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(light music)

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- [Narrator] Reflective
cracking is a type of cracking

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that occurs when a new
asphalt overlay is placed

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over older pavement with
pre-existing cracks.

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Often new cracks will
form, mirroring the cracks

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in the underlying layer.

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Geogrids placed between the two layers

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have shown promise in
mitigating the issue,

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but further research was needed

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to develop design criteria.

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The Texas Department of Transportation

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and researchers with the Center

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for Transportation Research
conducted a field study

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to quantify the structural
benefits of geogrids.

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- We use the same concept
for this geosynthetics

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because we've been using
geosynthetics for a long time,

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textile on bases, on the
soils and aggregates.

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But now this research

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was using the same materials,
a little bit modified

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for the asphalt, for the top layers.

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- By having that
geosynthetic reinforcement,

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not only you mitigate
the reflective cracking,

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but you also increase
the structural capacity.

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And we knew that that happened,
but we had not quantified

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and we even, and without
being able to quantify it,

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we do not know how to
incorporate it into the design.

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So the objective of this
project was to quantify

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the structural benefits of geosynthetics

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when used with asphalt overlays.

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- The research included a
comprehensive, full scale monetary

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program included in SH21
in Bastrop county, Texas.

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This program involved the use

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of varied geosynthetic
reinforcement products,

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placed between the asphalt layers

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across multiple test sections,

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- Something on the order of
24 test sections, all of them

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with different types of geosynthetics,

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some of them without geosynthetics.

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Now, the problem with roadway
projects when we have these

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test sections is that we
need to wait 15, 20 years

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to understand the
differences between these 24

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test sections.

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So in order not to have
to wait for that long,

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we installed a significant
number of sensors.

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- [Speaker] Some of these
test sections were equipped

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with a range of sensors,

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including asphalt strain
gauges, thermocouples,

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geophones, and moisture
sensors to monitor performance.

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- These were all
instrumented test sections,

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so we were able to understand the response

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and the benefits immediately
or soon after construction.

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And we gather a lot of data
from this monitoring project,

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and we evaluated the data.

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- We will continue
monitoring projects like SH21

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to document the long-term benefits

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of the geosynthetic reinforcement.

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Updating specifications

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and test procedures will also help

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to ensure the technology
is applied effectively.

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- Essentially, when we use
geosynthetic to reinforce

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as faultic layer, we have an
increased structural capacity.

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This increased structural
capacity has not been

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accounted for in the past,

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and by accounting for it,

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we can have significant cost benefits,

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either by decreasing the thickness of,

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or the required thickness
of a given asphalt overlay,

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or for a given thickness
of the asphalt overlay

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to extend its design life.

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- [Narrator] For more information

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and to find the publications
for this project,

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please visit the TX DOT Research Library

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at the link shown below.