What is Hot Mix Asphalt?

How is Hot Mix Asphalt made?

What are the benefits of asphalt pavements?

What does the Asphalt Industry do for its employees?

What is the Asphalt Construction Industry anyway?

Are asphalt pavements safe?

Is asphalt an environmentally sound product?

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The asphalt is placed, then compacted using a heavy roller which is driven over the asphalt. Because the temperature of the Hot Mix Asphalt drops rapidly after spreading and because compaction of the Hot Mix Asphalt to achieve a specified density must take place at temperatures above 175 degrees Fahrenheit, compaction usually takes place within a matter of minutes after the paver spreads the Hot Mix Asphalt. Traffic is generally permitted on the pavement immediately following compaction.

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Asphalt also makes sense because it is the paving material of choice on roads in this country. Of the 2.27 million miles of paved road in the US, 94% is surfaced with asphalt, including 65% of the interstate system.

Asphalt pavements provide the user with a smooth, quiet, safe ride surface. A smooth pavement saves wear and tear on vehicles. Properly designed, built and maintained asphalt pavements enhance vehicle safety by providing a renewable, skid-resistant surface. A smooth surface maximizes tire contact, increasing skid resistance.

Economic/Engineering Benefits
Costs due to traffic delays demonstrate that the speed of construction using asphalt saves time and money. While each road needs to be analyzed based on its own merits, for building roads, asphalt saves taxpayers dollars.

In a 3-year analysis conducted by the Florida Department of Transportation, initial construction of an asphalt pavement cost $544,981 to concrete's $765,729. After wear and tear and maintenance, the residual value of the asphalt pavement was 203% more than the concrete road.

While each road needs to be analyzed based on its own merits, for maintaining roads, the Florida Department of Transportation calculated their routine annual maintenance costs as $132 per lane mile for asphalt pavement and $261 per lane mile for concrete pavement.

Cold milling and recycling of old asphalt saves costly readjustment of manholes, curbs and sewer drains when rehabilitating urban streets.

Asphalt gives the best return on investment of any paving material.

Environmental Benefits
One hundred percent of an asphalt pavement can be picked up, remixed with a portion of fresh materials, and used again.

Recycling of asphalt pavement is more cost effective than using only virgin materials. The quality of a recycled asphalt pavement is as good, or even better, than brand new pavement.

Recycling of asphalt not only conserves our precious natural resources and speeds construction, it also saves American taxpayers over $300 million a year.

If you don't reuse worn-out asphalt pavement, you have to dispose of it, usually in a landfill. Hauling old pavement to dispose of it adds to the costs and does not make best use of a product that can be recycled. Asphalt pavements can be recycled numerous times.

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The Industry conducts several training programs in Hot Mix Asphalt design and construction. The training is designed to address issues of quality control, troubleshooting and dispute resolution for all key paving personnel, paving contractor foremen, public agency inspectors and engineers and superintendents and consulting engineers and inspectors.

The Industry has created a scholarship program to encourage the best and brightest young men and women to choose careers in the asphalt industry. Students, employees of Hot Mix Asphalt companies who are also going to school and are interested in a technical asphalt education are prime scholarship candidates.

NAPA has developed an extensive array of publications and videos on Hot Mix Asphalt construction, all directed towards the labor force.

In partnership with Auburn University, the National Asphalt Pavement Association's Research and Education Foundation established the National Center for Asphalt Technology (NCAT). One of NCAT's purposes is to advance the technical and managerial state-of-the-art of Hot Mix Asphalt production, pavement design and construction.

Along with the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), and other industry groups, NAPA is a signatory to the National Quality Initiative (NQI), a program designed to provide quality products, information and services. NAPA fully supports the continuous improvement of pavement quality.

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The Hot Mix Asphalt Industry directly employs about 300,000 people. Another 600,000 jobs revolve around the HMA Industry: equipment manufacturers, state and local personnel, AC suppliers, aggregate suppliers, consulting engineers, etc.

While asphalt roads have provided smooth, safe travel for American motorists for most of the century, the industry and the art of building asphalt pavements has gained much sophistication. The industry is very progressive.

The industry has a commitment to quality and continuous improvement.

Through the National Asphalt Pavement Association's Research and Education Foundation and Auburn University, the industry has established the National Center for Asphalt Technology (NCAT), where research projects related to asphalt technology are conducted in an academic setting. NCAT has also produced a textbook on asphalt technology and conducts an annual Professor Training Program which teaches courses in asphalt technology to university educators from across the country.

The paver modification effort was started because a contractor wanted better conditions for his workers. Now we are very close to having equipment that removes paving workers from exposure to asphalt fumes on the job site.

Many of our Members are advocates of Total Quality Management. They work hard to ensure that the product they produce is of high quality and that workers have the equipment and authority they need to do their best work and produce and place pavements of consistently high quality.

