BERKELEY -- Like the materials he has studied for nearly 60 years at the University of California Pavement Research Center at Berkeley, the center's recently retired director, professor Carl Monismith, was built to last.
Leading a tour of the facilities -- an expectedly gritty series of labs lined with machines resembling industrial ovens, turkey-roast-sized pans filled with asphalt in various stages of disintegration, and endless rows of cylindrical or bar-shaped test samples -- the 85-year old researcher speaks with the unbridled enthusiasm of a recent college grad.
"I've been working with pavement since 1952 -- forgive me if I get carried away," he begins, before launching into the department's history.
After World War II, California's highway system was in bad shape. The university's engineering program was assigned to physically test pavement materials. The goal was to develop properties that enabled people to design, maintain and rebuild roads resistant to rutting and fatigue. California's Department of Transportation was the primary partner, and, eventually, Caltrans and federal agencies jumped on the wagon.
"We hit the big-time in 1989 with the National Strategic Highway Research Program and a $9.5 million project to develop tests of asphalt," Monismith recalls. "Then in 1994, Caltrans wanted to develop an accelerated pavement test program. We bought two heavy vehicle simulators. Today, each one would cost $2.7 million. We got two for
By running real wheels (ceaselessly) across samples, the center has unearthed the secrets buried in soil, granular materials, cement and lime stabilizers, polymers, asphalt and concrete.
"Pavements don't fail catastrophically, they decay over time," Monismith instructs. He shows off the center's Simple Sheer Tester, repeatedly loading an asphalt widget -- and a Hamburg Wheel Tracking Tester that immerses samples underwater and produces pitted, deformed or near-perfect results.
Ironically, the solution to reducing decay and hydroplaning, the white-knuckle skid caused by excess moisture on the road, is not eliminating water but allowing it. The application of a thin, porous layer over denser layers allows water to percolate through and either recharge the ground water below or run off to the sides.
"Plus, skid resistance doesn't drop as quickly as it does on denser pavements," Monismith adds, "and you get rid of that film of water that settles in ruts."
Beyond fixing potholes, the bane of drivers' existence, Monismith points to current research aimed at reducing the environmental impact of roads. A sustainable mindset permeates the center; fueled by ongoing interest in conserving and recycling road materials, improving fuel economy and reducing road noise.
Doctoral candidate Ting Wang at the center's Davis location reports preliminary study results showing that "for highway sections with high-traffic volumes, the energy and GHG (greenhouse gas) savings due to reduced rolling resistance can be significantly larger than (savings) from material production and construction, with the extent of the benefit dependent on constructed smoothness."
In simple terms, smoother roads lead to lower fuel consumption. The numbers make it clear: comparing a good pavement with an International Road Index of 70, to a bumpy road rated at 170, reveals a 4 percent fuel increase.
"Over the years, pavement design has not had a revolution, but an evolution," Monismith says, attributing the advances to computer capability and economics.
"We were developing materials to last only 10 to 20 years: now we're designing for 40 to 50 years. When (liquid) asphalt was 20 dollars a ton, adding an expensive polymer was unheard of. Today, (liquid) asphalt sells for $300 a ton or more, so adding an expensive polymer is no big deal."
Although regarded as experts in materials development, Monismith and his UCPRC colleagues emphasize that application is equally important.
"When rehabilitating freeways, our concern is more with using materials properly and making them so you don't have to use as much. The I-5 project in Southern California has a recycled-asphalt mix. It's ground up and (combined) with new softening materials to get a durable material," he says.
John Harvey, the center's Davis location director, spoke in an NPR report of next-generation pavements that allow air -- the major source of freeway "whooshing" noise -- to escape into the pavement, reducing the need for expensive sound walls. His research efforts are receiving considerable attention, especially in the "concrete versus asphalt" battle, which he and Monismith depict as missing the point.
'"We need to have pavement analysis systems that predict the design to make roads last longer and suit the intended use," Monismith says, summing up his life's work and the aspirations of his colleagues.
For information about the center's research, including investigations into longitudinal tining (grooving) and other matters beyond the scope of this article, visit www.ucprc.ucdavis.edu.