MIT Scan technology is a non-destructive method to measure the alignment of dowel bars placed in transverse joints of jointed plain concrete pavements (JPCP). Misalignment of dowel bars can potentially lead to reduced load transfer efficiency (LTE), cracking, spalling and faulting. Several agencies across the U.S. have adopted specifications for dowel bar misalignment, many using the joint score methodology. However, this methodology has never been validated using field studies. National Cooperative Highway Research Program (NCHRP) Report 637 provides a methodology to determine an effective dowel diameter; however, this was based on laboratory testing and limited field studies. This paper presents results of a Federal Highway Administration (FHWA) project to collect MIT Scan data on Long Term Pavement Performance (LTPP) sections. The analysis did not indicate any definitive relationship between joint score and cracking/spalling within the analysis range for most States. This is not to say that severely misaligned dowel bars do not affect pavement performance, particularly localized distresses. Analysis of effective dowel diameter as a measure of dowel misalignment for use with Pavement ME suggests that using effective dowel diameter is a less biased estimator of long-term LTE as modeled using Pavement ME than using actual dowel diameter, thus suggesting a relationship between dowel misalignment and long-term LTE. The remaining bias and scatter suggests that models (effective dowel diameter model and LTE model in Pavement ME) can be improved using the data collected as part of this study.

Wind energy serves as one of the most sustainable sources of energy, typically harvested by very large turbines. The combined weight of the turbines may exceed 1,000,000 pounds and are typically installed in land areas serving as agricultural developments or currently underdeveloped altogether. These areas, mostly with county roads, do not have robust transportation infrastructure and are not capable of accommodating the increased truck traffic, used to haul the components and materials involved in a wind farm development. A simple yet scientific approach to evaluate the structural and functional capacity of the pavements is presented in this study. Once the haul routes are established, the projected truck traffic is converted in terms of an Equivalent Single Axle Load (ESAL) for future improvement (overlay) requirements of the pavements, if any. Dynamic cone penetrometer (DCP), coring and Falling Weight Deflectometer (FWD) testing are performed to assess the in-situ subgrade conditions and current structural capacity of the pavements. Condition rating surveys (CRS) are conducted from Geo-referenced images of the pavement network to evaluate the surface condition of the pavements. The last step is to determine the scope of required improvements to the pavement structure. Additionally, mechanistic pavement design checks are performed using Layered Elastic Analysis (LEA) techniques to insure the validity of the structural capacity and overlay design calculations. This procedure will serve as 'insurance' for pavements used for developing the wind farms and will prove to be an efficient and cost-effective methodology.

Accurate pavement performance prediction represents an important role in prioritizing future maintenance and rehabilitation needs, and predicting future pavement condition in a pavement management system. The Illinois State Toll Highway Authority (Tollway) with over 2000 lane miles of pavement utilizes the condition rating survey (CRS) methodology to rate pavement performance. Pavement performance models developed in the past for the Illinois Department of Transportation (IDOT) are used by the Tollway to predict the future condition of its network. The model projects future CRS ratings based on pavement type, thickness, traffic, pavement age and current CRS rating. However, with time and inclusion of newer pavement types there was a need to calibrate the existing pavement performance models, as well as, develop models for newer pavement types.

Accurate pavement performance prediction represents an important role in prioritizing future maintenance and rehabilitation needs, and predicting future pavement condition in a pavement management system. The Illinois State Toll Highway Authority (Tollway) with over 2000 lane miles of pavement utilizes the condition rating system (CRS) methodology to rate pavement performance. Pavement performance models developed in the past for the Illinois Department of Transportation (IDOT) are used by the Tollway to predict the future condition of its network. The model projects future CRS ratings based on pavement type, thickness, traffic, pavement age and current CRS rating. However, with time and inclusion of newer pavement types there was a need to calibrate the existing pavement performance models, as well as develop models for newer pavement types. This study presents the results of calibrating and developing new models for the various pavement types in the Illinois Tollway network. The predicted future condition of the pavements is used in estimating its remaining service life to failure, which is of immediate use in recommending future maintenance and rehabilitation requirements for the network.

Because of the widespread use of modifiers and additives in asphalt bitumen, this study revisits and evaluates the adaptation of the time–temperature superposition principle that is incorporated into the low-temperature Superpave ® binder specifications. The study builds on results of bending beam rheometer (BBR) tests conducted on samples of asphalt binders used in seven different surface layer mixtures. Both 240-s and 2-h BBR tests were conducted at three different temperatures: the low temperature of the asphalt performance grade (T L ), 10°C higher than the low-temperature grade (T L+10 ), and at −5°C to construct the flexural creep stiffness master curves. Additionally, indirect tensile tests were conducted on the surface layer mixtures to determine the low-temperature properties. The BBR test results show that the methodology adopted in using the equivalence principle to formulate the low-temperature Superpave binder specifications does not accurately apply for some of the binders used in this study. Thus, modifications to the specifications for loading times and test temperatures are suggested. Further, the time–temperature shift factors for the binders evaluated are compared with the universal shift factors used in the SHRP study. The observed mismatch in the shift factor sets is in disagreement with the implicit assumption that all asphalt binders can be characterized by similar shift factors at low temperatures. The shift factors of the binders and mixtures used in this study tend to match well, particularly at high testing temperatures.

