This set of Construction and Building Materials Multiple Choice Questions & Answers (MCQs) focuses on “Properties of Cement Concrete”.
1. The __________ is a mixture of cement, sand, pebbles or crushed rock and water, which, when placed in the skeleton of forms and are allowed to cure, becomes hard like a stone.
a) Cement concrete
b) Cement slurry
c) Cement grouting
d) Cement mortar
Explanation: The cement concrete has attained the status of a major building material in all branches of the Modern construction because it can be readily moulded into durable structural items of various sizes and shapes as practically no considerable labour expenditure and many other reasons like this.
2. Cement concrete is prove to be more economical than ______
Explanation: This is due to the fact that sand and pebbles or crushed rocks, forming the bulk of cement concrete, to the extent of about 80% to 90%, usually available at moderate cost. The form work, which is of Steel or timber, can be used over and over again or for other purposes after it is removed.
3. There is initial ________ of cement concrete which is mainly due to loss of water through forms, absorption by surfaces of forms, etc.
Explanation: The shrinkage of cement concrete occurs as it hardens. This tendency of cement concrete can be minimised by proper curing of concrete.
4. Cement concrete has tendency to be _________
Explanation: The tendency to be porous is due to the presence of voids which are formed during and after it’s placed. To prevent Porosity, there should be proper grading and consolidation of aggregates. The minimum water cement ratio should be adopted.
5. ________ is the commonly accepted theory of corrosion.
a) Direct corrosion
b) Chemical action theory
c) Electro osmosis theory
d) Electrolytic theory
Explanation: In Electrolytic theory, the corrosion takes place due to chemical reaction in combination with electrolysis. It takes place at or near the room temperature when the metal comes into contact with moisture orbit and liquid solutions of salt acid or base.
6. The _________ is the simplest corrosion produced by means of chemical attack.
a) Direct corrosion
b) Indirect corrosion
c) Electro osmosis process
d) Electro Chemical action
Explanation: In Chemical Action theory or Direct corrosion, corrosion produced by means of chemical attack and it includes oxidation in which the oxygen of atmosphere combines with all or a part of surface of material.
7. The ______ is most liable to corrosion.
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, some preventive measures may be taken such as avoiding heavily congested reinforcement especially at the intersection of beams and columns, etc.
8. Most important affect of corrosion is the formation of ________
Explanation: It should however be remembered that action of corrosion becomes more intensive when it is combined with adverse effects of internal and external stresses. One important effect of corrosion is the formation of cracks and these cracks usually progress on advanced most rapidly where the shearing stresses are the greatest.
9. It is found that the ________ does not lead to the corrosion of reinforcement, provided that the concrete is dense and there is enough cover to the enforcement.
a) Ground water
b) Lake water
c) Sea water
d) Stream Water
Explanation: The minimum cement content for concrete permanently under sea water should be 3 kN per metre cube and the minimum cover over there enforcement should be 75 mm. However it is not advisable to take the risk of corrosion of reinforcement for prestressed concrete and hence the sea water should not be used for the making of the prestressed concrete.
10. All _______ tend to accelerate the setting of cement and to improve the strength of concrete in early stages.
Explanation: On other hand, the sulphates tend to retard the setting of cement and to discourage the strength of concrete in early stages. It is found that the net effect of these two contradiction reactions in the fall in strength of concrete to the tune of about 8% to 20%.
Sanfoundry Global Education & Learning Series – Construction and Building Materials.
To practice all areas of Construction and Building Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.