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Pavement Design Multiple Choice Questions on “Soil-Bitumen Stabilization – 1”.
1. What is the content of bitumen allowed in sands?
a) 4 to 8%
b) 4 to 10%
c) 2 to 6%
d) 2 to 8%
Answer: b
Clarification: The bitumen content allowed in sands ranges from 4 to 10%; for fine-grained soils, it is from 4 to 8% and for gravel, the range is from 2 to 6%. Generally, the bitumen content for various soil type ranges anywhere from 2 to a maximum of 10%.
2. What are the basic principles involved in the soil-bitumen stabilization?
a) Waterproofing and Stability
b) Binding and Strength
c) Waterproofing and binding
d) Stability and binding
Answer: c
Clarification: Bitumen stabilization has two main principles involved – waterproofing and binding. Using these two principles, the stabilization process is brought about. The soil particles are coated with bitumen and made waterproof and binding is provided between the particles.
3. Which type of asphalt is commonly used in the soil stabilization process?
a) Cracked asphalt
b) Straight run asphalt
c) Blown asphalt
d) Liquid asphalt
Answer: b
Clarification: Straight run asphalt is produced by the vacuum distillation. It has a low softening temperature and low melt viscosity. Hence, it is the most commonly used asphalt type.
4. What is the limit of plasticity index for a soil to be stabilized by bitumen?
a) <18%
b) >18%
c) <40%
d) >40%
Answer: a
Clarification: Soils having a liquid limit of less than 40% and plasticity index of less than 18% are preferred for the stabilization by using bitumen. Soils with these properties yield the best results.
5. Longer curing periods are found to decrease the strength of the soil-bitumen mix.
a) True
b) False
Answer: b
Clarification: When the curing period is longer and the curing temperature provided is warmer, greater amount of volatiles are lost. Volatile content is inversely related to the strength of the soil-bitumen mixture. Hence, a longer period of curing results in strength gain.
6. What is the main principle behind stabilizing cohesive soil using bitumen?
a) Binding
b) Waterproofing
c) Allow easy compaction
d) Block capillary action
Answer: d
Clarification: For cohesive soils, it is necessary to block the capillary action within aggregate voids to avoid moisture changes within the aggregates. Complete waterproofing is not desired and is not the primary principle behind using bitumen for cohesive soils.
7. Which of the below is not a process involved in the construction of soil-bitumen?
a) Aeration
b) Compaction
c) Spreading
d) Pulverization
Answer: c
Clarification: The first step in the construction process is the pulverization of the soil. Then the bitumen is added to the soil and mixed thoroughly, bitumen is not spread over the soil. The mix is then subjected to aeration and compacted to the desired thickness.
8. Foamed bitumen can be used for the stabilization of soil.
a) True
b) False
Answer: a
Clarification: Foamed bitumen is a mixture of bitumen, water and air. It can be used for the stabilization of soil. Bitumen is heated on site and water is injected into it, creating foam by the explosive expansion to about fifteen times its original volume.
9. Aeration is provided to ensure that the soil mixture can be ______ easily.
a) Compacted
b) Mixed
c) Stabilized
d) Cured
Answer: a
Clarification: Sufficient aeration is provided during the process of mixing and spreading, but sometimes additional aeration must be provided so that the compaction of the mix becomes easier. Aeration helps in the evaporation of diluents that were used to ease the mixing process, and hence allows easy compaction.
10. which field control test is conducted after compaction?
a) Moisture content
b) Bitumen content
c) Density
d) Pulverization
Answer: c
Clarification: The field control test for moisture content and bitumen content of the mix is carried out before compaction. The field control test for the pulverization of wet soil mixture is carried out before compaction. The field control test to determine the dry density is carried out after compaction.