A New Laboratory Test for Predicting Very Early Chip Seal Performance

This paper describes how the adhesive and cohesive strength of the emulsion residue used as the binder in a chip seal is directly related to when the chip seal can be opened to traffic after construction. This strength is usually judged subjectively during construction by experienced personnel. Unfortunately, this experience is often gained by trial and error, the error leading to vehicle damage when residues that have not gained sufficient strength release chips under traffic loads. This research was conducted to help eliminate the subjectivity involved in determining when a chip seal can be safely opened to traffic without undue chip loss. The study began with the hypothesis that the existing ASTM D7000 sweep test could be used for this purpose. The ASTM procedure was evaluated and it was determined the test would be adequate for relative comparison of different emulsions for the same aggregates, but not sufficient to evaluate different aggregates for the same or different emulsions. The reason for this is because D7000 uses a template to establish residue depth. Chip gradation is roughly controlled so embedment depth is relatively equal for different chips but variability remains high so predicting actual project materials could be used and time to trafficking could be estimated. Results indicate the amount of water remaining in the emulsion is directly related to residue strength, as expected. Therefore, by establishing the relationship between water content and chip loss in the revised sweep test the time required in the field before traffic is allowed on the fresh chip seal can be estimated in advance. Results indicate little correlation between emulsion particle charge and aggregate type and also that chip loss is directly related to aggregate moisture content upon embedment.

Language

  • English

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Filing Info

  • Accession Number: 01158694
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 11 2010 12:05PM