www.concreteproducts.com June 2015 • 37
FEATURE
PICP LOAD TEST
The university study began with a literature review that found
little domestic or international research. Investigators then load test-
ed local PICP projects with an 18,000-lb.-rated truck axle to better
understand deflection and pavement strength. Deflection data was
used to estimate the stiffness (elastic modulus) of each pavement
layer by conducting computer-based mechanistic analysis modeling
that correlates modeled and measured stresses, surface deflections,
and permanent strains (rutting) to pavement layer strengths. This
data was also used to determine subbase thicknesses for full-scale
testing at a 96-ft. long PICP test track over which the HVS could run
truck tires and loads.
The track facilitated the first full-scale load testing on PICP in the
Western Hemisphere. It included three subbase thicknesses (approx-
imately 18 in., 27 in. and 37 in.) instrumented to provide data on
stresses while loaded and rutting. The weak clay soil subgrade was
compacted and non-woven geotextile placed on the subgrade and
sides of the excavation. Above the subbases was a 4-in. thick lay-
er of #57 aggregate, 2 in. of #8 aggregate, and 3-1/8 in. thick con-
crete pavers with permeable jointing #8 aggregate. A concrete curb
restrained the #57 aggregate, bedding, and pavers.
The UC Davis design charts go to one million 18,000-lb. equiva-
lent single axle loads (ESAL) as also provided on the 2011 ICPI design
chart. Revised charts will appear in an emerging American Society
of Civil Engineers national standard on PICP as well as in an updated
edition of the ICPI PICP manual. Both are scheduled for 2016 release.
Assisting ICPI in project funding were the ICPI Foundation for Edu-
cation and Research, Concrete Masonry Association of California and
Nevada, and California Nevada Cement Association. A copy of the UC
Davis report is available from ICPI Technical Services Director David
Smith, dsmith@icpi.org.
Engineered to replicate in one month of
test cycles the effect of two decades of
traffc service, the Heavy Vehicular Sim-
ulator subjected the 96-ft. PICP track to
an 18,000-lb. single axle loading.