Learn more about the components - Concrete Maturity (ASTM C1074) Monitoring System (using RFID instead of wires)...
Introduction to Concrete Maturity - a detailed guide to using RFID to provide accurate concrete maturity data.
Concrete Maturity Testing in Michigan - February 2004 by Andrew J. DeFinis P.E. A white paper on Wireless Concrete Monitoring System. (PDF file: 4.6 MB) NEW White Paper!
Concrete Solutions - Summer 2003 Edition - by Robert Risser, Jr., Executive Director of Michigan Concrete Paving Association.
New Technology Puts Road Work in the Fast Lane - Reprint of article by David R. Miller, Associate Editor of CAM (Construction Association of Michigan)
Maturity Meters: A Concrete Success - a reprint from the October 2002 edition of FOCUS published by the Federal Highway Administration.
Deadlines are unavoidable in the construction industry. From the minute contracts are awarded, contractors can hear the ever-present ticking of an invisible clock. Construction firms that send projects into overtime risk their reputations for timely work and can even face financial penalties in some cases. Although all contractors endure these risks, they are particularly worrisome for road builders. In addition to any penalties that are spelled out in their contracts, tardy road builders also incur the wrath of the motoring public. Since even a single lane restriction on a major thoroughfare can impact thousands of motorists, road builders strive to finish these demanding projects ahead of schedule.
One of the biggest delays associated with road building is the time that it takes for concrete to cure firmly enough to support vehicular traffic. Tony Angelo Cement Company and MDOT are utilizing a new concrete maturity meter, distributed by Wake, Inc., to expedite this time-consuming step.
The Maturity Concept
"The maturity concept has been around for about 60 years," said Tim Stallard, concrete engineer for MDOT. "The technique allows us to predict the strength development of a given concrete mix design by monitoring temperature development. It wasn't very popular in the past because you needed to record the temperatures and calculate the values."
Engineers typically pour several beams or cylinders at the start of each project to determine the strength of the concrete mix. These samples are brought back to a laboratory and placed under either compressive or flexural stress until they break. Once a sample surpasses a preset strength, contractors can safely open the concrete to traffic. Since testing is an expensive proposition, tests are usually separated by a span of several hours. Because they do not know exactly when concrete will be strong enough, contractors are forced to divert traffic until sufficient strength can be demonstrated in a laboratory. Maturity testing was devised as a way to make traffic and reconstruction projects flow more smoothly be opening roadways precisely when they are ready.
One of the many drawbacks associated with maturity testing is the complicated task of detecting and recording the data that is needed to make accurate strength predictions. Most maturity meters use thermocouple wires to connect roadside data collectors with sensors that are embedded within the concrete.
"The thermocouple wires are easily damaged," said Stallard. "If a contractor wants to strip forms or does some grading near a paving job, the wires are in danger. If the wires get cut, you lose all of your information."
The system distributed by Wake replaces thermocouple wires with imbedded concrete sensors that use wireless technology to transmit thermal data to handheld PDAs. Software installed on the PDA automatically compares the thermal data against the strength curve of the concrete mix, allowing the precise strength of the concrete to be determined. The first full-scale test of the new technology took place during the recent reconstruction of Grand River Avenue from Novi Road to Beck Road.
The meters that were used on the Grand River project need to be placed vertically upright to be able to send a signal. Zip-ties were used to secure the sensors to tie-bars and they were placed at mid-depth in the nine-inch thick roadway, about two feet from the edge of metal, or the joint between the curb and the roadbed.
"The position allowed me to get a hand on them if there was a problem, instead of having to go into the center of the road," said Andrew DeFinis, project engineer for Tony Angelo Cement Company.
The signal from the meters can be read by the PDAs at depths of up to eight inches. Since they are placed at mid-depth, this allows them to be used on roadways with a thickness of up to 16 inches. Range extension tags allow for temperature monitoring at depths greater than eight inches for specialized paving applications.
Test cylinders were still utilized as a back up on the Grand River project, but the maturity meters have performed exceptionally well in their Michigan debut.
"This is a great planning tool," said DeFinis. "I could go out and take a reading. If it was close, I would be able to predict the strength myself. If it was a couple hundred PSI short, I could say, 'We'll have it in another two or three hours.' " Armed with these accurate predictions, DeFinis was able to schedule work more efficiently and complete the project faster. For more information about wireless concrete maturity meters, contact Wake at 1-800-588-6393 or send an e-mail inquiry to firstname.lastname@example.org.