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HOT MIX ASPHALT
Longitudinal Joint Study for Hot Mix Asphalt
Longitudinal joint separation along hot mix
asphalt pavements has been a problem for a number of years
due in part to poor construction techniques. Deterioration
of the joint has increased the cost of maintaining these
projects and caused unnecessary reflective cracking when
overlaid.
This study was conducted to developed a standard
paving and/or compaction technique to reduce or eliminate
longitudinal joint separation.
On September of 1996 three modified rolling
techniques, a cutting wheel, a commercially manufactured
product labeled the Joint Maker as well as the standard
compaction procedure were used on a project on Route 1A
between the towns of Caswell and Van Buren. This project
was selected due to the excellent condition of the existing
longitudinal joint, effectively eliminating reflective
cracking of the new surface.
The experimental area contains six sections
averaging 600 meters (1969 feet) in length.
Section I used the Joint Maker and was compacted
from the low to high side of the mat.
Section II is the control section and was
compacted from the low side to within 150 millimeter (6
inch) of the longitudinal joint then pinched with 610
millimeters (2 feet) of the roller over the cold mat.
Section III was compacted with the first pass
of the roller on the hot mat with a 150 millimeter (6
inch) overlap on the cold mat then rolled from the low
to high side.
Section IV was compacted from the cold mat
with a 150 millimeter (6 inch) overlap on the hot mat
then compacted from the low to high side.
NATIONAL TRANSPORTATION
PRODUCT EVALUATION PROGRAM (NTPEP)
The National Transportation Product Evaluation
Program (NTPEP) was established by the American Association
of States Highway and Transportation Officials (AASHTO)
member departments in order to test materials, products
and devices of common interest. The primary goal of the
program is to provide cost-effective evaluations for the
states by eliminating duplication of testing. It can also
reduce duplication of effort by the manufactures that
provide products for evaluation.
The NTPEP Oversight Committee is comprised
of representatives of every participating AASHTO member
departments, the Federal Highway Administration and industry
associations (in a nonvoting capacity). The committee
guides the NTPEP by establishing policies and operating
procedures in accordance with stated program goals. The
committee develops an annual test program and makes decisions
and appointments to execute it. The NTPEP Oversight Committee
reports to the Standing Committee on Highways.
The project panel services at the pleasure
of the NTPEP Oversight Committee for the purpose of developing
a project work plan and providing oversight and guidance
throughout the evaluation process. The panel develops
the evaluation procedures and chooses the agencies to
perform the evaluation. The panel membership (six to ten
members) consist of transportation agency and industry
personnel who have an interest in the subject and have
background knowledge on the panel subject matter. Each
project panel will have a chairman and vice chairman that
coordinate the function of the project panel.
Present projects include:
Concrete Admixtures
Erosion Control Products
Geotextiles
Joint Sealers
Pavement Marking Materials
Raised & Snow Plowable Pavement Markers
and Adhesives
Sign Sheeting Materials
Structural Steel Coatings
Temporary Traffic Control Devices
Rapid Set Concrete Patching Materials
The Department is currently active on three
committees: Rapid Set Concrete Patching Materials, Erosion
Control Products, and the Concrete Admixtures.
The MDOT pays a membership fee of $4500 per
year to the NTPEP program as does each of the other states
and Puerto Rico. Therefore it is important that we maintain
an active roll in the NTPEP testing process to make certain
our Department's needs are met. Also the Department should
evaluate those products that the NTPEP report to be effective.
Initial data analysis appears to indicate
a potential savings exists when using some form of material
metering equipment.
Add just a pinch of salt...
For many years MDOT has used sand as its primary
material for treating highways in winter conditions. Increasing
prices, depleting reserves, and poor quality of sand has
caused the MDOT to rethink its material of choice. Salt
is beginning to emerge as a viable replacement for sand.
Environmental concerns and economic issues make it necessary
to be able to meter and track salt usage. A successful
transition to salt will require a trained workforce, a
willingness of the workforce to learn new techniques,
and the Departments commitment to supplying the proper
equipment (Road Temperature Sensors, Road Weather Information
Stations - RWIS, Ground Speed Control, Zero Velocity,
PPS, etc.).
Gate settings are very critical to the accurate
distribution of material. Several times during the winter
these settings were changed resulting in lost data.
For additional information or comments, please
feel free to contact Steve Colson at (207) 941-4529 or
email at "stephen.w.colson@state.me.us".
MDOT's Research Advisory Council selects Projects
for FY 2000 & 2001
A total of eleven research problem statement
submittals were presented to RAC in February. Six were
approved for funding for the next program.
Pedestrian Safety - This study
combines two submittals. The first will conduct a literature
review and analyze vehicle-pedestrian accidents with the
purpose of finding causes and developing recommended solutions
for pedestrian safety. The second component will investigate
the effectiveness and safety concerns of nonstandard crosswalk
devices such as barrels, cones, and signs.
Composite Action in Fiber Reinforced
Polymer Bridge Decks on Steel Girders - FRP bridge
deck systems have potential for use in bridge deck construction
and replacement projects. There is a lack of knowledge
in the amount of composite action between FRP decks and
steel girders. This study will investigate the composite
action by laboratory experiments and finite element modeling. |
Section V involved a first pass of the roller on the
hot mat 150 millimeters (6 inches) from the longitudinal
joint, then pinching the 150 millimeter (6 inch) uncompacted
mix with the second pass, then rolling from the low to
high side.
