Date of Award

5-1-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Konstantin Sobolev

Committee Members

Habibolah Tabatabai, Rani El-Hajjar, Ilyav Avdeev, Ahmed Faheem

Keywords

Aging Resistance, Asphalt Mastics, Coal Combustion Products, Constructability, Damage Resistance, Fly Ash

Abstract

Developing a cost-efficient and long-term road infrastructure requires innovative approaches that are both green and environmentally sustainable. Today, building a sustainable, long-lasting, and efficient road infrastructure with little or no repairs is a challenging task and highly innovative technological breakthroughs are urgently needed. For many years fly ash has been effectively used as a partial replacement of portland cement in the production of different types of concrete, as well as in embankments and soil stabilization. On the other hand, the use of Coal Combustion Products (CCPs), including fly ash, as a mineral filler in asphalt pavements has been very limited. Only few researchers have reported on the benefits of CCPs in asphalt concrete. In this way, potential performance benefits that CCPs can offer to asphalt concrete are under-investigated.

Increasing the durability of asphalt pavement with CCPs additives is a promising technology that can significantly reduce the escalating costs related to rehabilitating and reconstructing of asphalt concrete pavements while offering a green and sustainable solution. In this study, asphalt binders from different sources and levels of modifications were blended with different types of CCPs particulate and natural filler to make mastics of different composition. This study investigates the beneficial effects of CCPs potential on rheological and performance related parameters of asphalt binders. Experiments were conducted at the mastics level to determine the effects of CCPs on stiffness, constructability, rutting, fatigue damage, thermal resistance and aging of asphalt binders utilizing the Superpave® methodology. As expected, increase in stiffness of the asphalt binders with CCPs was observed. The addition of up to 15% CCPs (by volume) produces no significant change in the rheological properties as measured by the shear complex modulus (G*). At higher dosages, such as 25% and 40%, the changes in stiffness appear to be significant. Statistical evaluation of the performance of mastics rheological and physical and chemical properties of CCPs demonstrated a good correlation with Rigden Voids, as well as content of CaO, SO3 and Al2O3. The research results proved that the particulate materials (CCPs and fillers), at all concentrations, improve the high temperature rutting resistance of mastics. Intermediate temperature fatigue damage results demonstrated significant dependency on CCP, binder and polymer modification types. In general, Class F fly ash is very beneficial material improving rutting, elastic recovery, and aging of mastics. At the same time, these mastics maintain the performance for workability and low temperature resistance without detrimental effects. Class C fly ash improved workability, and low temperature resistance without detrimental effects on the other performance indicators. At lower concentrations Spray Dryer Absorber (SDA) materials have demonstrated potential of extending the asphalt binder, but in general, due to variability of SDA materials test, results are not consistent; it is difficult to predict the influence of these CCP due to sensitivity to the type of binder and dosage. Therefore, further investigation is needed to understand the potential synergy between this type of CCPs and polymer modified binders.

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