Jeffrey S Uhlmeyer

Calibration of Flexible Pavement in Mechanistic-Empirical Pavement Design Guide for Washington State

The Mechanistic–Empirical Pavement Design Guide (MEPDG) is proposed as an advanced pavement design tool that integrates up-to-date pavement practices. Since MEPDG was released in 2004, the Washington State Department of Transportation (WSDOT) has continuously worked on calibrating and evaluating the program with regard to implementation for state and local agencies. This paper presents WSDOTs latest efforts on calibrating the flexible pavement portion of MEPDG with data obtained from the Washington State Pavement Management System. It describes preparation of required input data and provides detailed descriptions of input values, as they may apply to states with similar conditions. The calibration process is described, and results and potential implications are discussed. Major observations and general issues encountered in the calibration process are emphasized. An implementation plan is being prepared that may replace the 1993 AASHTO Design Guide with MEPDG in Washington State. This study provides valuable conclusions for national applications: (a) the flexible pavement distress models were calibrated successfully, (b) WSDOT flexible pavements require local calibration different from the defaults, and (c) a software bug does not allow calibration of the roughness model. By making a few improvements and resolving software bugs, MEPDG software can be used as an advanced tool to design flexible pavements and predict future pavement performance.

Sensitivity of Axle Load Spectra in the Mechanistic-Empirical Pavement Design Guide for Washington State

The Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures [referred to as the Mechanistic–Empirical Pavement Design Guide (MEPDG)] is proposed as an advanced pavement design tool that integrates up-to-date pavement practices. The use of axle load spectra instead of the equivalent single-axle load is a dramatic change. However, the collection of an adequate amount of data over years is required for the accurate characterization of future traffic for design; this gives primary importance to pavement designers having a good understanding of the axle load spectra. This paper presents the typical truck load spectra that satisfy the MEPDG requirements for the Washington State Department of Transportation (WSDOT) and that were developed on the basis of the data collected from selected WSDOT weigh-in-motion stations. Sensitivity analysis was conducted with various typical design parameters of WSDOT flexible pavements. The significant findings are that (a) one type of axle load spectrum can present load characteristics for WSDOT in MEPDG, (b) MEPDG is moderately sensitive to the axle load spectra for typical WSDOT pavement designs, and (c) WSDOT needs to calibrate MEPDG before use. The results have been verified in the calibration of the flexible pavement distress models for WSDOT. It is recommended that agencies that lack data resources test and use the default MEPDG axle load spectral inputs and that the bias may be corrected through model calibration efforts.

Pavement Performance Modeling Using Piecewise Approximation

A successful pavement management system requires an accurate pavement performance prediction model. A novel pavement performance model using the piecewise approximation approach was developed to estimate the pavement serviceable life. It can be broadly applied to estimate pavement performance of any distress types or indexes. The basic theory of the piecewise approximation is to divide the whole pavement serviceable life into three zones: Zone 1 for early age pavement distress, Zone 2 in rehabilitation stage, and Zone 3 for overdistressed situations. Historical pavement performance data are regressed independently in each time zone. This approach can accurately predict pavement distress progression trends in each individual zone by eliminating possible impacts from biased data in other zones. This paper describes the theoretical piecewise approximation process of data classification and model regression and then demonstrates an implementation for a group of Washington State Department of Transportation asphalt concrete pavements. The results are compared with the Mechanistic–Empirical Pavement Design Guide incremental damage approach, the current Washington State Pavement Management System (WSPMS) exponential model, and ordinary regression on all data points. Results indicate that the proposed approach is able to estimate the most accurate rehabilitation due year and to predict the performance trends for each divided zone. The piecewise approximation approach is planned for implementation into the WSPMS and will play an important role in decision making for future pavement rehabilitations.

Quieter Hot-Mix Asphalt Pavements in Washington State

Historically, traffic noise has been reduced through the construction of noise walls and berms, which can be costly (US

Local Practice of Assessing Dynamic Modulus Properties for Washington State Mixtures

2 to

Preservation Strategies for Concrete Pavement Network of Washington State Department of Transportation

3 million per kilometer in Washington State). Open-graded friction courses (OGFCs) have been found to reduce tire–pavement-related noise. However, OGFC pavement surface lives of less than 10 years, and as short as 4 years, have occurred in Washington State. The primary reason for early failure is surface wear caused by studded tires. In 2006, the Washington State Department of Transportation (WSDOT) placed the first of three test sections (the second test section was placed in 2007 and the third will be placed in 2009) to evaluate noise reduction qualities and pavement performance with the Arizona Department of Transportation (Arizona DOT) asphalt rubber–asphalt concrete friction course, Arizona DOT asphalt concrete friction course modified with styrene–butadiene–styrene, and a standard WSDOT 12.5-mm dense-graded hot-mix asphalt. This paper focuses on pavement surface life and quantifies the reduction and sustainability of tire–pavement-related noise for the project placed in 2006. Initial findings suggest that the OGFC noise reduction benefits quickly diminish as a result of increased surface wear caused by studded tires.

Use of Recycled Concrete Aggregate in PCCP: Literature Search

The dynamic modulus (|E*|) is one of the key elements of a mechanistic–empirical–based flexible pavement design procedure. The dynamic modulus is used to characterize the material properties of asphalt mixtures and to determine the stress–strain responses of a pavement at different loading conditions. The dynamic modulus is also a direct input parameter in several pavement performance models to estimate field fatigue cracking and rutting performance. To provide a better understanding of the local materials, this study aimed to test the typical asphalt mixtures used by the Washington State Department of Transportation and to establish a material catalog for dynamic modulus. In this study, seven plant-produced mixtures from five regions of Washington State were sampled and tested. These mixtures represented the typical asphalt binder, gradation, and mix designs of the state. One warm-mix asphalt project was also included in the analysis. On the basis of the experimental results, it was found that mix properties including air voids and binder properties had an important impact on the dynamic modulus. Because of the limited aggregate gradations, the effect of aggregate gradation on the dynamic modulus was inconclusive. The measured dynamic modulus data were compared with the prediction results by using the traditional Witczak E* model, the new Witczak E* model, and the Hirsch model. The Hirsch model was found to be the most promising and was modified further by including mastic property into the model. The modified Hirsch model greatly improved prediction quality and can be used as both a design tool and a screening tool to estimate the dynamic modulus of a mixture at early stages of the mix design process.

What we don’t know about pavement preservation

The Washington State Department of Transportation (DOT) has about 2,400 lane miles of mainline concrete pavements. The pavements have far exceeded their design lives and have carried several times the estimated traffic loading. Initial Washington State DOT estimates place the cost of reconstructing and rehabilitating the concrete pavement network in the next 10 years at approximately

Dowel Bar Retrofit – Do’s and Don’ts

1.1 billion. However, as for most DOTs, Washington States roadway preservation budget has been reduced. Maintaining a good performance level with reduced funding requires innovative techniques and the best investment choices. A preservation strategy was developed for the Washington State DOTs concrete pavement network to allow delay or avoidance of capital construction spending. The strategy accounts for current pavement conditions, predicted future conditions, and financial constraints. The DOTs pavements division uses a detailed four-step process to select the proper preservation methods for a project: (a) monitor the current concrete pavement performance annually, (b) use updated indices to evaluate pavement conditions, (c) scope the rehabilitation needs by the least life-cycle cost, and (d) propose preservation strategies within various scenarios of constrained funding. The states pavement management system provides a framework for evaluating and monitoring the performance of the Washington State DOTs roadway investments.