Candidate for fully permeable shoulder retrofit validation site
Full Depth Reclamation: Shrinkage Crack Mitigation Methods for Cement Stabilized Layers.
Full depth reclamation (FDR) has been used for rehabilitating pavements in California since 2001. The FDR layers
are stabilized with foamed asphalt (FDR-FA) or portland cement (FDR-PC) to improve the rut resistance, fatigue
life and moisture susceptibility of the layers. This study focused on addressing the well-known concern of
early age shrinkage cracks in cement stabilized layers, using a process known as microcracking. Microcracking was
first investigated in Austria in the 1990s, and further developed in Texas from 2003. It involves applying
vibratory roller passes on the cement treated layer, two to three days after construction with the goal
of reducing the rate of curing in the cemented layer to decrease layer stiffness by creating a fine
network of cracks throughout the layer, which relaxes the initial tensile stresses caused by cement hydration.
This Caltrans/UCPRC study was launched to refine the current method specification required in
the 2015 Caltrans standard specifications. This specification requires three 12-ton vibratory roller
passes at maximum amplitude, two to three days after construction. The specification does not consider
different mix designs, and no testing is required to validate the microcracking effort. The development
of laboratory methods to determine the optimum method for microcracking, and mechanistic models to
determine the effect of microcracking on pavement life were also included in the project objectives.
The study was approached in two phases. The first was started in the summer of 2014, with the goal of
modeling microcracking in the laboratory and monitoring stiffness changes over time on a number of
field projects. The second phase covered the construction, instrumentation, and intense evaluation
of a 1.1 mile long test road with 37 test sections covering a range of variables including cement
content, and timing and intensity of the microcracking. Controls with no microcracking were
included for comparison.
The test road was constructed during the summer of 2016 on Levee and Brooks Roads on the
UC Davis campus. The road is visually monitored for shrinkage on a weekly base. Stiffness
testing with a falling weight deflectometer is conducted frequently to observe the
differences in stiffness gain on the different sections. Laboratory testing is being
conducted in parallel with field monitoring to simulate field performance and to develop
mechanistic models of microcracking and to predict performance of pavements with
microcracked FDR-PC layers.
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