Q:
What is Asphalt?
A: Asphalt is a dark brown or black cementitious
material which is a natural constituent of most crude oils found throughout the world.
Q:
What is Tar or Coal Tar?
A: A dark brown to black cementitious material
produced by the destructive distillation of Bituminous coal. This product is not used in the
Industry.
Q:
What is Aggregate?
A: A hard granular material of mineral composition
such as sand, gravel, or crushed stone used in prescribed
graduated fractions.
Q:
What is Hot Mix Asphalt (abbreviated as HMA)?
A: Specification grade asphalt (binder) is
heated and combined with specification crushed dried sand-gravel in a quality controlled
mixing plant. The HMA is then loaded onto trucks for
delivery to construction sites or kept in storage
silos.
Q:
What is an Asphalt Plant?
A: A manufacturing facility that produces asphalt
paving mixture.
Q:
What is Reclaimed Asphalt Pavement (RAP) Mix?
A: Removed asphalt (commonly called old Blacktop)
that is used in the recycling of asphalt pavements
along with new aggregate and new asphalt (binder)
being added. According to a study published by
the Federal Highway Administration and the
Environmental Protection Agency, asphalt pavement is
America's most recycled product. The asphalt
industry recycles 80.3 million tons of its own product
every year, the largest tonnage of any industry.
And, asphalt's 80% recycling rate is higher than any
other material's.
Q:
Is Asphalt and Hot Mix Environmentally Sound?
A: Yes, in fact it is the most recycled product
in the USA at 80 percent. That compares to significantly lower percentages for aluminum cans,
newsprint, plastic and glass beverage containers,
and magazines. Asphalt roads are removed, recrushed,
mixed with additional aggregate and asphalt
cement (binder), remixed, and placed back on the road.
In fact, in 2002, the EPA de-listed HMA plants as a
major source of emissions based on data leading them
to conclude that no asphalt concrete manufacturing
facility has the potential to emit hazardous air
pollutants (HAP) approaching major source levels.
See
http://beyondroads.com/visual_assets/EPA_Delisting_report.pdf
for more information.
Q: How Can Asphalt Reduce Noise Pollution?
A: Many studies over the years have shown that HMA
pavements reduce the sound produced at the
tire-pavement interface. Special surfacings such
as open-graded friction course (OGFC), stone matrix
asphalt (SMA), and gap graded blends provide excellent
skid resistance while reducing highway noise.
When the concrete Superstition Freeway in the Phoenix
area was overlaid with open-graded mixture, the
reduction in noise was so dramatic that residents of
other areas began demanding to have the concrete
freeways through their neighborhoods get the same
treatment. Arizona's state and local governments
soon responded with a $34 million resurfacing plan
that will encompass 115 miles of existing concrete
freeways in Maricopa County, which surrounds Phoenix,
the state capital. Several European countries
are using HMA as a means to mitigate noise issues on
their roadways at the source.
Q:
What is Flexible Pavement?
A: The ability of an asphalt pavement structure
to conform with loads and withstand temperature changes. Generally, flexibility of the
asphalt paving mixture is enhanced by a slightly higher
asphalt content.
Q:
What is a Pavement Structure?
A: A pavement structure with all its’ courses
of asphalt-aggregate mixtures, or a combination of
asphalt courses and untreated aggregate courses placed
above the subgrade.
Q: How Can Asphalt Pavements Reduce Delays for Road
Users?
A: Paving with asphalt cuts construction project
time significantly and eliminates long curing times.
As a result, traffic flows more smoothly, impact on
commerce is minimized and safety hazards are reduced.
Asphalt paving projects can be planned and carried out
to take advantage of low-traffic periods, like nights
and weekends, minimizing the project's impact on
motorists, residences and businesses.
Q: What Pavement Type Costs the Taxpayers Less?
A: For both the short term and the long haul,
asphalt pavement saves money on construction and
maintenance. Research shows that selecting the
right paving material, like HMA, will result in lower
initial costs and long term costs to the motoring
public compared to competing paving media. A
comparison by the Florida Department of Transportation
calculated initial construction costs to be nearly 30%
less for HMA than concrete. The department's
figures on long-term residual value of the HMA
pavement, meanwhile, were even more impressive: With
proper maintenance, the department concluded that
HMA's maintenance requirements, at about half those of
concrete, gave asphalt an advantage, the Florida
highway officials concluded. Similar savings
have been documented in other states including Kansas
and North Dakota.
Q:
What is Full-Depth Asphalt Pavement?
A: The term FULL-DEPTH (registered by the Asphalt
Institute with the U.S. Patent Office) certifies that the pavement is one in which
asphalt mixtures are employed for all courses above
the subgrade or improved subgrade.
Q:
Can Asphalt Pavement Be Used For Heavy Loads?
A: Asphalt pavement is the pavement of choice
for big or small parking lots, expansive shipping yards, areas for material handling, railroad
facilities, airports, etc., because it can take the
weight and the punishment.
