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Publication Number: FHWA-HRT-06-133
Date: March 2007

The Use of Lithium to Prevent Or Mitigate Alkali-Silica Reaction in Concrete Pavements and Structures

 

Chapter 1. Introduction

Alkali-silica reaction (ASR) was first identified as a form of concrete deterioration in the late 1930s (Stanton 1940). About 10 years later, it was discovered that lithium compounds could be used to control expansion due to ASR. Recently there has been increased interest in using lithium technologies both to control ASR in new concrete and to retard the reaction in existing ASR-affected structures.

This book provides information on lithium, its origin and properties, and its applications. The mechanism of alkali-silica reaction is discussed together with methods of testing to identify potential alkali-silica reactive aggregates. Traditional methods for minimizing the risk of damaging ASR are presented; these include the avoidance of reactive aggregates, controlling the levels of alkali in concrete, and using supplementary cementing materials such as fly ash, slag, and silica fume.

The final two sections of the book discuss the use of lithium, first as an admixture for new concrete construction, and second as a treatment for existing concrete structures affected by ASR.

The information in this document was obtained primarily from the FHWA publication Interim Recommendations for the Use of Lithium to Mitigate or Prevent Alkali-Silica Reaction (ASR) (Publication No. FHWA-HRT-06-073). For further information, the reader should refer to the above publication.

Chapter 2. Lithium-Properties and Production

Lithium is the third element in the periodic table (see figure 1) and is denoted by the chemical symbol "Li." Its atomic number is 3 and its atomic mass is 6.941 grams (g), making it the third lightest element on earth after hydrogen (H) and helium (He).

Figure 1. Image. Periodic table showing the position of lithium. This photo shows the periodic table of elements. Lithium is located top left, under helium. The lithium element is highlighted in yellow, and a red circle is shown over the element.

Figure 1. Periodic table showing the position of lithium.

As a pure element, lithium is a soft, silver-white metal and belongs in the Alkali Metal Group together with sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

Lithium has only one electron in its outer shell (i.e., valence = +1) which makes the pure metal very unstable and reactive to moisture. Stable lithium compounds can be manufactured for commercial use; examples are lithium carbonate (Li2CO3), lithium chloride (LiCl), lithium sulfate (Li2SO4), and lithium nitrate (LiNO3).

Lithium metal does not occur naturally in the environment, and lithium is most commonly found in lithium-bearing minerals such as spodumene (LiAlSi2O6) in pegmatite rocks or as dissolved salt such as lithium chloride (LiCl) in brines (see figures 2 and 3). Table 1 provides a list of common lithium-containing minerals.

 

Figure 2. Photo. Photograph of lithium metal. This image shows two grey-colored lustrous rocks.
Figure 3. Photo. Photograph of the lithium-bearing mineral spodumene. It shows a close-up view of a jagged, tan-colored rock.

Figure 2. Photograph of lithium metal.

Figure 3. Photograph of the lithium- bearing mineral spodumene.

Table 1. Principal lithium minerals and their sources (after Lumley, 1997).

Mineral Formula Locations of Deposits (in Alphabetical Order)

Spodumene

LiAlSi2O6

Australia, Brazil, Canada, China, Russia, United States

Petalite

LiAlSi4O10

Australia, Brazil, Namibia, Russia, Sweden, Zimbabwe

Amblygonite

(Li,Na)Al(PO4)(F,OH)

Brazil, Canada, Mozambique, Namibia, Rwanda, South Africa, Suriname, Zimbabwe

Lepidolite

K(Li,Al)3(Si,Al)4O10(F,OH)2

Brazil, Canada, Namibia, Zimbabwe

Eucryptite

LiAlSiO4

Zimbabwe

 

Spodumene is the most abundant of the lithium-containing minerals from which lithium is extracted. To extract lithium in this process, spodumene ore concentrate is first heated in a rotary kiln at about 1,000 °Celsius (C) (1,832 °Fahrenheit (F)) to decrepitate the spodumene. This clinker is then roasted with sulfuric acid at about 250 °C (482 °F) to leach out an aqueous extract of lithium sulfate. This lithium sulfate is then converted to lithium carbonate, the primary compound from which other lithium compounds are manufactured.

Processing ore deposits is energy-intensive, but less expensive lithium extraction methods exist. For instance, much of the lithium produced today is extracted from subsurface salt brine deposits. The largest deposits of lithium-containing brines are found in Argentina and Chile. Solar evaporation is used to precipitate the salts, which are then processed chemically to separate the lithium (as Li2CO3) from the other compounds; figures 4 and 5 show aerial views of these deposits.

Figure 4. Photo. Aerial view of lithium-bearing brines in Argentina (Salar del Hombre Muerto). The image shows a mountainous terrain.
Figure 5. Photo. Aerial view of lithium-bearing brines in Chile (Salar de Atacama). The image shows several rectangular-shaped lots, grey in color.

Figure 4. Aerial view of lithium-bearing brines in Argentina (Salar del Hombre Muerto).

Figure 5. Aerial view of lithium-bearing brines in Chile (Salar de Atacama).

Lithium carbonate (Li2CO3) is used as a feedstock for other processes to produce a variety of lithium compounds which are then used in a wide range of applications. Table 2 provides a list of common lithium compounds and different applications.

The main application for lithium in the construction industry is in the formulation of chemical admixtures for concrete. Various lithium compounds (Li2CO3, LiOH, Li2SO4) are used in the formulation of set accelerators for calcium-aluminate-cement concrete and both lithium hydroxide monohydrate (LiOH•H2O) and lithium nitrate (LiNO3) have been used to control ASR in portland cement concrete.


Table 2. List of lithium compounds and applications for lithium.

Forms of Lithium Common Applications

Lithium metal (Li)
Lithium carbonate (Li2CO3)
Lithium nitrate (LiNO3)
Lithium hydroxide (LiOH)
Lithium hydroxide monohydrate (LiOH•H2O)
Lithium chloride (LiCl)
Lithium fluoride (LiF)
Lithium sulfate (Li2SO4)

Air treatment
Alloys
Batteries
Construction (e.g., chemical admixtures or
treatment of ASR-affected structures)
Fine chemicals
Glass and ceramics
Greases and lubricants
Pharmaceuticals
Polymers
Pool water treatment
Other specialty applications

 

 

 


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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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