What is Alkali-Silica Reactivity (ASR)?
How Do I Know if I Have ASR?
What Can I Do to Prevent, Mitigate or Arrest ASR?
Why is Lithium the Best Choice?
Why Should I Partner with FMC Lithium?

What is Alkali-Silica Reactivity?
Lithium technologies prevent and mitigate a reaction in concrete called alkali-silica reactivity (ASR) that is most noticeable by "Y" shaped cracking with no preferred restraint direction, map cracking patterns, spalling and popouts. When left unchecked or untreated, ASR can result in the premature deterioration of concrete structures that lead to a shortened lifespan of the structure, and potential safety issues in applications such as runways, bridge decks and pylons. ASR is a two-step reaction. The first step occurs when silica in the aggregate react with alkali in the cement to produce a silica gel. Subsequently, the gel absorbs water, causing expansion and hydraulic pressures sufficient to crack the concrete. If left untreated, this reaction will continue through the structure resulting in expansion and cracking. The cracking caused by ASR leaves the concrete vulnerable to a number of deterioration mechanisms such as corrosion of rebar, freeze-thaw damage and sulfate attack. Once this occurs, only the costly replacement of the structure will solve the problem making prevention and intervention of ASR a critical concern.
Three Necessities of ASR: Reactive silica, sufficient alkali, sufficient moisture.

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How Do I Know if I Have ASR?
The ASR reaction has now been reported to occur not only in most of North America, but also is a worldwide problem. This issue has resulted in significant unplanned expenditures of both private and government dollars. In North America, a significant portion of the aggregate used in the manufacture of concrete has been tested and identified as potentially ASR reactive or non-reactive.

The ASTM tests recognized to evaluate ASR are:
     • C 295 (petrographic exam)
     • C 227 (mortar bar)
     • C 1260 (rapid mortar bar)
     • C 1293 (concrete prism)
     • C 856 (concrete petrography)
The easiest solution for avoiding ASR issues would be to simply utilize a non-reactive aggregate. This is possible in some areas of the country; however, we have found that if you need to truck aggregate from a distance greater than 50 miles, it is probably not as economically sound as simply adding the proper lithium-based admixture.

Contributing Factors for Deleterious ASR:
     • Reactive Aggregates
     • High Alkali Cement
     • External Alkali SourcesMarine Environments
     • Weather Conditions (Freeze-Thaw / Wetting-Drying Cycles)
     • Corrosion Causing Agents (Deicing Salts and Chlorides)
     • Traffic Loading
Since many factors end up contributing to the concrete’s distress, ASR is often misdiagnosed.

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What Can I Do to Prevent, Mitigate or Arrest ASR?
Prevention and/or Mitigation

Conventional attempts to prevent or mitigate ASR damage have been limited to three options:
     1. Avoidance of the reactive aggregate
     2. Reduction of cement alkali and/or total alkali in concrete
     3. Use of suitable pozzolans as mineral admixtures or blended cement

Avoidance of the Reactive Aggregate
Avoiding reactive aggregate can be difficult. It is a matter of geography and geology. Sources of nonreactive aggregates are diminishing. Some areas of the country do not exhibit ASR in their aggregate, so why not just use that aggregate in your concrete project? Unfortunately, acquiring non-reactive aggregate in areas where ASR has been identified does not usually make sense logistically or economically. FMC has developed spreadsheets to calculate relative costs of the options for preventing ASR, so the civil engineer can compare the costs and effectiveness of the options in a particular job and make the best economic and technical decision. These are available from FMC upon request.

Reduction of Cement Alkali
Reducing cement alkali may be effective in many cases, but there are drawbacks and limitations. Low-alkali cements are becoming more difficult to manufacture and increasingly expensive. The processes used to lower the cement alkali result in production of an environmental waste and increase energy consumption for cement manufacturing. In addition, they are not readily available in some areas with reactive aggregates, and reductions in alkali may not be sufficient enough to mitigate the problem with very reactive aggregates. Furthermore, it will not be effective in the presence of significant external sources of alkali such as alkaline soils and deicing salts. Its effectiveness in mitigating ASR decreases as the cement content of the concrete increases because the amount of total alkalis increases in these situations.

Use of Pozzolans as Mineral Admixtures
Some of the most popular used pozzolans include:
     • Class F ash
     • Class C ash
     • Ground Granulated Blast-Furnace Slags (GGBFS)
     • Silica Fume
     • Natural Pozzolans

The issue in using these mineral admixtures is that they are all, with the exception of the natural pozzolans, essentially by-products. They must be routinely tested against appropriate specifications and a calculated amount added to the concrete. The amount needed for ASR mitigation varies according to source, aggregate, and time. All pozzolans do improve overall durability of concrete by decreasing its permeability; so their use is desirable, but it may be difficult to develop mixes that are practical in field placement with sufficient quantity of pozzolans that improve durability while mitigating ASR.

