Date of Award

January 2020

Document Type

Thesis

Degree Name

Master of Engineering (MEngr)

Department

Civil Engineering

First Advisor

Nabil Suleiman

Abstract

The number of Superpave mix design of gyrations (Ndesign) has been adopted by North Dakota Department of Transportation (NDDOT) to produce mixes of same density representing the field conditions for a specified amount of traffic. As Superpave mix design was developed for high volume roads, various research suggests that there is a need to develop a new mix design criterion for medium and low volume traffic. For low volume roads durability performance is generally affected by the environment and not the traffic volume. Some researchers notice that the Ndesign of 75 gyrations for a 20-year traffic loading (in millions of ESALs) between that 0.3 and 3 are too high and needs to be reduced. High Ndesign numbers tend to lower the asphalt binder, thus lower the durability of asphalt mix. In contrast, if Ndesign is reduced it tends to increase the asphalt binder, thus increase the durability of asphalt mix.

The main objective of this study is to determine the effect of varying number of design gyrations on hot mix asphalt (HMA) performances in terms of low-temperature cracking (LTC), fatigue cracking (FC), and rutting distresses. Project mixes that were chosen were constructed based on Ndesign values of 75, 65, and 55 or 50 gyrations. Test results showed that the higher number of gyrations with less asphalt the lower fatigue cracking and lower low-temperature cracking resistance. In contrast, the mixes with lower number of gyrations with higher asphalt contents showed higher resistance to cracking. Also, results showed that PG 58H-28 had slightly better fracture energies than PG 58H-34. Lastly, lab mixes had better fracture energies as compared to field mixes.

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