The experience of New Jersey with pavements, like that of many other states, goes back to the last century. Highways constructed early in this century are still in service. During these extensive service lives, several maintenance and rehabilitation activities were applied to keep the pavements in good condition. These activities ranged from patching to full reconstruction. Also, most of New Jersey pavements have been widened at least once. With all these factors, it is difficult to identify the limits of homogeneous sections that should receive the same rehabilitation treatment. In 1996, the New Jersey Department of Transportation started a limited network level falling weight deflectometer (FWD) program. This program has short- and long-term goals. The short-term goals include identifying the limits of homogeneous sections (sectionalization), assessing the pavement structural capacity, estimating the remaining service life, and determining the future rehabilitation needs. The long-term goal of the project is to use the FWD measurements for the ongoing development and refinement of the models used to predict remaining structural life for use in economic evaluation models. The procedure followed to achieve the short-term goals of the project and an outline of the findings of the project are summarized.

A study was performed to evaluate the long-term performance of different pavement materials in California. The performance of many special materials, including recycled asphalt pavement (RAP), was evaluated for actual field performance rather than laboratory-based performance. The sections considered in this study were selected to allow the environmental impact on the performance of a specific treatment to be addressed and comparative analysis between two or more treatments to be performed. This paper focuses on a comparative analysis performed on 47 RAP sections located in three California environmental zones: desert, mountain, and north coast. Comparisons were made between the performance of the RAP sections and those of other treatments located within a reasonable distance on the same route. In total, 131 sections covering seven different treatments were considered. The performance comparisons were made with respect to in situ structural capacity, distress condition, roughness condition, and consistency of construction. Deterioration models were developed and used to estimate the in situ structural capacity, distress condition, and roughness condition for all sections at the same age (5 years) to allow fair comparisons. The expected structural, distress, and roughness service lives were also estimated for all treatments on the basis of the field-observed conditions. The results of the analyses suggested that in all three environmental zones, long-term RAP performance is likely to be comparable to other treatments located within a reasonable distance on the same route.

Multi-layer analyses are commonly used to analyze falling weight deflactometer (FWD) measurements and back calculate pavement layer moduli. This type of analysis assumes static loading conditions and linear elastic material properties. The FWD loading cycle cannot be considered in any sense as a static load. It is a dynamic load with a duration in the range of 30 to 40 msec. Also, paving materials and subgrades are not linear elastic materials and their response to static loads is different than that to dynamic loads, such as FWD loading. The difference between the multi-layer analysis assumptions and actual loading and material conditions is significant. In this paper a three-dimensional dynamic finite element program (3D-DFEM), ABAQUS, is used to conduct a non-linear dynamic analysis of FWD tests on a flexible pavement section. Verification studies have, been conducted of the 3D-DFEM to verify its static and dynamic analysis of both rigid and flexible pavements and no significant difference was found between the predicted pavement response using the 3D-DFEM and the field measured pavement response. A design of experiment was developed to study the effect of layer thicknesses and moduli on pavement surface deflections at various offset distances. Analysis of variance (ANOVA) and regression analysis were conducted to develop statistical models which can be used to predict pavement surface deflection at different offset distances as a function of layer thicknesses and moduli.

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