Faheem A.,Bloom Companies LLC |
Hintz C.,University of Wisconsin - Madison |
Bahia H.,University of Wisconsin - Madison |
Al-Qadi I.,University of Illinois at Urbana - Champaign |
Glidden S.,Mathy Technology and Engineering Services Inc.
Transportation Research Record
This study proposed the fractional voids test for mineral fillers introduced by Rigden in 1947 and currently adopted as the European norm, as part of asphalt mixture design and quality control. Laboratory testing conducted in this study included a large collection of natural and manufactured fillers currently used in various regions of the United States. Results showed that filler fractional voids influenced mastic viscosity and nonrecoverable compliance. These mastic properties were also found to be highly correlated with mixture performance measures. This study used mixture performance limits to derive mastic limits based on mixture-to-mastic correlations. Regression models developed to predict mastic performance as a function of filler fractional voids and asphalt binder properties were proposed as a means for incorporating fractional voids into the mix design procedure as a quality control measure. This paper discusses the tested materials and the analysis approach and summarizes the data justifying the proposed limits. Source
Baumgardner G.L.,Paragon Technical Services Inc. |
Reinke G.R.,Mathy Technology and Engineering Services Inc.
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions
The more common science used in determination of a material's coefficient of friction is known as tribology. Tribiology is defined as the science and technology of interacting surfaces in relative motion, including the study of friction, wear, and lubrication and is derived from the Greek tribo (to rub) and the Latin logia (study or learning). The coefficient of friction of a material is empirical - it has to be measured experimentally and cannot be calculated. Rough surfaces like hot-mix aggregates tend to have higher coefficients than smooth surfaces. Boundary fluids (like asphalt binders) can serve to reduce the coefficient of friction of aggregates during production of asphalt mixtures. Reinke and Baumgardner first introduced the concept of testing asphalt binders in thin films and suggested lubricity and internal friction reduction as a potential explanation of the mechanism allowing production of asphalt mixtures at reduced temperature, warm-mix asphalt (WMA), at the Warm-Mix Technical Working Group (WMA TWG) in Baltimore, MD, December 2007. Further work in this area was later reported by Hanz, Faheem, Hahmoud and Bahia at the 89th Annual Meeting of the Transportation Research Board, January, 2010. This paper presents a continuation of the work of Reinke and Hanz moving from gap-dependent rheology to tribology utilizing a standard tribology fixture and new methods for testing asphalt binders with a dynamic shear rheometer. The work consists of evaluations of various asphalts used to produce hot-mix asphalt (HMA) mixtures and the effect they might have on friction characteristics, allowing production of warm-mix asphalt through non-chemical techniques such as foaming; and evaluation of Lubricity Optimized Asphalts™ (LOA) and the effect additives have on friction characteristics in asphalt mixtures produced with LOA asphalt binders. © 2013 Taylor & Francis. Source
Wang H.,University of Illinois at Urbana - Champaign |
Wang H.,Rutgers University |
Al-Qadi I.L.,University of Illinois at Urbana - Champaign |
Faheem A.F.,Bloom Companies LLC |
And 3 more authors.
Transportation Research Record
This study, part of the NCHRP 9-45 Project, analyzed the effect of mineral filler properties on asphalt mastic and the rutting potential of asphaltic mixture. The mineral filler properties were characterized by four tests: Rigden voids (RV), fineness modulus (FM), calcium oxide (CaO) content, and methylene blue value. The rheological properties of asphalt binder and mastic were characterized with the use of apparent viscosity and multiple stress creep recovery tests. Dynamic modulus and flow number tests were conducted to examine the asphaltic mixture rutting potential. The tested mixtures included several variables: four asphalt binder types, including virgin and polymer modified; two aggregate gradations; and a selected group of fillers. The study concluded that asphalt mastic performance was significantly affected by the fractional voids in the filler and possibly by the CaO content and FM. This effect, however, depended on binder type. On the one hand, the styrene-butadiene-styrene modified binder showed the strongest effect as a result of the mineral filler inclusion when tested as mastic. On the other hand, RV and CaO content showed relatively greater correlation with the mixture rutting potential, as compared with other filler properties. Addition of RV improved the prediction models for dynamic modulus and flow number. The effect of RV on the mixture rutting potential was more pronounced for the coarse mixture than for the fine mixture. Source
Effect of Temperature, Fuming Time, and Distance from Source on the Polycyclic Aromatic Compound (PAC) Content of Bitumen Fumes: Assessment Using a Laboratory Fuming Protocol in Combination with a Sensitive Method for Determining Relative Aggregate Levels of PACs in Complex Mixtures
Blackburn G.R.,PetroLabs Inc |
Bleicher Jr. W.T.,PetroLabs Inc |
Glidden S.,Mathy Technology and Engineering Services Inc. |
Reinke G.,Mathy Technology and Engineering Services Inc.
Polycyclic Aromatic Compounds
A laboratory fuming procedure was used in combination with a previously reported variation of the Ames Test (the Nitration Assay) to investigate the relationship between temperature, time at temperature, and distance from source, on the relative PAC content of fumes generated from paving bitumens. The test method, whose endpoint is mutagenic potency (Nitration Mutagenicity Index, NMI), takes advantage of large amplifications of Ames Test mutagenicity resulting from nitro-derivatization of PACs. NMIs were similar and quite low for fumes generated at 110°C, but increased exponentially up to 160°C. NMIs increased linearly with fuming time up to 40 min, after which they remained constant. With some initial fluctuation, they also remained constant with increasing distance of the condenser from the bitumen surface up to 100 cm. NMI increased with temperature at a faster rate than fume weight suggesting that the increases in NMI were related to both quantitative and qualitative changes in the PAC content of the fumes. © 2012 Copyright Taylor and Francis Group, LLC. Source