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