BASICS INTERVIEW QUESTIONS

CIVIL_ENGINEERING

Along with some grip on the subject(which obviously is important), they should know some other things:

1. When it comes to engineering,

a. Opportunities: Structural engineering is a good option for further studies, but not the only branch available after completing civil engineering.

What are the better options after BE Civil for doing Masters in India?

Follow this for more:

Opportunities for Civil Engineers in India

b. Research: Concrete is not the only available topic for research.

There are thousands of research topics. Just search ASCE journals and let me know if I am wrong.

c. Misconception: Common misconception is that all civil engineers will be site engineers which is wrong. There will be civil engineers in the following functions too.

1. Planning

2. Contracts

3. Quantity survey

4. Tendering and bidding

5. Design

6. Quality Control,

2. When it comes to site execution,

Every civil engineer must know that the supervisors working under them are not their slaves.

We earn respect only when we show some respect to our juniors level engineers or supervisors.

When safety department in-charge says something, civil engineers need to follow to avoid any unwanted circumstances (like accidents or death in the site).

Don’t waste the scrap. Recycle it and reuse it.

Ex: You can even use unwanted cut steel bars for barricading purpose.

3. When it comes to project execution,

Every civil engineer’s ultimate aim should be completing the project within the stipulated time without any delay and within the specified budget.

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I found these good enough from Internet.

• Minimum thickness of slab is 125 mm.
• Water absorption should not be more than 15 %.
• Dimension tolerance for cubes + – 2 mm.
• Compressive strength of Bricks is 3.5 N /mm2
• Maximum Free fall of concrete allowed is 1.50 m.
• In soil filling as per IS code for every 100 sqm 3 sample for core cutting test should be taken.
• Electrical conduits shall not run in column
• Earth work excavation for basement above 3 m should be stepped form.
• Any back filling shall be compacted 95% of dry density at the optimum moisture content and in layers not more than 200mm for filling above structure and 300 mm for no structure
• A set of cube tests shall be carried out for each 30 cum of concrete / each levels of casting / each batch of cement.
• Water cement ratio for different grades of concrete shall not exceed 0.45 for M20 and above and 0.50 For M10 / M15 contractor
• For concrete grades M20 and above approved admixture shall be used as per mix design requirements.
• Cement shall be stored in dry places on a raised platform about 200mm above floor level and 300mm away from walls. Bags to be stacked not more than 10 bags high in such a manner that it is adequately protected from moisture and contamination.
• Samples from fresh concrete shall be taken and at least a set of 6 cubes of 150mm shall be prepared and cured. 3 Cubes each at 7 days and 28 days shall be tested for compressive strength. The test results should be submitted to engineer for approval. If results are unsatisfactory necessary action/rectification/remedial measures has to be exercised.
• Water used for both mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalies, salts, sugar and organic materials or other substances that may be deleterious to concrete or steel. The ph shall be generally between 6 and 8.
• Cement shall be tested for its setting. 
  1. The initial setting time shall not be less than 30 minutes.
  2. The final setting time shall not be more than 10 hours.
• Slump IS 456 
  Lightly reinforced 25 – 75 mm
  Heavily reinforced 75 – 100 mm
  Trench fill (insitu & Tremie) 100 – 150 mm (For Tremie no need of vibrator)
• Curing Days Required 
  Super Sulphate cement : 7 days
  Ordinary Portland cement OPC : 10 days
  Minerals and Admixture added cement : 14 days

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​Should raking piles of a bridge abutment be placed under an embankment?

CIVIL_ENGINEERING

Should raking piles of a bridge abutment be placed under an embankment? 

For a bridge abutment to be supported on raking piles with different orientations, the 

movement between the ground and the pile group is difficult to predict. For instance, if 

some of the raking piles of the bridge abutment are extended beneath an embankment, then 

the settlement of embankment behind the abutment may cause the raking piles to 

experience severe bending moment and damage the piles as recommended by Dr. Edmund 

C Hambly (1979). 

​What are the functions of different components of a typical expansion joint?

CIVIL_ENGINEERING

What are the functions of different components of a typical expansion joint? 

In a typical expansion joint, it normally contains the following components: joint sealant, 

joint filler, dowel bar, PVC dowel sleeve, bond breaker tape and cradle bent. 

Joint sealant: it seals the joint width and prevents water and dirt from entering the joint and 

causing dowel bar corrosion and unexpected joint stress resulting from restrained 

movement. 

Joint filler: it is compressible so that the joint can expand freely without constraint. 

Someone may doubt that even without its presence, the joint can still expand freely. In fact, 

its presence is necessary because it serves the purpose of space occupation such that even if 

dirt and rubbish are intruded in the joint, there is no space left for their accommodation. 

