Permanent deformation or rutting is a major hot mix asphalt (HMA) performance distress. Implementation of the Superior Performing Asphalt Pavement (Superpave) HMA mix design system was due, in part, to limit HMA rutting. Along with the Superpave system, performance testing equipment was developed to evaluate rutting potential; however, this equipment proved largely ineffective. As a result, agencies developed their own performance equipment, with the Asphalt Pavement Analyzer (APA) currently being used by many agencies for HMA rutting evaluation. The Mississippi Department of Transportation (MDOT) is utilizing the APA to evaluate HMA performance, but does not currently have established pass/fail criteria. Field rutting analysis and coring were conducted for twentyour pavements throughout Mississippi to determine in-service performance. Asphalt pavement analyzer testing was conducted on field cores and lab prepared specimens to evaluate mix characteristic influence on rutting and to develop APA failure criteria.

Asphalt concrete pavements on commercial airports in the United States are constructed according to the Federal Aviation Administration Advisory Circular 150/5370-10B, Item P-401, “Plant Mix Bituminous Pavements.” This specification does not provide guidance for using the Superpave gyratory compactor in the design of asphalt mixtures. This thesis describes a laboratory study of hot mix asphalt (HMA) mix design for airport pavements that uses the Superpave gyratory compactor. These recommendations are based on comparisons of volumetric property measurements of HMA mixtures compacted using Marshall compaction and Superpave gyratory compaction.

