Concerned with sustainability, cost-efficiency, and extending the life
of pavements, this summer Caltrans and the UCPRC will continue investigating
materials and strategies for “greening” pavement rehabilitation projects. Two
projects underway are evaluating pavement rehabilitation strategies using full-depth
recycling (FDR), which allows construction crews to rebuild cracked roadways with
existing materials. This strategy reduces project costs and the environmental
footprint by eliminating the removal of the old pavement as well as excavation and
transport of virgin materials. Roads can also be reopened to traffic each day,
thereby minimizing impacts to the road user.
One focus area of this research examines the use of foamed asphalt
as a stabilizer in the FDR process. This entails mixing hot asphalt binder with
water and air to produce asphalt bubbles that are injected directly onto material
pulverized from the existing road by a customized pavement recycling machine. The
material is then shaped and compacted similar to conventional aggregate bases. Thin
asphalt concrete is then placed as a wearing course. Analyses of data gathered in
the laboratory and the field (from pilot projects on State Routes 20, 33 and 89)
culminate this summer when UCPRC and Caltrans researchers present results and
recommendations for mix and structural designs, and construction procedures for
using foamed asphalt with FDR.
A related line of research looks into the efficacy of FDR without
the addition of stabilizers. Data gathered from field sites and in the laboratory
showed that the recycled material could successfully replace the typical aggregate
base used by Caltrans and that less of the pulverized material is needed to obtain
the same stiffness. From this research comes a revised “gravel factor” for designing
pavements, and a life-cycle cost analysis that Caltrans can use when selecting
among pavement rehabilitation strategies.
Important Note for Caltrans Users: Prior
to scheduling pavement preservation (preventive maintenance or CAPM) or roadway
rehabilitation work on flexible pavement highway sections, the District Materials
Engineer and/or the Project Manager should review
this spreadsheet to
ensure that the proposed project does not include sections active in
the “Quieter Pavement Research” (QPR) testing program. If the proposed
project is within a QPR test section, please
contact Linus Motumah of the
Caltrans Office of Pavement Design before scheduling the work.
To view maps that show where the sections are located, click the following
link: http://maps.google.com/maps?q=http://ucprc.ucdavis.edu/qpsectionsmap.kmz
(or copy-and-paste it into a new browser window for a slightly larger view).
For more information,
contact Erwin Kohler of the UCPRC or
Linus Motumah.