Civil Engineering interview questions and answers 16 to 20

16. Describe briefly the advantages and disadvantages of using plastic and timber fenders? 

The advantages and disadvantages of using plastic fenders are as follows:

Plastic fenders are low in strength with a relatively high resistance to abrasion. Plastic fenders are resistant to chemical and biological attacks. Plastic fenders have moderate energy absorption capacity. The berthing reactions are also comparatively moderate and depends on the point of contact. Also since they are made from recycled material they are environmental friendly.

The advantages and disadvantages of using timber fenders are: timber fenders are low in strength and are very susceptible to marine borer attacks and rotting. The energy absorption capacity is very low. Also generally the contact pressure between the vessels and the fender are high.

17. Explain why concrete barriers have curved surface profiles? 

The concrete safety fencings are made to contain vehicles in their carriageway being travelled so as to reduce the chances of rebounding into the roads leading to more hazards. In the case of normal fencings upon vehicle crashes the fencings give away so as to absorb as much energy as possible henceforth reducing the impact on the vehicles.

But in the case of concrete barriers their purpose is not to absorb energy of vehicles crashing into the barrier but to retain them. They have a curved design so as to allow the vehicles that hit them to slightly go up on the barrier but not overturn. They also prevent the vehicle from again getting back on the road by rebounds. This helps in vastly reducing the chances of other vehicle hazards.

18. Why is the use of granular sub-base in concrete carriageways not preferred, explain? 

Some of the reasons why granular sub-base is not preferred in concrete carriageways:

Sub bases are permeable and hence water can seep through them easily. The soil particles get pumped out through the joints on the application of traffic loads. This results in the creation of voids underneath the pavement structure. This leads to the weakening of the concrete surface and it can crack easily upon intense traffic loads.

Instead if lean concrete is used for carriageways it greatly increases the strength of the roads and the load carrying capacity of the roads is increased.

Sub-bases implementation requires a lot of workmanship which can lead to an ununiform distribution of the sub-base. This can lead to the cracking of the carriageway when there is severe traffic loading.

19. Why are separation membranes used between concrete pavement slab and sub-base? 

The purpose of separation membrane between the concrete pavement slab and the sub-base are as follows:

The separation membrane reduces the frictional forces between the concrete slabs and the sub-base. The membrane aids the movement of the concrete slab in reference to the sub-base when changes in the level of the moisture and temperature occurs.

It aids in the segregation of sub-base materials from freshly placed concrete.

The separation membrane also helps in the reduction of cement and water loss in the form of immature concrete. Immature concrete greatly affects the strength of the concrete. It also affects the durability of it.  A good example of a separation membranes is polythene sheeting which is commonly used.

20. In the roof of a pumping station explain briefly the components of a waterproofing system. 

The components of a typical waterproofing system on the roof of a pumping station are as follows:

Right above the structural finish level of the roof ( concrete ) a uniform thickness screed is applied so as to facilitate the application of the waterproofing membrane. The surface provide for the membrane should always possess good cohesion properties and must be thin so as to prevent any un-uniformity. This thin layer also acts as a layer of thermal insulation.

Right above this layer the waterproofing membrane is deployed to secure the water tightness of the roof.

In order to enhance the thermal insulation of the roof an insulation board is sometime placed right above the waterproof membrane. The insulation board helps in the maintenance of a stable temperature in both weathers.


 
Civil Engineering interview questions and answers 16 to 20 Civil Engineering interview questions and answers 16 to 20 Reviewed by Parag Pal on 8:19 AM Rating: 5

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