Being living systems unable to adjust their location to changing environmental conditions, plants display homeostatic networks that have evolved to maintain transition metal levels in a very narrow concentration range in order to avoid either deficiency or toxicity. Hence, plants possess a broad repertoire of mechanisms for the cellular uptake, compartmentation and efflux, as well as for the chelation of transition metal ions. A small number of plants are hypertolerant to one or a few specific transition metals. Some metal tolerant plants are also able to hyperaccumulate metal ions. The Brassicaceae family member Arabidopis halleri ssp. halleri (L.) O´KANE and AL´SHEHBAZ is a hyperaccumulator of zinc (Zn), and it is closely related to the non-hypertolerant and non-hyperaccumulating model plant Arabidopsis thaliana (L.) HEYNHOLD. The close relationship renders A. halleri a promising emerging model plant for the comparative investigation of the molecular mechanisms behind hypertolerance and hyperaccumulation. Among several potential candidate genes that are probably involved in mediating the zinc-hypertolerant and zinc-hyperaccumulating trait is AhHMA3. The AhHMA3 gene is highly similar to AtHMA3 (AGI number: At4g30120) in A. thaliana, and its encoded protein belongs to the P-type IB ATPase family of integral membrane transporter proteins that transport transition metals. In contrast to the low AtHMA3 transcript levels in A. thaliana, the gene was found to be constitutively highly expressed across different Zn treatments in A. halleri, especially in shoots. In this study, the cloning and characterisation of the HMA3 gene and its promoter from Arabidopsis halleri (L.) O´KANE and AL´SHEHBAZ and Arabidopsis thaliana (L.) HEYNHOLD is described. Heterologously expressed AhHMA3 mediated enhanced tolerance to Zn and to a much lesser degree to cadmium (Cd) but not to cobalt (Co) in metal-sensitive mutant strains of budding yeast. It is demonstrated that the genome of A. halleri contains at least four copies of AhHMA3, AhHMA3-1 to AhHMA3-4. A copy-specific real-time RT-PCR indicated that an AhHMA3-1 related gene copy is the source of the constitutively high transcript level in A. halleri and not a gene copy similar to AhHMA3-2 or AhHMA3-4. In accordance with the enhanced AtHMA3mRNA transcript level in A. thaliana roots, an AtHMA3 promoter-GUS gene construct mediated GUS activity predominantly in the vascular tissues of roots and not in shoots. However, the observed AhHMA3-1 and AhHMA3-2 promoter-mediated GUS activity in A. thaliana or A. halleri plants did not reflect the constitutively high expression of AhHMA3 in shoots of A. halleri. It is suggested that other factors e. g. characteristic sequence inserts within the first intron of AhHMA3-1 might enable a constitutively high expression. Moreover, the unknown promoter of the AhHMA3-3 gene copy could be the source of the constitutively high AhHMA3 transcript levels in A. halleri. In that case, the AhHMA3-3 sequence is predicted to be highly homologous to AhHMA3-1. The lack of solid localisation data for the AhHMA3 protein prevents a clear functional assignment. The provided data suggest several possible functions of the AhHMA3 protein: Like AtHMA2 and AtHMA4 it might be localised to the plasma membrane and could contribute to the efficient translocation of Zn from root to shoot and/or to the cell-to-cell distribution of Zn in the shoot. If localised to the vacuolar membrane, then a role in maintaining a low cytoplasmic zinc concentration by vacuolar zinc sequestration is possible. In addition, AhHMA3 might be involved in the delivery of zinc ions to trichomes and mesophyll leaf cells that are major zinc storage sites in A. halleri. / Pflanzen sind lebende Systeme, die nicht in der Lage sind ihren Standort sich ändernden Umweltbedingungen anzupassen. Infolgedessen weisen Pflanzen homöostatischeNetzwerke auf, welche die Mengen an intrazellulären Übergangsmetallen in einem sehr engen Konzentrationsbereich kontrollieren um somit Vergiftungs- oder Mangelerscheinungen zu vermeiden. Eine kleine Anzahl von Pflanzen ist hypertolerant gegenüber einem oder mehreren Übergangsmetallen. Einige wenige dieser metalltoleranten Pflanzen sind fähig Übergangsmetalle in beträchtlichen Mengen zu speichern, sprich zu hyperakkumulieren, ohne Vergiftungserscheinungen zu zeigen. Die Haller’sche Schaumkresse (Arabidopis halleri ssp. halleri (L.) O´KANE und AL´SHEHBAZ) aus der Familie der Kreuzblütler (Brassicaceae) ist ein solcher Hyperakkumulator für Zink (Zn). Sie ist nah verwandt mit der Modellpflanze Ackerschmalwand (Arabidopsis thaliana (L.) HEYNHOLD), die jedoch nicht-hypertolerant und nicht-hyperakkumulierend für Übergangsmetalle ist. Diese nahe Verwandtschaft erlaubt vergleichende Studien der molekularen Mechanismen, die Hypertoleranz und Hyperakkumulation zu Grunde liegen. Zu der Gruppe von Kandidatengenen, die möglicherweise von Bedeutung für die Zink-hypertoleranten und -hyperakkumulierenden Eigenschaften von A. halleri sind, gehört AhHMA3, ein Gen mit großer Ähnlichkeit zu AtHMA3 (AGI Nummer: At4g30120) aus A. thaliana. Es kodiert ein Protein aus der Familie transmembraner Übergangsmetall-Transportproteine, den P-typ IB ATPasen. Im Gegensatz zu den niedrigen AtHMA3 Transkriptmengen in A. thaliana wird das AhHMA3 Gen in A. halleri in Gegenwart verschiedener Zn Konzentrationen konstitutiv hoch exprimiert, insbesondere im Spross der Pflanze. Diese Arbeit beschreibt die Klonierung und Charakterisierung des HMA3 Gens und seines Promoters aus A. halleri und A. thaliana. Es wurde gezeigt, dass heterolog exprimiertes AhHMA3 Protein in metallsensitiven Hefestämmen eine erhöhte Toleranz gegenüber Zink und zu einem geringen Grad gegenüber Kadmium (Cd) jedoch nicht gegenüber Kobalt (Co) vermittelt.Weiterhin wurden im Genom von A. halleri mindestens vier AhHMA3 Genkopien, AhHMA3-1 bis AhHMA3-4, nachgewiesen. Eine Genkopie-spezifische Echtzeit-RT-PCR (real-time RT-PCR) deutete darauf hin, dass eine zu AhHMA3-1 und nicht zu AhHMA3-2 oder AhHMA3-4 ähnliche Genkopie die Quelle der konstitutiv hohen Transkriptmengen in A. halleri ist. In Übereinstimmung mit erhöhten mRNS Transkriptmengen inWurzeln von A. thaliana, vermittelte ein AtHMA3 Promoter-GUS (ß-Glucuronidase) Genkonstrukt GUS-Aktivität hauptsächlich in den Leitgeweben der Wurzeln jedoch nicht des Sprosses. Die vermittelte GUS-Aktivität durch Promoterfragmente von AhHMA3-1 und AhHMA3-2 in A. thaliana oder A. halleri Pflanzen spiegelte jedoch nicht die konstitutiv hohe AhHMA3 Expression im Spross von A. halleri wieder. Es wird vermutet, dass andere Faktoren die konstitutiv hohe Expression ermöglichen wie zum Beispiel die gefundenen kopiespezifischen Sequenzinsertionen innerhalb des ersten AhHMA3-1 Introns. Weiterhin ist es denkbar, dass der unbekannte Promoter der AhHMA3-3 Genkopie die Quelle der konstitutiv hohen AhHMA3 Transkriptmengen ist. In diesem Fall wird eine sehr hohe Ähnlichkeit zwischen den Sequenzen von AhHMA3-3 und der AhHMA3-1 vorhergesagt. Es konnten keine deutlichen Ergebnisse zur intrazellulären Lokalisierung gemacht werden, die eine exakte Einordnung der Funktion des AhHMA3 Proteins erlauben würden. Die bisher ermittelten Ergebnisse schlagen jedoch mehrere mögliche Funktionen für AhHMA3 vor: Ähnlich den AhHMA3 homologen Proteinen, AtHMA2 und AtHMA4, könnte AhHMA3 in der Plasmamembran der Zelle sitzen und dort zur effizienten Translokation von Zink aus der Wurzel in den Spross und/oder zur Zell-zu-Zell Verteilung von Zn im Spross beitragen. Falls AhHMA3 in der Membran der Vakuole sitzt, könnte es eine Rolle bei der Aufrechterhaltung niedriger zytoplasmatischer Zinkkonzentrationen durch vakuoläre Zinksequestrierung spielen. Zusätzlich ist es denkbar, dass AhHMA3 an der Abgabe von Zinkionen an Trichome und Blattmesophyllzellen beteiligt ist, die die Haupteinlagerungsorte für Zink in A. halleri darstellen.

