United States Department of Transportation
i
Controlling conductivity of asphalt concrete with graphite.
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2014-08-01
[PDF-3.63 MB]
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Abstract:Electrically conductive asphalt concrete has a huge potential for various multifunctional applications such as
self-healing, self-sensing, and deicing. In order to utilize the full spectrum of applications of electrically conductive
asphalt composites, precise control of the asphalt mixture resistivity is needed. Most of the previous research using
conductive fibers as the primary conductive additives observed a sudden transition from the insulated to conductive
phase, commonly known as the percolation threshold, which obstructs more precise conductivity control. Aiming to
control the electrical conductivity of asphalt concrete with a smooth transition from the insulated to conductive
phase, the researchers have selected graphite powders as an alternative conductive additive in this study. Nine types
of graphite having different particle shape, size, and origin were mixed with asphalt binders, and their effects on
imparting conductivity were investigated. Based on the results, the research team selected two types of graphite and
evaluated the effects on the electrical conductivity of asphalt concrete. The team also examined the effects of
aggregate gradation, binder content, and binder type.
The results showed that the electrical conductivity of asphalt mastic is sensitive to the graphite type. The
natural flake graphite is effective to mitigate the percolation threshold, and a sufficiently high conductivity can be
achieved by replacing a part of the fillers with graphite (the conductivity ranged from 10−6
to 10−2
/Ω•cm). The results
also showed that the binder type does not make a significant change in the mixture conductivity, but the aggregate
gradation brings approximately two order differences in the volume resistivity. Mechanical performance of the
conductive asphalt is also an important factor for practical field applications. The indirect tension test results showed
that the addition of graphite improves the indirect tensile strength up to 41 percent. The electrical and mechanical
data obtained from this study provide essential information on the selection of graphite type and asphalt mixture
design to achieve the proper electrical conductivity required for the probable multifunctional applications of asphalt
concrete, which will lead to technical innovations for sustainable pavements.
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