Colorado rebuilt part of US 24 by reconditioning its old asphalt in place; the $5.7 million project avoided hauling in more than 40,000 tons of new base

Every road crew faces the same challenge when tearing up an old highway: tons of cracked, weathered asphalt with nowhere to go. On US Highway 24 in Colorado Springs, crews found a clever way to reuse the old pavement and save time and money by grinding it up and using the material in place, rather than hauling it away and bringing in new material. (cuts the redundant "to replace it") The Colorado Department of Transportation reported that crews reopened all lanes of US 24 between Constitution Avenue and Garrett Road on the evening of Saturday, Aug. 19, 2017, marking the end of a huge project in the works for a $5.7 million reconstruction job led by contractor Flatiron Constructors. The project shows how in-place asphalt recycling can work on a real-world, high-traffic highway project.

What in-place asphalt recycling means for a highway contract

Usually, a major highway reconstruction takes the form of a loop: break up the old road, haul the debris to a landfill or recycling center, then bring in new base material from a quarry by the truckload. Each step adds cost, emissions from transport vehicles, and traffic congestion in the construction area. On westbound US 24, CDOT milled the old asphalt pavement and reconditioned the roadway base before paving over it with new concrete pavement. This combination, a recycled asphalt base topped with a new concrete surface, is a recognized approach in highway engineering; a stabilized base built through full-depth reclamation can support either an asphalt or concrete top layer. The agency also used an on-site concrete batch plant during construction, which reduced the need for ready-mix trucks from an outside supplier.


US 24 rebuild by the numbers: material savings and speed

According to CDOT's own project release, by reprocessing the pavement on-site, the project saved over 40,000 tons of new base course material, which the agency estimates is roughly 1,600 loads that would not have had to make the trip. The work also moved quickly, with crews laying more than 14,800 cubic yards of concrete in under two weeks, all of it made at the on-site batch plant. Both directions of US 24 had been narrowed to one lane since late June while the westbound side was being reconstructed, so a quick turnaround was critical to traffic flowing over that corridor every day.

The technique used on US 24 has an official name: full depth reclamation, or FDR for short. The Federal Highway Administration defines it as a process in which an entire asphalt layer, along with a specified depth of the underlying material, is pulverized and mixed with a binding agent, such as cement or asphalt emulsion, and formed into a new stabilized base course. The process involves shaping, compacting, and paving over the reclaimed base course. The same federal guidance also states that full-depth reclamation can restore a pavement's structure without altering its width or footprint, and it can address issues such as cracking, rutting, and roughness that develop over time. A 2023 Federal Highway Administration technical brief, Asphalt Pavement Recycling Technologies (FHWA-HIF-23-036), found that methods such as full-depth reclamation and cold in-place recycling can be cost-effective and sustainable ways to rehabilitate roadways.

Why recycled road base saves money for drivers and taxpayers

For drivers, fewer material deliveries through a work zone can mean fewer disruptions on nearby streets. For taxpayers, reusing the material under the road instead of buying and hauling in new rock and gravel can cut costs because fuel, equipment hours, and disposal fees add up on a standard tear-out-and-replace project. Reclaiming full-depth pavement isn't an answer for every road. However, engineers study the existing pavement and underlying soil before recommending it, and some stretches of highway still require new construction. For a major commuter corridor like this section of US 24, recycling the old base made more sense.

CDOT's rebuild of US 24 included intersection work at the US 24/Garrett Road intersection and Sand Creek culvert scour repairs, with the full project scheduled for completion in fall 2017. The next time you see a stretch of highway repaved faster than expected, the crew may have recycled the base material in place instead of hauling it away.