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In recent years, more and more states have
transferred primary responsibility for quality control over construction
materials to the asphalt producers doing the work. In the industry, it’s
called “going to QC-QA,” and by this year, 34 states have done just that
in hot-mix asphalt, says Mike Rafalowski, a materials engineer with the
Federal Highway Administration.
Meanwhile, the industry’s shift to Superpave has
created a whole new generation of laboratory equipment that is much more
complex than previous testing devices. Brad Cruea is quality control
manager for Milestone Contractors LP, Indianapolis, which operates 12
plant laboratories and employs 17 state-certified technicians.
“Instead of the old Marshall compaction hammer
we have a $25,000 gyratory compactor to compact specimens and help us
calculate voids in the mix,” says Cruea. “And to determine binder
contents, we have a $10,000 ignition oven. In the past that was done
with a $500 centrifuge. As the industry has developed, the technology
has grown more complex and the people have had to grow along with it.”
As more and more asphalt producers shoulder the
load of this intensive quality control, those same producers find
themselves responsible for hiring, training, and retaining good
technicians to work in their laboratories. And the next step — making
required hot-mix plant adjustments to maintain quality control — is even
trickier, and requires people with even more experience.
“We do most of our training in-house,” says
Cruea. “We train in the proper application of the piece of equipment,
and we train people how to adjust the mix to meet specifications and
standards. We bring people into our three mix-design laboratories in
January and February, and for two solid months we just train technicians
and do mix designs for the following year.”
State certifications
Not just anyone can test bituminous materials
for federally-funded highway work. The FHWA requires all sampling and
testing technicians to be certified by a state-sanctioned organization,
says Lee Gallivan, pavements and materials engineer in the FHWA’s
Indianapolis office. “The state Departments of Transportation come up
with their own certification programs and determine how they’re going to
get the programs out to the people,” he says. |
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Gallivan agrees that today’s plant laboratory people
are challenged by the new technology for testing both asphalt mixes and
binders. How does he deal with it? “We just try to communicate better, to
get the latest stuff out the door,” says Gallivan. As resources for
training, he mentions The Asphalt Institute and the National Center for
Asphalt Technology.
“Our biggest challenge is to maintain the
proficiency of our technicians and to have enough certified technicians to
do the work,” says John Ingraham, superintendent of quality assurance at
Tilcon Connecticut Inc., Newington, Connecticut. Tilcon has 22 asphalt
plants and 19 plant laboratories in Connecticut. “The pool of people that
want to work construction is not that great,” says Ingraham. “Many people
don’t want to do this kind of work anymore.”
The answer, he says, is simply to hire entry-level
people, give them some on-the-job training, and get them certified. In six
New England states, the New England Transportation Technician Certification
Program is responsible for certifying construction laboratory technicians.
If you’re certified by NETTCP, you can work anywhere in Maine, New
Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut.
“I interview people and hire them on their merits,”
says Ingraham. “I’ve got 40-year-old mothers and 18-year-old kids. It’s not
a bad job,” he says of his technician position. “But it can get a little
strenuous when you have a 50-pound sample of rocks to carry around.”
Ingraham says his on-the-job training takes six
months to a year. Then, the technician attends a certification course
operated by NETTCP. The hot-mix asphalt technician training takes a week.
Then the candidate is tested and can become certified. Most states require
certification to be updated periodically — in New England it happens at
five-year intervals.
“Typically most of our technicians are certified
within two years of employment,” says Milestone’s Cruea. “Finding these
people is difficult. We’re a union contractor, and we don’t have a pool of
people to draw from the way we do with construction workers.” Usually,
classified advertisements in two or three local newspapers will draw “a
decent response,” says Cruea.
In Oregon, the Asphalt Pavement Association of
Oregon has a contract with the state DOT to train materials technicians for
certification. APAO annually trains more than 300 technicians in mix design,
Asphalt Tech 1 and 2, aggregates, and density. The program is set up to
simulate field conditions for sampling and testing, says Jim Huddleston,
APAO’s executive director.
Qualifications of personnel
The National Asphalt Pavement Association publishes
a booklet called Quality Control for Hot Mix Asphalt Operations, (QIP 97).
For four job titles, the booklet contains a job description, qualifications
and training, and a description of role in the job. The four jobs are:
Facility Superintendent and Foreman, Quality Control Supervisor, Quality
Control Technician, and Facility Operator. Furthermore, says the NAPA
booklet, a quality control training program should include:
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Aggregate sampling and splitting.
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Aggregate gradation tests.
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Hot-mix asphalt temperatures, sampling, and
splitting.
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Asphalt content testing.
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Compaction of laboratory specimens.
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Bulk specific gravity measurements.
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Maximum specific gravity.
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Strength tests.
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Calculation of voids, voids filled, and voids in
the mineral aggregate.
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Development of the mix design.
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Controlling the cold feeds and the hot bins.
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Facility operations and controls.
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Paving operations and control.
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Random sampling.
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Pavement sampling.
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Plotting control charts.
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Keeping records and reports.
The
aggregate challenge
Maintaining proper control over aggregates and their
gradations is another major challenge, industry officials told Better Roads
editors. In Germany, for example, where extremely durable hot-mix asphalt
pavements are built routinely, asphalt producers fractionate their
aggregates into 10 or 12 bins, each containing a different size of stones.
“Europeans spend a lot of time getting their
aggregate gradations done correctly, and less time in testing during
production than we do,” says Huddleston of Oregon. “Their theory is that if
they get the right sizes and proportions of rock, the product will be there.
They simply use recipe mix designs that specify certain amounts of each
rock.
“In a lot of states, U.S. asphalt producers buy
their aggregates from a supplier,” says Huddleston. “And our aggregate
suppliers need to make sure that they understand exactly what specifications
our mixes call for. In general, they tend to do the least amount of
screening and checking that they can get away with.”
An example of the aggregate challenge comes from
Illinois, where Pat Koester manages plant operations and quality control for
Howell Asphalt Co., based in Mattoon. The company operates 10 hot-mix plants
and as many plant labs. “If we pick one problem, it’s maintaining proper
gradations from the quarries,” says Koester. “Let’s say you design a mix
based on 32% passing the No. 4 sieve, and the material you get from the
quarry has 44% passing the No. 4 sieve. Now you have to adjust your mix
blend. More than likely, that rock will put more voids into the mix. You’ll
probably have to reduce or add sand, depending on how the rest of the blend
below the No. 4 reacts to the added finer material.”
Milestone’s Cruea agrees that changes in aggregates
from the quarry can present a challenge. “We keep in good communication with
our aggregate suppliers, and we hope they have a good quality control
program,” says Cruea. “They need to let us know if they change a crusher,
change the ledge they’re working on, or add a piece of equipment.
“If they go to a different ledge, or location, the
main thing affected is the specific gravity of the aggregate,” says Cruea.
“And when specific gravity or the absorption value of the rock changes, it
pretty well changes the whole mix design. You have to make adjustments or
even redesign a mix. |
