This set of Repair and Rehabilitation of Structures Multiple Choice Questions & Answers (MCQs) focuses on “Techniques for Repairing Cracks – Set 2”.
1. The chase used in blanketing technique is usually cut square.
a) True
b) False
View Answer
Explanation: The square chase id usually used in blanketing technique and the bottom of the chase should be as smooth as possible to facilitate the bond between sealant and concrete.
2. Which of the following is the criterion for selecting the sealant material in blanketing technique?
a) Amount of movement anticipated
b) Shelf life of the sealant
c) Pot life of the sealant
d) Viscosity of the sealant
View Answer
Explanation: Only when the magnitude of the crack is anticipated the sealants can be chosen so as to minimize the rate of the growth of the crack. All other mentioned properties are the mandatory criteria that must be checked during the purchase of the sealant irrespective of the crack repairing technique.
3. Sealing of active crack using an overlay requires not only flexible but also _____ sealant.
a) compressive
b) tension
c) elastic
d) extensible
View Answer
Explanation: In case when the sealant is only flexible then the sealant can be bent but it can’t be stretched all through the crack area and so sealant with extensible property are used in addition to flexible property to seal the active crack.
4. _______ sealing involves routing and cleaning a crack then filling it with a flexible sealant?
a) Flexible
b) Compressive
c) Compact
d) Tension
View Answer
Explanation: In the flexible sealing technique the crack is routed and sealed with the suitable filed molded flexible sealant and this is not same as that of routing and sealing. In this technique, the active are filled with the joint and merely filling up the crack.
5. Bond breakers that are used in the flexible sealing are made of _________
a) epoxy strip
b) ether strip
c) acetylene strip
d) polyethylene strip
View Answer
Explanation: Bond breakers used in the flexible sealing technique are placed at the bottom of the crack slot to prevent the stress concentration at the bottom of the structure. They are made of polyethylene strip so that they don’t bond with the sealant during the curing process.
6. The type of polymer overlay adopted is chosen based on the thickness of the overlay.
a) True
b) False
View Answer
Explanation: Thin overlays that are 1 inch thick are overlaid with epoxy mortar and for thick overlays ranging from 1inch to 2 inches are overlaid with latex modified concrete. And thus, depending on the thickness of the overlay the type of polymer overlay is adopted.
7. Which of the following is not the surface where gravity soak can be done?
a) Column
b) Bridge decks
c) Industrial floors
d) Parking decks
View Answer
Explanation: Gravity soak is done to prevent the penetration of cracks into the reinforcing steel and are done only in the horizontal surface. Bridge decks, industrial floors and parking decks are horizontal surface and so gravity soak can be adopted. But columns are vertical surface and so gravity soak can’t be adopted.
8. Which of the following is used to fill very fine cracks?
a) Flexible sealing
b) Gravity soaks
c) Hydraulic cement grouting
d) Chemical grouting
View Answer
Explanation: Very fine are normally filled with chemical grouting where two or more chemicals combine to create a gel or solid precipitate and this method decreases fluidity. So, this method is used to fill very fine cracks.
9. Which of the following is the common method for repairing cracks in concrete?
a) Flexible sealing
b) Gravity soaks
c) Hydraulic cement grouting
d) Chemical grouting
View Answer
Explanation: The dormant cracks in concrete is usually repaired by adopting hydraulic cement grouting which is less expensive than chemical grout and is suited for large volume applications.
10. Hydraulic cement grouting is mainly used to fill the cracks in __________
a) foundation
b) brickwork
c) ceiling
d) outer falls
View Answer
Explanation: Very fine cracks that are formed in the foundation are filled by hydraulic cement grouting and the built-up seats are installed at regular intervals across the cracks which provides a pressure tight contact with the injection tool.
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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