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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP102-01

Date: 

September 1, 1987

Author(s):

William G. Hime and Bernard Erlin

Publication:

Symposium Papers

Volume:

102

Abstract:

The wide variety of disciplines involved with the corrosion of steel in concrete has caused difficulties in communication. Each discipline has its own terminology; at times two disciplines use conflicting terms or explanations for the same phenomenon. This paper addresses some areas of such confusion, and presents chemical mechanisms to explain half-cell potentials and causes for chloride-induced corrosion. Examples of such corrosion are presented.

DOI:

10.14359/1631


Document: 

SP102-05

Date: 

September 1, 1987

Author(s):

David Chin

Publication:

Symposium Papers

Volume:

102

Abstract:

Two important properties of calcium nitrite are that it is an accelerator and a corrosion inhibitor when used as an admixture in concrete. With its performance as an accelerator enhanced, calcium nitrite can be used as an effective non-corrosive, non-chloride accelerator in normal and fly ash concrete. The calcium nitrite-based accelerator provides good accelera-tion in initial setting times at 50°F (10°C) and 72°F (22°C) produces a significant improvement in compressive strengths at early ages. Electrochemical solution tests can be used to conduct a quick screening test to determine the potential corrosivity of a non-chloride accelerator. Potential and linear polarization resistance measurement tests provide a quick indication regarding the potential corrosivity of a non-chloride accelerator.

DOI:

10.14359/1619


Document: 

SP102-02

Date: 

September 1, 1987

Author(s):

John Fraczek

Publication:

Symposium Papers

Volume:

102

Abstract:

Corrosion of steel in concrete proceeds at a far greater rate in the presence of chloride ions. Most researchers agree that chloride ions act as an essential part of the corrosion cell by 1) lowering the pH of the concrete pore water in contact with the steel, thereby dissolving the passive oxide film on the steel surface, or 2) penetrating the film to react with and trans-port the metallic iron into the electrolyte. In the latter process, the resulting iron chloride complex ion combines with hydroxyl ions to form ferrous hydroxide in solution and lower the pH. This, in turn, thins out the oxide film and speeds penetration of chloride ions. Eventually the continuing cor-rosive action results in a pit. To initiate corrosion, a threshold concentration of chloride is needed in excess of the amount immobilized by reaction with tricalcium aluminate in the cement. Investigation of the chloride ion content in concrete adjacent to corroding reinforcing steel shows the concentration to be 1.0 to 1.4 lb of chloride ion per cubic yard of concrete (0.59-0.83 kg/m3).

DOI:

10.14359/1633


Document: 

SP102

Date: 

September 1, 1987

Author(s):

Editor: Frances W. Gibson

Publication:

Symposium Papers

Volume:

102

Abstract:

SP102 As a designer you need the wealth of information presented in "Corrosion, Concrete and Chlorides -- Steel Corrosion in Concrete: Causes and Restraints," a compilation of 11 papers covering the corrosion phenomenon. Prompted by the nationwide corrosion problem with concrete, there have been extensive field and laboratory investigations into the specific phenomena that induce corrosion, methods for identifying the magnitude and extent of corrosion in structures, techniques for stabilizing corrosion once it has begun, and design of structures and concretes so that corrosion will not occur. Presenting an in-depth analysis into a variety of aspects dealing with corrosion, this state-of-the-art publication includes such topics as: the marked influence of chloride in causing corrosion, ways for controlling corrosion by using chloride-free accelerators, the reduction of chloride penetration through the use of pozzolanic blast-furnace slag as an admixture in concrete, and the conductive coating aspects of cathodic protection. "Corrosion, Concrete and Chlorides" provides important answers to a complex problem.

DOI:

10.14359/14218


Document: 

SP102-03

Date: 

September 1, 1987

Author(s):

Philip A. Smith

Publication:

Symposium Papers

Volume:

102

Abstract:

Effects of two non-chloride accelerating agents -- sodium thiocyanate and calcium nitrate -- in time to achieve initial set of two brands of Type I cement were determined at 70 F (21 C) and 40 F (4 C). Results with these two non-chloride accelerators were compared with results with calcium chloride, the conventional accelerator. Tests show:Low or moderate dosages of the two non-chloride accelerators can reduce time to achieve initial set by l-2 hr.- Any one of the three accelerators may be more effective with one ce-ment than with another cement having similar setting characteristics without accelerators In general, all three of the accel-erators are more effective at 40 F than at 70 F.

DOI:

10.14359/1635


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