Dowel bar: This is a major component of the joint. It serves to guide the direction of 

movement of concrete expansion. Therefore, incorrect direction of placement of dowel bar 

will induce stresses in the joint during thermal expansion. On the other hand, it links the 

two adjacent structures by transferring loads across the joints. 

PVC dowel sleeve: It serves to facilitate the movement of dowel bar. On one side of the 

joint, the dowel bar is encased in concrete. On the other side, however, the PVC dowel 

sleeve is bonded directly to concrete so that movement of dowel bar can take place. One 

may notice that the detailing of normal expansion joints in Highways Standard Drawing is 

in such a way that part of PVC dowel sleeve is also extended to the other part of the joint 

where the dowel bar is directly adhered to concrete. In this case, it appears that this 

arrangement prevents the movement of joint. If this is the case, why should designers 

purposely put up such arrangement? In fact, the rationale behind this is to avoid water from 

getting into contact with dowel bar in case the joint sealant fails. As PVC is a flexible 

material, it only minutely hinders the movement of joint only under this design. 

Bond breaker tape: As the majority of joint sealant is applied in liquid form during 

construction, the bond breaker tape helps to prevent flowing of sealant liquid inside the 

joint . 

Cradle bar: It helps to uphold the dowel bar in position during construction. 

​In designing concrete structures, normally maximum aggregate sizes are adopted with ranges from 10mm to 20mm. Does an increase of maximum aggregate size benefit the structures?

CIVIL_ENGINEERING

In designing concrete structures, normally maximum aggregate sizes are adopted with ranges from 10mm to 20mm. Does an increase of maximum aggregate size benefit the structures? 

To answer this question, let’s consider an example of a cube. The surface area to volume 

ratio of a cube is 6/b where b is the length of the cube. This implies that the surface area to 

volume ratio decreases with an increase in volume. Therefore, when the size of maximum aggregate is increased, the surface area to be wetted by water per unit volume is reduced. 

Consequently, the water requirement of the concrete mixes is reduced accordingly so that 

the water/cement ratio can be lowered, resulting in a rise in concrete strength. 

However, an increase of aggregate size is also accompanied by the effect of reduced 

contact areas and discontinuities created by these larger sized particles. In general, for 

maximum aggregate sizes below 40mm, the effect of lower water requirement can offset 

the disadvantages brought about by discontinuities as suggested by Longman Scientific and 

Technical (1987). 

​What are the major problems in using pumping for concreting works?

CIVIL_ENGINEERING

What are the major problems in using pumping for concreting works? 

In pumping operation, the force exerted by pumps must overcome the friction between 

concrete and the pumping pipes, the weight of concrete and the pressure head when placing 

concrete above the pumps. In fact, as only water is pumpable, it is the water in the concrete 

that transfers the pressure. 

The main problems associated with pumping are the effect of segregation and bleeding. To 

rectify these adverse effects, the proportion of cement is increased to enhance the cohesion 

in order to reduce segregation and bleeding. On the other hand, a proper selection of 

aggregate grading helps to improve the pumpability of concrete. 

​What are the disadvantages of curing by ponding and polythene sheets?

CIVIL_ENGINEERING

What are the disadvantages of curing by ponding and polythene sheets? 

The purpose of curing is to reduce the rate of heat loss of freshly placed concrete to the 

atmosphere and to minimize the temperature gradient across concrete cross section. 

Moreover, curing serves to reduce of the loss water from freshly placed concrete to the 

atmosphere. 

Ponding: This method of thermal curing is readily affected by weather condition (cold 

wind). Moreover, a large amount of water used has to be disposed off the construction sites 

after curing. 

Polythene sheet: This method of curing is based on the principle that there is no flow of air 

over the concrete surface and thereby no evaporation can take place on top of the freshly 

concreted surface by provision of polythene sheets. However, it suffers from the demerit 

that polythene sheets can be easily blown off in windy condition and the performance of 

curing would be affected. Moreover, for water lost due to self-desiccation, this method 

cannot replenish these losses. 

​Is it desirable to use concrete of very high strength i.e. exceeding 60MPa? What are the potential problems associated with such high strength concrete?

CIVIL_ENGINEERING

Is it desirable to use concrete of very high strength i.e. exceeding 60MPa? What are the potential problems associated with such high strength concrete? 

To increase the strength of concrete, say from 40MPa to 80MPa, it definitely helps in 

improving the structural performance of the structure by producing a denser, more durable 

and higher load capacity concrete. The size of concrete members can be significantly 

reduced resulting in substantial cost savings. However, an increase of concrete strength is 

also accompanied by the occurrence of thermal cracking. With an increase in concrete 

strength, the cement content is increased and this leads to higher thermal strains. 

