Willing to take a silver bullet

News October 05, 2000
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State departments of transportation are benefiting from new tools -- like new research and lithium admixtures -- now available to identify and fight destructive alkali-silica reactivity (ASR) in portland cement concrete roads and bridges.


Partly as the result of research into ASR by the Strategic Highway Research Program (SHRP) -- and from states encountering ASR in their own backyards -- state DOTs are realizing that ASR is a real problem that has the capability of striking any state in the union.


Most recently, new guideline specifications released late last year by an ASR Lead States Team will help states deal with ASR. These model specs show government agencies new pathways to mitigation of ASR. Among other remedies, the model specs state "lithium compounds are capable of suppressing deleterious ASR," and provide guidance for lithium's use.


The guidelines -- now under evaluation by subcommittees of the American Association of State Highway & Transportation Officials (AASHTO) -- join other documents that are helping states protect their pavements and structures from ASR, such as an ASR identification guide available at no charge off the Internet.


And these ASR-fighting documents are available at a time when the most widely available lithium-based admixture -- LiNX lithium nitrate alkali-silica reactivity inhibitor from Boral Material Technologies Inc. -- is proving its mettle in fighting ASR on a long-term basis. The synergy of new knowledge and new materials will accelerate the fight against ASR in coming years.


"In my opinion, lithium is the 'silver bullet' to stop ASR in new concrete," said Roger Surdahl, technology coordinator for the Central Federal Lands Highway Division of the FHWA. "When we mix fresh concrete with lithium, deleterious ASR will not occur. And if we can get lithium into existing concrete, it won't repair the existing damage, but I believe it will stop further damage. But the challenge is getting the lithium into the concrete in the first place."


Surdahl is in a good position to observe how ASR can be tamed, as he quarterbacked the FHWA's showcase program on ASR mitigation. In addition, he is a member of the ASR Lead States Team and is authoring the team's final report of its activities, due later this year.


"Lithium-based ASR inhibitors can have a huge impact on the durability and long-term performance of a concrete structure," said Russell Hill, Ph.D., vice president of technology development, Boral Material Technologies Inc. "When you look at service life or life-cycle cost analysis, this kind of product can have a dramatic effect."


For more on the story, read the October issue of ROADS & BRIDGES.

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