Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
Ronald C. Williams
With the prices of crude oil increasing and reserves of natural nonrenewable resources dwindling over time, the needs for adopting greener and more sustainable approaches in various construction activities are stronger. The asphalt production industry has been keen during the last few decades to reduce the impact of its activities on the environment especially regions adjacent to its operating activities and on natural resources. Thus, recycled materials such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) are increasingly being used in the production of asphalt mixtures. Moreover, different techniques to produce and place asphalt mixtures at lower temperatures than the typical hot mix asphalt (HMA) temperatures are recently being used. These techniques are currently known as warm mix asphalt (WMA) technologies.
The performance of three commonly used warm mix technologies: Advera, Evotherm J1 and Sasobit were examined in comparison to a control HMA mixture with respect to dynamic modulus and permanent deformation (flow number). Each mixture was developed using a PG 64-22 binder and two types of aggregates: limestone or quartzite. In addition, this study will look into whether WMA additives enable the production of high RAP content (30%) mixtures with comparable performance to HMA.
Warm mix asphalt mixtures prepared at 120°C and compacted at 110°C showed no concerns regarding workability or compactability even in mixtures incorporating 30% RAP. Dynamic modulus and flow number tests were conducted to assess the stiffness and permanent deformation resistance, respectively. The performance tests data suggested that there is a significant difference in the performance of HMA mixtures and the three WMA technologies investigated. Dynamic modulus data of WMA mixtures were consistently lower compared to HMA, with the difference in E* values decreasing with increasing temperature. The incorporation of RAP increased the dynamic modulus of all mixtures but HMA mixture was still higher than WMA mixtures. The impact of RAP incorporation decreased as temperature increased. Finally, the rutting resistance of WMA mixtures was considerably lower compared to HMA mixes even after incorporation of RAP. Thus, WMA technologies suitability for hot regions needs to further investigated.
MEPDG design runs were performed to assess the performance of lab produced asphalt mixtures incorporating WMA and RAP and compare it to the performance of corresponding control mixtures. MEPDG output agreed with laboratory test results specifically for rutting prediction and terminal IRI values. The statistical analysis of variance indicated that the EvothermTM mixtures performance was generally different from the control mixtures regardless of type of aggregates used.
Finally, the rheological behavior of two binders: a base binder and a polymer modified binders incorporating two types of warm mix asphalt (WMA) additives were studied through an extensive testing scheme. The warm mix additives used were an organic wax and an oily chemical additive. Tests performed comprise basic rheological tests such as rotational viscometer, viscous flow, creep, temperature and frequency sweeps. The output data of these tests were used to construct Viscosity-Temperature Susceptibility (VTS) curves and master curves to study the behavior of the binders tested. The performance of the unmodified WMA binders was similar to the control binder at the midrange and high test temperatures. On the other hand, the modified binder incorporating the waxy WMA additive exhibited stiffer behavior indicating the presence of more advanced polymer networks within the binder structure. Moreover, the wax additive had an anti-oxidizing effect on the aging rate of the binder using pressure aging vessel (PAV).
Mohamed Hamada Rashwan
Rashwan, Mohamed Hamada, "Characterization of Warm Mix Asphalt (WMA) performance in different asphalt applications" (2012). Graduate Theses and Dissertations. 12891.