Tech Bytes
Pavement Research
By Jodi Richards
October 2004
Jodi Richards, Associate Editor
The Innovative Pavement Research Foundation (IPRF) is a non-profit created jointly by the ACPA (American Concrete Pavement Association), PCA (Portland Cement Association), and NRMCA (National Ready Mixed Concrete Association) to conduct applied research (see page 32).
According to IPRF cooperative programs manager and ACPA director of airports, Jim Lafrenz, the organization is working to develop a device called a maturity meter. Lafrenz describes this device as a “small computer chip that records the temperature of the concrete and the time since the chip was placed in the concrete.”
In other words, he says, “You have an electronic history of what we call the time temperature. And we can correlate that to the strength of concrete.”
Lafrenz says this data is critical because FAA uses the strength of concrete to determine when the pavement can be opened up to traffic. “The current criteria says that you have to wait until it’s at 550 lbs. per sq. inch flexual, or 14 days,” says Lafrenz. “If I’m doing a runway repair and I’m placing concrete and expecting to open to traffic the next morning, it’s hardly realistic to expect me to wait 14 days to put traffic on the pavement.”
This maturity meter allows workers to know what the strength is in the field beginning from the time of placement until it is to be opened to traffic. “It’s a real-time feedback test procedure that allows you to safely open pavement to traffic based upon the strength of the concrete,” adds Lafrenz.
The device, he says, is nothing more than a little computer chip. “They come in different sizes and colors, just like lollipops, but in essence it just records the temperature, history, and the time from the time of placement. You calibrate it in the laboratory with the concrete that you’re going to use to make the repair. So you insert the chip in the concrete in the field; then if you know the temperature time history, you can tell at what point in time it will be strong enough for traffic.
“It’s just a simple graphic solution to an age old problem.”
This is one of the newer research programs (one of 28) with which the IPRF is currently involved. Lafrenz expects the report will be available in a year.