Master of Science / Department of Civil Engineering / Mustaque Hossain / Because of recent rises in asphalt binder prices, state agencies and contractors are now willing to use higher volumes of reclaimed asphalt pavement (RAP). In this project, the effects of increasing RAP percentage and using fractionated RAP (FRAP) in hot-mix asphalt (HMA) mixtures have been studied. Fractionation involved processing and separating of RAP materials into at least two sizes, typically a coarse fraction and a fine fraction. This study evaluated the effects of increasing the proportions of RAP and FRAP on moisture resistance, rutting, and fatigue cracking of Superpave mixtures. Furthermore, the effect of using different sources of RAP in the mix has been investigated. HMA mixtures with five varying RAP and FRAP contents (20, 30, and 40% RAP, and 30 and 40% FRAP) were studied. The Hamburg wheel-tracking device (HWTD) test (TEX-242-F), the Kansas standard test method no. 56 (KT-56), or modified Lottman test, and the dynamic modulus test (AASHTO TP: 62-03) were used to predict moisture damage, rutting potential, and fatigue cracking resistance of the mixes. HMA specimens were made based on Superpave HMA mix design criteria for 12.5-mm (1/2-inch) nominal maximum aggregate size (NMAS) and compacted using the Superpave gyratory compactor. For the first source of RAP, results of this study showed that although mixture performance declined as the percentage of RAP increased, mixtures with even 40% RAP met minimum performance requirements. The second source of RAP, however, almost failed to meet minimum requirements even at 20% RAP. Results proved the maximum percentage of RAP allowed in the mix is highly influenced by its source. Although some improvements have been observed, especially for the second source of RAP, when RAP is compared to FRAP, FRAP does not seem to considerably affect performance of the HMA mixture.

Master of Science / Department of Civil Engineering / Mustaque Hossain / A recent study at Kansas State University has shown that asphalt producers in Kansas are producing hot-mix asphalt (HMA) mixtures with lower asphalt contents than those in the job-mix formula. These drier mixtures are thought to be susceptible to moisture. This project evaluated the effect of asphalt content on rutting and moisture resistance of HMA. Two different mixtures and four varying asphalt contents, optimum and lower, were selected. Another large-size mixture with four varying asphalt contents was also studied. The Hamburg Wheel Tracking Device (HWTD)test (TEX-242-F) and the Kansas Standard Test-56 (KT-56), or modified Lottman test, were used to predict moisture damage and rutting potential of these mixes. All specimens tested were prepared with the Superpave gyratory compacter. Results of this study showed the drier mixtures performed better in rutting and were less susceptible to moisture.Asphalt content significantly affects the number of wheel passes in the HWTD test. The study also revealed a weak correlation between asphalt film thickness and performance test results. Thus, the effect of varying asphalt content is nonconclusive from a durability point of view. However, performance simulations using a theoretical model show that very dry mixes in asphalt pavements are likely to have shorter performance lives.

