State transportation engineers say they have found an especially hard rock that could almost double the life of chuckhole-riddled Southcentral pavement and save tens of millions of dollars in the years to come.
The promising new rocks, cracked from boulders at the base of Panorama Mountain near Denali National Park and Preserve, have been blasted with steel bearings and sloshed with water in tests designed to simulate studded-tire abuse.
The conclusion: The volcanic basalt is far burlier than the geologic crumbs shed off Southcentral Alaska's mountains, a relatively soft rock that helps make Anchorage's roads the most rutted in the state.
"It's why you don't see many rock climbers along the Seward Highway," said Michael San Angelo, statewide materials engineer for the state transportation department. "The rocks are weak stuff. You put protection into some of those cracks and it comes right out."
'Symbols of success'
Not so for the rubble on Panorama Mountain, made available this summer for use by contractors. So far, it's been crushed and spread as asphalt on two resurfacing projects spanning 3 miles each, along Dimond Boulevard (between Seward Highway and Jewel Lake Road) and along Debarr Road (between Airport Heights and the Muldoon Curve).
"They are the first symbols of success," said San Angelo.
With occasional surface maintenance, roads built with the new material should last 15 years instead of the usual eight, cutting the costs of replacement by hundreds of thousands of dollars a mile.
"But it's not just about the money," said San Angelo. "When we get in there and disrupt Dimond Boulevard, what do you think that does to the economy? Some of those small businesses can't afford the disruption."
Less wear and tear will make for safer, smoother roads as well.
But the projects on Dimond and DeBarr are just the beginning. A new state policy requires busy roads -- those averaging more than 5,000 cars per lane a day -- be armored with asphalt made only from hard rock. That means hundreds of miles of state-maintained roads, mostly in Anchorage, Fairbanks and Juneau, will one day get the durable asphalt.
That should be welcome news for jostled drivers. Anchorage recently ranked 20th on a list of mid-size American cities with the roughest roads in the nation, according to a new report from TRIP, a national transportation research group. The report said 29 percent of major roads in Anchorage are in bad shape, costing motorists nearly $500 a year in car maintenance.
San Angelo said he and others would like to strike Anchorage from that list forever. At the materials testing lab where he works, engineers are busy looking for solutions, including injecting water and chemical additives into asphalt to prevent potholes.
San Angelo talks about his job like a soldier at war: "We're fighting like heck, using all our arsenal to make sure those pavements last as long as they can."
Assaulting the ruts
The key material in road asphalt is the aggregate -- typically crushed rock -- making up 94 percent of the mixture. In Southcentral, that rock is rich in shale, which shatters into plates relatively easily, said John Fritz, a former state geologist for the transportation department.
The asphalt it produces is easy prey for studded tires, leading to the car-jolting ruts that appear in Anchorage's highways.
Fairbanks, however, doesn't have a problem with ruts in part because the Interior city of about 30,000 people has less traffic than Anchorage, said Jeff Currey, a state materials engineer. Also, Fairbanks' extreme cold allows for better traction than the near-freezing temperatures often seen in Anchorage. As a result, studless winter tires work better in Fairbanks, and a larger percentage of drivers use them, he said. Ice coats the roads longer in the Golden Heart City, too.
"Obviously, you're not wearing down the roads if there's ice on them," said Currey.
Finally, the gravel is tougher in the Interior, making for tougher roads.
In the past, if Anchorage contractors needed to make asphalt with really hard rock, they could barge it in from Washington state or Canada. But that required planning months in advance.
To find an alternative, the transportation department sent geologists scrambling over mountains about a decade ago. Buckets in hand, they collected rocks along roads or railways, looking for an accessible source.
At Panorama Mountain -- along the Parks Highway 216 miles road miles north of Anchorage -- they found the hardy, volcanic rock with small, tight grains, said Fritz.
"That fine-grain texture gives it its strength," he said.
The rock went through rigorous testing, such as the thrashing with steel balls in a high-speed mixer that works a lot like the spin cycle on a washing machine.
"It's so loud you can't stand next to it. We hammer this stuff," San Angelo said.
The state found the rock was as tough as the imported hard rock. But at Panorama Mountain, it took years to overcome access issues involving all the parties -- the landowners, a mining operator in the area, and the Alaska Railroad.
1 million tons within easy reach
There was also the question of how to get it to Anchorage without too much expense.
A study commissioned by the state found that it could be extracted, crushed and shipped on railroad cars for about the same price as the hard rock from Outside.
Just as important, it was readily available. And with an estimated 1 million tons of rock sitting on the surface of Panorama Mountain, the supply could potentially last decades.
And that, San Angelo hopes, could help Anchorage get off the rough-roads list, and into a better category.
"My goal is to have us make the top 20 smoothest roads in the country," he said.
Contact Alex DeMarban at alex(at)alaskadispatch.com.