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Benefits of Smooth Pavements
1. Smoother roads are important to the road users (taxpayer)
2. Smoother roads last longer
3. Smoother roads stay smoother longer
4. Smoother roads save money
5. Smoother roads are safer
6. Smoother roads improve mobility
A Mobile Silo and Mixer
• The MTV is a part of the asphalt mixing plant on the
job site.
• It receives the material from the delivery truck and then remixes and blends
this to the original plant specification.
Why Use a MTV
• Eliminate Physical Segregation
• Re-Mix HMA
• Provide Site Storage
• Stop Truck Delays
• Eliminate Paver Stops/Start
• Smoother Roads Last Longer
• Require Less Maintenance
Stopping Cost Money!
35’ / min * 60 min= 2100’ / HR
150’ stop for 2.5 min
2100’ stopped 14 times
35’ / min * 2.5 min= 87.5’
87.50 * 14= 1225’
2100 – 1225= 875’ / HR
Production
Thermal Segregation
• 20°F (11°C) Differential = 1%
to 2% Air Voids
• Over 7% Air Voids Reduces Life
• Each 1% Over 7% Reduces Life
by 10%
Source: WSDOT
Thermal Segregation
Temperature Differentials greater
than 25°F results in 2% increase
in air voids and result in failing
density profiles approximately 90
percent of the time.
Source: WSDOT
Both Loose Heat
Thermal Segregation is one of the reasons that
asphalt pavement prematurely fails.
Aggregate Size Segregation is caused by the
same movement of the delivery vehicle as
Thermal.
Bring your machine up to the truck and then raise the bed when
possible.
When unloading a truck, discharge the material as a mass instead
of dribbling the material into a paver.
RP195
Truck Exchanges
What about Time ? Time =Production
Pulling Force( Force P )
Head Of Material( Force M )
Shear Force BetweenThe Material and the Screed. ( Force F )
Reaction Of MaterialUnder The Screed
( Force R )
Weight Of The Screed( Force W )
FR
M
P W
Forces acting on the screed
6.4%
Voids14.8%
Voids
Severe Thermal Segregation
Mean mix temp has dropped ~ 20 F
Localized temperature differential is key
Paver stop ~ 35 minutes ~ 20 ft of
mat not rolled during this time.
Area becomes low density
regardless of temp at time
of placement Bump felt at transition
Rolling delay
Surface temp ~ 117
F before rolling
15.0 % Voids
Paver Stops
• Remove trucks from paver
• Trucks are not bumping
paver causing it to change
speed and put marks in mat
Non-Contact Paving
Constant Speed Paving
• Changing speeds while
paving changes the forces on the screed
• Shuttle Buggy allows paver
to keep moving
• Stores mix on site
• Paver doesn’t slow down to accept truck
Dump Person
Be sure the truck driver and the paver operator know
when you are between them.Be aware if the back up alarms on the trucks are not
working.
Communicate well with the truck driver when it comes
time to pull out in live traffic. Make sure it is safe.
Keep unwanted material off the road in front of the
paver
Looks out for power lines and limbs
Material Flow & Loading Material
RP195
Remember, make sure that the C2 has at least 1/3rd to
2/3rd capacity at all times.
Proper material transfer
RP195
If the insert is always out or low, you will
see the same problem with Material
Segregation.
What about the Insert?
If the insert is always out or low you will see
problems with Material Segregation.
Stop the paver before the material drops
below flow gate.
Keep the conveyor deck covered with a
minimum of 12 to 24 inches of material.
CONCLUSION:
• Initial Ride Quality can be improved by minimizing stops and including a material transfer device
• When used properly, Shuttle Buggy improved the ride quality and eliminated thermal & physical segregation
• Results show no significant thermal segregation when a material transfer device was used
Source: Texas Transportation Institute