With little new construction going on because of the lack of a long-term highway funding bill, pavement preservation has become a priority for most agencies and municipalities. This is an area where concrete overlays are showing great promise.
“Concrete overlays have been around for a while, but within the last seven to eight years in particular, we’ve seen a tremendous growth in the use of the technology,” says Bill Davenport, vice-president of communications at the American Concrete Pavement Association (ACPA). “The downturn in the economy has played a part in that. Agencies are required to do more with less. They don’t have the money to do everything they’d like to do or everything they need to do, so that’s where the concrete pavement overlay comes into play.”
There are several types of concrete overlays that fall into two categories, bonded or unbonded. Within these categories, overlays are placed over distressed asphalt, concrete or composite pavements. One of the most common applications is bonded concrete over asphalt. In these applications, generally, the top 2 to 5 inches of the asphalt wearing course is milled off and replaced with concrete. The thin concrete overlay goes down quickly in comparison to complete road replacement, which allows the road to be opened to traffic much quicker.
“As an industry, we’re trying to educate agencies and contractors about the benefits of concrete overlays, as well as make them aware of potential applications,” Davenport says. ACPA is working through its staff engineers, affiliated associations and the National Concrete Pavement Technology Center to provide information and technical assistance but Davenport says there’s still work to be done. One example: the questions raised during a recent ACPA concrete overlay webinar. “They underscored the point that we still need to get the information out there on how to take advantage of concrete overlay technology, where the overlays can be used and the keys to building them right,” he says.
Stringless technology can play a big part in concrete overlays, making them easier to construct. A paver can use computerized electronic guidance systems and laser technology to control overlay thickness and smoothness and make adjustments as it moves along. “Stringless technology is taking hold with many contractors, as it makes the work site safer and helps improve final smoothness results when applied correctly,” Davenport says. “As we move forward, it is going to increase production and reduce some of the inconvenience to motorists.”Roller compacted concrete
Although not a new technology, roller compacted concrete (RCC) is still new to many people. It started out as a specialty product placed by specialty contractors, but there has been growing interest in its use in different applications, including turning lanes, low-volume streets and roads, parking lots, and also in limited highway applications such as on shoulders.