As challenges arise, our engineers create new mixes. For example, new mixes such as Stone Matrix Asphalt and Superpave have been developed for heavy traffic, high performance pavements.

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Q: Are asphalt pavements safe?
Safety is largely a function of maintaining tire contact with the pavement surface and skid resistance of the surfacing. Smooth asphalt roads have superior road contact and high skid resistance.

Asphalt pavements have distinct advantages over other paving materials when driving in inclement weather.

Asphalt is impervious to de-icing salts and chemicals and is unaffected by winter road safety maintenance.

Asphalt pavements can be designed so that water drains through the surface layer of the pavement, thus reducing splash and tire spray and increasing tire-road contact during wet weather.

Asphalt retains heat better than other materials so ice doesn't form as quickly and melts faster.

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Liners
Asphalt paving materials have been used to line the surfaces of everything from fish hatcheries to industrial retention ponds. In the case of fish hatcheries, an inert material was needed that would not chemically react with the water. This allows fish and game experts to precisely monitor and control the environment during the delicate stages of incubation and early growth for various fish species.

For example, Oregon and Washington state fish and wildlife agencies began using HMA to line their fish rearing ponds in 1987. Typically 1/2-acre in area, the ponds are home to chinook salmon and other fry for about 18 months before the fish are released into rivers and streams. Both the Washington and Oregon state agencies are pleased with the effectiveness of the HMA liners and plan to use them for additional fish hatcheries in the future.

For decades asphalt paving materials have been used as liners for water reservoirs.

For example, The Metropolitan Water District of Southern California (MWDSC) has been using HMA-lined water reservoirs for more than four decades. Currently, the California Water Resources Board is completing construction on the Devil's Canyon Reservoir to store MWDSC drinking water. The 19-inch thick asphalt liner for the huge facility will hold 800-acre-feet of water. The East Bay Municipal Utility District (EBMUD) in Oakland, California, has also been using Hot Mix Asphalt to line domestic water supply reservoirs since the 1950s. A total of ten reservoirs store water in the EBMUD system.

Asphalt cement has also been used to line water pipes that supply potable water to humans.

When used for industrial retention ponds, the inertness of asphalt paving materials keeps liquid industrial waste material from percolating into the soil. This gives industry time to treat the liquid waste, and if needed, provides a platform with which to bring in mobile equipment to move the material to a processing location.

The ability of asphalt paving materials to be both chemically inert and strong enough to provide a structure for heavy equipment accounts for its use as both a landfill liner and cap. In landfills lined with asphalt paving materials modified earthmoving equipment can be employed to organize and compact landfill waste without fear of breaking the impermeable shell between the solid waste material and the soil.

Clean Fill
Many states have tested discarded asphalt pavement and determined that it should be categorized as clean fill.

Even the Environmental Protection Agency's Toxicity Characteristics Leaching Procedure (TCLP) test, their most extreme and rigorous test for determining the toxicity of a substance, failed to show any appreciable quantities of toxic materials from asphalt pavement material.

Recreational Uses
Asphalt pavements are a boon to the recreational industry. For years asphalt has been used to pave running tracks, bicycle and golf cart paths, in addition to its traditional use for basketball and tennis courts.

Recently, there has been a move in the recreation marketplace to combine exercise with nature. Throughout the country old nature paths and abandoned rail lines are being converted into thoroughfares for bicyclists, roller skaters and roller bladders, besides the occasional pedestrian who wants to view nature while they exercise.

Asphalt pavements provide a safe and durable surface with which to accommodate both wheeled and foot traffic.

Recycling
Asphalt pavements are completely recyclable. Asphalt roads are removed, recrushed, mixed with additional aggregate and fresh asphalt cement, remixed and placed back on the road.

Recycled asphalt pavement can be made to perform better the second, or even the third time around.

If you don't reuse worn-out asphalt pavement, you have to dispose of it, usually in a landfill. Hauling old pavement to dispose of it adds to the cost and does not make best use of a product that can be recycled. Asphalt pavements can be recycled numerous times.

Recycling asphalt makes roads "driver friendly." Replacing the surface layer renews skid resistance and smoothness, making the road safer and quieter.

In a report to Congress, the Federal Highway Administration estimated that over 70 million tons of asphalt paving materials were recycled in 1992.

Recycling our roads not only conserves natural resources and speeds construction, it saves the American taxpayer over $300 million each year.

Other Uses
Asphalt mixtures are used to pave cattle feed lots, poultry house floors, barn floors, and greenhouse floors. Asphalt not only provides an all-weather platform, it also provides protection against disease from waste materials. Asphalt is easy to clean and prevents pollution from getting into water supplies.

Asphalt mixtures are also used in sea walls, dikes and groins to control beach erosion. Its strength, waterproofing capability and inertness to sea water helps prevent the eroding action of tides and waves.

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