• Purchasing Notes
• Applications
• Features & Benefits
• Product Information
• Specifications

M-Meter™

Measures the developing strength of maturing concrete (ASTM C-1074 &C-918).

Purchasing Notes:

• Consumables: M-M-3009 Temperature Sensor

Applications:

• Premature Form Stripping in cold weather can be avoided.

• Excessive summer heat exposure is controlled.

• Loading, prestressing or post tensioning as well as lifting and/or form removal can be performed safely

• Optimum scheduling of form removal, prestressing, post tensioning, and highway loading.

• Artificial heating and cooling of concrete is minimized

• Rework due to concrete not fully cured is reduced.

Features & Benefits:

• Premature form stripping in cold weather can be avoided. Excessive summer heat exposure is controlled. Loading, prestressing or post tensioning as well as lifting and/or form removal can be done safely.

• Large difference in concrete strength caused by variations in temperature during curing, can be eliminated and uniformity of concrete strength achieved. Maturing concrete strength can be monitored continuously, and documented.

• Optimum scheduling of form removal, prestressing, post tensioning and highway loading achieved. Artificial heating or cooling minimized. Rework due to concrete not being cured to specified strength reduced. Costly cylinder testing reduced.

The M-Meter™ Maturity System is a six-channel microprocessor based instrument that integrates time and temperature for monitoring freshly poured concrete, on-site. The maturity number is calculated and updated every six minutes, and together with the lapsed time and temperature readings, are stored each hour. This information can be transferred to hard copy by a field printer (optional M-M-3010) attached to the M-Meter™. Battery capacity allows for up to 20 days of continuous operation.

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-channelM-Meter™ , the sensor showing the lowest maturity number indicates the area containing the least matured concrete.

Typical Application

A multi-level concrete building is under design and its construction is to be controlled with the M-Meter™ to meet performance specifications.

Laboratory tests indicate that the concrete specified is of satisfactory quality. The maturity vs. strength relationship obtained during the lab tests is shown in the figure below.

To allow for unanticipated variations in the concrete properties, the contractor has decided that he will remove the forms when the concrete strength is at least 5% greater than the required 3500 psi, i.e., when the strength is 3675 psi. The figure below shows that this strength level will be reached when the maturity is 3600°C-Hr.

The M-Meter™ probes, therefore, should be inserted in the freshly placed concrete at critical locations and maturity values monitored. When the lowest maturity value reaches 3600°C-Hr, the forms can be removed.

Specifications:

M-M-3009 Sensor
10 K Ohm NTC Thermister with 10 ft. of 18 GA
STP-1 lamp cord
Temperature Range: -10°C to 80°C
Accuracy: ±0.2%

M-M-3010 Printer
Type Impact Dot Matrix - 6 x 8
Power Source - Rechargeable Battery