Consequently, additional reinforcement has to be introduced to control these additional 

cracks caused by the increase in concrete strength. Moreover, the ductility of concrete 

decreases with an increase in concrete strength. Attention should be paid during the design 

of high strength concrete to increase the ductility of concrete. In addition, fire resistance of high strength concrete is found to be less than normal strength concrete as suggested by 

Odd E. Gjorv (1994). 

Though the tensile strength of high strength concrete is higher than that of normal concrete, 

the rate of increase of tensile strength is not proportional to the increase of compressive 

strength. For normal concrete, tensile strength is about one-tenth of compressive strength. 

However, for high strength concrete, it may only drop to 5% of compressive strength. 

Moreover, owing to a low aggregate content of high strength concrete, creep and shrinkage 

increases. 

COMPRESSION TEST

CIVIL_ENGINEERING

In concrete compression test, normally 150mmx150mmx150mm concrete cube samples is used for testing. Why isn’t 100mmx100mmx100mm concrete cube samples used in the test instead of 150mmx150mmx150mm concrete cube samples? 

Basically, the force supplied by a concrete compression machine is a definite value. For 

normal concrete strength application, say below 50MPa, the stress produced by a 

150mmx150mmx150mm cube is sufficient for the machine to crush the concrete sample. 

However, if the designed concrete strength is 100MPa, under the same force (about 

2,000kN) supplied by the machine, the stress under a 150mmx150mmx150mm cube is not 

sufficient to crush the concrete cube. Therefore, 100mmx100mmx100mm concrete cubes 

are used instead to increase the applied stress to crush the concrete cubes. 

For normal concrete strength, the cube size of 150mmx150mmx150mm is already 

sufficient for the crushing strength of the machine.

​What is the function of shear keys in the design of retaining walls?

CIVIL_ENGINEERING

What is the function of shear keys in the design of retaining walls? 

In determining the external stability of retaining walls, failure modes like bearing failure, 

sliding and overturning are normally considered in design. In considering the criterion of 

sliding, the sliding resistance of retaining walls is derived from the base friction between 

the wall base and the foundation soils. To increase the sliding resistance of retaining walls, 

other than providing a large self-weight or a large retained soil mass, shear keys are to be 

installed at the wall base. The principle of shear keys is as follows: 

The main purpose of installation of shear keys is to increase the extra passive resistance 

developed by the height of shear keys. However, active pressure developed by shear keys 

also increases simultaneously. The success of shear keys lies in the fact that the increase of 

passive pressure exceeds the increase in active pressure, resulting in a net improvement of 

sliding resistance. 

On the other hand, friction between the wall base and the foundation soils is normally 

about a fraction of the angle of internal resistance (i.e. about 0.8φ ) where φ is the angle of 

internal friction of foundation soil. When a shear key is installed at the base of the retaining 

wall, the failure surface is changed from the wall base/soil horizontal plane to a plane 

within foundation soil. Therefore, the friction angle mobilized in this case is φ instead of 

0.8φ in the previous case and the sliding resistance can be enhanced. 

​If on-site slump test fails, should engineers allow the contractor to continue the concreting works?

CIVIL_ENGINEERING

If on-site slump test fails, should engineers allow the contractor to continue the concreting works? 

This is a very classical question raised by many graduate engineers. In fact, there are two 

schools of thought regarding this issue. 

The first school of thought is rather straightforward: the contractor fails to comply with 

contractual requirements and therefore as per G. C. C. Clause 54 (2)(c) the engineer could 

order suspension of the Works. Under the conditions of G. C. C. Clause 54(2)(a) – (d), the 

contractor is not entitled to any claims of cost which is the main concern for most engineers. 

This is the contractual power given to the Engineer in case of any failure in tests required by the contract, even though some engineers argue that slump tests are not as important as 

other tests like compression test. 

The second school of thought is to let the contractor to continue their concreting works and 

later on request the contractor to prove that the finished works comply with other 

contractual requirements e.g. compression test. This is based upon the belief that 

workability is mainly required to achieve design concrete compression strength. In case the 

compression test also fails, the contractor should demolish and reconstruct the works 

accordingly. In fact, this is a rather passive way of treating construction works and is not 

recommended because of the following reasons: 

(i) Workability of freshly placed concrete is related not only to strength but also to 

durability of concrete. Even if the future compression test passes, failing in slump 

test indicates that it may have adverse impact to durability of completed concrete 

structures. 

(ii) In case the compression test fails, the contractor has to deploy extra time and 

resources to remove the work and reconstruct them once again and this slows down 

the progress of works significantly. Hence, in view of such likely probability of 

occurrence, why shouldn’t the Engineer exercise his power to stop the contractor 

and save these extra time and cost?