By: Fred Faridazar
Find out the latest technology for treating and preventing
alkali-silica reactivity (ASR) in concrete at a new workshop series sponsored
by the Federal Highway Administration (FHWA). ASR is a pervasive durability
problem that strikes beneath the surface of portland cement concrete (PCC),
causing premature deterioration of various types of concrete structures across
the country and worldwide. It occurs when silica substances in aggregates react
with alkali in the cement and absorb water. The result is a gel-like mass that
can cause the concrete to expand and eventually crack, potentially causing
severe damage. The development of ASR also can expedite other damages to the concrete,
such as freeze-thaw or corrosion of reinforcing steel.
As the workshop details, lithium compounds, which have been
recognized for more than 50 years as being effective in preventing concrete
expansion due to ASR, are now getting increased exposure as a method of both
treating existing structures and preventing ASR in new construction. With more
state highway agencies setting goals for building longer-life pavements and
structures, preventing and treating ASR is becoming even more important. Using
lithium compounds, especially lithium nitrate (LiNO3), is a viable approach to
controlling ASR-induced damages.
The FHWA workshops provide practitioners with the necessary
information and guidance to test, specify and use lithium compounds in new
concrete construction, as well as to repair and extend the service life of
existing structures. The workshop provides a basic overview of ASR, including
information on mechanisms, symptoms of ASR damage in field structures,
mitigation approaches, test methods and specifications. The workshop then
presents a comprehensive summary of lithium compounds, including information on
their production, availability, use in laboratory concrete studies and field
applications. In addition, participants can learn from a range of case studies.
The workshop also covers:
* Guidelines for using lithium compounds as an admixture in
new concrete and as a method of treating existing structures suffering from
ASR-induced damage;
* Information on how to assess the effectiveness of lithium
compounds in laboratory tests;
* Information on the economics of using lithium both in new
concrete and as a treatment for existing structures; and
* A summary of technical and practical issues that should be
considered for future laboratory studies and field applications.
To date, workshops have been held in Nebraska, New
Hampshire, California and Vermont. A second California workshop will be held in
Los Angeles in September. Other states looking at scheduling workshops this
fall include Texas and Delaware. There is no charge to highway agencies for the
workshop, but they are responsible for hosting the event and providing the
necessary facilities.
For more information on the workshop or to find out more
about scheduling a workshop in
your state, call 202/493-3076; fax: 202/493-3161; e-mail:
[email protected].
Information on the use of lithium to combat ASR also is
available in a new FHWA publication, Guidelines for the Use of Lithium to
Mitigate or Prevent ASR, by K.J. Folliard, M.D.A. Thomas and K. Kurtis. Copies
can be requested from FHWA's Product Distribution Center, 9701 Philadelphia
Court, Unit Q, Landham, MD 20706 (phone: 301/577-0818; e-mail:
[email protected]).
About The Author: Faridazar is a highway research engineer at FHWA's Turner-Fairbank Highway Research Center in McLean, Va.
