|
Frequently Asked Questions
Cement & Concrete
Technology Home > FAQs> Diagnosing
ASR Damage
Q: How do you diagnose damage from alkali-silica
reaction (ASR) in a concrete structure?
 A:
The diagnosis of alkali-silica reaction (ASR) in a concrete structure
requires a combination of recognition of the visual symptoms of ASR,
appropriate testing to verify the presence of ASR gel, and deterioration
of the concrete in the structure. Typical visual symptoms include
unusual expansion of the concrete evidenced by longitudinal cracks,
map cracking (random cracking pattern), closed joints, spalled surfaces,
displacement of adjacent structural components, popouts, efflorescence,
or discoloration (darkened or blotchy areas). If site inspections
reveal one or more of these visual symptoms it may be appropriate
to sample and test the concrete to verify the presence of ASR gel.
In addition, the source of any other deterioration mechanisms should
be noted and the structure should be evaluated for soundness. Appropriate
testing can be performed using one of the following methods:
- Petrographic Analysis (ASTM C 856 or AASHTO T 299)
- Uranyl-Acetate Treatment (discussed in the Annex to ASTM C 856
or AASHTO T 299)
- Los Alamos Staining Method (Powers 1999)
More on test methods for
ASR.
More information on ASR.
References
Diagnosis
and Control of Alkali-Aggregate Reactions in Concrete
(IS413) This 26-page document provides leading-edge approaches
to identify and control alkali-silica reactivity and alkali-carbonate
reactivity in concrete.
Guide
Specification for Concrete Subject to Alkali-Silica Reactions
(IS415) provides the specifier with a variety of methods to
control ASR, including tests to determine if aggregates are potentially
reactive and methods to demonstrate how pozzolans and blended cements
can effectively control ASR. Also available as a PowerPoint®
presentation (PT404).
|