Q: At big commercial airports, is asphalt
tough enough to take the punishment of
heavy planes?
A: Yes. Just ask the people who
operate some of the busiest airports in the country.
Some of the commercial airports with asphalt runways
include Baltimore-Washington International, Lindbergh
Field in San Diego, McCarren International (Las
Vegas), Memphis International, Newark International,
Oakland International, O'Hare International (Chicago)
and San Francisco International.
Q: Can You Give Examples Of How HMA Has Been Used
For Airport Runway
Reconstruction?
A: Sure! Here are a few:
►Between 85-90% of
all runways at the nation's 3,364 commercial airports
are surfaced with HMA, according to the Federal
Aviation Administration. Busy commercial
airports such as those in Boston, Las Vegas, Newark,
Oakland, San Francisco, and Toronto have main runways
surfaced with asphalt.
►Runway
4R-22L at Newark International Airport was completely
reconstructed in just 10 days. The contractor
placed 105,000 tons of HMA, meeting extremely
aggressive paving specifications. In addition to
paving, the contractor removed and replaced all runway
lights and saw-cut and sealed all joints on the
9,300-foot-long, 150-foot wide runway.
►In
rebuilding the main runway at Eglin Air Force Base in
Florida, the contractor met 100 percent of the
smoothness specs.
►At
the Front Range Airport in Colorado, the contractor
used a paver with a computerized grade control to
place a 4-inch overlay, and corrected an average of 25
inches per mile of deviation to 2 inches per mile.
►Two
7,500-foot-long runways at the Marine Air Corps
Station, Cherry Point, North Carolina needed paving.
The Marine Air Corps asked the contractor to minimize
transverse joints on the surface, so the contractor
built the runways with no joints whatsoever.
Q: Where Else Can Asphalt Pavements Be Used?
A: Streets and Highways: According to the
Bureau of Transportation Statistics, 94% of the 2.27
million miles of paved roads and highways in the U.S.
are surfaced with asphalt.
Race Tracks: Of the 35 NASCAR race tracks
across the country, 31 are paved with asphalt
surfaces.
Industrial Applications: Even where the
traffic is heaviest, such as at port container yards,
timber yards, and rail transfer yards, asphalt paves
the way.
Bike Paths, Sidewalks, and Recreational
Facilities: HMA is ideally suited for providing
paths that are aesthetically pleasing and blend well
with natural settings.
Hydraulic Structures: Fish hatcheries,
drinking water reservoirs, pond linings, and canal
linings count on asphalt for a long-lasting,
contamination-free surface.
Q: What is Deep Strength Asphalt Pavement?
A: A flexible HMA pavement in which the asphalt
base course is placed in one or more lifts of 4 or more inches compacted thickness.
Q:
What is Design Thickness?
A: The total pavement structure thickness above
the subgrade.
Q:
What is Capillary Action?
A: The rise or movement of water in the voids
of a soil or granular material caused by capillary forces.
Q:
What is Hydrostatic Pressure?
A: The pressure in a liquid under static conditions;
the product of the unit weight of the liquid and the difference in elevation between
the given points and the free water elevation.
Q:
What is Stone Matrix Asphalt (SMA)?
A: A tough, stable, rut-resistant, gap-graded
European technology mixture, originally known as Split
Mastix Asphalt.
Q:
What is Long Lasting or Perpetual HMA Pavement?
A: Perpetual Pavements use multiple layers of
highly engineered HMA material to produce a safe,
smooth, long-lasting road. The hot-mix asphalt (HMA)
design begins with a strong yet flexible bottom layer
constructed on a good foundation. The bottom
layer resists tensile strain caused by traffic, and
thus stops cracks from forming in the bottom of the
pavement. A strong intermediate layer completes
the permanent structural portion, and a final layer of
rut-resistant HMA yields a surface that lasts many
years before scheduled restoration. A Perpetual
Pavement provides a durable, safe, smooth,
long-lasting roadway without expensive, time-consuming
and traffic-disrupting reconstruction or major repair.
The concept is similar to that of a house that
periodically may need to be painted or re-roofed, but
that still stands the test of time.
Q: What is Rubblization?
A: Rubblization is a cost-effective means of
rehabilitating deteriorated portland cement concrete (PCC)
pavements. The concrete is broken into pieces,
and then it is overlaid with HMA. It minimizes
delays and allows for construction during off-peak
hours. The rubblized roadbed is left in place,
so that it does not have to be trucked off to a
landfill. This not only saves landfill space, it
eliminates many trips by trucks, saving diesel fuel
and reducing traffic congestion. The new asphalt
pavement will remain smooth, safe, and quiet for
years.
SUMMARY OF MINNESOTA RESEARCH FINDINGS
MAPA commissioned Erland Lukanen of ERES
Consultants to evaluate the performance history of HMA
Pavements with Aggregate Base and of Portland Cement
Concrete Pavements on the Mn/DOT Highway system. The
reports on both of these projects are now complete and
the results are interesting indeed.
Full Story
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