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Subgrade soil, as the critical underlying support for other pavement layers and traffic loads, should be stiff enough to maintain the integrity of pavement structures and the smoothness of pavement surface. The resilient modulus, as an indicator of subgrade stiffness, is an essential input in the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG). At input level 1 of MEPDG, the MEPDG generalized model is required to describe resilient modulus of subgrade soil, and the coefficients of this model are used for pavement design. The change of the resilient modulus model has raised the interest of many state highway agencies and made it necessary to convert old resilient modulus test data into new ones required for the MEPDG model. In this study, the coefficients of the generalized and the universal models for soil resilient modulus were obtained through regression of the results of 13 soils in Tennessee. The coefficients of the two models were also compared. There is a potential risk that the coefficients from the universal model may be mistakenly used in the MEPDG instead of those coefficients from the generalized model. The consequence of this improper use was demonstrated in the comparison between the miscalculated and the real resilient moduli. The coefficients of the generalized model were correlated to soil physical properties, which provided an alternate time-saving and economical method to obtain soil resilient modulus as level 2 inputs. The coefficients were obtained at different post-compaction water contents, to allow the estimation of pavement response under seasonal moisture variation of subgrade. Rutting and roughness of two typical pavement sections were analyzed to investigate the influence of the seasonal variation of soil resilient modulus on pavement performance. The results showed that moisture variation had a significant effect on subgrade resilient modulus and, subsequently, on pavement performance. It is recommended that seasonal change in soil resilient modulus be considered in the analysis on pavement performance. [ABSTRACT FROM AUTHOR]

To implement the Mechanistic-Empirical Pavement Design Guide (MEPDG) developed by AASHTO for pavement construction and rehabilitation, it is necessary to evaluate its performance prediction models using actual pavement performance data, material properties, traffic information, and environmental factors. This paper validated the MEPDG models using the performance of typical pavements in the state of Tennessee from pavement management system (PMS). With traffic and pavement structural information collected from PMS, the performance of selected highway pavement sections was analyzed with MEPDG Version 1.100 software. The predicted present serviceability index (PSI) and rutting were compared with the actual measurement values. An initial value for the international roughness index (IRI) was suggested for Tennessee highways through investigation into the actual roughness data. The dynamic moduli of asphalt mixtures for input level 1 were obtained from laboratory testing. Those for input level 3 were estimated with the Witczak model. The results show that rutting of asphalt concrete (AC) pavements was more accurately predicted at input level 1, whereas it was overpredicted at input level 3. Traffic level was found to be an important factor affecting predicted pavement roughness. It was also found that MEPDG software was relatively conservative for highway pavements with low traffic level. However, MEPDG with nationally averaged default parameters was not sensitive enough to differentiate various climates, traffic, and materials in Tennessee for the prediction of PSI. [ABSTRACT FROM AUTHOR]

Abstract: A laboratory study was conducted to evaluate the moisture susceptibility of plant-produced foamed warm mix asphalt (WMA) containing high percentages of recycled asphalt pavement (RAP) in Tennessee. WMA loose mixtures were collected and compacted at asphalt plant and were compared to hot-mix asphalt (HMA) samples through laboratory performance tests. In addition to widely-used AASHTO T283 freeze and thaw (F–T) and tensile strength ratio (TSR) tests, Superpave indirect tension (IDT) tests, dynamic modulus test, and Asphalt Pavement Analyzer (APA) Hamburg wheel tracking test were also utilized to evaluate asphalt mixtures subjected to freeze–thaw (F–T) and moisture-induced stress tester (MIST) moisture conditioning. The results indicated that the Superpave IDT tests and the dynamic modulus test had potential to accurately characterize moisture susceptibility. With incorporation of RAP, foamed WMA is expected to perform as well as HMA in terms of moisture susceptibility. [Copyright &y& Elsevier]

Longitudinal joints between lanes of hot-mix asphalt (HMA) pavements are commonly susceptible to moisture damage and other failures. In 2006, the Tennessee Department of Transportation (TDOT) identified longitudinal joint failure as one of the major distresses for local HMA pavements. It was determined necessary to evaluate available practices and technologies to reduce longitudinal joint failure. This paper presents the results from a field project in Tennessee constructed with seven different longitudinal joint construction techniques. These techniques could be divided into three major categories: joint adhesives including an anionic emulsion and a polymerized emulsion commonly used by the TDOT, a hot-applied high-polymer rubber, and a high-polymer emulsion; joint sealers including a polymerized maltene emulsion and a polymerized agricultural oil; and infrared joint heater. Laboratory tests were conducted on the field cores taken from the test sections constructed with these techniques. Based on the different mechanisms of these techniques, the following laboratory tests were employed: air void content, permeability, indirect tensile (IDT) strength, and water absorption tests. Field cores were also scanned with the X-ray computed tomography to investigate the effect of infrared heating on air void distribution. The test results showed general consistency in the joint quality; i.e., the lower the air void content, the lower the permeability and the higher the IDT strength. The infrared heater exhibited the best effectiveness in improving joint quality among all the joint construction techniques used in this study. [ABSTRACT FROM AUTHOR]

Objective: Kidney stone formers are at risk for opioid dependence. The aim of this study is to describe opiate exposure and determine predictors of prolonged opiate use among kidney stone formers after surgery. Materials and Methods: A retrospective review was performed among patients who underwent ureteroscopy for upper tract stone disease. Prescription data were ascertained from a statewide prescribing database. Demographic data and surgical factors were collected from the electronic medical record. Predictors of additional postsurgery prescriptions filled within 30 days and persistent opiate use 60 days after ureteroscopy were determined. Results: Among 208 patients, 127 (61%) had received preoperative opiate prescriptions within 30 days before surgery. Overall, 12% ( n  = 25) of patients required an additional opiate prescription within 30 days after ureteroscopy, and 7% ( n  = 14) of patients continued to use opiate medications more than 60 days postoperatively. Patients continuing to use opiates long-term were not chronic opiate users. For both outcomes, preoperative opiate exposure, including number of prescriptions, days prescribed, and unique providers had significant associations (all p  < 0.05). Additionally, younger age ( p  = 0.049) was associated with obtaining an additional opiate prescription within 30 days. Lower BMI ( p  = 0.02) and higher ASA score ( p  = 0.03) were predictors of continued opiate use more than 60 days after ureteroscopy. Conclusions: The majority of stone formers have had opiate exposure before surgery, often from multiple providers. Approximately 1 in 8 stone formers who undergo ureteroscopy require additional opiate prescriptions within 30 days. A small but significant population receive opiates beyond the immediate postoperative period.