Field verification process for open-graded HMAC mixes : final report.

PDFTech ReportFHWA-OR-DF-03-01SPR 304-051Open graded aggregatesHot mix paving mixturesMix designField testsThicknessOregonOregon. Dept. of Transportation. Research GroupThompson, GaryRemily, Michael D.Oregon. Dept. of Transportation. Research GroupUnited States. Federal Highway AdministrationUS Transportation CollectionThe State of Oregon uses significant amounts of open-graded HMAC mixes as primary wearing courses on state highways. The primary materials design system for these mixes relies heavily on laboratory draindown to select the design asphalt content. Subsequent adjustments in the field rely heavily on the visual draindown characteristics as well. Draindown is a limiting characteristic in terms of constructability of open-graded mixes, but adjustments made to mitigate draindown may reduce the long-term performance of the wearing surface.This research looked at the viability of using conventional film thickness measurements as a means of field verifying the quality of the open-graded mixtures being produced. The findings were that conventional film thickness measurements were too sensitive to the material passing the 75 \uc2\ub5m sieve and were therefore not a practical tool.The authors proposed a simple alternative involving measuring the volume change that occurs when asphalt cement is added to uncoated aggregate. This measurement tool uses readily available field laboratory equipment and provides a simple means of measuring a fundamental mixture property