Stress-absorbing membrane interlayer in Rural Nevada
In Washoe County, Nev. County Highway 447 was improved by cold in-place recycling, placement of a fiber-reinforced SAMI, and finished with a Type III slurry surfacing as the final wearing surface instead of a costly total reconstruction.
“With fuel prices going up, we are seeing a lot more truck traffic on 447,” said Bill Gooch, road supervisor, County of Washoe Road Division, Gerlach, Nev. “It’s a short cut; one truck driver told me taking 447 saves him three hours driving from Portland or Seattle to Phoenix or Las Vegas.”
Also, the highway is burdened once a year by the week-long, end-of-summer Burning Man art festival celebrated in the desert north of Gerlach.
“Basically the highway was just sand and oil, mixed together,” said Greg Belancio, P.E., senior licensed engineer, Engineering Division, Washoe County Department of Public Works. “The section averages 4-inches thick and the county had been doing it that way since the 1970s.”
“The cold in-place process is really going to help us out,” Gooch said. “It’s totally redone the road surface. All the cracks are gone. And we follow with the fiber membrane, which should resist future cracking and provide strength against lateral loading. We anticipate that it will bring not just lateral and horizontal strength, but strength in all directions.”
The crack-resistant membrane, called FiberMat by Colas Solutions, Inc., is a specially formulated, polymer modified, fiber-impregnated membrane binder for use with chip seal applications or as an interlayer with various overlays (e.g. HMA, slurry surfacings or micro surfacing).
FiberMat provides strength and flexibility due to the utilization of chopped fiberglass strands that form a high-tensile strength matrix. The system is installed by a truck-mounted machine that uniformly applies the fiberglass strands – cut from onboard spools – in a random, continuous application.
In placement, the strands are sandwiched between two layers of sprayed latex polymer-modified CRS emulsion, prior to the application of an aggregate cover. Much like a conventional chip seal, the final product then is gently rolled with rubber-tired compactors to seat the aggregate into the product. The combination of highly modified asphalt residue and a fiberglass reinforcement matrix creates a crack-resistant membrane that can stand up to heavy traffic loadings.