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51. Base course is used in rigid pavements for ___. |
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A. prevention of slab cracking |
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B. prevention of subgrade settlement |
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C. prevention of thermal expansion |
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D. prevention of pumping |
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Answer: D prevention of pumping |
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Explanation: In rigid pavement base course is used to (i) Prevent pumping (ii) Protect the subgrade against frost action. |
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52. Dowel bars in concrete pavement are placed ____. |
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A. perpendicular to the direction of traffic |
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B. along the direction of traffic |
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C. can be placed along any direction |
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D. along 45° to the direction of traffic |
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Answer: B along the direction of traffic |
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53. Temperature stresses in concrete pavements may cause the slab to crack. If a slab cools uniformly then the crack will develop at the which of the following locations of the slab? |
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A. Near edges |
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B. At centre |
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C. Near edges and at corners |
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D. At corners |
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Answer: B At centre |
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The corners and edges are free to contract while cooling. Hence, the cracks due to stresses will develop at the centre of the slab. |
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54. In the context of flexible pavement design, the ratio of contact pressure to tyre pressure is called the Rigidity Factor. This factor is less than unity when the tyre pressure is ____. |
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A. equal to 0.56 N/mm2 |
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B. more than 0.7 N/mm² |
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C. equal to 0.7 N/mm2 |
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D. less than 0.56 N/mm² |
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Answer: B more than 0.7 N/mm² |
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55. In highway pavements emulsions are mainly used in ____. |
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A. patching and maintenance |
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B. bitumen macadam |
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C. asphaltic concrete |
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D. surface dressing |
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Answer: A patching and maintenance |
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Explanation: Emulsions are used in bituminous road constructions, especially in maintenance and patch repair works. Even if it is raining, emulsion can be used. |