This set of Repair and Rehabilitation of Structures Multiple Choice Questions & Answers (MCQs) focuses on “General Measures for Prevention of Cracks”.
1. Which of the following is not a measure for the prevention of cracks?
a) Choice of material
b) Design of building
c) Construction techniques and practices
d) Aggregate with low coefficient of thermal expansion
View Answer
Explanation: Aggregate with a low coefficient of thermal expansion is a prevention method for reducing the thermal stress developed in concrete and remaining are the preventive measure for crack prevention in buildings.
2. Masonry units should be built with only well burnt bricks.
a) True
b) False
View Answer
Explanation: Only when well burnt bricks are used in the construction of masonry units, they don’t form cracks when water enters them during plastering and other works. Use of other partially will result in the formation of cracks when loaded and during plastering.
3. Burnt clay bricks should be exposed to atmosphere for almost ______ weeks in summer and ____ weeks in winter after unloading from the kilns.
a) 2, 3
b) 4, 5
c) 3, 2
d) 1, 3
View Answer
Explanation: When burnt clay bricks are exposed to atmosphere for a period of 2 weeks in summer and 3 weeks in winter, they are made to absorb the naturally atmosphere thereby they get hardened, by which the strength and load bearing capacity increases and when used after this period they have good durability.
4. Excessive wetting of masonry at the time of plastering and curing should be avoided when using concrete blocks and sand lime bricks.
a) True
b) False
View Answer
Explanation: Concrete blocks and sand lime bricks have high drying shrinkage value and when water enters them the chances of undergoing shrinkage is much higher leading to the formation of cracks and so excessive wetting of them during plastering and curing should be avoided.
5. Use of brick aggregate containing excessive amount of soluble sulphates for concrete in base course should be avoided.
a) True
b) False
View Answer
Explanation: When the brick aggregate containing excessive soluble sulphates are used in concrete then during the addition of water, the sulphates get dissolved and attacks the rebar leading to corrosion which then ultimately results in the crack formation and so that are avoided.
6. Alkali content of cement should not exceed __________
a) 2%
b) 0.5%
c) 0.6%
d) 3%
View Answer
Explanation: When alkali content in cement exceeds 0.6% then these alkalis chemically react with the siliceous materials that are present in the concrete leading to expansion and disintegration of concrete, and in case of RCC members it causes corrosion of rebar leading to crack formation.
7. Calcium Chloride content should be limited to ______% of cement content.
a) 3
b) 5
c) 2
d) 4
View Answer
Explanation: When calcium chloride exceeds 2% of cement concrete then the air entrainment property of concrete gets affected which in turns affects the compressive strength and workability of concrete. And so, it should not exceed 2% of cement concrete.
8. Mortar for plaster should be stronger than the background.
a) True
b) False
View Answer
Explanation: Usually the mortar for plaster should not be stronger than the background if not, due to shrinkage it tends to forcefully peels off the surface layer of the weak bricks. And also, usage of weak mortar reduces shrinkage cracks when compared to plain cement mortar and so they are mostly preferred.
9. Plastering of external walls are usually done with coarse _____ sand or stone chips.
a) finely graded
b) coarse graded
c) poorly graded
d) well graded
View Answer
Explanation: Usually external plastering of walls is done with coarse well graded sand and stone chips are used so that it suffers less from shrinkage cracks and also provides resistance against moisture penetration through walls.
10. Curing should be done for a minimum period of __________ days.
a) 7 to 10
b) 10 to 12
c) 15 to 20
d) 20 to 25
View Answer
Explanation: Curing is done for a minimum period of 7 to 10 days and is terminated gradually to avoid drying. Because when quick drying occurs, the chances for development of shrinkage cracks are maximum.
Sanfoundry Global Education & Learning Series – Repair and Rehabilitation of Structures.
To practice all areas of Repair and Rehabilitation of Structures, here is complete set of Multiple Choice Questions and Answers.
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