While the oxidation of binders in hot mix asphalt (HMA) pavements and its subsequent detrimental effects on pavement life have been well recognized in the last few years, many important issues have not yet been investigated. Understanding how best to design mixtures taking this phenomenon into account and achieving maximum durability is an important and complex issue. This study was aimed at characterizing the effects of oxidative aging on durability in terms of mixture fatigue resistance of laboratory mixed-laboratory compacted (LMLC) samples. Direct tension tests were conducted on HMA samples to measure mixture stiffness and a Modified Calibrated Mechanistic with Surface Energy (CMSE*) analysis method was used to predict fatigue life. The effect of various mix design parameters was evaluated to understand their importance with respect to the aging phenomena and mixture fatigue resistance. Analysis of the results showed that aging has a significant negative effect on mixture fatigue resistance. Considerable increase in the stiffness modulus (Eve) of the mixtures was observed with age for all three mixtures analyzed. Air voids (AV) played a substantial role in affecting the fatigue resistance with aging, but a difference of 0.5% in binder content near the optimum level did not statistically change mixture durability in terms of fatigue resistance with aging. For the three mixtures in Texas included in this study, when comparing Eve, one month of artificial aging in the laboratory was equivalent to 10.5 months of natural aging in the field. A good correlation was also found between the Eve of the mixture and the Carbonyl Area (CA) and Dynamic Shear Rheometer (DSR) function of the extracted binder. Thus, a connection exists between the properties of the extracted binder, laboratory mixtures and field mixtures. This relationship will facilitate development of a more mechanistic aging component in pavement performance prediction models.

The infiltration of water in asphalt pavements promotes moisture damage primarily through damaging the binder cohesive bond and the adhesive bond between aggregates and binder. Moisture damage is associated with excessive deflection, cracking, and rutting. The first step in addressing the problems caused by the presence of water within pavement systems is quantifying the permeability of hot mix asphalt (HMA) mixes. This dissertation deals with the development of empirical-analytical and numerical approaches for predicting the permeability of HMA. Both approaches rely on the analysis of air void distribution within the HMA microstructure. The empirical-analytical approach relies on the development of modified forms of the Kozeny-Carman equation and determining the material properties involved in this equation through three dimensional microstructure analyses of X-ray Computed Tomography (CT) images. These properties include connected percent air voids (effective porosity), tortuosity, and air void specific surface area. A database of materials and permeability measurements was used to verify the developed predicting equation. The numerical approach, which is the main focus of this study, includes the development of a finite difference numerical simulation model to simulate the steady incompressible fluid flow in HMA. The model uses the non-staggered system that utilizes only one cell to solve for all governing equations, and it is applicable for cell Reynolds number (Rec) values that are not restricted by |Rec|≤2. The validity of the numerical model is verified through comparisons with closed-form solutions for idealized microstructure. The numerical model was used to find the components of the three-dimensional (3-D) permeability tensor and permeability anisotropy values for different types of HMA mixes. It was found that the principal permeability directions values are almost in the horizontal and vertical directions with the maximum permeability being in the horizontal direction.

