Evaluation of tack coat bond strength for mixtures containing baghouse fines

摘要

This study investigated the causes of delamination distresses observed in Division 13 of North Carolina Department of Transportation (NCDOT). The two factors that were believed to contribute to the delamination distress—intermittent purging of baghouses in AC mixes and improper selection and/or application rate of tack coat, vis-a-vis the use of CRS-2 emulsion versus PG64-22 binder—were investigated. Test results based on field cores and laboratory prepared specimens indicated that mixtures containing baghouse fines produced more rut resistant mixes. However, these mixtures were found to be extremely water sensitive. Test results also indicated that asphalt cement used as tack coat (PG64-22) provided better interlayer bond strength compared to the CRS-2 emulsion. Based on the results of this investigation the cause of delamination was attributed to the combined effect of the intermittent purging of baghouse fines with the use of CRS-2 emulsion as tack coat.