This set of Construction and Building Materials Multiple Choice Questions & Answers (MCQs) focuses on “Different Types of Concrete”.
1. The concrete having bulk density between 5 kN/m3 to 18 kN/m3 is known as _________
a) Coloured concrete
b) Lightweight concrete
c) No-fines concrete
d) Heavyweight concrete
Explanation: The lightweight concrete is highly porous and hence, it leads to the corrosion of reinforcement, if not properly protected. For lightweight concrete, the loose porous materials are used as aggregates.
2. The sound absorption of light weight concrete is _________
d) Cannot say
Explanation: The sound absorption of light weight concrete is good because of the fact that the air borne sound energy is converted into heat in the minute channels of the concrete.
3. The sound absorption coefficient of lightweight concrete is nearly ___________ than that of ordinary concrete.
d) Eight times
Explanation: The depth within which corrosion can occur under suitable conditions, is nearly twice than that of normal concrete. Hence special care will have to taken to overcome sufficient problems.
4. The only drawback of lightweight concrete is that the ___________
a) Depth of carbonation
b) Heavy absorption
Explanation: The depth within which collision can occur under suitable conditions, is nearly twice than that of normal concrete. Hence special care will have to be taken to provide sufficient cover to the reinforcement of lightweight structure to grant protection against corrosion.
5. The use of lightweight concrete results in the reduction of cost to the extent of about _______
a) 30% – 40%
Explanation: The reduction in weight of concrete helps easy removal, transport and erection of precast products. The lightweight concrete does not present a special problem with respect to freezing and thawing.
6. The ________ Concrete consist of cement, coarse aggregate and water.
a) Heavyweight concrete
b) Lightweight concrete
c) Coloured concrete
d) No-fines concrete
Explanation: Here, the fine aggregate or sand is eliminated and such concrete has been adopted for cast in situ external load bearing walls of single and multi storey houses, small retaining walls, damp proof sub base material, etc.
7. As compared to conventional concrete, the ________ of no fines concrete is relatively low.
a) Swelling due to absorption
b) Drying shrinkage
c) Capillary action
d) Water transmission
Explanation: As there is an absence of capillary passages, there is no transmission of water by capillary action. It possesses better insulating characteristics than the conventional concrete because of the presence of large voids.
8. As no-fines concrete has little or no ___________ in the fresh state, it requires long time for the removal of forms.
Explanation: No-fines concrete is highly permeable as compared to conventional concrete and hence the rendering of walls become essential. However, in certain cases, such as the drainage layer in the soils, the advantage of quality of high permeability of no fines concrete can be taken.
9. The use of reinforcement in the no-fines concrete is generally ________
c) Not recommended
d) Corrosion proof
Explanation: However, if reinforcement in the no-fines concrete is to be used, it is to be coated with a thin layer of about 3 mm thickness of cement pastes so as to improve the bond characteristics and also to improve the resistance to corrosion.
10. The Unit Weight of no fines concrete is about ________ of the Unit Weight of conventional concrete.
Explanation: Hence the pressure of formwork is greatly reduced. Also, the formwork need not to be water tight and hence it is possible to use cheap formwork.
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