Ancient Rome was famous for built-to-last roads. Centuries after the Appian Way’s construction, the historian Procopius described its surface stones as having the appearance “not of being fitted together, but of having grown together.”
Now, that’s a smooth road.
Of course, the Romans designed for the tread of legionnaires and maybe short-haul wagons carrying 1,200 pounds of wood. Let’s roll some 80,000-pound tractor-trailers over the Via Appia, get them up to 45 mph and brake hard.
How do you like your via now, Procopius?
To meet this heavier demand, 21st-century Americans ride on blacktop, known in the business as hot mix asphalt. It’s made almost entirely of crushed rock blended with a dash of liquid asphalt refined from crude oil.
The ancients would have considered us unambitious. Rather than building new roads, D.C. area highway departments are usually just preserving what we’ve got.
It’s partly because our concerns have changed. In this millennium, if all roads lead to your capital city, you’ve got a congestion problem.
But this conservative approach to road work also reflects our simultaneous love of smooth roads and revulsion at having to pay for them.
That frustrates people in the paving industry. Marshall Klinefelter, a vice president at the Maryland Asphalt Association, doesn’t like what he sees in Congress, where long-term refinancing for surface transportation programs isn’t getting much traction.
“You can kick the can down the road, but the road’s pretty much gone,” he said, referring to the dwindling of the nation’s Highway Trust Fund.
Michael Day, who heads his family’s Rockville-based paving company, F.O. Day, wants travelers to consider the role that pavers play in easing congestion. The smoother the road surface, the fewer the ruts and potholes, the more quickly and safely traffic moves.
The public conflicting desires for smoothness and savings come down to this: A typical road project today is a “shave and pave.” Grind up and haul away the top layer of asphalt, brush off the dust, lay down a sticky, asphalt emulsion called tack and put down a fresh mat of hot asphalt mix.
“Scrape off two inches and put two inches back,” said Kevin S. Nowak, an assistant district engineer for the Maryland State Highway Administration.
It may be less glorious than what Appius Claudius Caecus accomplished for Rome in 312 B.C., but it’s no less challenging.
The SHA’s District 3, where Nowak is based, is responsible for projects on the congested state roads in Montgomery and Prince George’s counties. The roads can’t be shut down for resurfacing.
“Maximum production means maximum impact on the public,” Nowak said.
To avoid maximum impact, Nowak must avoid paving at peak travel times. He must be familiar not only with commuter hours but also with the schedules for football and baseball games, concerts and the annual Cherry Blossom Festival.
The standard work hours on paving projects are overnights Sunday through Thursday. The standard paving material is asphalt, which drivers can use as soon as the overnight pouring has cooled. Concrete, a more rigid material that was the surface on many roads during the rise of the automobile age, can take days to cure before it becomes drivable.
People who manage asphalt paving often refer to the work as choreography. They begin this dance at a plant where an asphalt mix heated to a few hundred degrees is poured into dozens of dump trucks. The trucks proceed to work zones, where they await a gradual closing of lanes with orange cones so they can unload the mix into a hopper that feeds a paver that rolls continuously down a lane, covering a mile or more on a good night.
The nightly hours available between the beginning of the lane shutdowns and the pulling up of the cones and barrels before the morning rush may be comparable to an overtime football game, said Dennis Favero, general manager for F.O. Day.
Conditions looked good for paving Greenbelt Road on a Monday night this spring. Orders went out to close lanes and bring in the asphalt trucks. As crews were setting out the orange cones, storm clouds sprang up in the west and rolled across Greenbelt.
The storm moved through quickly, but it had arrived at just the wrong moment, in time to dilute the adhesive coating of tack set down before the asphalt mix is poured. The night’s work on Greenbelt Road, part of a $4.5 million state project, was canceled.
Several nights later, the chain of paving vehicles moved steadily along an eastbound lane, taking care to avoid any stutter steps in the process that might leave the new pavement uneven. A few feet beyond a row of orange cones, a line of heavy traffic moved past the workers, illuminated by lights atop the paver.
In the paver’s wake, rollers move in, repeatedly pressing the surface to smooth it, increase its density and eliminate the seam between lanes. A seam that rain, snow or road treatments can penetrate will shorten the life of the pavement.
The state judges the pavement on its density, smoothness and ride quality. Core samples are taken to a state lab for testing.
F.O. Day has its own testing lab at the company’s headquarters in the middle of a Rockville quarry that provides much of the crushed stone for the pavement.
Above the lab sits a control room where Gene Yocum, the plant supervisor, watches over computers that regulate the mixing of various sizes of stone with the asphalt binder that the company imports. The mix also includes some old asphalt pavement scraped from roadways before resurfacing.
“It’s just like baking a cake — only it’s continuous,” Yocum said.
Because more than 90 percent of the nation’s paved roads use asphalt mixes, much federally supported research has been devoted to understanding how to select the best crushed rock, adjust the air pockets in the mix and strengthen the asphalt binder. Elements can be modified to improve the pavement’s performance in different weather and traffic conditions.
Nowak, with Maryland’s SHA for nearly three decades, said today’s pavement surfaces are tougher and more durable. He cited Route 301 in Maryland as an example. It’s a popular roadway for truckers who want to swing wide of the D.C. area.
That popularity was most noticeable at intersections where heavy trucks would halt a downhill run to wait for traffic signals. The stress deformed the pavement, creating ruts and ripples.
In recent years, improved mixes and application techniques have given the Route 301 pavement a better chance of bearing up under the big wheels.
These road potions may in turn look primitive to tomorrow’s engineers, but Appius Claudius would have killed for the stuff mixed today by Yocum’s computers.