Laboratory and Field Evaluation of Modified Asphalt Binders and Mixes for Alaskan Pavements

In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle (δ) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, ΔT, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation

Verification of Job Mix Formula for Alaskan HMA

INE/AUTC 14.1

Highly Abrasion-resistant and Long-lasting Concrete

Studded tire usage in Alaska contributes to rutting damage on pavements resulting in high maintenance costs and safety issues. In this study binary, ternary, and quaternary highly-abrasion resistant concrete mix designs, using supplementary cementitious materials (SCMs), were developed. The fresh, mechanical and durability properties of these mix designs were then tested to determine an optimum highly-abrasion resistant concrete mix that could be placed in cold climates to reduce rutting damage. SCMs used included silica fume, ground granulated blast furnace slag, and type F fly ash. Tests conducted measured workability, air content, drying shrinkage, compressive strength, flexural strength, and chloride ion permeability. Resistance to freeze-thaw cycles, scaling due to deicers, and abrasion resistance were also measured. A survey and literature review on concrete pavement practices in Alaska and other cold climates was also conducted. A preliminary construction cost analysis comparing the concrete mix designs developed was also completed

Characterization of Alaskan Hot-Mix Asphalt containing Reclaimed Asphalt Pavement Material

In order to properly characterize Alaskan HMA materials containing RAP, this study evaluated properties of 3 asphalt binders typically used in Alaska, PG 52-28, PG 52-40, and PG 58-34, and 11 HMA mixtures containing up to 35% RAP that were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (|G*|), and phase angle (δ) at high performance temperatures, MSCR recovery rate and compliance, BBR stiffness and m-value, DTT failure stress and strain for binders, and dynamic modulus, flow number, IDT creep stiffness and strength for mixtures. Binder cracking temperatures were determined through Thermal Stress Analysis Routine (TSAR) software along with BBR and DTT data. Mixture cracking temperatures were determined with IDT creep stiffness and strength data. It was found that rutting may not be a concern with Alaskan RAP mix, while low-temperature cracking concerns may still exist in RAP mix in Alaska. A savings of $13.3/ton was estimated for a 25% RAP mix, with consideration of Alaskan situations. Many recommendations for future RAP practice and research are recommended based on testing results and cost analysis.Alaska Department of Transportation Statewide Research Offic

Performance of TenCate Paving Interlayers in Asphalt Concrete Pavements

As a continued effort of a previously completed project entitled “Performance of TenCate Mirafi PGM-G4 Interlayer-Reinforced Asphalt Pavements in Alaska,” this project evaluated two newly modified paving interlayers (TruPave and Mirapave) through overlay, dynamic modulus tests and low-temperature performance tests. A field survey was conducted to further evaluate the performance of three paving interlayers (G4, G50/50, and G100/100) applied to field sections constructed in May 2013 at Milepost 148–156 Richardson Highway in Alaska. Overlay test results indicate that asphalt concrete (AC) with paving interlayers (TruPave and Mirapave) shows lower reduction in peak load, suggesting better cracking resistance. The dynamic modulus measurement of AC with paving interlayers reveals more rational results from the IDT mode test than the AMPT method due to similar stress conditions in the paving interlayer. With paving interlayers, the temperature sensitivity and cracking potential of AC material were reduced according to the results from the IDT creep test. Field survey results confirm that all sections reinforced with paving interlayers (G4, G50/50, and G100/100) had better cracking resistance than the control section.TenCate Geosynthetics North Americ

Continued Field Evaluation of Precutting for Maintaining Asphalt Concrete Pavements with Thermal Cracking

