Testing of asphalt binders and asphalt-aggregate mixtures using dynamic
mechanical analysis is becoming popular with improvements in high-speed
computers, precision equipment, and computer software. Researchers are trying
to describe the behavior of asphalt binders and asphalt-aggregate mixtures in
terms of their time- and temperature-dependent linear viscoelastic behavior.
The objectives of this thesis were to develop a simplified pneumatic test to
perform dynamic mechanical analysis (DMA), to evaluate the performance of the
pneumatic and hydraulic test systems using the computer software developed to
perform DMA tests, and, to develop a simplified method to evaluate the
experimental data obtained from DMA tests on aged asphalt-aggregate mixtures.
A simplified pneumatic test system was developed to perform DMA.
Computer software was also developed to perform DMA testing on both the
simplified pneumatic and hydraulic test systems. DMA was performed on both
test systems to compare their performance, and on aged asphalt-aggregate
mixtures to evaluate the application of the simplified method.
The results from the pneumatic and hydraulic test systems show that there
is about a 20 percent difference in the complex modulus, especially at high loading
frequencies. This is due to the compressibility of the air used in the pneumatic
test system. The compressibility of air is greater at warmer temperatures than at
cooler temperatures. Therefore, the application of the pneumatic test system to
perform dynamic testing should be limited to low frequencies ( < 2 Hz), low
temperatures ( < 25°C), and low load ( < 454 kg (1000 lbs.)) applications unless
a modification can be made to increase the pneumatic cylinder's response time to
match the hydraulic cylinder's response time.
The simplified analysis method developed in this thesis divides the DMA
results into four complex modulus and five phase angle parameters. These
parameters describe the shapes of the master stiffness and phase angle curves and
distinguished between the different asphalt-aggregate mixtures and the aging
methods performed on the aged asphalt-aggregate mixtures. The phase angle
parameters were reduced into two variables, peak frequency and peak angle,
which vary with the aging of each asphalt-aggregate mixture. The peak frequency
and peak angle decrease as the aging severity increases and the change of peak
frequency and peak angle vary with the asphalt-aggregate mixture and aging
treatment. Therefore, the complex modulus parameters and peak frequency and
peak angle may be good indicators to describe how a master curve's shape varies
with asphalt, aggregate, and aging type. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36228 |
| Date | 16 February 1993 |
| Creators | Ab-Wahab, Yunus Bin |
| Contributors | Bell, Chris A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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