ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Filtering by
- All Subjects: Rheology
- Creators: Mobasher, Barzin
- Creators: Kaloush, Kamil
The first phase of the work investigates the influence of supplementary cementitious materials (SCM) in combination with ordinary Portland cement (OPC) on the rheological properties of fresh paste with and without the effect of superplasticizers. Yield stress, plastic viscosity and storage modulus are the rheological parameters which were evaluated for all the design mixtures to fundamentally understand the synergistic effects of the SCM. A time-dependent study was conducted on these blends to explore the structure formation at various time intervals which explains the effect of hydration in conjecture to its physical stiffening. The second phase focuses on the rheological characterization of novel iron powder based binder system.
The results of this work indicate that the rheological characteristics of cementitious suspensions are complex, and strongly dependent on several key parameters including: the solid loading, inter-particle forces, shape of the particle, particle size distribution of the particles, and rheological nature of the media in which the particles are suspended. Chemical composition and reactivity of the material play an important role in the time-dependent rheological study.
A stress plateau method is utilized for the determination of rheological properties of concentrated suspensions, as it better predicts the apparent yield stress and is shown to correlate well with other viscoelastic properties of the suspensions. Plastic viscosity is obtained by calculating the slope of the stress-strain rate curve of ramp down values of shear rates. In oscillatory stress measurements the plateau obtained within the linear visco-elastic region was considered to be the value for storage modulus.
Between the different types of fly ash, class F fly ash indicated a reduction in the rheological parameters as opposed to class C fly ash that is attributable to the enhanced ettringite formation in the latter. Use of superplasticizer led to a huge influence on yield stress and storage modulus of the paste due to the steric hindrance effect.
In the study of iron based binder systems, metakaolin had comparatively higher influence than fly ash on the rheology due to its tendency to agglomerate as opposed to the ball bearing effect observed in the latter. Iron increment above 60% resulted in a decrease in all the parameters of rheology discussed in this thesis. In the OPC-iron binder, the iron behaved as reinforcements yielding higher yield stress and plastic viscosity.
This research is a comprehensive study of the sustainable modifiers for asphalt binder. It is a common practice to use modifiers to impart certain properties to asphalt binder; however, in order to facilitate the synthesis and design of highly effective sustainable modifiers, it is critical to thoroughly understand their underlying molecular level mechanisms in combination with micro and macro-level behavior. Therefore, this study incorporates a multi-scale approach using computational modeling and laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between selected modifiers and the constituents of asphalt binder, at aged and unaged conditions. This study investigated the effect of paraffinic wax as a modifier for virgin binder in warm-mix asphalt that can reduce the environmental burden of asphalt pavements. The addition of wax was shown to reduce the viscosity of bitumen by reducing the self-interaction of asphaltene molecules and penetrating the existing nano agglomerates of asphaltenes. This study further examined how the interplay of various modifiers affects the modified binder’s thermomechanical properties. It was found that the presence of wax-based modifiers has a disrupting effect on the role of polyphosphoric acid that is another modifier of bitumen and its interactions with resin-type molecules.
This study was further extended to using nanozeolite as a mineral carrier for wax to better disperse wax in bitumen and reduce the wax's adverse effects such as physical hardening at low service temperatures and rutting at high service temperatures. This novel technique showed that using a different method of adding a modifier can help reduce the modifier's unwanted effects. It further showed that nanozeolite could carry wax-based modifiers and release them in bitumen, then acting as a scavenger for acidic compounds in the binder. This, in turn, could promote the resistance of asphalt binder to moisture damage by reducing the quantity of acidic compounds at the interface between the binder and the stone aggregates.
Furthermore, this study shows that iso-paraffin wax can reduce oxidized asphaltene molecules self-interaction and therefore, reduce the viscosity of aged bitumen while cause brittleness at low temperatures.
Additionally, a cradle to gate life-cycle assessment was performed for a new bio-modifier obtained from swine manure. This study showed that by partially replacing the bitumen with bio-binder from swine manure, the carbon footprint of the binder can be reduced by 10% in conjunction with reducing the cost and environmental impact of storing the manure in lagoons.