Pavement Design Multiple Choice Questions on “Highway Materials – Sub Base and Base Course – 1”.
1. The sub-base course is also called as ______ sub-base.
Clarification: The sub-base course also called granular sub-base because the materials used for its construction include gravel and crushed stones. These are essentially made of stones to allow the drainage of water.
2. Which of the below base course types is the most preferred one because of its quality?
a) Open-graded premix carpet
b) Bituminous macadam
c) Built-up spray grout
d) Bituminous penetration macadam
Clarification: In the bituminous macadam, the aggregates and the bitumen are mixed in a hot mix plant and then transported to the sites to be laid. The aggregates are hence completely coated with bitumen and have better wear-resistant. In bituminous penetration macadam and built-up spray grout, the aggregates are partially coated with bitumen and hence are not as wear-resistant as bituminous macadam. Open-graded premix carpet is a surface course.
3. Under which situation is cutback bitumen used as a stabilizing agent?
a) Low density
b) High density
c) High natural moisture content
d) Low natural moisture content
Clarification: In case the natural moisture content of the material is low, cutback bitumen or emulsified bitumen can be used as stabilizing agents. For high moisture content, viscous cutback bitumen can be used.
4. Bituminous penetration macadam can be used as a ______ course in flexible pavement.
Clarification: Bituminous penetration macadam consists of coarse aggregates, bitumen spray and key aggregates. It can be used as the base course in the pavement for certain stretch or in small projects where hot mix plant facility is not available.
5. It is very necessary to provide a sub-base course in the pavement.
Clarification: Sub-base course is not a compulsory component of pavement, but it is usually provided in most cases. It is an additional layer that is provided when the subgrade is of poor quality.
6. In a rigid pavement, what type of traffic requires dry lean concrete as a base course?
a) Very heavy
Clarification: Granular base course is sufficient to be provided in low volume roads and moderate traffic roads. For heavy traffic loads, high quality materials are required to be used as a base course. Lean cement concrete or dry lean concrete can be used in the heavy traffic roads.
7. In unbound sub-base layer, how many layers must the sub-base be composed of?
Clarification: As per IRC:37-2012, the unbound sub-base can be composed of two layers. The bottom layer forms the separation layer and the top layer serves as the drainage layer.
8. What does MORTH stand for?
a) Ministry of Road Traffic and Highways
b) Model of Road Transit on Highways
c) Ministry of Road Transport and Highways
d) Model of Road Traffic in Highways
Clarification: MORTH stands for Ministry of Road Transport and Highways. It is the apex organization under the Central Government of India, that formulates policies for the road transportation system. They provide guidelines and specifications on the materials, construction, maintenance, etc. of roadways.
9. One of the functions of the sub-base is to provide a working platform for construction.
Clarification: Sub-base is a layer that is provided when the subgrade is weak. When provided, it can be used as a working platform for the construction of the most important layer – the base course. Sub-base has better quality material than subgrade, but lesser quality than the base course.
10. The higher the aggregate to cement ratio, the ______ the concrete will be in case of lean concrete.
Clarification: Lean concrete comprises of a mix consisting of a lower amount of cement than the amount of liquid in the strata. A higher ratio of aggregate to cement indicates that the mix is leaner. The water content is high and hence can be used to stabilize the soil in roadworks.