According to the American Concrete Pavement Association, for the time period of 2012 through 2017, concrete overlays on existing pavements made from concrete, asphalt or composites averaged 12.5 percent of the total concrete pavement volume in the U.S. And as reported in Equipment World, the increase in the use of these overlays has gone from about 4 percent 12 years ago to about 13 percent. The National Concrete Pavement Technology Center's "Guide Specifications for Concrete Overlays" states that around 75 percent of them are of the unbonded variety, which are typical when major rehabilitation work is necessary and are the best option for asphalt pavements in poor condition. The rest are bonded overlays, which are thinner and called upon more for minor work and preventative maintenance. https://tinyurl.com/y77cht5k