Just What is Hot Mix Asphalt?
It’s an engineered mixture of aggregate, or stones and sand, with liquid asphalt cement, a petroleum product. Varying sizes of aggregates are heated, then mixed, in exact proportions, with asphalt cement that has been liquefied at about 300 degrees. While the mixture is still hot, it is delivered to your driveway and paved on top of a base or subgrade that has already been prepared. Very soon after paving, the mixture cools and hardens and you can drive on it right away.

What You Receive with Hot Mix Asphalt
You’ll recognize several benefits with Hot Mix Asphalt, compared to other, more costly options.

It is strong and durable.
It is engineered to withstand freezing and thawing.
No need to worry about salting your driveway in winter. Hot Mix Asphalt is unaffected by salt. and
Unlike other, more rigid materials such as concrete, Hot Mix Asphalt is designed to flex and “give” with slight settlements or frost heave. Hot Mix Asphalt lends itself readily to the types of service that are usual in residential areas. If a utility line must pass under your driveway, repairs are more easily and quickly performed than with alternative materials such as concrete. The same is true if undue ground settlement should occur naturally.
And Hot Mix Asphalt is the most cost-effective option you can choose. Just as it has for millions of homeowners the world over, Hot Mix Asphalt can last many years for you—with only minimal maintenance.

About Quality Control
There are hot asphalt mixtures of various types. Some mixtures are smoother on top than others; some have a higher content of asphalt cement than others. A special type of asphalt mixture is even colored and imprinted to resemble paver blocks. Consult with your homebuilder or contractor to assure that your mixture will provide the surface and performance characteristics you want. Unfortunately, all consumers do not closely monitor their driveway design and construction. So it is possible for some builders and/or subcontractors to try to boost their profits at the expense of your driveway’s quality. Getting multiple bids, if possible, and having the willingness to work with your builder or contractor to control quality will serve you well. A word of warning: If someone knocks on your front door and says, “We have a load of asphalt that was left over from paving nearby, and we can pave your driveway at a bargain rate if you’ll pay cash,” don’t take him up on it. Asphalt that is “left over” from another job will be too cool to make a good pavement at your house. Anyway, as with any other business transactions, you want to know who you’re dealing with before proceeding, so making a deal on the spot doesn’t make sense for you. Checking references can save you money in the long run.

Full-depth Asphalt: The Best Option
Full-depth Hot Mix Asphalt driveways are built entirely of Hot Mix from the soil subgrade up. Full-depth driveways keep water out of the pavement. So water never enters the pavement to swell when it freezes. Full-depth asphalt provides a better balance of strength and flexibility—plus durability—than any other material. For improved soil stability, it is recommended that topsoil containing clay be removed or modified. A solid subgrade requires thorough compaction. Paving with Hot Mix follows. A 4-inch thickness may be adequate, but 5 or even 6 inches of full-depth Hot Mix will assure you of a stronger, stable driveway under a wider range of climate and loads. As an option, some contractors use 6 to 8 inches of compacted aggregate, or gravel, as a base under 3 inches of Hot Mix.

“We recommend full-depth asphalt for driveways,” says Dave Newcomb, NAPA Vice President of Research and Technology. “We calculate that Hot Mix Asphalt can replace aggregate on a ratio of 1:3 in thickness. That is, 1 inch of Hot Mix is equivalent to 3 inches of aggregate base.” Hot Mix Asphalt is best placed in “lifts,” or layers. For example, a total of 2 to 3 inches may be spread as two layers each 1-1/2 inches thick when compacted. A good way to pave a 4-inch “mat” is first to place 2-1/2 inches, compact it, then pave the remainder and compact again.

“If possible, we apply only the first course of Hot Mix during new-home construction,” says Jeff Terp of Merit Asphalt Inc., a Wisconsin-based NAPA Member. “We wait until construction is finished to pave the surface course. That way construction traffic, dirt, and little dents all happen on the base course. At the end we clean the base and pave the surface course, and it looks good.”