NACE SP0187: Design Considerations for Corrosion Control of Reinforcing Steel in Concrete Flashcards
Reinforcing steel in concrete is normally protected against corrosion by a stable oxide film. What are three conditions that may destroy this oxide film? (NACE SP0187, Section 1.2.3)
1) The concrete does not fully encase the steel;
2) Alkalinity is lost by reaction with aggressive gases; or
3) Excessive amounts of chloride or other aggressive ions are present.
What is the effect of concrete permeability on the corrosion of reinforcing steel? What are some factors in the concrete mix design that can reduce the permeability of the concrete? (NACE SP0187, Section 6.3)
Low permeability reduces aggressive ion and oxygen penetration of the concrete delaying the onset and slowing the rate of corrosion.
What effect does the addition of air-entraining admixtures have on the concrete mix and the cured concrete? (NACE SP0187, Section 7.2.1)
Improves durability and workability of the concrete while reducing the permeability and the net amount of concrete mixing water required.
Which accelerating admixture for concrete should only be used with caution when steel is present in the concrete? (NACE SP0187, Section 7.2.2)
Accelerating admixtures (calcium chloride)
What is the function of water-reducing admixtures? (NACE SP0187, Section 7.2.4)
Reduce the net amount of water necessary to achieve a given workability.
Careful attention to placement details and design of a workable concrete mix should produce what qualities in the finished concrete? (NACE SP0187, Section 5.1.2)
A quality concrete that is dense and homogeneous.
How can the concrete’s resistance to penetration of chloride and other aggressive ions be improved? (NACE SP0187, Section 7.4)
By using penetrants, coatings, and membranes on the surfaces exposed to attack.
What is necessary to ensure the integrity of concrete when in place and to minimize possible damage to coated reinforcement? (NACE SP0187, Section 11.2.1)
Proper concrete placement techniques are necessary to ensure the integrity of the concrete when in place and to minimize possible damage to coated reinforcement.
Concrete cover on the steel reinforcement can play an important role in protecting the steel from corrosion. What are two steps that can be taken to ensure proper placement of the reinforcing steel before the concrete is poured? (NACE SP0187, Section 11.2.1)
1) Ensure that reinforcing steel is adequately supported; and
2) Secured against displacement
What does proper consolidation of the concrete help to avoid? Why is this important in reducing corrosion on reinforcing steel? (NACE SP0187, Section 11.2.3)
Proper consolidation of the concrete helps to eliminate undesirable voids that can lead to increased corrosion on the reinforcing steel since the protective oxide film on the steel is destroyed if the concrete does not fully encase the steel.
