Evaluation of Modified Single Seal Surface Treatments

摘要

The report describes a field study of a multicourse asphalt emulsion chip seal,designated as a modified single seal. The treatment, already used in North Carolina, consists of an application of emulsion and coarse aggregate followed by another application of emulsion and a final layer of fine aggregate. Sixty sections were placed in three districts in 1986-88, totaling approximately 400 lane-km of surfacing. These sections were evaluated periodically by a team of local operations personnel and research staff. The operations personnel also provided estimates of service life for conventional single chip seals, used for a cost-benefit analysis. The modified seals performed better and were more cost-effective than conventional surface treatments. Also, the hazard of broken windshields caused by loose aggregate was virtually eliminated on the modified seal treatments. The report includes recommendations for ensurig that the final product is of high quality. The recommendations include using a pilot vehicle, limiting the speed of construction traffic, using clean dry blot aggregate, applying the coarse aggregate not more than one stone thick, and using the proper nozzles on the asphalt distributor.