This study focused on the evaluation of all 43 existing portland cement concrete pavements in Boone County, Iowa. The research was directed at the evaluation of the factors effecting the performance the county pavements. Equations relating the design parameters to the commonly identified concrete distresses in pavements are also presented. The knowledge of practicing engineers was utilized to develop guidance in rehabilitation or reconstruction planning timing for concrete pavements in relation to the presence of pavement distresses. Field surveys were conducted to obtain the necessary construction and condition data for use in the study. Some 15 separate distress types by location on the pavement, were identified and used to direct data collection on 100% of the sample pavements. These distresses were further combined to provide seven different distress types for the detailed identification of performance factors. Graphical and statistical analyses were used to evaluate the effect of measured variables on the individual pavement distresses. Results indicate that the pavements have provided adequate design performance and also identified variables effecting the pavement performance that are not commonly identified. The analysis resulted in the development of individual equations relating individual distress levels to performance noted in the sample pavements. Each of 99 county engineers in Iowa and 102 county engineers or superintendents in Illinois was surveyed to develop a knowledge based system that identifies a range of distress levels associated with pavement rehabilitation or reconstruction in a "Time of Opportunity" table. It represents the county engineers' mental measure of when and where to perform rehabilitation and reconstruction. The combination of the performance parameter equations and the "Time of Opportunity" table provide the local road engineer with ways to objectively and/or subjectively evaluate the current concrete pavement system condition and make better decisions as to the proper steps to take in meeting public expectations in road performance.

This synthesis report will be of special interest to pavement designers, materials engineers, and others seeking information on portland cement concrete resurfacings (overlays) placed over both portland and asphalt cement concrete pavements. Information is presented on the various practices in use for the design, material selection, and construction techniques associated with each pavement type. Additional information is provided on resurfacing experience and performance, including an Appendix cataloging more than 700 existing resurfacing projects in North America. Transportation agencies in the United States are continuing to develop pavement management systems which take an objective and structured approach to life-cycle cost analysis requirements for pavement rehabilitation project analysis. This report of the Transportation Research Board also discusses the considerations involved in the selection of technically feasible resurfacing alternatives. Based on the longitudinal experience of 375 resurfacing projects that were cataloged in 1982 and the more than 700 projects identified in 1993, much useful information on the performance characteristics of portland cement concrete resurfacing is presented.

The Specific Pavement Studies 6 (SPS-6) experiment, "Rehabilitation of Jointed Portland Cement Concrete Pavements," was designed as a controlled field experiment that focuses on the study of specific rehabilitation design features of jointed plain concrete pavements (JPCP) and jointed reinforced concrete pavements (JRCP). This experiment examines the effects of climatic regions (wet-freeze, wet-no freeze, dry-freeze, or dry-no freeze), type of concrete pavement (plain or reinforced), condition of existing pavement prior to rehabilitation (fair or poor), and traffic rate (as a covariant), incorporating the different methods of rehabilitation with and without asphalt concrete (AC) overlays. This report documents the first comprehensive review and evaluation of the SPS-6 experiment.