This set of Basic Pavement Design Questions and Answers focuses on “Highway Maintenance – Failures in Flexible Pavements – 2”.
1. Which failure gives a shiny glass-like reflective surface on top of the pavement?
Explanation: The excessive use of binder and low air void content can lead to a failure called bleeding in the flexible pavement that gives the surface a shiny and glass-like appearance. The binder starts bleeding and forms a thin sticky layer on top of the pavement.
2. In what shape is the edge cracking observed in the pavement?
Explanation: Edge cracking is a type of failure that is observed in case of an unconfined flexible pavement, like that found in parking lots or the edge of the street. During compaction, due to lack of confinement, the edge starts developing cracks in the form of C shape.
3. The dislodgment of aggregates from the pavement results in a failure called ______
Explanation: Raveling is the name of the failure where the aggregates are separated from the mix. The loss of bond between the binder and the aggregates results in raveling. The dislodgement of aggregates will slowly deteriorate the pavement from the surface downwards.
4. Which of the below is not an area where cold joints are prone to develop?
a) Edge of pavement
b) Parking lot
c) Inverted crown
d) Low traffic area
Explanation: The cold joints are essentially longitudinal joints that are formed when a hot bituminous mix is poured adjacent to an existing pavement. The possible areas where this can happen are the parking lots, inverted crowns and areas with low traffic.
5. The seeping of water from the edge of the pavement is called pumping.
Explanation: The seeping of water along with the fines from the cracks on the pavement surface results in a failure called pumping. It is visible on the top of the pavement as a white fine spray. This will result in instability of the layers beneath and also make the surface slippery.
6. The structural distress in flexible pavement occurs from ______
a) Top to bottom
b) Edge to centre
c) Bottom to top
d) Centre to edge
Explanation: The structural distress in flexible pavement occurs from bottom to top. These are physical failures found on the pavement surface due to various reasons like overloading, wet subgrade, frosting effect etc.
7. Ageing of flexible pavements reduces the effect of oxidation.
Explanation: Ageing of bitumen is the slow deterioration or loss of volatiles from it with time. The loss of volatiles makes the bitumen more prone to damage and attacks. Oxidation results in loss of volatiles and makes bitumen brittle. Therefore, the ageing of bitumen increases the effect of oxidation.
8. What is the main reason for the instability of the base course layer?
a) Improper drainage
b) Inadequate thickness
c) Poor mixing
d) Insufficient material
Explanation: There are two main reasons for the instability of the base course. The poor mix proportioning and inadequate thickness of the base course results in its instability. The use of poor-quality materials and lack of quality control are other reasons.
9. Which of the below is not a cause for the formation of bumps on the pavement surface?
a) Plant roots
b) Frost action
Explanation: There can be two types of unevenness on the pavement surface – bumps and sags. The displacement of pavement surface is a cause for the formation of sags. Bumps can be formed due to the action of frost, plant roots emerging from beneath or the oxidation.
Explanation: The figure represents a shear crack formed on the pavement surface. The shear failure of the pavement causes a upheave of the pavement materials by forming a fracture or cracking. Frost heave doesn’t cause cracking, it forms bumps which might crack.
Sanfoundry Global Education & Learning Series – Pavement Design.
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