Thesis (Ph.D.) - Carleton University, 2005. / Includes bibliographical references (p. 250-267). Also available in electronic format on the Internet.

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Includes bibliographic references (p.82-87).

Warm mix asphalt (WMA) represents a group of technologies that allows production of asphalt mixtures at lower temperatures compared to traditional hot mix asphalt (HMA). This results in less fuel consumption and reduction in CO2 ¬and fumes emission. This research was conducted in order to provide North Dakota department of transportation (NDDOT) with a thorough study on state of the practice of WMA in USA and compare WMA performance with HMA. Extensive literature study was conducted, collecting reports and field experiment data from DOTs of states with climate similar to ND. Viewpoints of experts in the field were collected and analyzed using a comprehensive survey. These were added to analysis of collected data on WMA performance. The research results suggest using foaming processes (Double Barrel Green in particular) and chemical additives (Evotherm in particular) at this early stage with guidelines for modifications in WMA specification and testing compared to HMA. / North Dakota Department of Transportation

Viscoelastic and viscoelastoplastic characterization of pavement materials by means of simple testing and simple equipment is of great concern to pavement technologists. Another area of great concern is the replacement of premium aggregates by local materials after improving the engineering properties of the local materials. Such replacement is for the avoidance of the high costs of hauling the well-graded aggregates whose resources are also being depleted. These two research areas were combined in this study. A uniformly graded dune sand which is abundant in desert-like areas was upgraded with hydrated lime and stabilized with asphalt to improve its engineering properties. By variation of some of the mix design variables, a mix that complied with Marshall and Hveem stability criteria was produced. The effect of lime on the engineering properties of the mix was studied, and substantial improvements due to the addition of lime were observed. A mix that contained 10% Type S lime was found to have engineering properties that were comparable with those of conventional asphaltic concrete. Also, the effect of lime on the thermorheological, thermal, and elastic properties of bituminous mixes in general was studied. In addition to complying with the above-mentioned stability criteria, the lime-sand-asphalt mix was characterized by creep compliance, over wide ranges of time and temperature, so that the mix is available for thickness design by both the empirical and the theoretical methods of pavement design. New, simple equipment by which repeated as well as constant load creep tests can be easily performed was introduced and used to develop a viscoelastic-plastic constitutive law of the designed lime-sand-asphalt mix. Both the equipment and the testing are simple and gave repeatable measurements. Models for the elastic, plastic, viscoelastic and viscoplastic responses of the designed mix were derived from measurements taken by this equipment and by using computerized regression analysis techniques. Generalized models for the viscoelastic strain during the N-th loading and the N-th recovery period were developed. A FORTRAN computer program was written for computing the four strain components mentioned above separately, and for computing the total strain component for large numbers of load repetitions.

This study aims to understand intermingling process between rejuvenators and aged asphalt binders in reclaimed asphalt pavement (RAP) materials during RAP recycling operations in pavement construction. This study presents results of a laboratory study on the use of rejuvenators to recycle age hardened asphalt binders in RAP. Laboratory Hot Mix Asphalt (HMA) samples were prepared with RAP millings from one specific pavement and a commercial rejuvenator, with 80 to 90 percent RAP content. The following mixes with various amount of the rejuvenator were evaluated: a control mix prepared from burned RAP aggregate and virgin asphalt binder, another control mix prepared with heated RAP, a recycled RAP mix with 1% rejuvenator (at the weight of the total mix), a recycled RAP mix with 0.5% rejuvenator, and a recycled RAP mix with 0.5% rejuvenator and 0.5% virgin asphalt binder. Dynamic modulus test results of laboratory prepared samples were obtained for a range of temperatures over an eleven-week period of accelerated aging at 60ºC in an inert gas oven and a conventional convection oven. Accelerated aging protocol was used to evaluate the intermingling process associated with diffusion mechanism between the rejuvenator and aged asphalt binder while an argon inert gas oven provides an environment where oxidation-related ageing and hardening in rejuvenated asphalt binders can be eliminated. The dynamic modulus data of six distinct mixes were statistically analyzed and compared to the results reported in the literature for virgin and low percentage recycled mixes. Collected data suggest that the use of rejuvenator is a viable option for recycling HMA with high RAP material content.

