"and there will always be the
need for new capacity and new
roadways, but we have a fairly
mature highway system in the
United States, so the majority of
the work now is maintaining the
roadways that we already have.
We need to keep encouraging
highway agencies to consider
the long-term value of perpetual
pavement design when those
projects do come along to build
a completely new pavement."
In perpetual pavement design,
the foundation is built so that no
damage occurs in lower layers,
so only periodic maintenance
of the top layer is required. The
pavement structure remains
intact, and only the top layer
is milled and replaced with a
Thinlay or other appropriate
surfacing. This type of pavement
has been designed so well that
the surface can go 15 to 20 years
between maintenance because
there is no stress occurring from
the base.
"There are groups trying to
promote perpetual pavement
as a long-term solution," Dylla
says. "If we are unable to have
the kind of budget necessary to
maintain every road on a regular
basis, we need to be building
perpetual roads that don't require
frequent maintenance."
EquipmentWorld.com | March 2015
61
For more information
Annual Asphalt Pavement Indus-
try Survey on Recycled Materials
and Warm-Mix Asphalt Usage:
2009-2013 –
www.asphaltpavement.org/PDFs/
IS138/IS138-2013_RAP-RAS-WMA_
Survey_Final.pdf.
An executive summary of the sur-
vey is available at www.asphaltpave-
ment.org.
Warm-Mix Asphalt: European Practice –
www.warmmixasphalt.com/
submissions/68_20080223_FHWA-
PL-08-007.pdf.
Reclaimed Asphalt Pavement in As-
phalt Mixtures: State of the Practice –
www.fhwa.dot.gov/publications/
research/infrastructure/pave-
ments/11021/11021.pdf.
Thin Asphalt Overlays for Pave-
ment Preservation –
www.asphaltpavement.org/images/
stories/is-135.pdf.
NCHRP Synthesis 464, Thin As-
phalt Concrete Overlays –
www.onlinepubs.trb.org/onlinepubs/
nchrp/nchrp_syn_464.pdf.
Porous Asphalt Pavements for
Stormwater Management –
http://store.asphaltpavement.org/
index.php?productID=179.
Perpetual Asphalt Pavements, A
Synthesis –
www.asphaltroads.org/assets/_con-
trol/content/files/Perpetual_Pave-
ment_Synthesis.pdf.
More information about these asphalt
paving technologies can be found online.
In perpetual pavement design, the
foundation is built so that no dam-
age occurs in the lower layers, so only
periodic maintenance of the very top
layer is required.
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