# Pavement Design Questions and Answers – Highway Materials – Stone Aggregate Properties

This set of Pavement Design Multiple Choice Questions & Answers (MCQs) focuses on “Highway Materials – Stone Aggregate Properties”.

1. Based on the strength property, the coarse aggregates can be classified into ____________
a) Hard and soft
b) Strong and weak
c) Resistant and non-resistant
d) Robust and non-robust

Explanation: The coarse aggregates are classified into hard and soft aggregates based on their strength property. Hard aggregates are used for superior quality roads and soft aggregates are used for low volume roads.

2. Which of the below represent the size range of medium gravel?
a) 2mm to 4mm
b) 8mm to 16mm
c) 4mm to 8mm
d) 16mm to 64mm

Explanation: Gravel size ranges from 4mm to > 256mm. There are fine, medium and coarse gravel types. The fine gravel ranges from 4mm to 8mm, medium gravel ranges from 8mm to 16mm and coarse gravel from 16mm to 64mm.

3. Which of the below is not an index to define the shape factor of stone aggregates?
a) Elongation index
b) Angularity number
c) Flakiness index
d) Group index

Explanation: Group index is a parameter that is used in the design of flexible pavements. All other options are indices that indicate the shape factor of aggregates.

4. Hardness indicates the strength requirement of an aggregate.
a) True
b) False

Explanation: Hardness is a property that gives a measure of resistance against abrasion. Strength is another property of the aggregate.

5. If the pavement is subjected to a prolonged period of water, then ______ of bituminous binder takes place.
a) Scraping
b) Skinning
c) Stripping
d) Striking

Explanation: Stripping of bituminous binder means that the bitumen coated on the aggregates comes off. This happens when it is subjected to water for a long period of time.
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6. How are most of the road aggregates prepared?
a) Recycling
b) Crushing natural rock
c) From river bed
d) Manufactured

Explanation: Most of the road aggregates used are obtained by crushing natural rocks. Gravel aggregates are small rounded stones usually obtained from river beds, but it is not a common method.

7. The presence of air voids will result in ______ specific gravity and indicate ______ strength characteristics.
a) Lower, lower
b) Lower, higher
c) Higher, higher
d) Higher, lower

Explanation: The air voids or pores present in the stones will decrease the specific gravity and that indeed will decrease the strength and durability of stone aggregates. Specific gravity is related to the density. The increase in air voids will lower the density, which will, in turn, reduce the specific gravity.

8. Toughness is defined as the resistance to ______
a) Deformation
b) Impact
c) Abrasion
d) Friction

Explanation: Toughness is a property of the aggregate that is a measure of the resistance against impact. Impact on the pavement is subjected by the heavy moving traffic. Resistance to deformation and friction are necessary to provide a smooth and comfortable riding surface. Resistance to abrasion is measured by the hardness property.

9. Which of the below is not a factor that affects the durability property?
a) Ageing of bitumen
c) Movement of traffic
d) Permeability

Explanation: Movement of traffic is a factor that affects the abrasion property. It is responsible for the wearing of the pavement surface. Ageing of bitumen, permeability and adhesion are all factors that affect the durability property. These are responsible for the weathering of the pavement.

10. Which of the below is not a type of soft aggregate?
a) Gravel
b) Crushed brick
c) Slag
d) Laterite

Explanation: Soft aggregates are the ones having less strength compared to hard aggregates. The hard aggregates consist of crushed stones, gravel that have high strength property. Soft aggregates include moorum, kankar, brick aggregates, laterite and slag.

11. Which of the below igneous rocks exhibit good hardness when used as a road aggregate?
a) Granite
b) Basalt
c) Shale
d) Marble

Explanation: Granite and basalt are the types of igneous rocks, out of which basalt exhibits good hardness property. Shale is a type of sedimentary rock and marble is a type of metamorphic rock.

12. Which of the below is supposed to be present in the aggregate?
a) Flaky pieces
b) Angular pieces
c) Rounded pieces
d) Elongated pieces

Explanation: If the pieces of the aggregate are too flaky or elongated, they will be easily crushed when subjected to compaction by roller and also under heavy loads. Rounded pieces possess good strength but don’t have proper interlocking, so angular pieces are preferred.

13. Which of the below accelerates the smoothening of pavement surface?
a) Water
b) Fines
c) Aggregates
d) Vehicle

Explanation: The fine particles like sand and dust are present between tyres of the vehicle and the pavement surface. When the vehicle moves, the fines provide a grinding effect on the surface and aid in the smoothening process.

14. Specific gravity is considered to be a measure of the strength or quality of a material.
a) True
b) False

Explanation: Specific gravity is related to the density of the material. If the specific gravity is less, then the material is found to be weaker. A weak material will have lesser quality compared to a stronger material.

15. The process of coating the aggregates with the binder is largely controlled by ______ of the binder.
a) Viscosity
b) Durability
c) Penetration
d) Surface tension

Explanation: Viscosity is the important property that controls the coating of aggregate with the binder. If the viscosity is high, the coating will be slower. Viscosity is dependent on temperature and it is low at higher temperatures.

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