Candidate for fully permeable shoulder retrofit validation site
Laboratory Evaluation and Accelerated Pavement Testing of Different Open-Graded Hot-Mix Asphalt Materials.
This study was part
of a long-term effort that started in 2005 to develop the specifications,
guidelines, standardized laboratory and field test methods,
and other information needed for quieter pavement research
to be incorporated into standard Caltrans practice. Based
on their performance in an earlier laboratory study, several
open-graded friction course (OGFC) mixes were selected for further evaluation
with accelerated pavement testing using the Heavy Vehicle
Simulator (HVS) and laboratory testing on plant-produced
materials. These selected mixes had shown good overall
laboratory performance in the previous study in terms of
durability and sound absorption.
The following HVS test cells were constructed for this experiment:
- Cell A: Caltrans 3/8 inch mix with PG 76-22PM binder, average as-built thickness = 0.06 ft
- Cell B1: #4P mix with PG 76-22PM binder, average as-built thickness = 0.06 ft
- Cell B2: Same mix as Cell B1, average as-built thickness = 0.07 ft
- Cell C: #4P mix with PG 64-16 binder, average as-built thickness = 0.05 ft
- Cell D: Georgia 1/2 inch mix with PG 58-34PM, average as-built thickness = 0.15 ft
The #4P mixes had nominal maximum aggregate size of
4.75 mm (#4 sieve) with “P” indicating a coarser aggregate
gradation identified in the earlier laboratory study. The
five test cells included three new OGFC mixes, with the
Caltrans 3/8 inch mix serving as the control mix.
The study examined the performance of the selected OGFC
mixes in terms of their constructability, rutting performance, moisture
damage susceptibility, surface texture, permeability, clogging
susceptibility, clogging and rutting mechanisms, and
The study found that while all of the mixes are feasible
for a given project, the preliminary indications with
regard to differences in expected performance are:
The #4P mixes offer superior noise and mechanical durability compared with the control mix. They
have similar skid resistance, as measured by California Test 342 (CT), and surface
permeability. They have lower macrotexture than the control, but more than the
dense-graded mixes. A rubberized binder may improve moisture sensitivity and
rutting performance, which was better or worse than the control mix
depending on the binder type.
The Georgia 1/2 inch mix is likely to provide superior skid
resistance and rutting performance compared to the control
mix, although it could not be fully investigated in this project
due to difficulties in getting it produced by local plants as
designed. This mix is also likely to cost more because of the
lime treatment and fibers recommended by the Georgia
DOT in addition to the polymer-modified binder.
Based on the results from this study, it is recommended that
several pilot sections using the #4P mix be placed using a
rubberized binder. For these mixes to be placed, the gradations
may need to be adjusted somewhat to be producible using
current crushed stone bin gradations. It is also recommended that
consideration be given to increasing the minimum surface and
air temperatures for paving of open-graded mixes.
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
(or copy-and-paste it into a new browser window for a slightly larger view).
For more information,
contact John Harvey of the UCPRC or