Incremental Costs and Performance Benefits of Various Features of Concrete Pavements

Previous | Table of Contents | Next

CHAPTER 4. SUMMARY

Various design features (such as dowel bars, tied shoulders, or drainable bases) may be added to a PCC pavement design to improve its overall performance by maintaining a higher level of serviceability or by extending its service life. However, the addition of these features also increases the initial cost of the pavement design, in some cases quite significantly. This then raises the question of whether the improved performance benefits gained by adding the design features are worth the increase in cost. Furthermore, the effects of adding more and more design features to a PCC pavement design may produce smaller and smaller performance gains, while significantly increasing the overall costs of the pavement structure. Unfortunately, current design practices do not always consider this trade-off between performance benefits and costs when design features are added to a PCC pavement design.

To address this need, this project was initiated to develop a methodology and an evaluation tool that can be used to assess the costs and benefits of incorporating design features in PCC pavements. To establish a foundation for quantifying the relative performance benefits and costs of the various PCC pavement design features, two detailed surveys were conducted. The first survey targeted SHAs and collected relative performance ratings for changes in design features; that is, the expected percent change in performance if a selected design feature is added to the Standard PCC pavement design. The performance ratings received from the SHAs were evaluated in conjunction with available PCC pavement performance prediction models to check their validity and reasonableness. The second survey targeted PCC paving contractors and collected relative cost ratings for changes in design features; that is, the expected percent change in cost if a selected design feature is added to the Standard PCC pavement design.

Each questionnaire was structured in a similar manner so that the relative performance and cost data could be matched up for each design feature. The results from these surveys form the basis of the default data sets used in the evaluation tool. Copies of the questionnaires sent to the participating agencies and contractors are presented in appendix B, with the raw data and summarized results presented in appendix C.

The primary product developed under this project is an analytical software tool that can be used to evaluate the relative performance benefits and costs associated with the addition of different design features to a PCC pavement design. The software tool can be used by pavement design engineers who are interested in investigating the cost versus performance trade-offs associated with the selection of different design features during the PCC pavement design process. By allowing pavement design engineers to compare the impact of different design features on a pavement's expected performance and its construction and life-cycle costs, insight can be gained on the most cost-effective combinations of design features for a particular PCC pavement design. A detailed explanation on the use and application of the analytical software tool is provided in appendix D.

It is important to recognize that the software developed under this project is merely a computational tool that allows for the comparison of costs and performance of PCC pavements with different design features. The tool can use the default cost and performance data sets that were developed in this study or it can use custom-defined data sets that are based on an agency's local conditions and experience. The tool is not intended to provide absolute answers on the effect of different design features, but rather to provide insight into general performance and cost trends associated with the use of different design features. In this way, the tool can be used in developing more cost-effective PCC pavement designs, and reflects the strong need to consider both the performance benefits and the costs associated with the inclusion of PCC pavement design features.

The anticipated users of the software tool include State highway engineers, design engineers, paving contractors, and industry representatives. It is recommended that the tool be distributed by FHWA to these users, either through direct mailings or through establishment of a Web page containing the software in downloadable format. In addition, regional workshops could be hosted by FHWA (either in conjunction with the FHWA's resource centers or perhaps with local ACPA chapters) as a further aid in implementing the software.