|FHWA > Engineering > Pavements > Concrete > Alkali-Silica Reactivity (ASR)|
So, how do you control ASR?
ASR can be successfully controlled by designing the mix properly. There are several ways to minimize the danger for ASR when designing a mix:
For existing concrete structures, research is still underway on establishing the best protocol for ASR suppression and repair. Focus is either on treating the cause or treating the symptoms. Methods for treating the cause include:
Methods for treating the symptoms include:
FHWA published their revised recommendations on the use of lithium for preventing and mitigating alkali silica reactivity in concrete in 2006, Interim Recommendations on the Use of Lithium to Mitigate or Prevent Alkali-Silica Reaction (ASR), as well as a “Lithium Facts Book” titled “The Use of Lithium to Prevent or Mitigate Alkali-Silica Reaction in Concrete Pavements and Structures”.
To download a copy of the Interim Recommendations, click here
To download a copy of the Lithium Facts Book, click here
CSA 684-00: Guide to the Evaluation and Management of Concrete Structures Affected by Alkali-Aggregate Reaction describes explicitly the techniques and procedures for preserving and extending the service life of a structure
Are there specifications for preventing ASR?
YES. There are many from Canada, Australia, the Republic of South Africa, France, the UK, and many other European nations. In the United States, there are guidelines by the American Concrete Institute (ACI), a guide specification by the Portland Cement Association (PCA), and individual state and local government specifications. This website will not attempt to address all of these specifications. For the most part, specifications are either prescriptive or performance-based.
Prescriptive specifications mandate what materials and proportions must be used to control ASR. These types of specifications usually limit alkali content of the cement or concrete, and require minimum levels of SCM replacement or admixtures.
Performance-based specifications require certain testing to establish an aggregate's potential for reactivity and additional testing to ensure the success of any method used for controlling ASR (e.g. SCMs or chemical admixtures). Performance-based specifications allow contractors to choose how they approach controlling ASR with their mix designs.
The Canadian Standards Association (CSA) seems to be the forerunner in its progressive and comprehensive specifications for controlling ASR. The specifications can be found in CSA 684-00: Guide to the Evaluation and Management of Concrete Structures Affected by Alkali-Aggregate Reaction (which can be found by clicking here).