While being an interesting concept, the equivalent age of concrete, in itself, is not a useful engineering measurement of concrete. In order to calculate the compressive strength (or other properties of concrete, such as tensile or flexural strength, which are all intrinsically linked to the concrete’s maturity) this must be combined with information about the concrete’s strength gain. This information is captured during the calibration process, and once strength data for a given mix has been produced, a curve can be generated which relates the equivalent age of the samples with the compressive strength. This is known as the “strength-maturity relationship”, and is unique for each concrete mix design.
Several functions are available through the ConcreteDNA platform to model the strength-maturity relationship. These are the logarithmic function, hyperbolic function, and exponential function.
To produce the curve, an optimisation of the parameters is performed for each of the functions, using least-squares regression. The function with the most optimal fit (as determined using the standard error of each) is then selected as the strength-maturity relationship for that mix. At the discretion of the user, it is also possible to add safety factor (either as a % of in MPa).
The strength-maturity relationship is then uploaded to the platform alongside the mix details (name, design strength, etc), where it can be assigned to a concrete pour to begin calculating the compressive strength.