Civil engineering interview questions in Roadway/Highway /Expressway department

 

Welcome friends,

We shall learn about the various questions which are frequently ask by an  interviewer In the field of infrastructure. 

So let's get start.......

EMBANKMENT/SUBGRADE/BORROW AREA

•Liquid Limit  <50%

•Plastic Limit  < 25%

•Proctor Density(Min. Value)
For Embankment =1.52 to 1.60 gram/cubic centimeter

For Subgrade= 1.75 gram/ cubic centimeter

Sub-grade top

• Field Dry Density (FDD)
For Embankment= min. 95%
For Sub grade = min. 97%

•Number of test
For Embankment = 1set/3000 sq.meter(1set=10pits)

For subgrade= 1set/2000 sq.meter
(1 set=10 pits)

GRANULAR SUB- BASE

•Maximum thickness of single compacted layer = 200 mm

• Minimum thickness of single compacted layer( only when GSB is laying in two layers) = 150 mm


•Max. Allowable size of aggregate =75mm

•Number of grading of GSB = 6

•Liquid limit  should not be  more than 25% ( test procedure as per IS 2720 (part 5)).

•Plasticity index should  not be more than 6%( test procedure as per IS 2720 (part 5)).

•Aggregate impact value should not be more than 40%.

•CBR value should be less than 30%.

•FDD(Field Dry Density) should not be less than 98% of MDD(Max. Dry Density).

•1 test/ 1000 sq. Met. should be done during checking of FDD.

•Moisture content  = 1-2% below OMC

For more updates about GSB please click on

https://gyanofengineering.blogspot.com/2019/02/full-details-about-gsb-including.html

WET MIX MACADAM (WMM)


 •Maximum thickness of single compacted layer = 200 mm


Minimum thickness of single compacted layer= 75 mm

•Plasticity index should  not be more than 6%(Test procedure as per IS 2720 (part 5)).

•Aggregate impact value should not be more than 30%.

• Los Angles Abrasion(LAV) should be more than 40%.

•Combined FI ( flakiness index ) & EI (elongation index) should not be more than 35%.

•FDD(Field Dry Density) should not be less than 98% of MDD (Max. Dry Density).

•1 set / 1000 sq. Met. ( 1 set = 3 pits) should be done during checking of FDD.

•Max. Allowable size of aggregate =53 mm

•After final compaction of WMM course, the bed of WMM shall be allowed to dry for 24 hours.

For more  about WMM kindly click on 

https://gyanofengineering.blogspot.com/2019/02/wet-mix-macadam-wmm-sub-base-base.html

DENSE BITUMINOUS MACADAM (DBM)

•  The thickness of a single layer shall be 50 mm to 100 mm.

•Combined flakiness and elongation index should not be more than 35%.

                            DBM(Grade-1)

•Los Angles Abrasion value(LAV) should not be more than 35%.

•Aggregate impact value(AIV) should not be more than 27%.

•Coating and stripping of bituminous aggregate mix should not be less than 95%.

•Grades of DBM

 # GRADING -1

Nominal size of aggregate - 37.5 mm

Layer thickness= 75-100 mm

Bitumen content % by mass of total mix should not be less than 4%.

# GRADING - 2

Nominal size of aggregate - 26.5 mm

Layer thickness= 50-75 mm

Bitumen content % by mass of total mix should not be less than 4.5%.

• DBM should be measured either in cubic meter,tonnes or square meter (only for specified thickness as indicated in contract drawing).

Temperature ranges of bituminous material for various grades of bitumen

•

For more updates about DBM please click on
https://gyanofengineering.blogspot.com/2019/08/bituminous-macadam-technical.html

OR
https://youtu.be/T-56t2ZxEL0

PRIME COAT 

• Quantity of SS1 grade bitumen Emulsion for various types of Granular surface

TACK COAT

 It should be provided over granular surface(like WMM) treated with prime coat,bituminous surfaces and cement concrete pavement.

