Theory
The maturity method is a technique for predicting strength based on the temperature history of the concrete. Strength increases as cement hydrates. The extent of the cement hydration depends on how long the concrete has cured and at what temperature. Maturity is a measure of how far the hydration has progressed.

There are two established maturity equations, and both equations conform to ASTM C-1074. The equation, developed by Arrhenius is used in the James M-3056 meter. The Arrhenius equation is more suitable when the temperature is outside the range given above and the maturity number is expressed as the equivalent age in hours referred to 20 C. The Arrhenius equation also recognizes that cement types vary with different energy activation levels. The mathematics of the Arrhenius equation is more complex but it gives more accurate strength predictions over a variety of cement types.

System
The James M-Meter™s are microprocessor based multi-channel instruments that measure the actual temperature of the maturing concrete with a disposable sensor inserted into the freshly placed concrete. Lapsed time is measured internally and integrated with the temperature reading to express the “maturity number” on the M-Meter™ display panel.

The maturity number is calculated every six minutes automatically (i.e. 10 “readings” per hour) and when the instrument is read the latest maturity number from each of the six channels is displayed in sequence. One reading per hour (i.e. every tenth reading) is stored in the nonvolatile memory. This reading consisting of maturity number, temperature, elapsed time in hours from the sensor connection and sensor identification. This information is available for later transfer to hard copy by a printer that can be attached to the M-Meter™.

Generally the sensors are inserted at the most critical points subject to the most temperature extremes. Using the multi-channel M-Meter™, the sensor showing the lowest maturity number indicates the area containing the least matured concrete.