Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1994-09-08
1998-05-12
Speer, Timothy
Stock material or miscellaneous articles
Composite
Of inorganic material
427136, 427140, 264426, 20415715, 205734, B32B 1700
Patent
active
057502765
DESCRIPTION:
BRIEF SUMMARY
It is known that concretes which contain certain forms of siliceous aggregate are prone to generate expansive reaction products (alkali-silica gel) if sufficient concentrations of sodium, potassium and hydroxyl ions are present in the concrete pore liquid. This phenomenon, known as alkali-aggregate reaction (AAR) or alkali-silica reaction (ASR), can give rise to deleterious expansion and cracking of the concrete.
It has already been proposed to use lithium compounds as a means of inhibiting AAR/ASR in concretes which contain potentially reactive aggregates.
What we now propose is the introduction into, or presence of lithium ions (or the like), in hardened concrete in conjunction with specific techniques of reinforcement corrosion control or concrete repair so that the lithium ions are conveyed to local sites within the concrete where AAR/ASR is most likely to be initiated. Alternatively the lithium compounds may be introduced during the manufacture of a concrete article when using a reinforcing technique. Thus we primarily intend to use lithium ions in solutions, slurries or admixtures for treatment of existing concrete structures, but lithium ions, or the like, could be deliberately provided in the original concrete in anticipation of some form of subsequent treatment of steel reinforcement corrosion.
A number of techniques that are used for the treatment of steel reinforcement corrosion in concrete structures can cause localised enhancement of the concentrations of sodium, potassium and hydroxyl ions in the concrete pore liquid, thereby increasing the risk of expansion and cracking due to AAR/ASR in concretes that contain susceptible aggregates. (Such corrosion treatment techniques include cathodic protection, electrochemical desalination, electrochemical realkalisation, and patch repair with cementitious mortar, grout or concrete).
The invention is concerned with the application of lithium compounds in conjunction with the aforementioned techniques for the treatment of steel reinforcement corrosion, with the aim of inhibiting or preventing AAR/ASR from arising as a deleterious side-effect. The effectiveness of lithium compounds as a means of inhibiting or arresting AAR/ASR in concretes which contain potentially reactive aggregates is thought to depend on the formation at the aggregate surface of an insoluble lithium silicate which has little tendency to expand in the presence of water.
According to a first aspect the invention comprises the use of lithium (or the like) compounds as inhibitors of alkali-aggregate/alkali-silica reactions in reinforced concrete subjected to cathodic protection, electrochemical desalination, electrochemical realkalisation, or patch repair treatments.
According to a second aspect the invention consists in a method of reducing AAR/ASR in concrete which is reinforced comprising the steps of providing mobile lithium ions in the concrete, and passing an electrical current through the concrete and/or reinforcement.
According to a third aspect the invention consists in a method of producing reinforced or prestressed concrete comprising the steps of providing metal reinforcing within the concrete, providing mobile lithium ions in or on the concrete, and ensuring that an electrical current is applied to the concrete and/or reinforcing.
In this way lithium ions may conveniently be introduced to a structure during its construction so that they are present if an electric current is passed at any stage during the life of a concrete structure.
Preferably the methods comprise arranging for the lithium ions to be conveyed to specific local sites within the concrete. The concrete thus has regions of high lithium concentration and regions of low lithium concentration.
According to a fourth aspect the invention consists in applying to concrete a chemical which contains a substance which migrates in an electric field through the concrete and which is attracted to regions of the concrete where AAR/ASR are likely to occur, and which preferentially reacts at said regions to form an insoluble sec
REFERENCES:
patent: 828976 (1906-08-01), Schneider
patent: 4062913 (1977-12-01), Miller
patent: 4506485 (1985-03-01), Apostolos
patent: 4536417 (1985-08-01), Shimizu
patent: 4609573 (1986-09-01), Omata
patent: 4832803 (1989-05-01), Vennesland
patent: 4931314 (1990-06-01), Takahura
patent: 5015351 (1991-05-01), Miller
patent: 5021260 (1991-06-01), Kitagawa
patent: 5039556 (1991-08-01), Cogliano
patent: 5252266 (1993-10-01), Brabston
patent: 5254228 (1993-10-01), Westhof
patent: 5312526 (1994-05-01), Miller
patent: 5422141 (1995-06-01), Hoopes
patent: 5554352 (1996-09-01), Jaques
patent: 5639358 (1997-06-01), Bennett
Speer Timothy
Tarmac Construction Limited
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