Page 10 - Mar-Apr19 Vol36 No7

KNOX COUNTY By Jessie Anna Boone

Full Depth Reclamation

Full Depth Reclamation using Portland Before During
cement on asphalt pavements is quickly After Curb and Gutters
growing in popularity in the state of Compaction Patch repairs
Tennessee. Although the process of
pulverizing soil and adding cement in
road projects has been around for 80+
years, advances in technologies and
processes in the early 1990s helped FDR
gain real traction. In modern reclamation
projects, high-power reclaimer units are
typically seen on FDR sites instead of the
old soil mixers used in the past. The new
reclaimers have upgraded horsepower
and larger cutting drums that better equip
the machines to pulverize asphalt and
produce uniform gradation of material.
While effective, FDR was primarily used
in smaller projects until 1994 when South
Carolina DOT used it for a 17-mile long
section of Route 97 in York County. This
stretch of road was a proving ground for
FDR on a large scale. Since then, FDR has
proven to be a versatile solution to rebuild
any type of worn out asphalt pavement
with subbase failure.

The FDR process uses what is known
as the reclamation train. The train uses
various pieces of equipment to pulverize
the existing asphalt surface and base to the
recommended depth, spread a measured
dose of cement, hydrate with a measured
dose of water, compact, and grade. The
speed of construction has made the FDR
application a very popular solution among
those who have used it.

When Knox County had a problematic
road in a small subdivision, they
considered two options to fix the issue.
Brad Warren, Director of Construction
Services with Knox County said “We
estimated it would take us 4-6 weeks to
undercut and repair the 8 inches of base
stone and 2 inches of binder. But with
FDR, we were able to complete the work
in 4 days.”

The road in question is Harvest Grove
Lane just off of I-75 North. It is a small
subdivision with a 12 year old road that
was never completed. “The developer
went bankrupt and never placed the
surface course on the road. Between the
lack of surface and heavy traffic from
tandem dump trucks hauling soil, the
road ultimately failed in multiple areas,”
said Warren.
10 TPW March/April 2019