WO1998022408A1

WO1998022408A1 - Lithium bearing ores in concrete and cement

Info

Publication number: WO1998022408A1
Application number: PCT/US1996/018613
Authority: WO
Inventors: David B. Stokes; Gary Earl Foltz
Original assignee: Fmc Corporation
Priority date: 1996-11-20
Filing date: 1996-11-20
Publication date: 1998-05-28
Also published as: AU1020797A

Abstract

A process for making concrete stabilized against alkali-silica reactivity from alkali containing cement, aggregate, sand and other components comprising adding to the fluid concrete pour mix containing a sodium and/or potassium alkali values sufficient lithium-aluminum silicate ores to provide a 0.1:1 to 10:1 equivalent of lithium to equivalents of sodium plus potassium in the concrete pour mix (term already defined).

Description

LITHIUM BEARING ORES IN CONCRETE AND CEMENT

This invention concerns incorporation of lithium bearing ores in hydraulic cement and concrete to mitigate or inhibit alkali-silica or alkali- aggregate reactions.

Concrete is a conglomerate of aggregate (such as gravel, sand, and/or crushed stone), water, and hydraulic cement (such as portland cement), as well as other components and/or additives. Concrete is generally fluidic when it is first made, enabling it to be poured or placed into shapes, and then later hardens, and is never again fluidic, in the general sense. Alkalis are elements from the first group in the periodic table of elements, of which the first three members are lithium, sodium, and potassium. Only sodium and potassium are generally considered detrimental in the alkali-silica reaction, as the heavier elements in the series are not normally present to any large extent in the concrete system as it usually exists in the world. Lithium, alone among the elements in this group, can prevent the detrimental effects of the alkali-silica reaction. The alkali- silica reaction is a reaction between the alkalis present in the concrete mix and silica present in the mix. Alkali materials are generally supplied by the cement, but are often supplied by the aggregate as well. They may also be supplied by additives to the mixture, and even from the environment in which the hardened concrete exists (such as salts placed on concrete to melt ice). Products of the alkali-silica reaction are generally referred to as alkali-silica gels, and may commonly be found in most concrete of sufficient age. Sometimes, however, the alkali-silica gels can expand to the detriment of the concrete, causing cracking and premature failure. Alkali-silica reaction is a subset of the larger class of reactions known as alkali- aggregate reactions. Lithium compounds have been added to concrete to inhibit or mitigate the alkali-silica reaction.

Lithium compounds (for example, lithium carbonate, nitrate, hydroxide, and fluoride) are expensive compared to other concrete additives. According to published price lists, lithium containing ores generally sell for 10-30% of the price of lithium chemicals for equivalent amounts of lithium. Moreover, a portion of the lithium added to concrete via lithium chemicals becomes bound in the hydration compounds formed from the hydrating hydraulic cement. Lithium that is locked into the hydration products is no longer available to participate in the inhibition of the alkali- silica reaction. The present invention provides a process for producing concrete that is resistant to the alkali-silica reaction induced degradation of concrete. This is done on one of two ways that are unique to this invention. One is to add lithium bearing ores (that may or may not have been specially treated) to concrete at the stage when the ingredients are mixed (this would be called a mineral admixture), and the other is to include these ores (specially treated or otherwise) in the manufacture of the hydraulic cement (this would be called a lithium cement) used to make alkali-silica resistant concrete. These would be added in an amount sufficient to prevent the alkali-silica reaction to proceed to a degree that would be harmful to the concrete. A major benefit of adding lithium ores rather than lithium chemicals is that lithium is released slowly compared to lithium chemicals such that less lithium is bound in the hydration compounds when ores are used.

Lithium bearing ores useful in practicing this invention include (but are not limited to) lithium aluminum silicates such as spodumene [Li₂0-AI₂0₃-4Si0₂], petalite [Li₂0-AI₂0₃-8Si0₂], eucryptite [Li₂0-AI₂0₃-2Si0₂], other such lithium-aluminate silicate ores, such as amblygonite [LiF-AIPO , and mixtures thereof. Some of these ores must be decrepitated by means of heat which produces a phase change in such ores so that the lithium can be slowly released into the concrete over time. By using lithium bearing ores, another benefit of this invention is that decrepitated ores such as spodumene have pozzolonic properties.

