Abstract

Author

Michael Scardina

Conference

Publication: American Council of Engineering Companies (ACEC) Newsletter

The Town of Monument, located at the base of the Rampart Range in El Paso County, Colorado, faces a challenge common to many agencies today – how do you get more life and less cracking from overlays? In 2018, Schmidt Construction brought Fiber Reinforced Asphalt Pavement (Nilex's ACE Fiber) to the Town’s attention.

What is Fiber Reinforced Asphalt Pavement (FRAP)? In the 1990s, research identified Aramid Fiber as a great option for asphalt with the Superpave mix design. Since concrete had been reinforced with various fibers for years, why couldn’t a fiber help asphalt? Manufacturing temperature was the biggest barrier for most fiber options. Asphalt needed a product that could withstand drum mixing at temperatures north of 500F. Aramid does not burn below 900F. Aramid is also five times the strength of steel – 400,000 psi tensile break. The only problem, Aramid was under patent by DuPont as the product commonly known as Kevlar. That’s right, the same fiber that makes bullet proof vests and firefighting clothing is a perfect reinforcement for hot mix. To make FRAP, Aramid is dosed into the mix typically through the RAP collar at the plant. Minimum dosage is 2.1oz Aramid per ton of mix, yielding up to 50% increases in rut resistance and up to 150% increases in crack resistance to any mix design. Aramid comes in two lengths, .75 inch and 1.5 inch. Increased dosage and longer fibers add rut and crack resistance when conditions and job requirements warrant.

With increased crack resistance, ACE Fiber offered several advantages for the Town. The price was less than interlayers, and construction time would not be affected. As a plant mix product, paving could directly follow patching and milling that was already on the schedule. Also, the mix could use a 58/28 binder and maintain the flexibility needed at Monument’s 6975 feet of elevation.

In addition to town streets, Tri-View HOA tried FRAP in 2018. Tri-View has launched an ambitions multi-year resurfacing and reconstruction program that is assisted by the Town. Tri-View was also trying to maximize performance for their budget and FRAP fit right in. Two streets in Tri-View were paved with FRAP in 2018.

How did it go? The Town’s Front Street overlay is right in the heart of the small commercial district and gets a good amount of traffic. It was paved in March 2018. When we checked in mid-September 2019, there were seven cracks, with only one longer than 2’. All the cracks are very tight, as the photo shows below.

This season, both the Town and Tri-View have done more paving with ACE Fiber. Martin Marietta did the overlay work for both Monument and Tri-View. The overlays went well and should provide improved performance for the driving public.

This year also saw a major reconstruction/overlay project. Jackson Creek Pkwy is being paved by Kiewit and is part of the Tri-View multi-year paving program. For the pavement, FRAP is being used for the bottom and top lifts, with 64/28 binder. Petrotac, a self-adhering paving membrane, is being used on a wheel path crack running the length of the job. Petrotac is a great way to address local pavement distress without the hassle and expense of traditional paving fabric.

With great initial results, Tri-View and Monument will continue to see the returns on their asphalt investments with long life pavements reinforced by Petrotac and ACE Fiber for years to come. 

   

For more information about this project or to learn more about Nilex's entire suite of roadway solutions, contact Michael Scardina at michael.scardina@nilex.com or 303-951-5787.