Wade Collins Pavement Technology

8/19/2019 Wade Collins Pavement Technology

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“Ways to Improve Asphalt

Pavement Performance”

Pavement Technology Inc.(PTI)

Wade CollinsVice-President


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Asphalt Pavement Analyzer Junior

(APA Jr.)


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APA Junior with Chiller


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Features of the APA Jr.

• Used to predict the Rutting, Fatigue, and Moisture susceptibilitycharacteristics of asphalt mixes in an environmentally controlledchamber wet or dry.

• Has the ability to run the Hamburg Test Method (AASHTO T 324-11)utilizing (2)Solid-Steel Wheels which apply a repeated loaddirectly atop the asphalt specimens.

• Has the ability to run APA Rut Test Method (AASHTO T 340-10)utilizing (2) Concave-Steel Wheels which apply a repeated load.The concave wheels run atop rubber pneumatic hoses.

• Can test 4 cylindrical (Marshall Pills, Superpave Gyratory

Specimens, Roadway Cores) or 2 beam specimens during onetest.

• The APA Jr. can also accommodate solid rubber wheels andpneumatic wheels

• Utilizes a PLC PC based Control System for all calibrations and

operations.


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Additional Features of APA Jr.

• Has an on-board “Hi-Pressure” Feature that allows a user to

test airport runway/taxiways(250+psi)

• Frequency Drive that allows a user to test mixes at multiple

speeds and multiple rates of loading

• Optional Chiller can be added to test low temperature FatigueTesting of Asphalt Mixes

• Ability to perform Studded Tire Wear Test

• Can be used to reduce mix design cost by comparing current

approved mixes with new innovative mixes


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BENEFITS OF PERFORMANCE

TESTING• Ability to identify marginal or poor mixes in the laboratory prior to

making an investment to place them on the roadway.

• Allows a user to develop a performance history of their mix designs,plant produced mixes, and in-place compacted mixes.

• Utilize it as a forensic tool when evaluating a road/runway slated forrehabilitation. Ex. Cores can be cut from the roadway/runway and eachlayer can be tested to determine where failures are occurring. Thisinformation can help determine the proper rehabilitation strategyneeded for a road.

• Allows a user to qualify aggregate sources.

• Allows a user to determine the performance of mixes with differentpercentages of RAP, RAS, Etc.


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AASHTO T340-10


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AASHTO T 340-10 Test Method

• Test Temperature: Hi-PG Temp(Ex. 76C, 64C,58C, 52C)

• Load 100lbs.

• Speed 60 cycles per minute• Test Duration 8,000 cycles (2 hours 15 minutes)

• Samples are tested in a dry environment

• Gyratory Samples(75mm or Design 115mm

samples are utilized for testing• Field Cores and Slab Specimens can also be

tested


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Rutted Beam and Cylindrical

Specimens Tested in the APA Jr.


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AASHTO T324-11


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AASHTO T 324-11 (Hamburg Test

Method)

• Test Temperature: 50C

• Load 158lbs.

• Speed 50 passes per minute

• Test Duration 20,000 passes (5-1/2 hours)• Samples are submerged in water during test

• Gyratory Samples(62+/- 2mm height x 150mmdiameter) will need to cut and “Butted

Together” inside the molds • Field Cores and Slab Specimens can also be

tested


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Hamburg-Type Cylindrical

Samples(Testing Complete)


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ASPHALT VIBRATORY COMPACTOR (AVC)


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AVC Features

• Compacts Hot Mix Asphalt into cylindrical and beam testspecimens. Target air void level can be controlled.

• Compacts specimens at the same amplitude, samefrequency, and same relative weight that is experienced

with a vibratory roller on the roadway.• Beam specimens are used for fatigue testing in the APA

• Can compact mixes at multiple frequencies and multipleamplitudes

• Produces beam specimens for the 4-point bending beamfatigue test

• Produce other geometric shaped samples


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250 lb

HMA Specimen

Bending Beam Fatigue Test


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Superpave Designed Beam

Properties Tested in APA

9.5mm HMA Rut

Susceptibility Tested in APA


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Superpave Designed Beam

Properties Tested in APA

12.5mm HMA Rut

Susceptibility

Tested in APA


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Fatigue Beam Tested to Failure


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Warm Mix Asphalt Laboratory Foaming System


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What Some States are Doing

Today-WMA?• 90% of all Warm Mix is the US today utilize water as the Foaming Agent

• States use the same design as conventional HMA for WMA. Some states use WMA designs due tothe reduced absorption of the asphalt binder into the aggregate if lower constructiontemperatures are utilized.

• Most states use the "drop-in method" where the mix is designed in the lab as a standard HMAand then the WMA additive (foam, chemical, etc) is dropped-in at the plant during construction.This tends to yield slightly lower air voids with the QC samples during production due to theincreased compactability offered by the WMA even at lower compaction temperatures. This canbe seen in the field as well where increased compactability causes lower air voids or higherdensities with the WMA compared to HMA.

• One of the main benefits of performing a Warm Mix Design in the Lab is that you will have a muchbetter idea of the densities expected in the field.

• In addition, if states use some type of water sensitivity test(TSR, Hamburg, APA, APA Jr., Etc), theresults with foamed asphalt may be different than with conventional HMA at elevated

temperatures.

• Finally, the mechanical properties of WMA are different from HMA in the early pavement life.These properties include rutting, stiffness (E*), fatigue and thermal cracking (tensile strength andstiffness) of the mixtures.


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R b ti T k S li D i


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Robotic Truck Sampling Device

(RTSD)


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RTSD at NCAT


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Benefits of the Robotic Truck

Sampling Device (RTSD)• Safely captures a representative sample along the cross section of

the mix

• RTSD can be used to sample asphalt or aggregate

• Sample sizes can be obtained up to 40lbs.

• Sampling time is less than a minute

• Volumetrics are more consistent (Asphalt Content, Gradation, VMA,VFA)

• Adjustments to the plant can be made in a timely manner

• Fewer adjustments have to be made

• Contractors have fewer test result disputes with DOT’s.

• Contractors can maximize pay factors by producing mix that is closeto the original job mix formula

• Prevents user from obtaining a segregated sample


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REAL-TIME QUALITY CONTROL SYSTEM (RTQC)


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Automatic Belt Sampler (ABS)


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DRYING OVEN


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Automatic Gradation Unit

R l Ti Q lit C t l (RTQC)


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Real Time Quality Control (RTQC)


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