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2 CHAPTER 1 Introduction This manual was developed for use in designing and con- improve the probability of success when designing and con- structing chip seals over hot mix asphalt pavements. It docu- structing chip seals, but they do not replace the significant ments best practices based on the findings of research during judgment required. Also, the success of any chip seal depends NCHRP Project 14-17, Manual for Emulsion-Based Chip Seals on conformance to best practices, and variance or elimination for Pavement Preservation. A summary of the research per- of these practices often leads to disappointing performance. formed in this project is provided in the attachment. Also, test methods developed in this research for use in conjunction 1.1 Definition of Chip Seals with this manual are provided in the appendix. In addition, certain subjective or qualitative judgments previously needed Chip seals described in this manual are based on emulsi- during chip-seal construction have been eliminated in favor fied asphalt binders and natural mineral aggregate chips. The of field and laboratory testing. These include the moisture con- chip seal is constructed by spraying the asphalt emulsion onto tent of the seal before traffic can be released, judging surface the existing asphalt pavement and then dropping the aggre- condition so emulsion application rate can be adjusted for gate chips into the asphalt emulsion. The purpose of the chip surface demand, and measuring the emulsion consistency in seal is to seal minor cracks in the surface of the asphalt pave- the field. The introduction of these new techniques should ment and provide additional friction.