Project:
Detroit Metropolitan Airport (DTW) $48 million Runway Project

Location:
Detroit, Michigan, USA
 
Owner:
Wayne County Airport Authority

Concrete Producer:
John Carlo Inc.

Architect:
Gensler Associates Inc.

Products:
CATEXOL LN
CATEXOL A.E. 260
CATEXOL 3500 N
CATEXOL 1000 N

Situation:
Alkali-silica reaction (ASR) is a significant cause for premature deterioration of concrete highways, runways, parking lots and bridges in certain areas. ASR takes place between the alkalies produced from the hydration of portland cement and specific siliceous rocks or minerals in the aggregates utilized in concrete production.

Challenge:
As the effects of ASR become more widely known, many engineers and architects are specifying lithium-based admixtures that can prevent ASR. AXIM Concrete Technologies provides a range of lithium-based admixtures and corrosion inhibitors that mitigate the effects of ASR and prevent the premature deterioration of concrete structures. AXIM's CATEXOL LN was selected to mitigate ASR on the $48 million runway project at the Detroit Metropolitan Airport.

Solution:
CATEXOL LN improves the durability of concrete, increases the life of concrete structures and permits the use of locally available aggregates, which can reduce costs. It is perfectly formulated for structures designed for long-service life and applications that are difficult to repair, such as airport runways.

Economics of Using Lithium Compounds in New Concrete
Source: FHWA

When considering using lithium nitrate as an admixture for concrete, the economics of this approach is often compared to other mitigation measures. The cost of lithium is probably higher than that of other technologies (e.g., fly ash, silica fume, low-alkali cement, etc.) typically used to control ASR-induced expansion. However, the delivered cost of concrete is just a part of the in-place cost of concrete, with the in-place cost depending on the type of structure, the amount of reinforcing steel, construction method, and other factors.

For example, the in-place cost of concrete for a bridge deck may be as high as $450/m3. Thus, one should regard direct comparisons of raw materials costs with caution because they do not reflect total delivered concrete or in-place concrete costs.

It is clear that adding lithium to concrete increases the cost of the raw materials and delivered concrete, and in many cases, other less-expensive alternatives are selected, such as using appropriate amounts of SCMs. However, when considering the use of lithium in new concrete, other factors must be taken into account:

- If the alternative is transporting non-reactive aggregates or low-alkali cement over a long distance, or if high-quality SCMs are not locally available, lithium becomes much more competitive. 

- For some highly reactive aggregates, relatively high dosages of fly ash or slag may be required to control expansion, but these higher replacement levels would have a significant effect on early strength gain and related constructability issues. Using lower dosages of fly ash or slag, in combination with lithium, can then improve the early strength properties, which improve the economics of the situation. 

- Some agencies and organizations have limited the maximum amount of SCMs mainly because of perceived concerns with salt scaling, and using lithium in these instances in combination with lower dosages of SCM becomes a viable alternative 

- For certain concrete structures (i.e., dams or airfield pavements), very little expansion can be tolerated before the expansion impacts performance or function of the structure. Using lithium in such structures, preferably in conjunction with SCMs, is a mitigation method worthy of consideration. Those designing and constructing these types of important or sensitive structures are generally more willing to spend additional money up front to ensure the desired function of the structure for the desired service life.