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65 CHAPTER NINE CONCLUSIONS INTRODUCTION Microsurfacing can be expected to provide an average service life of 7 years if the underlying road is in good Chapters one and two set the criteria used in this report for condition. drawing conclusions and identifying effective practices. That Microsurfacing is a pavement preservation and main- process was followed rigorously throughout the entire report. tenance tool with very few technical or operational The results are based on the four study instruments used to limitations. collect the information contained in the synthesis: a compre- Microsurfacing was shown to be effective for all lev- hensive literature review, survey of U.S. and Canadian agen- els of traffic, as well as useful in both urban and rural cies, microsurfacing specification content analysis, and case settings. studies. When two or more independent lines of information Microsurfacing was shown to be effective on both from one of those four sources intersected, a conclusion was asphalt and concrete pavements. reached or an effective practice was proposed. Lastly, when Microsurfacing can be effectively used in locations a gap in the body of knowledge was revealed, a suggestion where the work is to be done at night or in cool weather, for future research was made. Therefore, based on that foun- as well as where stresses resulting from stopping and dation, the conclusions, effective practices, and suggestions snow plowing are present. for future research are presented in this chapter. The majority of the respondents that use microsurfacing assign the contractor the responsibility for completing the job mix formula. That the majority of the same pop- CONCLUSIONS ulation rates their microsurfacing project performance as satisfactory indicates that contractor-furnished design The following conclusions were reached in the conduct of does not degrade final quality. this study. They are not listed in any order of importance. Microsurfacing can be procured using a performance- based contract. The content analysis found that a number Of all the standard microsurfacing specifications from 50 of agencies are already using performance specifications U.S. states plus the District of Columbia and the FHWA in their microsurfacing contracts. Federal Lands Highway Division, only 18 had sections Microsurfacing is one of the few pavement preservation that specifically contained the word "microsurfacing." and maintenance treatments that can restore the trans- As a result, there is a potential for confusion in the liter- verse geometry of a rutted road. Because U.S. agencies ature about the difference between microsurfacing and use it primarily as a surface course, they are not maxi- slurry seals, which spawns a potential for an inaccurate mizing the potential benefits of microsurfacing when exchange of technical information on the two treatments. they do not use it as the primary tool to fill ruts as their Only two agencies use microsurfacing on a regular Canadian counterparts do. preventive maintenance cycle and a number of survey Most agencies only use a single microsurfacing emul- respondents indicated that their agency uses micro- sion, and all agencies rated their microsurfacing perfor- surfacing to extend the life of the underlying pavement. mance as satisfactory. Therefore, an agency can select a That approach was validated by the majority of respon- single emulsion that works best for its specific climatic dents, indicating that they use service life as their mea- and traffic environment and achieve satisfactory results. sure of treatment success. That leads to the conclusion The majority of maintenance practitioners do not con- that microsurfacing is viewed as a valuable pavement sider environmental impact in their microsurfacing proj- preservation treatment rather than merely a pavement ect development process. maintenance treatment. Most of the U.S. and Canadian agencies do not perceive Microsurfacing is best suited to address rutting, ravel- that they have an adequate level of competition among ing, oxidation, bleeding, and loss of surface friction. qualified microsurfacing contractors for their programs. Microsurfacing is not appropriate for structurally defi- This may be because most microsurfacing programs do cient pavements. This makes project selection the most not advertise a consistent amount of work each year, important step in the microsurfacing design process making it difficult for interested contractors to develop with regard to impact on the final performance of the the technical capacity and equipment necessary to com- microsurfacing itself. petitively bid on these contracts.