Atlantic Canadian highways are vulnerable to impacts of climate change, including more frequent cycles of both wetting and drying, and freezing and thawing. These climate impacts coupled with continued increases in truck traffic can cause more severe and premature permanent deformation at high service temperature, fatigue and thermal cracking at low service temperatures, surface wear resistance, and ageing of the pavement. Such negative impacts can be mitigated with changes to the binder. However, replacing a local binder with a different imported binder can increase construction costs and cause supply problems. Alternatively, modifying agents can be used to adjust binder properties as required, but can also cause an increase in construction costs mainly due to their high cost and the need for highly specialized production techniques. The objective of this research project was to investigate the feasibility of utilizing underutilized household and packaging recycled plastics, that are generated in Atlantic Canada, as more cost effective alternatives or as co-modifiers to displace the amount of virgin modifiers used in hot mix asphalt application. The research study entailed analyzing physical characteristics of an array of modified binders and hot mix asphalt mixtures containing recycled low-density polyethylene, recycled polystyrene and the typical engineered virgin modifier (styrene-butadiene-styrene). The analysis included tests used commonly in pavement engineering to evaluate binders and asphalt mixtures. Results of this study suggests that these recycled plastics can be successfully utilized in asphalt binder as modifiers to enhance the functional properties of the mixture and reduce construction costs, thus creating an engineered value-added application of these underutilized resources as opposed to a disposal mechanism.

abstract: Perpetual Pavements, if properly designed and rehabilitated, it can last longer than 50 years without major structural rehabilitation. Fatigue endurance limit is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been implemented in the Mechanistic Empirical Pavement Design Guide software, currently known as DARWin-ME. This study was conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 9-44A to develop a framework and mathematical methodology to determine the fatigue endurance limit using the uniaxial fatigue test. In this procedure, the endurance limit is defined as the allowable tensile strains at which a balance takes place between the fatigue damage during loading, and the healing during the rest periods between loading pulses. The viscoelastic continuum damage model was used to isolate time dependent damage and healing in hot mix asphalt from that due to fatigue. This study also included the development of a uniaxial fatigue test method and the associated data acquisition computer programs to conduct the test with and without rest period. Five factors that affect the fatigue and healing behavior of asphalt mixtures were evaluated: asphalt content, air voids, temperature, rest period and tensile strain. Based on the test results, two Pseudo Stiffness Ratio (PSR) regression models were developed. In the first model, the PSR was a function of the five factors and the number of loading cycles. In the second model, air voids, asphalt content, and temperature were replaced by the initial stiffness of the mix. In both models, the endurance limit was defined when PSR is equal to 1.0 (net damage is equal to zero). The results of the first model were compared to the results of a stiffness ratio model developed based on a parallel study using beam fatigue test (part of the same NCHRP 9-44A). The endurance limit values determined from uniaxial and beam fatigue tests showed very good correlation. A methodology was described on how to incorporate the second PSR model into fatigue analysis and damage using the DARWin-ME software. This would provide an effective and efficient methodology to design perpetual flexible pavements. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2012

abstract: Heating of asphalt during production and construction causes the volatilization and oxidation of binders used in mixes. Volatilization and oxidation causes degradation of asphalt pavements by increasing the stiffness of the binders, increasing susceptibility to cracking and negatively affecting the functional and structural performance of the pavements. Degradation of asphalt binders by volatilization and oxidation due to high production temperature occur during early stages of pavement life and are known as Short Term Aging (STA). Elevated temperatures and increased exposure time to elevated temperatures causes increased STA of asphalt. The objective of this research was to investigate how elevated mixing temperatures and exposure time to elevated temperatures affect aging and stiffening of binders, thus influencing properties of the asphalt mixtures. The study was conducted in two stages. The first stage evaluated STA effect of asphalt binders. It involved aging two Performance Graded (PG) virgin asphalt binders, PG 76-16 and PG 64-22 at two different temperatures and durations, then measuring their viscosities. The second stage involved evaluating the effects of elevated STA temperature and time on properties of the asphalt mixtures. It involved STA of asphalt mixtures produced in the laboratory with the PG 64-22 binder at mixing temperatures elevated 25OF above standard practice; STA times at 2 and 4 hours longer than standard practices, and then compacted in a gyratory compactor. Dynamic modulus (E*) and Indirect Tensile Strength (IDT) were measured for the aged mixtures for each temperature and duration to determine the effect of different aging times and temperatures on the stiffness and fatigue properties of the aged asphalt mixtures. The binder test results showed that in all cases, there was increased viscosity. The results showed the highest increase in viscosity resulted from increased aging time. The results also indicated that PG 64-22 was more susceptible to elevated STA temperature and extended time than the PG 76-16 binders. The asphalt mixture test results confirmed the expected outcome that increasing the STA and mixing temperature by 25oF alters the stiffness of mixtures. Significant change in the dynamic modulus mostly occurred at four hour increase in STA time regardless of temperature. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013