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Lexington, KY, United States

Gallivan V.L.,U.S. Federal Highway Administration | Chang G.K.,Transtec Group Inc. | Horan R.D.,Asphalt Institute
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions

Intelligent Compaction (IC) is a major innovation in compaction technology that has been studied extensively in the US over the last five years. IC is defined as a process that uses vibratory rollers equipped with a measurement/documentation system that automatically records various critical compaction parameters in real time during the compaction process. The recorded information is then displayed for the roller operator and project personnel to improve the compaction process. Field studies by the authors and other researchers have shown that IC has many potential benefits that can result in better compaction processes and improved process/quality control/acceptance procedures. These benefits are likely to result in the construction of longer lasting asphalt pavements. Suppliers of IC technology have conducted extensive research and development and are geared up to make IC rollers commercially available. In short, the stage is now set for agencies that would like to implement the use of IC technology in a practical manner. It has been a well known fact for decades that effective compaction is a critical step in the construction of quality Hot Mix Asphalt (HMA) pavement. In recent years, the understanding has grown that pavement materials must be properly compacted in the field to obtain the desired long service lives. With this in mind, there have been many improvements and innovations in compaction equipment, as well as in situ test equipment and specifications related to compaction over the years. Manufacturers have been modifying their compaction equipment, State agencies have been modifying their specifications, and contractors have been modifying their processes over the years all in an attempt to improve the compaction of HMA pavements. This paper discusses the 21st century practical efforts to improve the compaction of HMA pavements by using " intelligent" equipment that provides the contractors and agencies real-time information regarding the effectiveness of their compaction operations. The results of multiple field demonstrations have shown that IC mapping of the underlying materials prior to paving can identify weak or non-uniform areas that affect the quality of the HMA pavement compaction efforts. The contractor can optimize rolling operations using IC with increased knowledge of the HMA surface temperatures and roller locations. Thus, IC is a technology that is increasingly being used nationally and internationally and has been shown to provide for greater control and oversight of the compaction process, resulting in improved and more uniform compaction. Source

Clements T.M.,Kentucky Transportation Cabinet | Blankenship P.B.,Asphalt Institute | Mahboub K.C.,University of Kentucky
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions

Recent improvements in warm mix asphalt technologies have spurred an aggressive adoption of these new practices within the asphalt paving industry. Concerns have arisen among federal and state agencies about the effects of this line of products on the performance of asphalt pavements. An investigation of the effects of lowering mixing, aging and compaction temperatures using Meadwestvaco's Evotherm 3G™ 09 chemical additive while varying the loose mix aging time was performed. Hamburg Wheel-Track Testing, Flow Number, Dynamic Modulus and Fracture Energy testing were used to evaluate mechanistic properties of the materials. It was found that lowering production temperatures has a significant influence on rutting related testing and a limited to negligible effect on dynamic modulus and low temperature fracture energy testing. Source

Xu Q.,Transtec Group Inc. | Chang G.K.,Transtec Group Inc. | Gallivan V.L.,U.S. Federal Highway Administration | Horan R.D.,Asphalt Institute
Construction and Building Materials

Conventional pavement analysis and design methods are based on the homogeneous or uniform material model such including the multi-layered analysis program and AASHTO design methods. With the Intelligent Compaction (IC) technology on hot mix asphalt (HMA) involved in recent years, the compaction uniformity of material property can be quantified. This paper intends to study the effects of compaction uniformity on pavement performances using the Bomag IC Evib - a measurement of elastic moduli with 100% coverage of the compaction area. The three dimensional (3-D) finite element (FE) model was built to simulate pavement responses with the heterogeneous HMA moduli derived from the field IC measurements. Then the Mechanistic-Empirical Pavement Design Guideline (M-E PDG) models were used to predict HMA performances of rutting and fatigue life. The geostatisical semivariogram model was studied to evaluate the uniformity of predicted performances. Different from conventional pavement analysis and designs, spatial-distributed heterogeneous moduli of the asphalt layer were considered in this work. Results show that spatial uniformity of material moduli affects pavement performances in terms of the distress severity and uniformity. Less uniform material moduli result in higher rutting depths and shorter fatigue lives. For the case study in this paper, the mean and peak values of fatigue lives for the heterogeneous model are 38.2% and 0.1% of those for the uniform model. A pavement section with overall lower material moduli does not necessarily correspond to inferior performances as the effects from uniformity of material property may dominate other factors. Therefore, it is recommended that the uniformity of pavement layer properties that emulate the typically more variable service condition be considered in future pavement designs and performance predictions. © 2011 Elsevier Ltd. All rights reserved. Source

Zeinali A.,University of Kentucky | Mahboub K.C.,University of Kentucky | Blankenship P.B.,Asphalt Institute
Road Materials and Pavement Design

Almost all of the current hot-mix asphalt (HMA) fracture tests are considered to be research tools. This paper describes the development of the indirect ring tension (IRT) fracture test for HMA, which was designed to be an effective and user-friendly test that could be used at the Department of Transportation level. Numerical modelling was utilised to calibrate the stress intensity factor formula of the IRT fracture test for various specimen dimensions. The results of this extensive analysis were encapsulated in a single equation. An experimental plan was developed to optimise the test parameters for HMA specimens. The experiment results revealed that the test is highly repeatable, and capable of capturing the variations in the fracture properties of HMA. Moreover, the data from laboratory tests were utilised to estimate the maximum allowable crack lengths for the pavements based on a viscoelastic model. © 2014 © 2014 Taylor & Francis. Source

Zeinali A.,University of Kentucky | Blankenship P.B.,Asphalt Institute | Mahboub K.C.,University of Kentucky
Transportation Research Record

Employment of conventional asphalt testing protocols for characterization of polymer-modified asphalts remains a challenge. NCHRP launched Project 9-39 to identify an approach to determine the mixing and compaction temperatures applicable to unmodified and modified asphalt binders. The Asphalt Institute, Lexington, Kentucky, in cooperation with FHWA, embarked on the research reported here to evaluate how mixture performance is affected by laboratory mixing and compaction temperatures. Samples were mixed and conditioned at various temperatures and conditioning durations with modified and unmodified binders. Volumetric analysis confirmed that slight changes in the mixing temperature did not change the results of volumetric testing. Compacted samples were tested to determine the dynamic modulus as an indication of pavement performance. A comprehensive statistical analysis was performed, and the overall results showed that the impact of the conditioning temperature and duration on the dynamic modulus was more significant than the influence of the mixing temperature. Further, for modified binders the significance of the impact of the mixing temperature seemed to be a function of the crude source of the binders. Source

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