The most commonly used pozzolan for this application is Class F Fly Ash. Quantities needed for Class C ash for ASR control can often be impractical in the field. Environmental regulations and geographical location have made good quality class F fly ash less available. Also, some reports indicate that fly ash alone may not be as effective in mitigating ASR in concrete exposed to chloride salts such as in marine environments and deicing salts with certain aggregates. The other pozzolans are not as readily available, present difficulties in placement, curing and finishing of concrete, or can add significantly to the cost.

The latest data indicates that some concrete believed to have been protected by conventional means is showing signs of ASR distress in the field. Research conducted for more than five (5) decades by FMC and many other interested agencies and researchers reveals that lithium compounds hold the answer to real resolution of the issues surrounding the on-set of ASR in concrete. Interest in lithium compounds to resolve ASR issues is on the minds of highway construction officials, civil engineers, DOT engineers and many others involved in building concrete structures. The Strategic Highway Research Program (SHRP) took the lead in this effort by conducting extensive research on the subject and by issuing report C343. Report C343 places lithium compounds on the short list of recommended preventatives and remedies for ASR.

Since SHRP, lithium based admixtures have been optimized to provide a range of products custom tailored for specific applications. In general, these admixtures are easy to handle, do not affect other concrete properties and are environmentally benign. While lithium admixtures can carry the whole burden of mitigating ASR, the best use of these products is obtained by combining the positive effects of pozzolans with the chemistries of lithium to economically manufacture concrete that is ASR resistant with enhanced durability. These technologies allow the use of any local material in construction. Based on a wide body of evidence on their efficacy in both the laboratory and in-field applications, several national and local specifications now include lithium technologies as a powerful tool to combat ASR.

Treating ASR in Hardened Concrete
It’s not too late. If you have witnessed the symptoms described, have completed the necessary tests and found that your concrete structure exhibits ASR distress, there are solutions. Even though it may sound very difficult to do or at least extremely expensive to perform --treating existing, ASR afflicted concrete is a viable option to extend its life.

There are two primary concerns when addressing ASR in hardened concrete:
     1. Mitigate further expansion from ASR
     2. Repair the damage already caused

Mitigate further expansion from ASR
Reduction of ASR expansion early in the process will lengthen the life of the structure and delay the time before repairs or replacement becomes necessary. By using a specially formulated lithium compound known as Renew® concrete treatment and applying by one of these methods, further expansion caused by ASR can be significantly decreased or stopped. Effectiveness is directly related to the amount of lithium that can be introduced in the concrete, which in turn is dependent on the application method.

Renew® Applied by:
     • Electrical Injection
     • Pressure Injection
     • Vacuum Impregnation
     • Topical Application
             -Ponding
             -Spraying

Repair the Damage Already Caused
Once a mitigation solution has been applied, then patching and repairs can be conducted using traditional concrete repair technologies. Best results are obtained when the cementitious systems used in the repair also incorporate one of our Lifetime® admixtures.

If the ASR problem is left unchecked, expansion will continue and the traditional repairs will fail. In fact, care should be taken when attempting to repair ASR afflicted concrete without lithium. The repair can enhance ASR distress in the hardened concrete by supplying a fresh source of alkali. Lithium is the only material that has shown promise in both the laboratory and the field in mitigating ASR distress in a wide variety of applications.

Why Is Lithium the Best Choice?
Many experts agree, lithium is the best and in some cases, the only truly effective choice when facing ASR. Lithium is effective even with the most reactive aggregates and allows the use of any local material. Many engineers have specified a lithium compound such as Lifetime®, Renew® and/or LifeTech® for their application.

Why Should I Partner with FMC Lithium?
We are the world experts in ASR control and mitigation using lithium technologies.

FMC Lithium has dedicated nearly twenty years of resources to thoroughly researching this problem and developing the products to prevent, mitigate and stop its progress. Our breakthrough technologies have provided new cost-effective techniques in infrastructure repair, retrofit, and renovation of ASR affected concrete structures. Our thorough understanding of alumina-based cementitious systems has allowed us to develop a range of accelerators specially tailored to our customer needs, as well as providing world-class technical assistance for implementing these technologies.

Our distinction comes not only from our technical expertise and in-field experience, but also from the commitment that our people make each and every day to every single customer and their unique requirements. This devotion is what sets us apart from the rest.

A partnership with FMC lithium assures you that we care about your needs, and those of your customers. Guided by our values, driven by market demands, and spurred by research and development, we have abandoned traditional thinking to intensify the development of innovative technologies supporting the construction industry. We have achieved our success by providing cost effective solutions to your problems and sharing our know-how.

A partnership with FMC lithium means the possibilities are boundless.

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