Crack Attenuating Mix (CAM) is relatively a new asphalt mixture type used by
the Texas Department of Transportation (TxDOT). These mixtures are fine graded,
designed using relatively small stone sized aggregates and screenings with a high asphalt
content, specifically for retarding the reflective cracking in thin asphalt overlays without
sacrificing rutting resistance. The main goal of this study is to promote the use of local
aggregates in CAM design. In order to achieve the goal, the development of a mix design
procedure and aggregate quality guidelines for CAM design with local aggregates are
essential. Several aggregate sources were identified and characterized in terms of their
frictional, strength, and durability properties. A refined mix design procedure is
recommended using a Superpave gyratory compactor with the capability to measure
shear stress during compaction. The emphasis was on preventing rutting and flushing
resulting from overfilling of binder in these mixtures, which was observed during
compaction by consistent shear failures. The Hamburg Wheel Tracking Device (HWTD)
was used for performance evaluation of rutting, whereas the Overlay Tester (OT) was
used for cracking evaluation. It is hypothesized that current performance criteria in terms
of HWTD and OT are too severe for being applicable to CAM mixes with local
aggregates. A modification in HWTD failure criterion is recommended and is used in
developing new aggregate guidelines. A correlation analysis was conducted relating
aggregate properties and CAM performance in rutting and cracking. Finally, aggregate
quality guidelines were developed for CAM using local aggregates based on the
correlation study. The mix design recommendations as well as aggregate guidelines and
quality criteria provided in the report are based on laboratory investigations and field
validation of these is strongly recommended before implementation. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2011-12-4801 |
| Date | 16 February 2012 |
| Creators | Buddhavarapu, Prasad Naga Venkata Siva Rama |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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