Question

In: Civil Engineering

1. Discuss the use of the C.B.R. value in the design of pavement. 2. Discuss some...

1. Discuss the use of the C.B.R. value in the design of pavement.

2. Discuss some of the defects you will encounter in maintenance of roads.

3. What is the use of a grader and a scraper in the construction of road?

4. Briefly explain the Marshall test. Discuss the use of the test.

5. Outline three methods by which the viscosity of bitumen can be reduced to facilitate its application.

6. Discuss the functions of a primer in bituminous surfacing.

8. A drainage system is an important part of any road. Discuss its functions.

9. Explain the concept of “equivalent standard axle”.

10. List the pre-construction activities which will be necessary for a new road deviation in a rural area.

Solutions

Expert Solution

1.Use of CBR test:

i)C.B.R (California Bearing Ratio ) test mainly used to determine the penetration value of subgrade soil or subgrade pavement and further thickness of the pavement.

ii) From the IRC, with this CBR value we can determine the required flexible pavement thickness value along with thickness of the each component of the pavement.

iii)By knowing the CBR value for penetration 2.5 mm and 5.0 mm, can also indicate the bearing capacity and soil strength.

2.Defects in maintanance of roads:

i) for major and minor highways and roads, pot holes on the roads should be checked.

ii) during monsoon, the roads should be inspected, as heavy rain fall cause failure of bitumen adhesion property.

iii) during maintanace, the roller should be properly rolled the road for removing the undulation.

iv) camber should be properly provided and drain besides the roads should be checked.If the drains are not cleared, there will be water logged situation on the road.

3. Use of Grader and Scraper:

Grader: Grader is mainly used in construction for grading snd maintaning the road mainly gravel road.It is also used to provide the base course of the pavement and to provide flat foundation under the buildings.It can also efficient to provide inclinef surfaces. Many time, in colder region, this equipment is also used to remove the snow from the roads and to clear the roads. Besides, Grader is used to provide camber on the roads to drainage the rain water.

Scraper:Scraper is mainly used in the construction as a hauling equipment.There is small hauling bowl is connected in front of scraper which is movable in vertical direction, by which we can cut the soil and then filled the soil in the bowl to borrow it to the required area.

4.Marshall Test: Marshall test is done mainly on bitumen concrete mix to know the load carrying capacity of the bitumiouns concrete mix.

Procedure: First we have to heat the specimens in water bath around 60°c for 30-40 minutes. Then, the speciens are brought out from the water bath and are placed on the breaking head. In the breaking head, upper portion of the specimen is in position and the whole system is put under the loading area and a flowmeter is set on the machine adjusted to zero. Then loading is given on the sample around 50mm/ minute.

The maximum loading value is taken from that in Newton.

Use:

i) we can determine the optimum binder content of the bitumen from marshall stability test.

ii) failure loading value of the bitumen concrete mix design can also be determined.

iii) flow value or marshall flow value of the specimen can be known from the test.


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