The Asphalt Pavement Analyzer (APA) device was used to characterize the impact of various mix factors on the development of permanent deformation in dense-graded mixes given a standard compactive effort. Factors included two aggregate sizes, three VMA levels, two fines contents, three binder contents and four binder types. All specimens received the same compactive effort (100 gyrations) using the Superpave Gyratory Compactor (SGC). For some tests, testing temperatures followed the standard APA test protocol (64C) and for some others, the test temperature was set at the high temperature of standard performance asphalt binder grade (e.g. 70C for a PG 70-22 asphalt binder). Statistical results showed that increased binder content increased permanent deformation in the 19.0 mm dense graded mixes prepared with the PG 64-22 binder irrespective of the other mix parameters. These effects were not noted in the mixes prepared with PG 70-22 and PG 76-22 binders, when tested at 64C. However, the same effect was noted when mixes prepared with PG 70-22, PG 70-22 Modified and PG 76-22 binders were tested at the high temperature of standard performance asphalt binder grade. All mixes prepared with the stiffer binders showed very low permanent deformation when tested at the standard 64C regardless of the value of the other mix parameters. The statistical analysis of permanent deformation provides evidence that the mixes prepared with the PG 76-22 and PG 70-22 Modified binders perform better than mixes prepared with the PG 70-22 and the PG 64-22 binders. The effect of VMA on permanent deformation depends on the maximum aggregate size used, test temperature, binder type and the fines content. It was not possible to separate these interaction effects. The results of this study suggest that the APA is relatively insensitive to changes in mix properties within the range of variables studied, when using the standard APA test temperature (64C). However, the APA device is sensitive when the test temperature matches the high temperature of the standard performance binder grade (e.g. 70C for a PG 70-22 binder). Based on the results of this study, it appears that the APA can be used to indicate the rut resistance of a mixture. Although some of the mix factors have an interactive effect in the mixes, the APA has a potential to predict the relative rutting of the hot mix asphalt mixes even when polymer modified mixes are used, provided that testing is conducted at the appropriate test temperature. / Graduation date: 2005

Environmental factors such as temperature, air, and water can have a profound effect on the durability of asphalt concrete mixtures. In mild climates where good quality aggregates and asphalt cement are available, the major contribution to deterioration may be due to traffic loading and the resultant distress is manifested in the form of fatigue cracking, rutting, and raveling. But, when more severe climates are coupled with poor materials and traffic, premature failure may result. The objectives of this research are twofold and includes: (1) development of a test system to evaluate the most important factors influencing the water sensitivity of asphalt concrete mixtures; and (2) development of laboratory testing procedures that will predict field performance. This research also addresses the hypothesis that much of the water damage in pavements is due to water in the asphalt concrete void system. It is proposed that most of the water problems occur when voids are in the range of about 5% to 12%. Thus, the term "pessimum" voids is used to indicate that range (opposite of optimum). In order to evaluate the hypothesis and the numerous variables, the Environmental Conditioning System (ECS) was designed and fabricated. The ECS consists of three subsystems: (1) fluid conditioning, where the specimen is subjected to predetermined levels of water, air, or vapor and permeability is measured; (2) an environmental cabinet that controls the temperature and humidity and encloses the entire load frame; and (3) the loading system that determines resilient modulus (M[subscript n]) at various times during environmental cycling and also provides continuous repeated loading as needed. The ECS has been used to evaluate four core materials and also to investigate the relative importance of mixture variables thought to be significant. Many details regarding specimen preparation and testing procedures were evaluated during a "shakedown" of the ECS. As minor variables were resolved, a procedure emerged which appears to be reasonable and suitable. An experiment design for the four core mixtures was developed, and the overall experiment design included three ranges of void ( <5% low; 5-12%, pessimum; > 12% high). Six-hour cycles of wet-hot (60° C) and wet-freeze ( -18° C) are the principle conditioning variables, while monitoring MR at 25° C before and between cycling. A conventional testing procedure (AASHTO T-283) was also used on the core mixtures to provide a baseline for comparison. Results to date show that the ECS is capable of discerning the relative differences in "performance" such as MR. Three hot cycles and one freeze cycle appear to be sufficient to determine the projected relative performance when comparing different aggregates, asphalts, void levels, loading, etc. Based on these results, a water conditioning procedure has been recommended and also a procedure for water conditioning specimens prior to testing in fatigue, rutting, and thermal cracking. / Graduation date: 1992

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 105-108). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; [256] p. : ill. (some col.). Includes abstract. Includes bibliographical references.