Tech Briefs Report on Partial Depth Spall Repair and Galvanic Cathodic Protection
Two new Tech Briefs summarizing recently concluded Federal Highway Administration
research projects will be available this fall. Each brief reports the
key findings of the research and details how these findings will affect
Portland Cement Concrete (PCC) Partial-Depth Spall Repair
(Publication No. FHWA-RD-99-77) describes the results of a 7-year study sponsored by
the Strategic Highway Research Program (SHRP) and FHWA. The study examined
the merits and deficiencies of various materials and practices for repairing
spalling, which is the cracking, breaking, chipping, or fraying of PCC slab
edges at joints and cracks. Common in jointed concrete pavements, spalling
can affect just a few millimeters of the concrete slab, or extend the full
depth of the slab. Because most spalls are repaired before they extend below
the top third of the slab, the repairs are often referred to as "partial
The Tech Brief summarizes the study, which evaluated more than 1,600
partial-depth patches on four highways in different regions of the country.
As a result of the study, the LTPP program recommends using a chip-and-patch
procedure rather than a saw-and-patch procedure when performing maintenance
The second new Tech Brief, Galvanic Cathodic Protection of Reinforced
Concrete Bridge Members Using Sacrificial Anodes Attached by Conductive
Adhesives (Publication No. FHWA-RD-99-113), describes the development
and testing of a zinc anode/hydrogel for use in galvanic cathodic protection
of reinforced concrete bridges. Although cathodic protection has proven
to be an effective technique for protecting reinforced concrete bridge
decks and substructures from corrosion caused by deicing salts or seawater,
some installations have experienced problems. Most of these problems have
been caused by improper maintenance on the complex impressed-current cathodic
protection systems that are typically used. Although galvanic cathodic
protection systems are simpler and require less maintenance, the anodes
often do not provide enough current.
A 7-year LTTP study examined
the merits and deficiencies of various materials and practices
for repairing spalling.
The study described in the Tech Brief was aimed at developing and testing
anodes and conductive adhesives that could provide sufficient current
to protect reinforced concrete structures and help reduce corrosion. The
zinc anode/hydrogel conductive system that showed the most promise was
installed on three bridges in Florida and Oregon and monitored over 3
years. The study found that the zinc anode/hydrogel system was easy to
install and provided adequate protective current flow, although more field
experience is needed to determine the anodes' long-term performance.
The cathodic protection study was aimed at
developing and testing anodes and conductive adhesives that
could provide sufficient current to protect reinforced concrete
structures and help reduce corrosion.
For more information on the PCC partial-depth study, contact Monte Symons
at FHWA, 202-493-3144 (fax: 202-493-3161; email: firstname.lastname@example.org).
For more information on the cathodic protection study, contact Y. Paul
Virmani at FHWA, 202-493-3052 (fax: 202-493-3442; email: email@example.com).
The Tech Briefs are scheduled to be available next month. To order the
PCC Tech Brief, contact LTPP Customer support services at 423-481-2967
(email: firstname.lastname@example.org). To order the cathodic protection Tech Brief, contact the FHWA Report Center at 301-577-0906 (fax: 301-577-1421).
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