From the beginning of asphalt mixture design it was desired to understand the interaction of aggregates, asphalt, and the voids created during their compaction. In asphalt mixture design, guidance is lacking in the selection of the design aggregate structure and understanding the interaction of that aggregate structure and mixture volumetric properties. Asphalt mixture design concepts are presented that use aggregate interlock and aggregate packing to develop an aggregate blend that meets volumetric criteria and provides adequate compaction characteristics. The concepts rely on coarse aggregate for the skeleton of the mixture with the proper amount of fine aggregate to provide a properly packed aggregate structure. The objective is to use aggregate packing concepts to analyze the combined gradation and relate the packing characteristics to the mixture volumetric properties and compaction characteristics. The new concepts presented for asphalt mixture design and analysis include an examination of aggregate packing and aggregate interlock, blending aggregates by volume, a new understanding of coarse and fine aggregate, and analysis of the resulting gradation. These concepts are the result of many years of field experience and are the backbone of the Bailey method for asphalt mix design. These methods are under continued development as the improved method for asphalt mixture design, which will assist with the transition to contractor mix design.

Pavement roughness is an expression of the irregularities in a pavement surface that adversely affect the ride quality of a vehicle. Roughness also affects vehicle delay costs, fuel consumption, tires, and maintenance costs. Roughness is predominantly characterized by the international roughness index (IRI), which is often measured with inertial profilers. Inertial profilers are equipped with sensitive accelerometers, a height-measuring laser, and a distance-measuring instrument for measuring vehicle vertical acceleration data and the pavement profile. Modern smartphones are equipped with several sensors including a three-axis accelerometer, which was used in this project to collect vehicle acceleration data with an Android-based application. In the study, acceleration data were double integrated numerically to obtain a pavement profile, which was input into the software program ProVAL. The pavement roughness was then calculated. For the initial validation, pavement profile and acceleration data were collected with both an inertial profiler and the newly developed smartphone application from three test sites. The initial validation results suggest that the newly developed smartphone application can measure IRI with good correspondence to the inertial profiler and with good repeatability between measurement replications. However, calibration is needed for rougher pavement sections because the current analysis techniques do not directly account for acceleration damping resulting from vehicle suspension systems. With improvements in analysis that consider the vehicle suspension effects and additional validation, the approach could be used to reduce the cost of acquiring pavement roughness data for agencies and to reduce user costs for the traveling public by providing more robust feedback about route choice and its effect on estimated vehicle maintenance cost and fuel efficiency.

This paper quantifies the environmental improvements in current versus past pavement materials and construction practices employed by the Illinois State Toll Highway Authority (tollway authority). Improvements in sustainability performance were measured with a life-cycle assessment (LCA) approach. Three scenarios were generated to evaluate tollway authority practices on the basis of eight 2013 Interstate reconstruction and rehabilitation projects. The first scenario, 2013 projects, analyzed the actual pavement material and designs of the 2013 projects. The second scenario, materials baseline, was based on the 2013 projects but modified to include mix designs with less-sustainable materials used by the tollway authority circa 2000. The third scenario, design and materials baseline, considered both mix designs and pavement design practices used circa 2000. To improve the spatial and temporal relevance of the analyses, two regional databases of life-cycle inventories representing processes from 2013 and 2000 were developed and applied to the 2013 projects and 2000 baselines. A tool developed by the Illinois Center for Transportation (ICT) of the University of Illinois at Urbana–Champaign, the pavement ICT-LCA 0.95, was used to evaluate the sustainability performance indicator (SPI), global warming potential (GWP), and cumulative energy demand (CED) for each scenario. The resultant savings in SPI, GWP, and CED from the first scenario ranged between 17% and 28%, 12% and 16%, and 13% and 26%, respectively, compared with the second scenario, and 12% and 33%, 8% and 26%, and 11% and 32%, respectively, compared with the third scenario.

