Civil Engineering

 

Date of this Version

Summer 8-18-2007

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor Yong-Rak Kim. Lincoln, Nebraska: May, 2007. Copyright 2007 Francisco Aragão.

Abstract

Superpave, a set of advancements in testing devices and specifications for asphalt binders and mixtures, was limited to address the effects of aggregates. Because aggregates represent around 95% in mass of the asphalt mixtures, it is important to understand how these materials affect properties and performance of such mixtures. This research focus on how different types and contents of aggregates affect properties of mastics and asphalt mixtures, and their performance considering the viscoelastic nature of the asphalt material.

Five different types of aggregates and hydrated lime were used for sample fabrication together with two different binders. Several different tests were performed to the aggregates separately. Viscoelastic properties for both mastics and hot mix asphalt mixtures were characterized. In addition, the mixtures produced with those aggregates were also evaluated for rutting and fatigue performances using the APA and UTM-25kN machines.

Among the studies conducted in this research work are: restricted zone, a controversial concept and its redundancy; rutting potential of mixtures with different coarse and fine angularities; the stiffening potential of binders provided by different fillers; the stiffening provided by different contents of hydrated lime to asphalt concrete mixtures and fatigue and rutting potential of mixtures with different contents of hydrated lime.

The results indicate that the restricted zone should not be a criterion for the selection of mixture gradations, that angularity somewhat affects the rutting potential of asphalt concrete mixtures, that fillers of different materials provide different gain in stiffness for binders and that this improvement is binder dependent. Also, hydrated lime was found to have higher stiffening potential than general mineral fillers used in this study. Hydrated lime was also proven to improve the stiffness of asphalt concrete mixtures. Even though stiffening the mixtures, hydrated lime was shown to improve the fatigue performance of the mixtures. Finally, this filler also improved the rutting resistance of mixtures.

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