Paragon Technical Services Inc.

Jackson, MS, United States

Paragon Technical Services Inc.

Jackson, MS, United States
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Howard I.L.,Mississippi State University | Baumgardner G.L.,Paragon Technical Services Inc. | Monismith C.L.,University of California at Berkeley
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2016

Mix testing that can properly characterize cracking of asphalt pavements is one of the most relevant present day issues for the industry. The 91st Annual Meeting (AM) of the Association of Asphalt Paving Technologists (AAPT) provides evidence to this effect as, in the assessment of the authors, cracking was far and away the meeting's prevailing theme. The 91st AAPT AM began with a Leading Edge Workshop (LEW) that focused exclusively on cracking and associated test methods, and a key factor in most of the remaining content presented at the meeting was cracking. This paper stemmed from the 91st AM LEW in response to cracking's perceived prevalence in the minds of so many AAPT members. The primary objective of this paper is to provide the state of the art in asphalt mix cracking from the perspective of the authors and to use this perspective to explain what has been accomplished in the cracking arena and what needs to be accomplished. First, a historical perspective beginning in the mid-1950s and ending in present day is presented that is generally divided into pre and post Superpave mix design. With this historical perspective as a reference, emphasis is shifted to the AM and LEW as they pertained to cracking. A set of prevailing themes was established and used as a segue into discussion of cracking test methods (first what has been accomplished and then what needs to be accomplished). Six areas were identified by the authors where advancement needs to be made with regard to mitigation of cracking: 1) closing the gap between the state of the art and the state of practice: 2) evaluating rapid mix test methods usable during production; 3) emphasizing education: 4) improving reliance on accelerated pavement testing; 5) improving cracking models; and 6) performing large test programs where parallel testing occurs on comparable mixes by way of several test methods. © 2016, Association of Asphalt Paving Technologist. All rights reserved.

Cooper S.B.,Louisiana State University | Negulescu I.,Louisiana State University | Balamurugan S.S.,Louisiana State University | Mohammad L.,Louisiana State University | And 2 more authors.
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2016

The use of recycled asphalt shingles (RAS) as a partial replacement for petroleum-based virgin asphalt binder has received considerable attention in recent years. The objective of this study is to correlate the molecular structure and corresponding compositional analysis of asphalt binders of conventional asphalt mixtures as well as of mixtures containing recycled asphalt shingles (RAS) and/or reclaimed asphalt pavement (RAP) with their cracking potential at intermediate temperature. Laboratory testing evaluated the molecular composition of asphalt binders obtained from asphalt mixtures evaluated in this study using thin layer chromatograph/FID (Iatroscan) and gel permeation chromatography (GPC). Fracture resistance of laboratory-produced mixtures was assessed using the semicircular bend (SCB) test at intermediate temperature. Molecular fractionation through GPC of RAS samples confirmed the presence of associated asphaltenes in greater concentrations than recycled asphalt pavement (RAP) samples. High concentrations of high molecular weight asphaltenes decrease the fracture resistance of the asphalt mixtures. The use of rejuvenating agents, Cyclogen-L, Hydrogreen, asphalt flux and re-refined engine oil bottoms (REOB), did not reduce the concentration of the highly associated asphaltenes; further they failed to improve the cracking resistance of the asphalt mixtures evaluated in this study. © 2016 Taylor & Francis.

Howard I.L.,Mississippi State University | Cox B.C.,U.S. Army | Alvarado A.,Mississippi State University | Jordan W.S.,Paragon Technical Services Inc.
Road Materials and Pavement Design | Year: 2017

Chip and scrub seal material selection is a long-standing challenge to favourable pavement performance and, historically, is based on empirical methods. This paper’s primary objective is to provide guidance for a seal treatment system (i.e. emulsion and aggregates) at high and low temperatures in the context of rejuvenation and aggregate retention. In contrast, commonly used methodologies are less comprehensive, focusing, for example, on only one performance aspect (e.g. aggregate retention) or one material (e.g. emulsion). Temperature is a major consideration of this paper since commonly used specifications call for test temperatures opposite of what may be optimal (e.g. viscosity testing at 135°C is commonly used to characterise rejuvenation, though rejuvenation seeks to address distresses typically associated with lower temperatures, such as cracking). Recommendations, which better align test temperatures, are to use bending beam rheometer mixture beam testing to evaluate rejuvenation and sweep testing to evaluate aggregate retention and traffic opening. © 2017 Informa UK Limited, trading as Taylor & Francis Group

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.

