Cho, Mun Jin (E-mail: mjcho@ex.co.kr) ABSTRACT PURPOSES : The performance of tack coat, commonly used for layer interface bonding, is affected by application rate and curing time. In this study, bonding strength tests were performed according to the application rate and curing time of asphalt emulsion. Based on finding from this study, optimum application rates and curing times are proposed. METHODS : In order to investigate bonding characteristic of asphalt emulsion, tests were performed on both asphalt concrete pavement and portland concrete pavement. Also, asphalt emulsions were tested at the application rate of 0, 0.2, 0.4, 0.6, and 0.8/m 2 and at the curing time of 0, 0.5, 1, 2, and 24 hours. Pull-off test and shear bonding strength test, which commonly used for bonding strength measurement of asphalt emulsion, were adopted for this study. To assess field performance under different testing condition, asphalt emulsions were applied to inservice pavement. Throughout coefficient of determination analysis between material index properties from asphalt emulsion and mechanical response from bonding strength tests, performance correlativity was analyzed. RESULTS : Test results show that optimum application rate for asphalt overlay on asphalt concrete pavement (AOA) and asphalt overlay on concrete pavement (AOC) was 0.4~0.5/m 2 and 0.3~0.5/m 2, respectively. According to the curing time increment, tensile strength and shear strength of AOC were increased to 22~44% and 20~39%, respectively. AOA case also show strength increment in tensile strength (42%) and shear strength (9%). We tested the applicability of tack coat materials at the field sites, and our findings demonstrated that the bonding (for D and E) and rapid curing (for B, C, and D, E) performances were superior than others. Among material index properties, there was a high correlation between penetration ratio and bonding strength test result. CONCLUSIONS : Result show that interlayer bonding strength was affected by asphalt emulsion type, application rate and curing time. AOC required slightly higher application (0.1/m 2 ) than AOA. Both AOA and AOC cases show higher strength at longer curing time. Up to 2hours of curing, rapid strength increments were observed, but strength increment ratio was decreased after 2hours of curing. From the observed correlation between penetration ratio and bonding strength, it is expected that penetration ratio can be used as one of important factors affecting bonding strength analysis. Keywords tack coat, asphalt emulsion, application rate, curing time, pull-off test, shear bond strength test Corresponding Author : Cho, Mun Jin, Researcher Pavement & Material Research Division, Expressway & Transportation Research Institute, Korea Expressway Corporation, 50-5 Sancheok-ri, Dongtan-myeon, Hwaseong-si, Gyeonggi-do, 445-812, Korea Tel : +82.31.371.3391 Fax : +82.31.371.3369 E-mail : mjcho@ex.co.kr International Journal of Highway Engineering http://www. ijhe.or.kr/ ISSN 1738-7159 (Print) ISSN 2287-3678 (Online) 85
86 International Journal of Highway EngineeringVol.15 No.4
87
88 International Journal of Highway EngineeringVol.15 No.4
89
90 International Journal of Highway EngineeringVol.15 No.4
91
92 International Journal of Highway EngineeringVol.15 No.4
93
Al-Qadi I. L., Cortina, A. S., Hasiba K. I., Ozer, H., Leng Z.(2012). Best Practices for Implementation of Tack Coat : Part 1, Laboratory Study., Research Report ICT-12-004, Illinois Center for Transportation. Donovan, E. P., Al-Qadi, I. L., and Loulizi A.(2000) Optimization of Tack Coat Application Rate for Geocomposite Membrane on Bridge Decks.Transportation Research Record : Journal of Transportation Research Record, Vol. 1740, pp. 143-150. KS F 4932, 2007, Waterproofing membrane coating for concrete deck of bridge, Korean Agency for Technology and Standards. KS M 5000, 2009, Testing Method for Organic and Their Related Materials, Korean Agency for Technology and Standards. Lee, K. H., Kang, M. S., Kim, I. S., Cho, M. J.(2012) Improvement of the Sustainability for the Asphalt Overlay on the Concrete Pavement., Korean Expressway Corporation. Leng Z., Al-Qadi I., Carpenter, S. H., Ozer, H.(2008) Tack Coat Type and Application Rate Optimization to Enhance HMA Overlay-PCC Interface Bonding: Laboratory and APT Testing, APT '08. Third International Conference, Madrid, Spain. MLTM, 2009, Road Construction Standard Specification, Ministry of Land, Transport and Maritime Affairs, Korea. Mohammad et al.(2012) Optimization of Tack Coat for HMA Placement., NCHRP Report 712, TRB. Ozer, H., Al-Qadi I., and Leng Z.(2008) A Fracture-Based Friction Model for Pavement Interface Characterization.Journal of Transportation Research Record, Vol.2057, pp. 54-63. Raab, C., Partl, M. N.(2004) Interlayer Shear Performance : Experience with Different Pavement Structures., 3th Eurasphalt & Eurobitume Congress, Vienna, Austria, Vol.1, pp. 535-545. 94 International Journal of Highway EngineeringVol.15 No.4