#### How Can Temperature-Controlled Specimens Be Compared to My Structure?

Calculating the in-place temperature into a maturity age enables a comparison with the concrete specimens done from the concrete lab. With the in-place temperature of the structure it is possible to calculate its maturity age (clock time * temperature). Then, the calibration curve is used to determine the relation between a maturity age and the compressive strength. For every new temperature measured, a new maturity age can be calculated – and thereby a new and increased strength can be estimated.

#### Why Do I Need a Concrete Calibration Curve?

A concrete calibration curve is used to have the relation between maturity age and the compressive strength. Concrete sensor solutions will not be able to estimate the strength without the calibration curve.

#### For How Long Is My Concrete Calibration Valid?

Theoretically, the concrete calibration would be valid as long as the concrete mix design or materials going into the concrete mix remain the same. But in the real world, a material supplier might change, the material provided by the same supplier might be different, the mixing machine may change in tolerances etc. Therefore, it makes sense to set up a running schedule for validating the concrete mix calibration. This could be for XX amount of concrete used or one time every second month or so.

Some clients of Maturix use this calibration validation to extend the calibration curve data set with more data. If they don’t exceed 10% difference, then they will just count as part of the natural daily variations you have when concrete is mixed. If differences between the previously done calibrations or the fitted curve exceeds 10%, it is recommended to redo the calibration curve.

#### How Reliable Is the Method?

The maturity method has over many decades shown great reliability. The biggest challenge experienced when you are new to sensors and maturity is to make the (1) correct calibration curve and (2) valid strength comparison. When this is in place, most people will have a good experience with the reliability of the strength estimations.

##### Correct Calibration Curve

One of the most common mistakes is not measuring the correct maturity age, when making the compression test to type into Maturix or a similar program. Typing in either clock hours or just rough numbers on the maturity age will have the potential impact of wrong strength estimations. The reason is that the correlation between the maturity age and compressive strength will be wrong. Maturix and other maturity systems won’t be able to calculate better than the data provided. A key is therefore to ensure a correct maturity age during the compression tests.

##### Valid Strength Comparison

Another common mistake is a wrong estimation of the in-place strength using sensors in comparison with break tests. The reason for this is often differences in curing conditions. This is described in section “2. Cubes/cylinders risk to show wrong results due to curing conditions”.

Some key limitations and requirements for making a reliable estimation of maturity strength using the concrete method concrete maturity are: