State of practice on the use of tack coats for micro-surfacing applications: A survey
Document Type
Conference Proceeding
Publication Date
1-1-2019
Abstract
This paper presents the results of the first comprehensive national survey on the state of practice on the use of tack coats for micro-surfacing applications and factors that affect the bond strength of micro-surfacing mixes. Surveys were sent to all state and provincial transportation agencies in the United States (US) and Canada. The survey questions were developed to collect information on the state of the practice related to: use of tack coat for micro-surfacing applications, types of tack coat materials, dilution rates of tack coat materials, residual application rates, determination of rate for different types of surfaces, methods used for tack coat distribution, and micro-surfacing failures related to tack coat application. The key findings of the survey are summarized. The results indicated that 11 of the transportation agencies that responded to the survey are currently using tack coat on all surfaces with micro-surfacing. In addition, ten agencies indicated using tack coat on some but not all surfaces with micro-surfacing, such as concrete surfaces or surfaces that are heavily raveled or oxidized. Finally, 18 agencies indicated that they do not use tack with micro-surfacing application. The survey results indicated that there is no consensus among responding transportation agencies about the importance of using tack coat for micro-surfacing applications. Most agencies that use tack coat with micro-surfacing believe that it is critical for providing adequate bonding with the underlying surface, while the majority of the agencies that do not use tack coat believe that it is not needed, as adequate bonding can be provided by the emulsion in the micro-surfacing mix. However, some agencies that stopped using tack coat with micro-surfacing (such as Indiana DOT and Michigan DOT) have noted some debonding issues and decided to or are considering adding a requirement for tack coat usage. The survey results also indicated that none of the responding agencies are performing field tests to evaluate the bonding strength of micro-surfacing mixes. Furthermore, four agencies indicated that they do perform tests to evaluate bonding strength between asphalt layers. The tests used included either a pull-off test on milled surfaces (Kansas) or a direct shear bond test (Tennessee, Texas, and West Virginia).
Publication Source (Journal or Book title)
Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions
First Page
157
Last Page
182
Recommended Citation
Nazzal, M., Mohammad, L., Abbas, A., Kim, S., Biehl, E., & Ricciardi, P. (2019). State of practice on the use of tack coats for micro-surfacing applications: A survey. Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions, 88, 157-182. Retrieved from https://repository.lsu.edu/civil_engineering_pubs/855