Date of Degree
PhD (Doctor of Philosophy)
Civil and Environmental Engineering
Hosin "David" Lee
First Committee Member
Hosin " David" Lee
Second Committee Member
Third Committee Member
Fourth Committee Member
M. Asghar Bhatti
Fifth Committee Member
R. Christopher Williams
To evaluate the performance of Warm Mixture Asphalt (WMA) with varying amounts of recycled asphalt pavement (RAP) in comparison with Hot Mix Asphalt (HMA), comprehensive laboratory and field evaluations were conducted. Mix designs were performed for both WMA with a LEADCAP additive and HMA with large amounts of fractionated RAP materials. Hamburg Wheel Tracking (HWT) test was performed to evaluate the rutting and moisture susceptibility of both HMA and WMA laboratory mixtures. HMA mixtures with up to 50% RAP materials by binder replacement exhibited a better performance than WMA mixtures. However, when RAP materials were increased to 75% both WMA and HMA mixtures showed a superior performance. When a specially designed LEADCAP additive for a mixture with a high RAP content called "RAPCAP" was used, the performance was significantly improved. The existing Asphalt Bond Strength (ABS) test (AASHTO TP91-11) was modified to better evaluate the adhesion bond between asphalt binder and aggregate surface. Based on the modified ABS test results, it was found that the asphalt binder type significantly influenced the adhesion bond.
To evaluate the performance of WMA mixtures in the field, test sections were constructed in Iowa, Minnesota and Ohio. The test sections were successfully constructed with less compaction effort than HMA and met the required field densities per each DOT's specification. All HMA and WMA mixtures collected from the test sections passed the HWT and the modified Lottman tests, which indicates high resistance to rutting and moisture damage. The asphalt binders were then extracted and recovered from the field samples then re-graded following AASHTO M320 and AASHTO MP19-10. The recovered asphalt binder grades were found to be higher than the target grades due to the existence of RAP materials in the mixtures except for asphalt binders extracted from WMA mixtures produced using "RAPCAP" additive.
Dentistry has changed from its humble beginnings to the present day. One of the areas that have advanced the most in dentistry is the understanding of diseases that affect the teeth as well as the supporting structures. However, despite all of these advancements, some diseases still prove problematic. One of the most prominent examples of these diseases is dental caries. Dental caries is a disease caused by bacteria that leads to the destruction of tooth structure.
Traditional management techniques involved removal of tooth structure that is affected by caries, and even extending further to prevent recurrence, and then replacing the removed tooth structure with restorative material. However one of the most significant issues with the excessive removal of tooth structure is weakening of the structure of the teeth, making it prone to further breakdown. Modern understanding of the disease process has led to the discovery that not all carious lesions require removal and that it is possible to reverse the progression of caries leading to preservation of tooth structure that would traditionally be removed. However, despite the available evidence of such treatment, not all dentists have adopted the modern management strategies.
There is considerable evidence in the literature indicating that a significant amount of dentists still practice traditional caries management techniques, However this data was never recorded for the dentists in Iowa, thus this study aims to investigate the treatment decisions and weather they are in accordance with the modern management standards through a case based survey.
Asphalt Bond Strength, Field Evaluation, Hamburg Wheel Tracking, Modiffied Lottman Test, Recycled Asphalt Pavement, Warm Mix Asphalt
xiv, 136 pages
Includes bibliographical references (pages 132-136).
Copyright 2014 Taha Ahmed Hussien Ahmed
Ahmed, Taha Ahmed Hussien. "Investigating the rutting and moisture sensitivity of warm mix asphalt with varying contents of recycled asphalt pavement." PhD (Doctor of Philosophy) thesis, University of Iowa, 2014.