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Knuth D.,Jacobs Engineering | Fortmann J.,Illinois Center for Transportation
Green Streets and Highways 2010: An Interactive Conference on the State of the Art and How to Achieve Sustainable Outcomes - Proceedings of the Green Streets and Highways 2010 Conference | Year: 2010

In January 2010, the Illinois Department of Transportation, the American Consulting Engineers Council - Illinois Chapter, and the Illinois Road and Transportation Builders Association released a sustainability guide and rating system entitled I-LAST, Illinois - Livable and Sustainable Transportation. The document was developed by volunteers from these organizations over a two-year period. This paper reviews the reasons for undertaking this project, the contents of the resulting document, and the decisions made during its development. © 2010 ASCE.

Al-Qadi I.,Illinois Center for Transportation | Wang H.,Urbana University | Tutumluer E.,Urbana University
Transportation Research Record | Year: 2010

A three-dimensional (3-D) finite element (FE) model was developed to investigate the dynamic responses of thin, flexible pavement under impulsive loading similar to a falling weight deflectometer test. The FE model simulated the hot-mix asphalt (HMA) surface layer as a linear viscoelastic material and considered the cross-anisotropic stress dependent modulus for the unbound base layer. Implicit dynamic analysis was used to consider the effect of inertia on pavement structural responses. Using two thinpavement structures of different HMA layer thicknesses, 76 and 127 mm, the study analyzed the effects of cross-anisotropic stress-dependent aggregate base modulus and dynamic analysis on pavement responses, including surface deflection, tensile strain at the bottom of the HMA layer, deviator stress in the base layer, and compressive strain on top of the subgrade. Results showed that use of the cross-anisotropic stress-dependent modulus for the unbound base layer resulted in greater predicted pavement responses and, hence, less estimated pavement life for rutting and fatigue cracking. It was found that as the thickness of HMA surface layer or the ratio of horizontal modulus to vertical modulus decreases, the effects of stress dependency and cross anisotropy become more significant. Analysis-predicted surface deflections were compared to field-measured values and they were in agreement when the stress dependency and cross anisotropy of the base layer and subgrade were considered.

Al-Qadi I.L.,Illinois Center for Transportation | Leng Z.,University of Illinois at Urbana - Champaign | Lahouar S.,Institute Superieur Des Science Appliquees Et Of Technology Of Sousse | Baek J.,University of Illinois at Urbana - Champaign
Transportation Research Record | Year: 2010

This research proposes the innovative use of ground-penetrating radar (GPR) for effectively, continuously, and rapidly estimating in-place hotmix asphalt (HMA) density. On the basis of electromagnetic mixing theories, three candidate models were developed to determine HMA's dielectric constant, considering dielectric and volumetric properties of its three major components of HMA: air, binder, and aggregate. Laboratory tests were conducted on midsize HMA slabs (60 cm × 60 cm × 7.5 cm) to evaluate the models. After evaluating and comparing the three models, it was determined that the prediction model based on the Rayleigh mixing theory was the most accurate. The selected model was calibrated with a field core and then validated using field GPR measurements of a composite pavement with an HMA surface. The selected model provided accurate HMA density within a reasonable range.

Shangguan P.,University of Illinois at Urbana - Champaign | Al-Qadi I.,University of Illinois at Urbana - Champaign | Coenen A.,Illinois Center for Transportation | Zhao S.,University of Illinois at Urbana - Champaign
International Journal of Pavement Engineering | Year: 2014

Ground-penetrating radar (GPR) is a promising non-destructive technique to be applied on monitoring the density change during asphalt pavement compaction. The utmost challenge of this application is the unknown effect of surface moisture, sprayed by the compactor during compaction, on GPR signals. To extract density information without the effect of surface moisture, a correction algorithm based on reference scan approach was developed. To evaluate the performance of the algorithm, a full-scale test site was constructed with compaction pass number from 0 to 10, and a large amount of GPR data were collected from the pavement with different surface moisture contents. A total of 22 cores were extracted for validation purposes. After applying the algorithm, it was found that the average density prediction error was reduced significantly. By using correction algorithm together with the density model, the density of asphalt pavement was obtained with high accuracy. © 2014 Taylor & Francis

Ozer H.,Illinois Center for Transportation | Solanki P.,Illinois State University | Yousefi S.,University of Illinois at Urbana - Champaign | Al-Qadi I.,University of Illinois at Urbana - Champaign
Transportation Research Record | Year: 2014

When properly installed, hot-poured crack sealants are widely accepted as a cost-effective, routine preventive maintenance practice that extends pavement service life by 3 to 5 years. However, current ASTM specifications for selection of crack sealants correlate poorly with field performance. Therefore, an improved sealant specification and selection system is urgently needed. Recently, performance-based guidelines were developed by the pooled-fund North American Consortium expert group for selecting hot-poured bituminous crack sealants. The work proposed a sealant grade system for selecting hot-poured crack sealant on the basis of environmental conditions. A special effort was made to use the equipment originally developed by SHRP, which was used to measure binder rheological behavior as part of the performance grade system. The equipment and testing procedures used for performance grading of binders were modified in accordance with crack sealant behavior. The main objective of this study was to validate the low-temperature selection thresholds for the newly developed performance-based guidelines for selecting hot-poured crack sealants. Thresholds for the crack sealant bending beam rheometer, crack sealant direct tension test, and crack sealant adhesion test were validated. Nine hot-poured crack sealants were installed in four test sites experiencing low temperatures. The field performance of crack sealants was evaluated for 2 consecutive years by detailed field surveys. The field database consisted of 40 sections containing 647 cracks. Overall, results showed good correlation between the proposed selection thresholds and sealant performance in the field.

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