The advancement of the Superpave gyratory compactor (SGC) has led to a recognized need for a simple test that preferably can be performed on SGC samples during mix design that would rank performance potential of the mixtures if used in a pavement. Although it has proved difficult to find one test that can rate mixture potential for rutting and fatigue cracking and modulus, a limited study was conducted on Illinois mixtures that provides evidence that a simple test performed during mix design has the potential to predict a diverse set of performance characteristics. The results are presented for 10 Illinois dense-graded mixtures of surface and binder (9.5 and 12.5 mm) gradations that were tested in an asphalt pavement analyzer (APA) and subjected to flexural beam fatigue, unconfined repeated load permanent deformation, and diametral resilient modulus testing. The mixtures were further subjected to a rapid triaxial test procedure using SGC compacted samples, as taken from the SGC machine, and tested at 50°C in a triaxial stress reversal mode. The triaxial testing provides data that predicts resilient modulus, APA rutting results, fatigue coefficients, and permanent deformation characteristics of accumulated strain at tertiary failure, loads to tertiary failure, and the exponent to the standard logarithmic permanent deformation curve. The excellent correlations obtained from this study provide direct evidence that this test protocol may provide a structural evaluation procedure to supplement the volumetric mix design process and warrants further study.

The Superpave volumetric mix design is based on compaction of mixtures to Nmax revolutions, yielding approximately 2 percent air voids, and then back-calculating the properties of the mixture at N design revolutions, which is the specified number of revolutions at which the sample should achieve 4 percent air voids. It has been shown, both in mixture design and in field quality control testing, that this back-calculation procedure is not always accurate for determining the number of gyrations that give 4 percent air voids in the compacted sample. The current back-calculation procedure is examined in this paper, and the observed inaccuracy in the current method is shown in both quality control/quality assurance (QC/QA) and the mixture design procedures. Also examined is an alternative method that has been shown to be more accurate in predicting the number of gyrations at which a mixture reaches a given air void level. This study recommends a method that gives higher accuracy in determining the number of gyrations at which a mixture reaches 4 percent air voids. A diverse group of mixtures, each having different properties, was examined, and an improved method for predicting the number of gyrations to accurately produce 4 percent air voids in the compacted mixture was determined.

The effect of various levels of flat and elongated (F&E) particles on the gyratory compaction characteristics in a standard bituminous mixture was examined. Compaction characteristics involve the effect of F&E particles on the void development in the gyratory compactor as well as the break-down characteristics. F&E particles could also affect the performance characteristics of the compacted mixtures. F&E particles in typical Illinois surface mixtures were examined. Two coarse aggregate sources, a dolomite and crushed gravel, were used. A cubical mixture was prepared in which all particles had an F&E ratio < 3:1 and baseline compaction characteristics were established. Coarse aggregates were individually measured to produce aggregate particles with measured F&E ratios < 3:1, between 3:1 and 5:1, and > 5:1. The coarse aggregates in the cubical gradation were replaced with various percentages of the same-sized aggregate with F&E ratios in the 3:1 and 5:1 range. These mixtures were compacted and the volumetric and gyratory characteristics were compared. Solvent extractions and binder ignition samples were obtained to indicate the relative breakdown in aggregates achieved with the different percentages of the F&E particles. The testing indicates the changes produced when different percentages of F&E particles are introduced into a mixture. When combined with performance testing, these data will provide a valid base upon which to recommend levels of allowable F&E particles in an asphalt mixture.

Mobile lane closures, which are increasingly used, are a potentially hazardous traffic control procedure for highway maintenance and operations activities. To improve the safety of workers and motorists, Applied Research Associates, Inc., studied driver behavior around full-scale field tests of mobile lane closures. Tests were conducted over a range of traffic, roadway, and driver conditions, and effects of various traffic control components (including truck number, spacing, and configuration; sign messages; and police presence) were evaluated. This report summarizes Phase I results and important findings regarding the behavior of motorists around mobile lane closures. Phase II research is ongoing and will recommend revisions to existing traffic control standards.

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