Keeping Denver on the Move with OneCem® Portland Limestone Cement
Colorado State Highway 470 (C-470) is a vital transportation link connecting southwest Denver with Interstate 70. More than 100,000 vehicles each day travel along a 12.5-mile heavily congested corridor of the C-470 freeway, which is projected to be 30 percent over capacity by 2025. With traffic volumes forecast to increase 40 percent by 2035, correcting C-470 mobility deficiencies was an urgent need.
To relieve congestion along this stretch of C-470, the Colorado Department of Transportation (CDOT) initiated a massive reconstruction project that included new express and auxiliary lanes, reconfiguration of substandard curves and ramps, and other improvements. As with all large design-build projects, the C-470 work faced significant challenges. There was 688,000 cubic yards of soil to move, 233,000 square feet of MSE walls to build, 1.1 million square yards of concrete pavement to place, and 20 miles of barrier to install. Keeping the traveling public moving safely through the work zones was a top priority.
Given the scope of the C-470 project and its economic impact in environmentally minded Colorado, achieving high standards in concrete pavement quality, safety, and sustainable construction practices was of paramount importance to both CDOT and Castle Rock Construction Company.
As part of its mission to continually improve its environmental performance, Colorado is committed to reducing emissions and promoting resource reuse in its transportation infrastructure. In support of this goal, CDOT relied on a variety of eco-friendly practices to reduce the environmental impact of C-470 construction activities. For example, all concrete removed during reconstruction was crushed and recycled on site into either Class 6 road base or concrete aggregate in the mix for the new pavement.
Another green approach involved the concrete mix design. At four strategically positioned plants at the jobsite, Castle Rock Construction produced concrete containing OneCem® Portland Limestone Cement (PLC) and 20 percent Class F fly ash. Used seamlessly as a direct substitution for ordinary Portland cements, OneCem®, part of the Envirocore™ Series,offers the same level of performance as Type I/II cements. Because it uses less clinker, carbon dioxide emissions are reduced by up to 10 percent per ton of cement. With 60,000 tons of OneCem used in the concrete, the reduced carbon footprint of the pavement was substantial.
Used in more than 30 projects by Castle Rock Construction over the past decade, OneCem has made significant contributions to improving the quality and sustainability of more than 900 lane miles of concrete pavement in Colorado. According to Amy Brooks, chief operating officer at Castle Rock Construction, the 9.5-inch pavement on C-470 was designed to last 30 years and the performance of the OneCem allowed the team to consistently surpass CDOT’s strength requirements and durability goals. “It also produced a consistent workable platform for the paver and a nice finish, eliminating delays due to problems of the mix in the equipment or reworking placement imperfections.”
The paving work on C-470 Express Lanes Project started in early 2017. The process of efficiently moving the traveling public through the work zones, keeping work crews going, and coordinating construction trucks in and out of the job site was a herculean effort.
Through some innovative thinking, Castle Rock Construction implemented various solutions to minimize construction delays and improve safety. For example, lack of room for a track line and string line due to phasing was solved by creating a new system to mount the string line directly on top of a temporary barrier wall. And to support paving operations for the middle segment of the project, a batch plant and conveyor system were built to transport concrete over the highway. This allowed the team to transport 6,000 truckloads of concrete to the paver and avoid taking those batch trucks in traffic.
C-470 construction also had an extremely demanding schedule and supply needs. “It was an ever-changing dynamic due to the phasing and other challenges of the work,” said Brooks. “The Holcim team’s logistics planning, flexibility, and responsiveness throughout the project were outstanding in ensuring we had on-time cement deliveries for an uninterrupted paving operation.”
Now open to traffic, the new extended-life concrete lanes along this stretch of C-470 will offer broad and lasting benefits to Denver’s transportation system, its economy, and environment for decades to come. With vehicles spread out over two extra lanes in each direction, motorists will enjoy a faster, safer, and more reliable commute with up to 18 minutes in travel-time savings.
"It [OneCem] also produced a consistent workable platform for the paver and a nice finish, eliminating delays due to problems of the mix in the equipment or reworking placement imperfections."