Compaction Is Key To Long-Lasting Driveway Pavements

There is a lot of overlap in the preparation for paving residential driveways and the bigger commercial work, typically parking lots, but that doesn't mean that the work is completely interchangeable. When taking on a driveway for an individual client, there are some key factors that need specific attention in order to ensure a long-lasting asphalt surface and, more importantly, a satisfied customer. The initial factor, and perhaps most important, is what type of installation you're doing. While there can be a lot of variances, they typically fall into one of three situations:

• Complete new install: requiring dirt work, grading, base, and asphalt
• New overlay: existing gravel driveway and/or minimal grading, preparing and compacting, and asphalt overlay
• Resurfacing: A mill-and-fill, placing back down exactly what was there, or, less commonly, laying a new surface directly on top of the old

One key to success that all of these driveway installations share is a critical focus on proper compaction at every step of the process:

• Dirt
• Base
• Asphalt

Pat Brown

Getting Dirty

Down in the historic city of Fredericksburg, Virginia, the dirt has a reddish clay-like quality in the majority of the area. It can take an experienced hand to know how to deal with it in different conditions. The contractor DrivewaysByUs, a family owned and operated asphalt business, does best exactly what its namesake says. They've grown over the years largely by word-of-mouth and by the calling card their work leaves behind. 

Operations Manager Jennifer Edgerton explained the first steps on a brand new installation for a house nearly two hundred years old. "It's been a mix of dirt and loose gravel at different times going back two centuries," she said. "But this is nice, solid ground we are cutting out to shape. Then we will bring in some gravel and fines, get that nicely compacted. That's to build all this up, because of how high the foundation of the new garage is. Everything has to flow away from it. Then it'll be ready for asphalt."

A tracked skid-steer with a standard angled bucket was used to cut in the outline of the driveway, as well as to grade the soil. The gravel came mixed with a heavy amount of fines to fill in all the gaps in the stone and ensure a solid fit. The same skid steer spread it the gravel out, grading it to match the soil, along with lutes, rakes, shovels to properly match the project parameters. Then the rollers came in to make their first passes.

All About That Base

DrivewaysByUs primarily uses a pair of Dynapac tandem rollers, the CC950 and the CC1000, for all their compaction needs. For DrivewaysByUs the CC1000 leads the way, and they follow behind it with the CC950 to smooth out any roller lines left by initial compaction. This is the same pattern they use for laying asphalt too. While almost identical in outward appearance, the CC1000 boasts an extra 800 pounds (3,900 total) of max operational weight, and has 4 more inches of compaction width (39 in. total) over the CC950's 3,100 lbs. max operational weight and 35 in. compaction width.

The Edgerton clan, led by their father and founder of DrivewaysByUs, Michael Edgerton, who's first asphalt truck in the 1980s was a converted milk truck, has used Dynapac rollers exclusively for decades.

"I've just found them to be super-reliable," Michael said. "They're workhorses. Day-in and day-out they do what they're supposed to and I can hardly remember having any issues with them. That's why, once they get up there in hours and we're ready to trade it in, we just turn it around on a new Dynapac. At the pace we work, two or three driveways a day, we can't afford to risk breakdowns."

Brandon Noel, Editor, compacting gravel base for a driveway.Pat Brown

Michael's youngest son Jesse, who's been on the job since he was a little boy has been operating the rollers since before he had a driver's license for a car. He jumped up on the CC1000 and throttled up before explaining the next step in the process.

"This is called a 21-A, and it has a lot of fines to lock in those voids in between the bigger stones," he said. "That way you when you roll, it's all tight underneath. You got to have a solid base, and the compaction is key. When we get done this pass done, it have a nice and smooth appearance, almost like blacktop, but, you know, gravel."

Edgerton said that not only the quality of the mat, but, ultimately, the lifespan of the driveway is more directly a result of these preparations that the asphalt itself. It's all about the base.

"The guys who mostly stick to commercial work, they don't mess with this as much," said Jesse. "We do that work too, so we know. The dirt work and the base is already there, it's in place. But when you're putting in a new driveway, it's on you. You gotta get this right."

Going To The Mat

After compacting the base, an important intermediary step for the rollers is washing off and cleaning the drums. This is especially true when compacting fines-heavy material where the dust can coat and collect on the surface. It doesn't take long, but it's essential to take a moderate-pressure water hose and thoroughly rinse off any excess from both the inside and outside of the drums.

"If you don't clean these off, it's going to leave streaks all over the mat," said Jesse. "It's not going to be very attractive to the customer, and it can be pretty hard to remove."

Additionally, the senior Edgerton watered down the top of the base with a mist of water to try and control the amount of dust kicked up in the air before the asphalt arrived. This is especially true on summer workdays like the one he was on then, where temperatures were hovering around ninety-five degrees, and with the southern Virginian humidity, it felt much hotter.

As the first asphalt truck load started backing in, Andy Edgerton, TITLE,  explained their set-up in order to meet the road and garage with flush edges from his seat driving the.

"We [typically] give it three inches, you know, the depth of the blacktop," he said. "That's so I can meet him flush with the road, the garage, a drain, or wherever you want to tie in."

Following the standard rule of adding one-quarter of material per inch of finished compacted depth, they will lay down three-and-three-quarters of hot mix asphalt in single lift runs. And in order to satisfy the discerning eye of residential clients who are expecting to see a high quality result for the costs associated with a new installation, the compaction process needs to be smooth and consistent with as little turns and adjustments as possible to avoid marking up or cutting the mat.

"Less is more with these rollers," said Jesse Edgerton. "You don't want to turn the wheel all the way, and then be fighting it to go back the other way. You just want to do small increments. It's not like a car, so you don't need to be turning the wheel that much. When you do that, and you're fighting it, you might be perfect at your line in the front, but when you come back now you're off by two feet away. That's when you miss areas that you need to roll."

After a pass over the mat with the CC1000 Jesse waited for the mat to cool down under the intense seasonal heat, wanting to use the CC950 for finish rolling, to get out any roll marks left behind without moving the asphalt too much. And after the finish rolling was complete, Michael Edgerton was back at it with his water hose, lightly spraying the entire surface of the asphalt. As he did, steam rose up all around him. 

At first this seemed counterintuitive and strange, but Michael explained, "I tell our clients to do this for a few days after, and before they start parking or driving on it. Even more when it's hot like this for days in a row. It helps the asphalt cool down and set hard in-place."