Geosynthetics June/July 2020 - 33

contents and determining the geotextile
air entry value. The researchers measured
the resilient modulus of the aggregate
base at 2% increments over moisture
contents ranging between 0% and 12%.
All samples were initially compacted at
the optimum moisture content of 8.5%
to ensure that each specimen had the
same microstructure. Specimens were
then either dried or hydrated to the target
moisture content and tested. Resilient
modulus testing was conducted according to AASHTO T307-99.
Results of the resilient modulus testing showed that a 2% increase in moisture content of the base course aggregate
from optimum caused a 60% decrease in
resilient modulus and a fivefold increase
in permanent deformation (Figure 9).
Conversely, a 2% reduction of the moisture content from optimum by the ELDG
results in a 200% increase in resilient
modulus and a 40% reduction in permanent deformation (Figure 10). The
benefit of the ELDG in reducing moisture
levels at or below optimum are clearly
shown in this research.

Instrumented test using ELDG
in expansive clays: University
of Texas at Austin (2015)
The development of longitudinal cracks
associated with the presence of expansive clay subgrade soils is a moisturerelated pavement distress. These environmentally induced longitudinal cracks
develop toward the pavement shoulders
because of moisture content variations
in the subgrade. Environmental moisture
variations such as wet or dry periods have
higher changes in moisture content at the
shoulder of the pavement compared to
the center of a pavement. Consequently,
the edges of the pavement will shrink
and swell more significantly during dry
and wet periods respectively. During particularly dry seasons, the flexion of the

FIGURE 9 Resilient modulus vs. moisture content at confining pressure of 20 psi

FIGURE 10 Deformation vs. moisture content at confining pressure of 20 psi

pavement will result in tension toward
the surface layer, leading to significant
longitudinal cracks (Zornberg et al. 2017).
A 6-mile (10-km) section of Texas
State Highway 21 (SH21), just north of
Bastrop, Texas, was constructed on an
expansive clay subgrade and in 2013 was
rehabilitated by the Texas Department
of Transportation (TxDOT). Prior
to this rehabilitation, the road had
received regular attention from the
TxDOT maintenance operations group.
Despite this regular maintenance, performance was deemed to be inadequate
due to the extensive network of lateral
shoulder cracking present. The 2013
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Geosynthetics June/July 2020

Table of Contents for the Digital Edition of Geosynthetics June/July 2020

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Geosynthetics June/July 2020 - Cover2
Geosynthetics June/July 2020 - 1
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