Long-Term Performance of SMA Mixtures Added with Crumb Rubbers in Dry Process

Crumb rubber, made from scrap tires, has been introduced into the production of
different types of Hot Mix Asphalt (HMA) in either wet or dry process. In the wet
process, the crumb rubber and binder are completely mixed to form Asphalt
Rubber (AR), which is then mixed with aggregates in a drum. In the dry process,
the crumb rubber is mixed directly with aggregates in the drum to produce an
HMA called Rubberized Asphalt Mix. In this paper, the long-term performance of
3-year in service testing pavement of Stone Matrix Asphalt (SMA) pavements
with crumb rubber added in dry process was examined through a visual inspection
and laboratory testing on cored samples. The results indicated that the distresses
of cracking, rutting, raveling, bleeding, pushing, and potholes were not found in
the rubberized PEM wearing layer under which rubberized SMA and polymer
modified asphalt cement (PMAC) SMA was used, i.e., the rubberized and control
PMAC SMA underlayers had similar effect on the performance of the surface
PEM. The rubberized SMA core samples taken from the field had slightly higher
stability and lower flow than control SMA ones.