Section VI involved trimming 50 millimeters (2 inches)
off the first mat using a cutting wheel attached to a
grader. The second mat was then compacted from the low
to high side.
A visual evaluation of the project was conducted in October
of 1998. This evaluation revealed the following:
The Control Section (II) is showing the least amount
of deterioration with 1% of separation and 4 % of slight
raveling followed by Sections I, IV, III, V and VI respectively.
Section I has very little cracking but has raveling throughout
20% of the joint. Section IV is performing well with 2%
cracking and 7% raveling. The Joint for Section III is
starting to show signs of separation with slight raveling
on 7% of the area. Section V has 4% joint separation and
the greatest amount of raveling 25%. Section VI has the
greatest amount of joint separation at 5% and the least
amount of raveling at 0.2%. One area of this section has
an 8 m X 250 mm (10 in) crack and tack is still visible
on 60% of the joint.
The Control and Joint Maker Sections appear to be performing
the best after two seasons.
For additional information, contact Brian Marquis at
(207) 941-4067 or email him at brian.marquis@state.me.us
You can check on NTPEP status on their website http://www.aashto.org/prog_svcs/ntpep_main.html
For additional information, contact Guy Berthiaume at
(207) 287-2257 or email him at guy.berthiaume@state.me.us
DASHING THROUGH THE SNOW
During the winter of 1998-1999 the Maine Department of
Transportation (MDOT), Bureau of Planning, Research and
Community Services conducted a research project to evaluate
the potential benefits of using new material metering
and application equipment in its winter maintenance practices.
This equipment included: Case-Tyler Zero Velocity, Dickey-john
Ground Speed Control, Compu-spread Ground Speed Control,
and the Swenson Precision Placement System (PPS). The
Ground Speed Control systems and PPS unit meter material
using a sensor located on the shaft of the bed chain to
count revolutions and a signal from the speedometer (or
transmission) to determine speed and distance traveled.
The PPS system also uses a "high-speed shrouded spinner"
to apply material at the same speed the truck is traveling
in the opposite direction, effectively negating the speed
of the truck and eliminating most of the "bounce and scatter"
of material. The Case-Tyler systems sensor is positioned
on the shaft of an auger system which delivers material
to a "venturi" where forced air is introduced to propel
the material out the back of the truck. As with the PPS,
this saves material by minimizing "bounce and scatter"
and negating vehicle speed. Two conventional units were
also included in this research for comparison purposes.
During snow storms four research personnel weighed the
trucks before and after each trip and compared the actual
weight of material applied to the readings on the metering
equipment. Ratings were also conducted on several areas
of the highway to determine the effectiveness of the material
applied.
Numerous variables were encountered which impacted the
accuracy of the data collected. Slush, snow and ice buildup
on the trucks caused weights to be inaccurate. One truck
was weighed with this slush intact then washed clean.
The resulting difference was 1,275 pounds of material
washed from the truck.
Evaluation of Permeability of SUPERPAVE Mixes
- MDOT has fully implemented the use of SUPERPAVE
mixes. Accumulation of water between pavements layers
is detrimental to pavement life. SUPERPAVE mixes are exhibiting
a more porous or open pavement surface compared to our
traditional mixes. This research will evaluate field samples
and lab samples for permeability.
Utility Pole Crash Modeling - MDOT ranks
7th in the nation in vehicle - utility pole crashes based
on vehicle miles traveled. This study will investigate
current offset policies, review accident reports, and
review utility and clear zone policies of other transportation
agencies. Recommendations for improvements will be made.
And last but not least....MDOT, the USGS, and the Maine
Emergency Management Agency are collaborating on a small
drainage area study that will improve our ability to predict
peak watershed flows. Phase 1 will gage approximately
30 watersheds over a three year period to provide actual
flow data. This will be compared to flow data calculated
using current prediction equations. The impacts of this
study could not only save the state DOT dollars in having
more accurately sized culverts but could save significant
money by avoiding flood related damages.
For additional information or comments, please feel free
to contact Dale Peabody at (207) 287-5662 or email at
"dale.peabody@state.me.us".
RECENT PUBLICATIONS:
-
Airborne GPS Controlled Photogrammetry,
The Maine Experience, Tech. Report 98-10
-
Estimating the Magnitude of Peak Flow for Streams
in Maine for Selected Recurrence Intervals, Tech.
Report 96-7.
-
Instrumentation and Performance of Geosynthetics
Beneath Flexible Pavements in Winterport and Frankport,
ME, Tech. Report 97-14.
-
Computer Mediated Decision Making Phase II, Tech.
Report 96-6.
-
Hot Mix Asphalt Longitudinal Joint Specification,
Problem Solving 98-12.
-
Construction Behavior Report: Effects of Bitumen
Coating on the Axail and Lateral Loadings of Abutment
Piles Subject to Downdrag, Tech. Report 95-4.
-
Construction Report: Innovative Solutions to Buried
Portland Cement Concrete Roadways, Report 99-11.
-
First Year Intern Report: Potential Benefits of Adding
Emulsion to Reclaimed Base Material, Report 98-3.
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