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Baumgardner G.,Paragon Technical Services Inc. | D'Angelo J.,DAngelo Consulting LLC
Transportation Research Record | Year: 2012

Crumb rubber modifier (CRM) has been used for many years in asphalt binder to provide improved field performance. Historically the increase in viscosity of CRM binder was measured with crude vane viscometers to quantify binder performance characteristics. The Superpave® system introduced far more accurate tools in the asphalt binder testing system to measure performance characteristics. As a result of testing geometry limitations, Superpave binder tests, specifically high-temperature testing, have generally not been applicable in testing CRM binders. This inability to test the material fully has limited the use and adoption of CRM binders. Well-known geometries in the rheology field, specifically coaxial cylinder geometries or cup and bob, can handle the larger particle sizes typically used as CRM. However, these geometries are not familiar in the asphalt industry. This study investigated the ability of the cup-and-bob geometry to test neat, polymer-modified, and CRM binders to determine if it could provide similar rheological results for both Superpave and multiple stress creep recovery (MSCR) testing. It concluded that the cup-and-bob geometry could accommodate large CRM particles and provide similar results for Superpave as well as MSCR testing. Source

Baumgardner G.L.,Paragon Technical Services Inc. | Rowe G.M.,Abatech Inc. | Reinke G.H.,Mathy Technology Inc
RILEM Bookseries | Year: 2012

A simple Bending Beam Rheometer (BBR) test to determine binder low temperature properties from asphalt mixtures was recently developed by the University of Minnesota. The mixture BBR test was performed concurrent with binder BBR testing to evaluate the effect wax addition has on stiffness/physical hardening and potential for low temperature cracking in asphalt mixtures. Asphalt mixture and binder BBR tests were performed at low temperatures typical of binder grading, after equivalent low temperature conditioning in air for incremental extended periods up to 32 days. Results from temperature saturation are compared to conditioning corresponding to normal 20 hours of PAV aging and testing in accordance with parameters specified in AASHTO M320. Data produced by the BBR suggests that at temperatures close to or below the glass transition temperature mixture beams became less stiff with time when held at a constant temperature. This effect appears to be reversible if a heating/annealing cycle is applied to the beams. This paper reports further investigation of the observed phenomenon and the potential that observations may be indicative of low temperature micro-cracking and subsequent healing in asphalt mixture. © RILEM 2012. Source

Rowe G.M.,Abatech Inc. | Baumgardner G.L.,Paragon Technical Services Inc.
Journal of ASTM International | Year: 2011

The increased understanding of material behavior with rheology has existed for approximately 80 years as a science and has been applied to roofing products for over 50 years. With asphalt binders, several techniques exist for understanding rheology via the use of models. One of the best recognized models for the evaluation of the rheology of unmodified asphalt binders is the Christensen-Anderson model, and various developments of that model have occurred, enabling its use with filled systems such as those used in roofing applications. In addition to this model, the Rowe-Baumgardner-Sharrock model (developed by the authors) is introduced as an alternate method for defining the properties of roofing products that exhibit visco-elastic solid properties. When rheological data are fitted to master curve functional forms, changes in the model parameters can be rapidly visualized. The performance of various products can be assessed using this technique and can be related to the rheological parameters developed from this model (for example, the rheological index, crossover frequency, etc.). An analysis of the data is presented that includes testing using various rheometers over a wide range of temperatures. These data have been combined into a single master curve and plotted in various formats. The data show how the rheological index and the crossover frequency of the materials change over time, particularly with aging. Performance products can then be assessed and evaluated from both the historical data and models that enable the prediction of cracking and deformation. A discussion of the key parameters and a trend analysis are shown. Furthermore, the analysis is applied toward understanding the effectiveness of polymer networks in the roofing materials. As materials age, their properties change, and this can be observed, allowing the study of the effects of polymer network degradation with aging. This paper offers some further understanding of how key rheological parameters change. Copyright © 2011 by ASTM International. 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 | Year: 2013

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

D'Angelo J.A.,LLC LLC | Baumgardner G.,Paragon Technical Services Inc.
Asphalt Pavements - Proceedings of the International Conference on Asphalt Pavements, ISAP 2014 | Year: 2014

The use of Recycled Tire Rubber (RTR) to produce PG modified binders has seen a tremendous increase in interest. Under the current economic conditions it is quite cost effective to produce RTR modified binders that will meet typical extended PG grades and Multi-Stress Creep and Recovery (MSCR) grades. One major question is, are RTR modified binders equivalent to typical polymer modified binders currently being used. To evaluate the binder properties new tools, such as the cup and bob Searle system, have been developed. This testing system is used to evaluate the binder properties of RTR modified binders under the AASHTO M 320 and MP 19 specifications. This study evaluates binders modified with multiple RTR sizes and percentages to typical SBS modified binders. Sizes such as 60, 30 and 20 mesh RTR are blended with neat binders at zero, 5, 10, 15 and 20 percent to produce modified binders. The properties of the blends are being evaluated using both parallel plate and cup and bob geometries and M 320 and MP19 specifications against typical SBS modified binders. These blends will see further testing in asphalt mixtures to look at performance properties and make comparisons of these properties. © 2014 Taylor & Francis Group, London. Source

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