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13 summarizes the survey responses from those respondents that Number of Survey Responses indicated that microsurfacing was used in their organizations. 8 7 6 6 Table 5 shows that microsurfacing constitutes a relatively 6 low percentage of most agencies' programs. Texas ($12 mil- 4 3 lion), Tennessee ($9.3 million), Louisiana ($6.3 million), 2 2 and North Dakota ($6.3 million) had the largest U.S. micro- 2 1 11 1 1 1 1 1 surfacing programs. In Canada, Saskatchewan ($10 mil- 0 lion) and Manitoba ($9 million) led the provinces. The table 2 3 4 5 6 7 8 9 10 11 12 13 14 15 shows that microsurfacing is largely installed by contract Microsurfacing Service Life crews. Only one U.S. DOT and two Canadian MOTs have (years) the capability to apply microsurfacing using agency per- US Canada sonnel. Minnesota puts approximately 5% of its annual program down with DOT maintenance crews. Quebec and FIGURE 5 Summary of survey microsurfacing service life Saskatchewan agency personnel install 2% and 5%, respec- responses. tively. The study found no specific information as to why microsurfacing constitutes such a small percentage of the range of 1 year to 15 years. Canadians agencies reported an typical agency's pavement preservation and maintenance average microsurfacing service life of 7 years, with a low of program. However, a check of the bid tabulations for a 3 years and a high of 10 years. May 2010 letting by the Utah DOT shows roughly equiva- lent quantities of microsurfacing and chip seal being bid at SUMMARY AND CONCLUSIONS $2.07 per square yard and $1.72 per square yard, respec- tively, roughly a 20% difference in price. Therefore, eco- Microsurfacing is an effective tool for pavement preservation nomics may be the factor, as an agency can preserve 20% and maintenance programs in North America. It is not used more lane-miles of its roads each year by using the lower in large amounts nor is it a technology that is kept in-house priced treatment. by public highway agencies. Overall, the survey respondents were satisfied with their microsurfacing contractors' perfor- Finally, because microsurfacing can be used as a tool in an mance and depend on the technology to extend pavement ser- agency's preventive maintenance program, the survey respon- vice life. The output from the study instruments discussed in dents were asked if they applied it on a regular cycle as well as this chapter will be used to present a more detailed discussion the length of the cycle if they did. The Indiana and Utah DOTs of the state of the practice in microsurfacing in the following reply affirmatively and Indiana stated that the preventive chapters. It will also be used to identify effective practices that maintenance cycle averaged 8 years. Nova Scotia was the only can be implemented by both agencies with extensive micro- other respondent to reply yes to this question and it reported surfacing experience or agencies that are contemplating adding that it used a 6-year cycle. The written comments on this issue it to their pavement preservation toolbox. suggest that microsurfacing is viewed primarily as a pavement preservation tool in North America. Several respondents stated The following conclusion was found in this chapter: that their agencies use it specifically to extend the underlying pavement's surface life when asked to estimate microsurfacing Microsurfacing is fundamentally viewed as a tool to extend service life. Figure 5 summarizes the survey responses. The the service life of the existing pavement and thus it is used service life reported by U.S. DOTs averaged 6 years within a primarily as a pavement preservation treatment.