Dynamic modulus mastercurves are essential for the design and modeling of asphalt concrete (AC).One way of improving the accuracy of the upper asymptote of the mastercurve is to test at extremely high frequencies or extremely low temperatures.Ultrasound is used extensively in the nondestructive testing of materials and the work completed here demonstrates the potential for the application of this technology to AC.Since testing at extremely low temperatures is not practical, a new ultrasonic technique is developed for measuring the complex moduli of AC.A theoretical explanation of the measurement process is provided.Two AC specimens were tested using the ultrasonic method and the dynamic modulus method in the indirect tensile test (IDT) mode.Both test techniques were performed at four different temperatures.The mastercurves were constructed using time-temperature superposition on the IDT test data and the upper asymptotes were extrapolated.The ultrasonic data was shifted to the desired reference temperature and the predicted moduli were compared to those of the IDT test.It was found that the moduli predicted using the ultrasound measurement agreed well for the specimen with a lower air-void content and differed more for the specimen with a higher air-void content.The phase angles predicted by the ultrasonic method were higher than those obtained from the IDT test.It is believed that this was a result of wave scattering from air-voids and aggregates.Suggestions are made to further increase the accuracy of the technique.

The objective of this study is to evaluate the creep compliance (D(t)) of asphalt concrete (AC) mixtures for thermal cracking prediction of flexible pavements. Various AC overlay design factors influencing the thermal cracking resistance of flexible pavements, such as mixture properties and pavement structure, were included in the evaluation. Two sources of D(t) data were considered: (1) measurement from indirect tensile test and (2) numerical interconversion of complex modulus E*. Design input levels in the mechanistic-empirical design guide software do significantly impact the predicted thermal cracking distresses. For AC maintenance overlay design purposes, level 1 and 2 analyses yield very similar thermal cracking predictions, whereas level 3 analysis significantly underpredicts the extent of cracking when compared with to level 1 analysis. Some discrepancy exists in the thermal cracking predicted from measured and interconverted D(t) due to the inherent approximation nature of numerical interconversion methods. However, level 1 and 2 analyses using interconverted D(t) values provide results closer to the predictions from measured D(t) values than does level 3. Three mixtures are used in this study. The various analyses indicate that using a more ductile AC mixture for the surface layer significantly reduces the amount of thermal cracking at failure.

The characterization of materials is an integral part of the overall effort to validate the Superpave system and to calibrate the performance prediction models for the environmental conditions observed in the Commonwealth of Pennsylvania. Material properties are among the most important input parameters to the models of the Mechanistic Empirical Pavement Design Guide for flexible pavements. An extensive laboratory testing program was followed during Phases I and II of the Superpave In-Situ Stress Strain Investigation (SISSI) project to determine binder properties, mix volumetric properties, and mix engineering properties. Testing of SISSI binders during Phase II with the bending beam rheometer at various temperatures and loading times showed that the equivalence principle of testing at low temperature is not satisfied. The indirect tensile creep and strength tests on wearing layers of SISSI provided a ranking of these mixtures based on their low temperature material properties. Fracture analysis of SISSI mixtures indicated that the maximum tensile stress is independent of the type of asphalt concrete mixtures. Considerable deviations were observed between the calculated fracture energy from linear elastic and linear viscoelastic solutions. Results of repeated shear testing at maximum pavement temperature indicate performance of SISSI mixtures to be in the range of good to excellent since no excessive permanent deformation was observed from these laboratory tests. The present report is one of four volumes, Volume I: Summary Report; Volume II: Materials Characterization; Volume III: Field Data Collection and Summary; Volume IV: Mechanistic Analysis and Implementation.

To address Superpave design concerns the Pennsylvania Department of Transportation (PennDOT) sponsored a comprehensive 5-year project called Superpave In-Situ Stress/Strain Investigation (SISSI). Phase I ran from May 2001 - May 2006. The second phase was completed on November 30, 2008. This project was a unique, state-of-the-art instrumentation, validation and analysis project that encompassed eight different pavement sections in the northern and southern parts of Pennsylvania. With the very extensive amount of data collected during Phase I of the project, it was decided that Phase II would focus on extensive analysis of the collected data and implementation of results from Phase I. The major goal of Phase II was to use the SISSI data with the AASHTO newly developed mechanistic design guide (MEPDG). The present report is one of four volumes, Volume I: Summary Report; Volume II: Materials Characterization; Volume III: Field Data Collection and Summary; Volume IV: Mechanistic Analysis and Implementation. This is the summary report for Phase II of the Superpave In-Situ Stress/Strain Investigation.