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.

Baumgardner G.L.,Paragon Technical Services Inc. | Hardee J.R.,Henderson State University | Negulescu I.I.,Louisiana State University | Williams E.R.,Poly Vulc Inc | And 2 more authors.
Road Materials and Pavement Design | Year: 2014

Ground tyre rubber (GTR) has been employed to modify asphalt binders used in hot-mix asphalt construction since the early 1960s. Proper formulation of GTR-modified asphalt binders provides for substantial improvement in performance over conventional asphalt binders, while providing an outlet for disposal of waste tyres. Physical characteristics of GTR are considered to be vital to the final performance of the asphalt paving mixture, with some state agencies specifying chemical composition requirements for GTR used in binder modification. Adequate analysis and understanding of the functional polymer content, polymer available in GTR to improve asphalt binder properties, and other chemical characteristics of GTR remain lacking. Thermogravimetric analysis (TGA) is a method used to measure the change in mass of a material measured as a function of temperature or time facilitating acquisition of information on properties of the material and its composition. This paper introduces an instrumental TGA method to analyse recycled tyre rubber, also known as ground tyre rubber or GTR, for better understanding and quantification of the functional polymer content, as well as general chemical characteristics, of GTR used to modify asphalt binders. © 2014 © 2014 Taylor & Francis.

Howard I.L.,Mississippi State University | Doyle J.D.,U.S. Army | Hemsley J.M.,Paragon Technical Services Inc. | Baumgardner G.L.,Burns Cooley Dennis Inc. | Cooley Jr. L.A.,Burns Cooley Dennis Inc.
International Journal of Pavement Engineering | Year: 2014

This paper presents results of a study on hot-mixed and warm-compacted asphalt incorporating warm mix technologies for use in emergency construction following a natural disaster. Case studies were first reviewed to investigate feasibility of the concept. Next, an overall emergency paving framework was developed, complemented by a two-component laboratory investigation. Component one developed a series of short-term ageing protocols for use in preparation of test specimens; component two evaluated those specimens for compactability and rut resistance. Results indicated that (1) material could be hauled up to 6 h and still be effectively used in emergency paving, (2) the two warm mix additives studied improved compactability of hot-mixed and warm-compacted asphalt and (3) rut resistance was acceptable for emergency applications. A discussion on the post natural disaster permanent residual value of the hot-mixed and warm-compacted material is also provided. © 2012 Taylor & Francis.

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.

Baumgardner G.L.,Paragon Technical Services Inc. | Hemsley J.M.,Paragon Technical Services Inc. | Jordan III W.,Paragon Technical Services Inc. | Howard I.L.,Mississippi State University
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions | Year: 2012

Ground tire rubber (GTR) is commonly used to modify asphalt binder for use in hot-mix asphalt construction. Various additives have been recommended for use as co-modifiers with GTR in asphalt binder modification for asphalt pavement construction. More recently co-modifiers have been promoted to be incorporated into hot-mix asphalt through dry addition of GTR, and additive, into asphalt mixtures. These additives are represented to provide an improved modified asphalt paving binder by incorporating a small amount of additive into GTR modified asphalt binder which in turn leads to easier mixing, reduced tackiness, reduced cracking, less permanent deformation, lower life-cycle cost, and longer service life. This paper reports the results of a comprehensive evaluation of trans-polyoctenamer (TOR) modified binder additive incorporated with GTR in modification of asphalt binder. Four binders were evaluated in dense, OGFC, and SMA mixtures: 1) PG 67-22, 2) GTR wet pre-blended, 3) Styrene-Butadiene-Styrene block copolymer (SBS) modified PG 76-22, and 4) GTR dry added to mixture.

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.

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