Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

Laboratory Design Procedures
• Chip Seals: The literature review mentions a few of the many design procedures
for chip seals, most of which have evolved from McCloud’s original work. Dr.
Kim’s recent studies for NCDOT specifically address aggregate quality, evaluate
various design procedures for chip seals, and offer excellent recommendations
that should be considered for FLH guidelines (103). Although the current ASTM
method needs modest revision, the Sweep Test is viable for ranking curing time,
and should be included in the FLH field study. While there are several laboratory
test methods for long-term chip seal performance, none has universal
acceptance. This is an area where further study is needed, and that is currently
being investigated by other research projects such as NCHRP 14-17. If possible,
the FLH report-only study should remain flexible to include recommendations
from such projects as they become available. The MMLS3, as developed in S.
Africa and as investigated by Dr. Kim and Dr. Epps, remains a valuable
performance testing tool (100). It can be run wet or dry and its rubber tires
simulate uni-directional traffic loading on samples. At approximately $100,000,
the machine cost is prohibitive as a specification tool, but it can serve as an
accelerated simulator for field performance to accelerate validation of other
methods.
• Microsurfacing / PME Slurry: Current ISSA mix design and performance testing
guidelines offer acceptable performance standards for microsurfacing (39).
However, better residue specifications and improved mix design protocols are
still needed. As discussed elsewhere, the Fugro pooled-fund study should serve
as a source for new tests and methods applicable to microsurfacing mix design.
Leveraging Resources and Information Sharing
This project has begun leveraging available knowledge and pooling information (test
methods, data, pavement performance) with suppliers, and other researchers and
agencies (Federal, State, City and County). The recently released “TSP Preservation
Research Roadmap” also recognizes the need for improved, performance-related
112