It is important that lithium be added via ores such that there is enough lithium to mitigate the detrimental effects of sodium and potassium, yet not too much ore to make the use of lithium ores too expensive to use in concrete. According to the present invention, lithium is added to concrete via these ores (treated or otherwise) in amounts that provide molar ratios of lithium to sodium equivalent of 0.1 :1 to 10:1 in the concrete.

Advantages of this invention are many. Common to both ways of introducing the lithium in the concrete (whether by mineral admixture or by lithium cement) is the lower cost of the lithium in the ores (compared to the cost of lithium after its extraction and purification). In the case of the lithium cement, a further advantage is the lowering in the energy requirements of the cement manufacture for a given unit of cement, since the lithium acts as a flux in this process. In the case of the lithium as a mineral admixture, two advantages are 1) that less lithium is needed to inhibit the alkali-silica reaction than in purified forms because the lithium is released slowly, after much of the hydraulic cement has hydrated, and will not be bound up in the hydration products, and 2) that the concrete will be made less permeable by the reaction of other ingredients in the ore by the pozzolonic reaction. (The pozzolonic reaction is a reaction between calcium hydroxide (lime), siliceous materials (such as the mineral admixture), and water.)

Claims

CLAIMS:

1. A process for making concrete stabilized against alkali-silica reactivity from alkali containing cement, aggregate, sand, and other components comprising adding to the fluid concrete pour mix containing a sodium and/or potassium alkali values sufficient lithium-aluminum silicate ores to provide a 0.1 :1 to 10:1 equivalent of lithium to equivalents of sodium plus potassium in the concrete pour mix (term already defined).

2. Concrete, comprising alkali containing cement, sand, siliceous aggregates that contain high levels of sodium and/or potassium and a lithium-aluminum silicate ore in an amount to provide a ratio of 0.1 :1 to 10:1 lithium equivalents to sodium equivalents in the concrete.

3. The process of claim 1 in which the lithium-aluminum silicate ore is selected from the group consisting of spodumene [Li₂0-AI₂0₃-4Si0₂], petalite, [Li₂0-AI₂0₃-8Si0₂] eucryptite [Li₂0-AI₂0₃-2Si0₂], amblygonite [LiF-AIPO , and mixtures thereof.

4. The cement of claim 2 in which the lithium-aluminum silicate ore is selected from the group consisting of spodumene [Li₂0-AI₂0_3.-4Si0₂], petalite, [Li₂0-AI₂0₃-8Si0₂] eucryptite [Li₂0-AI₂0₃-2Si0₂], amblygonite [LiF-AIPOJ, and mixtures thereof.

5. The use of lithium silicate ores in the preparation of concrete containing siliceous aggregates which contain sodium and/or potassium comprising adding to the alkali containing concrete pour mix containing cement, sand, water, aggregate, and other materials, an amount of lithium- aluminum silicate ore to provide a ratio of 0.1 :1 to 10:1 equivalents of lithium per sodium equivalent in the concrete.

6. The use of lithium-aluminum silicate ore of claim 5 wherein the lithium-aluminum silicate ore is selected from the group consisting of spodumene [Li₂0-AI₂0₃-4Si0₂], petalite, [Li₂0-AI₂0₃-8Si0₂] eucryptite [Li₂0-AI₂0₃-2Si0₂], amblygonite [LiF-AIPOJ, and mixtures thereof.

7. A process for the making of cement such that lithium bearing ores or mixtures thereof are mixed with limestone (and any other materials which accompany limestone) which enters a cement kiln to produce cement.

8. The use of such lithium-aluminum silicate ore of claim 7, wherein the lithium aluminate ore is selected from the group consisting of spodumene [Li₂0-AI₂0₃-4Si0₂], petalite, [Li₂0-AI₂0₃-8Si0₂] eucryptite [Li₂0- AI₂0₃-2Si0₂], amblygonite [LiF-AIPOJ, and mixtures thereof.