Alkali-aggregate reaction (AAR) is only one of the many factors that might be fully or partly responsible for the deterioration and premature loss in serviceability of concrete infrastructure. A subset of AAR is alkali-silica reaction (ASR), which involves various types of reactive silica (SiO2) minerals and alkali-carbonate. ASR relies on the formation of a secondary reaction product called alkali-silica gel that can generally be observed in concrete members affected by this reaction. ASR can result in expansion and cracking of concrete elements, leading to a reduction in the service life of concrete structures.
The Federal Highway Administration (FHWA) published a report describing an approach for the diagnosis, prognosis, and mitigation of alkali-aggregate reactivity in transportation structures. A preliminary investigation program is first proposed to allow for the early detection of ASR, followed by an assessment (diagnosis) of ASR completed by a sampling program and petrographic examination of a limited number of cores collected from selected structural members. In the case of structures showing evidence of ASR that justifies further investigations, this report also provides an integrated approach involving the quantification of the contribution of critical parameters with regards to ASR.
This course is intended for civil engineers who are interested in preservation & restoration of concrete structures. Course material is based on publication FHWA-HIF-09-004.
To earn PDH credit, you must complete a quiz consisting of thirty (30) multiple choice questions.
Specific Knowledge or Skill Obtained
This course teaches the following specific knowledge and skills:
- Investigation program level 1: condition survey
- Investigation program level 2: preliminary studies
- Measurement of the Cracking Index (CI)
- Preliminary sampling program
- Petrographic examination
- Investigation program level 3: detailed studies
- In-situ investigations
- Laboratory investigations
- Damage Rating Index (DRI)
- Numerical modeling
- Mitigation measures: causes vs. symptoms
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