This set of Construction Materials Interview Questions and Answers for freshers focuses on “Cement Concrete Construction – Corrosion of Steel in Concrete”.
1. The term ________ is define as an act or process of gradual wearing away of a metal due to chemical or electro chemical reaction by its surrounding such that the metal is converted into an oxide, salt or some other compound.
a) Precipitation
b) Dissolution
c) Erosion
d) Corrosion
View Answer
Explanation: A substance known as rust results from corrosion. In other words, the Corrosion indicates the deterioration and loss of material due to chemical attack.
2. The ____________ is the simplest corrosion produced by means of chemical attack.
a) Electrolytic theory
b) Chemical action theory
c) Galvanic action theory
d) High temperature oxidation
View Answer
Explanation: Chemical action theory or Direct corrosion includes oxidation in which the oxygen of atmosphere combines with all or part of surface of a material. In this the combined action of oxygen, carbon dioxide and moisture on steel results in corrosion or rust.
3. ________ is the commonly accepted theory of corrosion.
a) Direct corrosion
b) High temperature oxidation
c) Electrochemical corrosion
d) Galvanic action theory
View Answer
Explanation: According to Electrolytic theory or Electrochemical corrosion, the corrosion takes place due to chemical action in combination with electrolysis. It takes place at or near the room temperature when the metal comes into contact with moisture in contact with aqueous solution of salt, acid or bases.
4. ___________ corrosion takes place at or near the room temperature when the metal comes into contact with moisture or with aqueous solutions of salt, acids or bases.
a) Direct corrosion
b) Dry corrosion
c) Galvanic corrosion
d) Electrochemical corrosion
View Answer
Explanation: Electrolytic theory or Electrochemical corrosion is the commonly accepted theory of corrosion. For electrochemical corrosion to occur, conditions that should be satisfied are- there should be an electrolyte; the current should be passed through the circuit and the circuit must be closed.
5. The _______ corrosion occurs when two dissimilar metals are in electrical contact with each other and exposed to an electrolyte.
a) Galvanic corrosion
b) High temperature oxidation
c) Dry corrosion
d) Electrochemical corrosion
View Answer
Explanation: Whereas, the rusting of ferrous alloys at high temperatures from scales and oxides. It indicates high temperature dry corrosion.
6. One of the important effects of the collision is the formation of _______
a) Slug
b) Cracks
c) Gases
d) Shine
View Answer
Explanation: It should however be remembered that action of corrosion become more intensive when it is combined with adverse effects of external and internal stresses. Cracks usually progress or advanced more rapidly where the shearing stresses are the greatest.
7. The ________ is most liable to corrosion.
a) Steel
b) Aluminium
c) Copper
d) Nickel
View Answer
Explanation: The steel is most liable to corrosion and hence the study of Steel corrosion is of Paramount importance. To minimise the chances of development of corrosion of Steel in concrete, there should be avoiding of heavy congested reinforcement especially at the intersection of beams and columns.
8. The ________ water tends to develop dampness and inflorescence of the concrete structures.
a) Lake
b) Mineral
c) Sea
d) River
View Answer
Explanation: Hence, the sea water can be adopted for concrete structures where finishing characteristics are not important or where persistent dampness of surfaces permissible.
9. It is found that the _______ water does not lead to corrosion of reinforcement, provided the concrete is dense and there is enough cover to the reinforcement.
a) Sewage
b) Fresh
c) River
d) Sea
View Answer
Explanation: The minimum cement content for concrete permanently under sea water should be 3 kN per m^3 and the minimum cover over the reinforcement should be 75 mm.
10. What is minimum cement content for concrete permanently under sea water to avoid the corrosion of reinforcement?
a) 5 kN/m3
b) 5 N/m3
c) 3 kN/m3
d) 3 N/m3
View Answer
Explanation: However it is not advisable to take the risk of corrosion of reinforcement for prestressed concrete and hence the seawater should not be used for making the prestressed concrete.
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