You’ve heard that real estate is all about location, location, location. When it comes to roads, the key is drainage, drainage, drainage.
That’s how Jim Moulthrop, co-chair of the national Task Force on Roadway Pavement Preservation for Surfaced and Unsurfaced Roads, explained the importance of handling water when working to preserve roads.
Without proper drainage, a road will fail no matter what measures are taken to preserve it, he said. Various preservation methods can seal the surface, he continued, but if water can’t drain out of bar ditches or pipes and inlets are clogged, the road will suffer damage.
Other experts agree.
Joe Graff, deputy director of the Texas Department of Transportation’s Maintenance Division, said water is the biggest enemy of a road.
“If you can keep it out of the foundation, you can solve 95 percent of problems,” Graff said.
When vehicles drive over a wet surface, they pump moisture down into a road, he said. And a long period of light rains also can do a lot of damage as the road doesn’t have time to dry out.
“There’s nothing worse than two weeks of drizzle,” Graff said.
Central Texas counties, in particular, should pay attention to drainage, Moulthrop said, because of the clay soil in the subgrade. From Dallas to San Antonio, this clay soil can swell if it stays wet, causing cracks in pavement.
Gary Fitts, senior field engineer for the Asphalt Institute, said counties should inspect drainage sites to make sure nothing is building up.
The best way to preserve a road, he said, is to “address the disease, not just the symptom.”
While working to keep the water off their roads, counties also can implement several strategies to extend the life of their pavements.
Timing is Everything
Fitts said the key in preservation is protecting the pavement while it is in good condition.
“You can’t wait until it begins to deteriorate,” he added.
While preservation methods won’t increase the structural capacity of a road, Fitts said they can provide long-term benefits for a road that was adequately constructed for the loads and the volume of traffic it must withstand.
Graff explained the deterioration curve, which can be greatly reduced through roadway preservation.
When a road is new, consider it a 100, he said. In five years, a well-built road probably would rank somewhere around a 99 and in 10 years around 90. In 15 years, a road might still remain in fairly good condition. Shortly after that, however, a road begins to drop to a rank of 50 or even as low as 30, Graff said.
By starting preservation methods around years seven or eight, a county can extend the life of a road by another seven or eight years before that downward curve starts. If preservation is done in a timely manner, it can slow the deterioration by about seven years each time.
“Preservation is an inexpensive way for long-term benefits to maintain the function of a roadway,” Fitts said.
A seal coat, a mix of liquid asphalt with aggregate on top, is the most commonly used method to preserve roads. This procedure seals cracks and creates a weatherproof surface.
Seal coats are a fairly inexpensive way to preserve a road and work to keep water out and provide a skid-resistant surface.
TxDOT is promoting the use of spot sealing, Graff said. In this method, problem areas, such as hairline cracks or areas where a road is holding water, are sealed to prevent future damage.
Through its spot sealing, TxDOT has nearly cut in half – from 1 million in 1996 to a little more than 600,000 in 2004 – the number of potholes on its roadways.
Fog sealing, a light liquid asphalt suspension, can be used to rejuvenate old pavement. This low-cost method, about 1/10th the cost of a seal coat, can work well over a chip seal to minimize the loss of aggregate.
Microsurfacing and slurry seals, mixes of asphalt emulsion and aggregate, are other ways to preserve pavement. Because these techniques require specialized equipment and expertise, Moulthrop said these methods usually are done by contractors.
Seal coating and fog sealing, in contrast, usually can be done with equipment counties have and by road and bridge staff.
Many preservation decisions boil down to economics – what a county can afford. But the experts agree that preservation can pay off for a long-lasting road.