•Rate of application of tack coat

BITUMINOUS CONCRETE (BC)

•  The thickness of a single layer shall be 30 mm to 50 mm.

•Combined flakiness and elongation index should not be more than 35%.

•Los Angles Abrasion value(LAV) should not be more than 30%.

•Aggregate impact value(AIV) should not be more than 24%.

Bituminous concrete 

•Coating and stripping of bituminous aggregate mix should not be less than 95%.

•Grades of BC

 # GRADING -1

Nominal size of aggregate - 19 mm

Layer thickness= 50 mm

Bitumen content % by mass of total mix should not be less than 5.2%.

# GRADING - 2

Nominal size of aggregate - 13.2 mm

Layer thickness= 30-40 mm

Bitumen content % by mass of total mix should not be less than 5.4%.

•BC should be measured either in cubic meter,tonnes or square meter (only for specified thickness as indicated in contract drawing).

To get more details about BC,  Kindly click on below link

https://gyanofengineering.blogspot.com/2020/05/bituminous-concrete-bc-specifications.html

Reinforced soil earth wall (RS/RE Wall) 

 • Minimum thickness of RS/RE wall panels is 180 mm. (including facia textures, logos and embellishments)

•Minimum Concrete grade of RS/RE panels is M 35.

• Minimum width of geotextile strip to cover gaps between panels is 100 mm. 

•Height of point of impact at crash barriers above top of pavement  is 800 mm. 

•Maximum spacing of reinforcing elements shall not exceed 800 mm for RS/RE wall using panels and blocks. 

•Minimum thickness of strip footing ( levelling pad PCC) is 150 mm. 

•Minimum width of strip footing ( levelling pad PCC) is 350 mm. 

•Minimum concrete grade for levelling pad  PCC( strip footing) is M 15.

•Minimum depth of embedment below finished ground level at the foot of wall is 1000 mm. 

•Maximum compacted soil thickness of each layer is 200 mm. 

•Various types of reinforcements used in RS/RE wall

1 - Metallic elements like bars,  strips,  plates etc. 

2 - Metallic reinforcement in form of mesh

3 - Polymeric elements like strips, grids, rods mesh etc. 

•Minimum length of reinforcement shall be 0.7 H to 3 met. Whichever is greater.

Where H is design height (depth of embedment plus height above  ground level) of the RS/RE wall. 

•Crash Barrier : Horizontal impact load of 29 kN/m shall be considered in the design of crash barrier, which load shall be resisted by the upper two layers of the reinforcement over the full length. 

Dry Lean Concrete (DLC)

•The minimum cement content shall be 150 kg/cu.m of concrete. In case flyash is blended at site as part replacement of cement, the quantity of flyash shall not be more than 20% by weight of cementitious material and the content of OPC( Ordinary Portland Cement) shall not be less than 120 kg/cu.m.

•The DLC shall be laid in such way that it is atleast 750 mm wider on each side than the proposed width including paved shoulder of the concrete pavement.

•The minimum dry density obtained shall not be less than 98% of that achieved during the trail length construction (of max dry density). The density achieved at the edge I.e. 0.5 meter from the edge shall not be less than 96% of the that achieved during the trail length construction (of max dry density).

•The spreading,compacting and finishing of the lean concrete shall be carried out as soon as possible and time between the mixing of first batch of concrete in any transverse section of the layer and the final finishing of the same shall not exceed 90 minutes when the temperature of concrete is between 25°C and 30°C, and 120 minutes if less than 25°C.

• It is desirable to stop concreting when the ambient temperature is above 35°C.

•Transverse joints in Dry Lean concrete shall be staggered from the construction butt type joint in Concrete pavement by 800-1000 mm. 

Longitudinal joint in Dry Lean Concrete shall be staggered by 300-400 mm from the longitudinal joint of concrete pavement. 

• The curing compound shall be applied over the entire exposed surface of the Dry Lean Concrete, including sides and edges, at the rate of 0.2 litres/sq.m, or as recommended by the supplier.

