Think potholes, then think plastics

Anyone who drives a car knows the drill. When a pothole lies ahead, veer quickly to the right or left or risk tire-and-suspension damage.

More than 100 million potholes pepper the roadways from coast to coast, costing motorists and maintenance crews added time and money. Highway agencies shell out more than one-fourth of the $90 billion spent each year on highway systems to fill them.

But a new pothole repair approach could change that. It strengthens fillers so they last 10 times as long using components made mostly from recycled plastic, according to Parsec Roadway Application Systems Inc., the company that introduced the idea. City officials say it lowers repair costs and causes fewer traffic jams due to road work.

Normally, asphalt fills last from six to nine months, but this latest technique, which costs more than standard repairs initially, gives them a 10-year lifespan, says Guy Wormald of Dallas-based Parsec.

The system acts as a foundation before pouring asphalt or concrete fillers. First, workers lay a water-vapor barrier across the hole's bottom and walls. It's made of a cross-laminated polyethylene liner that seals the repair to prevent washout and siphoning. (A main reason road fillers don't last is water seepage.)

Over that comes a "geo-grid mesh" that helps distribute weight from cars more evenly. The third component is recycled plastic rebar tubes, which are woven into the grid to form a cross-hatch pattern. The combination helps absorb impact, provides stability, and prevents the fill from deteriorating. Hot asphalt is poured over the layers.

A city also benefits from improved productivity of work crews and fewer lawsuits filed by disgruntled drivers, Mr. Wormald adds.

The process is applied near bus stops, which tend to experience greater problems with road tears caused by stop-and-go bus traffic. Before the installation, Dallas was dispatching work crews to fix roads near these stops every month. It was time consuming and costly, says Coy Evans, a manager of the western division of street maintenance in Dallas.

Back then, "the asphalt was crumbling ... very cracked up, very rough," he says. Drivers called and complained about the bumpy rides. But "five years later, they're not buckling, they're not cracking.... We haven't made any repairs," he exclaims.

(c) Copyright 1999. The Christian Science Publishing Society