Interview questions for a civil(Structure) engineer(Concrete/Aggregate/Reinforcement (Steel bar,TMT/HYSD Bar)/Cement/ sand) A civil engineer must know.......

STRUCTURE DEPARTMENT MOST IMPORTANT INTERVIEW QUESTIONS

specification related to concrete

• Allowable free fall height of concrete = 1.5 meter
• Minimum thickness of slab = 125mm
•Tolerance limit of cube= +2mm
• Number of cubes required with respect to concrete quantity

•Grades of concrete

•Min. Concrete deposition temperature= 5°C

• Max. Concrete deposition temperature= 30°C ( in no case 40°C)

•Density of PCC(plain cement concrete) = 2400KG/cubic meter

• Density of RCC = 2500KG/cubic meter

•Concrete placing time when it has been discharged from Transit Mixer(Agitator)=30 minute

• Size of cube = 0.150 * 0.150 * 0.150 ( All dimensions are in meter)
 =150 * 150 *150 (All dimensions are in mm)

•Fly ash when used, Shall neither be less than 20% nor shall be greater than 30% of the total by mass of OPC and fly ash and shall be conform to grade - 1of IS:3812

specification related to Reinforcement ( Re- bar)

•Requirement of Binding wire per metric tonn = 8 KG

• Minimum diameter of bar used in slab

 Main bar= 8mm (HYSD bar) and 10mm (plain bar)

  #Distribution bar

minimum diameter of bar =8mm

 Max. Diameter of bar =1/8 of slab thickness 

• Minimum number of bars in square column= 4 bars

• Minimum number of bars in circular column= 6 bars

• Density of steel bar= 7850 KG/Cubic meter

• Minimum longitudinal reinforcement in column = 0.8%

•Maximum longitudinal reinforcement in column( including lap length) =6%

• Minimum diameter of Chair bar= 12mm

• Minimum diameter(Φ) of dowel bar= 12mm

• Requirement of chair bar per square meter= 1

• Grades of Re- bar
Fe-250,Fe-415,Fe-415D,Fe-415S,Fe-500,Fe-500D,Fe-500S,Fe-550,Fe-550D,Fe-600

Where (Fe-500D)
Fe- It stand for iron
500- Minimum yield strength
D-  Ductility (Not for diameter)

S- grade bars are generally used in the
 earthquake sensitive areas

•Anchorage value of Hook= 16D centimeter

•Anchorage value of 90° bend= 8D centimeter

• Lap length in compression= equal to development length but not less than 24D

• Lap length in flexture tension without hook = Development length or 30D which ever is greater

•Lap length in flexture tension with hook= Development length or 30D which ever is greater and (length of hook = 15D of 200 mm whichever is greater)

• Maximum provided slope of bar during lapping in cloumn=1:6


•For mild steel (Fe-250) bar U- type hooks are provided and for deforned bar(HYSD Bar) L- tpye hooks are provided.

• Lap splices shall not be used for bars larger  36 mm diameter except where welded

•column bars of diameter larger than 36 mm in compression can be spliced with dowels at the footing with bars of smaller size and of necessary area.

Cement

•Density of cement(of loose cement bag)= 1440 KG/ Cubic meter

• Weight of one cement bag= 50 KG

• Initial setting time = 30min.

•Final setting time = 600 min (10hours)

•Volume of cement bag=
0.03472 cubic meter = 1.2262cubic feet = 34.722=liter

• Grades of Cement

1.  33 Grade
2. 43 Grade
3. 53 Grade

Here Grade value like 33,43 & 53 indicates the Strength of cement (in Newton/ mm^2 or mega pascal(MPa)) that is achieved after 28 days of cruring.

•Type of Cement

 #

1. Ordinary Portland Cement (OPC)
2. Portland Pozzolana Cement (PPC)
3. Rapid Hardening Cement(RHC)
4. Quick setting cement(QSC)
5. Low Heat Cement
6. Sulphates resisting cement
7. Blast Furnace Slag Cement
8. High Alumina Cement
9. White Cement(WC)
10. Coloured cement
11. Air Entraining Cement
12. Expansive cement
13. Hydrographic cement

• strength achieved by cement in Mega pascal (MPa) after proper curing in different days

Aggregate 

• Types of Aggregates

 1- Fine Aggregate (Also known as Sand)

 2- Coarse Aggregate

• Aggregate size smaller than 4.75 mm falls in the category of fine aggregate.

• Aggregate size larger than 4.75 mm falls in the category of coarse aggregate.

• Max. Allowable water absorption of aggregate = 2% (Maximum)

•Range of Specific gravity = 2.4 to 3.0

•size range of coarse aggregate = 4.75 mm 63 mm (only in concrete work)

•Size range of fine aggregate (Sand)= 150 micron to 4.75 mm

Thank you

Mukesh kumar
(www.Gyanofengineering.blogspot.com)