maturity Method, select Temperature-Time Factor (Nurse-Saul) or Equivalent Age (Arrhenius).
Optionally, enter a Datum temperature in °C.
Under Inputs (probes), select Cylinder 1 and Cylinder 2.
The Portal averages the inputs you select. You can select up to three.
The probe inputs, the start of the data to use, and a preview of the selected inputs. Under Use Data Starting From, enter the Start Date and Start Time when the probes went into the concrete-filled cylinders.
Enter the break results
For each break time, enter the Age in hours and the average Strength.
The Portal calculates Maturity for each row from the probe data. Leave Override empty: it's for entering your own maturity values when EXACT didn't record the cylinder temperatures. The Portal accepts as few as two results, but enter every break time.
If you need more rows, select ADD 5 ROWS or ADD 50 ROWS.
Check that the graph beside the table looks logical: strength should rise as maturity increases, with no point far off the curve.
The strength graph for the results above. The points sit close to the fitted curve.
Finish the equation
Enter a Safety Factor, or leave it at 0. The Portal subtracts it from every estimated strength.
Optionally, set a Strength Range. The Portal only displays estimated strengths inside it. You can set a minimum, a maximum, both or neither.
Under Testing, enter a value in TTF (Temperature-Time Factor) and check the Estimated Concrete Strength it gives.
For example, the equation shown gives 783.43 PSI at a TTF of 200, close to the 789 PSI measured at a maturity of 202.5.
Test the equation, then save it. Select Save.
Done. The maturity equation is saved with the mix.
Troubleshooting
The calibration Element shows no temperature data
Check that the probes are connected to the Logger inputs you named Cylinder 1 and Cylinder 2 on the Element's Hardware tab. For a LoRa Logger, check that a working Relay is within 300 m (1,000 ft). A LoRa Logger that shows offline is usually out of a Relay's range.
My last break is after the end of the Element's monitoring period
Extend the Element's Duration. The Logger keeps recording after an Element ends, so no readings are lost.
The two cylinders from one break time don't agree
If their strengths differ by more than 10% of their average, break a third cylinder and use the average of all three (ASTM C1074).
A point on the strength graph sits far from the curve
This is usually a typing error, or a break time recorded to the hour instead of the minute. Check the Age and Strength in that row against your break record.
Getting help
Contact EXACT Technology support with the mix label and the name of your calibration Element.