In continuation of a previously completed project entitled Evaluate Presawn Transverse Thermal Cracks for Asphalt Concrete Pavement, this project was a further effort to understand important variables in the thermal cracking process through continued field monitoring of three precutting test sites in Interior Alaska. The test sites included (1) Phillips Field Road, precut in 1984 (≈ west ¼ mile of this road), (2) Richardson Highway precut in 2012 (≈ MP 343–344), and (3) Parks Highway precut in 2014 (≈ MP 245–252). Preliminary results at relatively short periods (up to 4 years) indicate that precutting is an economically promising way to control natural thermal cracks. Even short-term economic benefits appear to range between about 2% and 21%. The degree to which precutting works for an AC pavement appears to be a function of the thickness and general structural robustness of new construction. Shorter precut spacing, along with stronger and/or thicker pavement structures, looks promising with respect to crack control. Continuing evaluation and monitoring of test sections are needed to recommend an effective design methodology and construction practice for Alaska and cold areas of other northern states.Alaska Department of Transportatio

Performance of Tencate Mirafi PGM-G4 Interlayer-Reinforced Asphalt Pavements in Alaska

Geosynthetics has been used in hot mix asphalt (HMA) overlays in a variety of design and construction situations for more than three decades. A number of positive benefits have been identified such as waterproofing control for base and subgrade protection, improved fatigue resistance and reduced propagation of reflective cracks. In cold regions such as Alaska and other northern states, pavements are more prone to distresses due to extreme climatic conditions. Research is needed to explore how interlayers functions in asphalt pavements in cold regions. The interlayers used for pavement reinforcement applications and available in the market are primarily biaxial. Biaxial grids with equal strength in both the machine and cross machine directions allow stress transfer at low strain mainly in longitudinal and transverse directions. The new PGM-G4 paving composite developed by Tencate Geosynthetics contains multi-axial fiberglass filament yarn, which changes the aperture geometry from a rectangular to a quad angular grid structure. This unique feature improves the structure radial stiffness and efficiently distributes stress from surface layer to the geogrid throughout the full 360o. This isotropic feature could deliver optimal asphalt concrete (AC)/grid interaction and more efficient reinforcement. There is a need to identify/validate its expected performance and added value over conventional biaxial grids. Hence, a study has been conducted on interlayer-reinforced asphalt pavements in Alaska that included two phases: laboratory index testing (Phase I) and field performance evaluation (Phase II). Phase I focused on laboratory evaluation of engineering properties of PGM-G4 composite paving grid-reinforced asphalt pavement structure and comparison with other types of interlayers. Five types of interlayers were evaluated in this study for various laboratory tests and they were PGM-G4 (multi-axial composite grid), PGM-G100/100 and PGM-G50/50 (bi-axial composite grid), TruPave® (engineered paving fiberglass and polyester hybrid mat), and MPV500 (conventional polypropylene interlayer). The performance tests included asphalt retention and grab strength tests of interlayers, and shear strength, permeability and indirect tension (IDT) tests of interlayer-reinforced asphalt mixtures. Further, a typical Alaska flexible pavement structure was used, and pavement structure analyses and simulation were conducted by Bisar, Alaska Flexible Pavement Design (AKFPD) and ABAQUS programs to investigate the effects of paving interlayers on the pavement performance.Tencate Geosynthetics North Americ

Financial Impact of Fines in the Unbound Pavement Layers

INE/AUTC 14.1

Similarity of ionized gas nebulae around unobscured and obscured quasars

Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III]5007 emission line. We find that ionized gas nebulae extend out to ~13 kpc from the quasar, that they are smooth and round, and that their kinematics are inconsistent with gas in dynamical equilibrium with the host galaxy. The observed morphological and kinematic properties are strikingly similar to those of ionized gas around obscured (type 2) quasars with matched [O III] luminosity, with marginal evidence that nebulae around unobscured quasars are slightly more compact. Therefore in samples of obscured and unobscured quasars carefully matched in [O III] luminosity we find support for the standard geometry-based unification model of active galactic nuclei, in that the intrinsic properties of quasars, of their hosts and of their ionized gas appear to be very similar. Given the apparent ubiquity of extended ionized regions, we are forced to conclude that either the quasar is at least partially illuminating pre-existing gas or that both samples of quasars are seen during advanced stages of quasar feedback. In the latter case, we may be biased by our [O III]-based selection against quasars in the early "blow-out" phase, for example due to dust obscuration.Comment: 17 pages, 10 figures, 2 tables. Published in MNRAS, 201