Thin Surface Overlay Requires Fine-milling Preparation

"TexOp is cutting with the Multiplex system, sometimes on both sides, sometimes with Multiplex on one side and wire rope sensor on the other," Barnes says. "The NTTA ran a profilograph over the existing highway, and then marked stations, so they knew where their worst areas were. And that's where most of the fine texturing efforts were focused."

Proving the process

Wirtgen and TexOp both worked with the toll authority to show the efficacy of the fine-milling process, culminating in test sections cut for the NTTA and the Texas Department of Transportation.

"We did a test project for Texas DOT using the fine-texture drum," Simpson says. "People came out, took a look and liked what they saw, including the smoothness of the ride and the pattern of the drum. They were skeptical, until they saw the process work. This job will give the turnpike back its rideability, and provide a surface that will bond well to the NovaChip paving."

The project had been designed with diamond grinding in the contract, so a change order was needed to switch to the cold mill process. The process is applicable to Portland cement concrete pavements and decks, as well as asphalt. But while fine-tooth milling of concrete is done elsewhere in the world, it's not common in the United States.

Wirtgen would like to change that. "Not only does this process mill for smoothness on asphalt, but it also has application for Portland cement concrete, benefiting the owner with low costs, short time-frame and the end product we get," Barnes says. "I have seen projects done by Wirtgen machines, such as airports in Germany, and I know it will work in Texas. The best way to level faulted slabs and improve traction on polished concrete is with a Wirtgen cold mill and fine-toothed drum. It's been done all over the world and the market is growing here."

Family business and reliable mills

TexOp has five cold mills, including Wirtgen's largest machines, a W 2000, W 2100, and W 2200. And there's a reason why TexOp leaves its biggest work to the biggest Wirtgen mills: their reliability.

"As a family-owned business we can't afford the downtime that you get with other machines," Simpson says. "Our Wirtgens have been up and running constantly since we've had them. Their engineering makes them so reliable. They're the right size for what we want to do on large or small jobs. With the four track design, they're very stable, and have been virtually trouble-free."

Simpson also found the Wirtgen fine-toothed drum superior to what he'd experienced with other machines. "In the past I've used fine-toothed drums with other machines, but I like to use the Wirtgen," he says. "They are of very high quality, with a beautiful pattern. It's German engineering at its best."

"What amazes me about a Wirtgen milling machine, and what impresses customers everywhere, is how clean it leaves the cut," Barnes says. "It mechanically sucks the millings up like a Hoover. On this particular application, we have taken the pressure off the drum housing back door and got it off the ground, because we wanted to leave the longitudinal striations to keep the appearance of a diamond cut. We are sure that the adhesion of the NovaChip will be enhanced by the greater surface area offered by the striations."

Now that fine grinding using a Wirtgen mill and fine-texture drum has made an impact in Texas, TexOp's Simpson sees a growth area. "In the long run, we see this getting much bigger," he says. "Most of the jobs now include a ride spec, whether they're on asphalt or concrete. Our machines have us positioned to take advantage of that spec."