Pavement Quality Concrete (PQC)

•The maximum size of coarse aggregate shall not exceed 31.5 mm for pavement concrete. 

•No aggregate which has water absorption more than 2 percent shall be used in the concrete mix. 

•The Los Angeles Abrasion value shall not exceed 35. 

•The combined flakiness and elongation index of aggregate shall not be more than 35 percent.

•The pH value of water shall be not less than 6.

•When Ordinary Portland Cement (OPC) is used the quantity of cement shall not be less than 360 kg/cu.m. In case fly ash grade I (as per IS:3812) is blended at site as part replacement of cement, the quantity of fly ash shall be upto 20 percent by weight of cementitious material and the quantity of OPC in such a blend shall not be less than 310 kg/cu.m.

•the maximum free water cement ratio shall be 0.45 when only OPC is used and 0.50 when blended cement (Portland Pozzolana Cement or Portland Slag Cement or OPC blended with fly ash or Ground Granulated Blast Furnace Slag, at site) is used.

•A slump value in the range of 25 ± 15 mm is reasonable for paving works but this may be modified depending upon the site requirement and got approved by the Engineer.

• A separation membrane shall be used between the concrete slab and the sub-base. Separation membrane shall be impermeable PVC sheet 125 micron thick transparent or white in colour laid flat with minimum creases.

•Wherever overlap of plastic sheets is necessary, the same shall be at least 300 mm

•Transverse and longitudinal joints in the pavement and Dry Lean Concrete sub-base shall be staggered so that they are not coincident vertically and are at least 800 to 1000 mm and 300 to 400 mm apart respectively.

•Sawing operation could start as early as 4-8 hours after laying of concrete pavement but not later than 8 to 12 hours depending upon the ambient temperature, wind velocity, relative humidity and required maturity of concrete achieved for this purpose.

•Contraction joints shall consist of a mechanical sawn joint groove, 3 to 5 mm wide and one-fourth to one-third depth of the slab ± 5 mm or as stipulated in the drawings and dowel bars as stipulated in the drawings.

•After minimum 14 days of curing, in case OPC cement is used and 16 days of curing when flyash or blended cement is used, the construction joint shall be widened to accommodate the sealant to dimensions shown on drawing or as per IRC:57.

•The thickness of the sheath shall not exceed 0.5 mm and shall be tightly fitted on the bar for at least two-thirds of the length from one end for dowel bars in contraction/construction joints and half the length plus 50 mm for expansion joints.

•Tie bars shall be positioned to remain in the middle from the top or within the upper middle third of the slab depth as indicated in the drawings and approximately parallel to the surface and approximately perpendicular to the line of the joint, with the centre of each bar on the intended line of the joints within a tolerance of ±50 mm, and with a minimum cover of 30 mm below the joint groove. Spacing of tie bars on curves of radius less than 360 m shall not be less than 350 mm. 

To check the position of the tie bars, one metre length, 0.5 m on either side of the longitudinal joint shall be opened when the concrete is green (within 20 to 30 minutes).

•No concreting shall be done when the temperature of the concrete reaching the paving site is above 30°C.

•No concreting shall be done when the concrete temperature is below 5°C and the temperature is further falling.

•The total time taken from the addition of the water to the mix, until the completion of the surface finishing and texturing shall not exceed 120 minutes when concrete temperature is less than 25°C and 90 minutes when the concrete temperature is between 25°C and 30°C. When the time between mixing and laying exceed these values, the concrete shall be rejected and removed from the site. Tipping trucks delivering concrete shall normally not run on plastic sheathing nor shall they run on completed slabs until after 28 days of placing the concrete. 

•As soon as the side forms are removed, edges of the slabs shall be corrected wherever irregularities have occurred by using fine concrete composed of 1:1:2, cement : sand : coarse agg (10 mm down) with water cement ratio not more than 0.4 under the supervision of the Engineer.

Thank you
Mukesh kumar(www.gyanofcivilengineering.com)