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METHODOLOGY FOR SUBGRADE CONSTRUCTION

Subgrade is the main part of the any  earth work .They are widely used in  road, railway and airport runway construction but here we will discuss sequence wise working methodology for the earthwork in subgrade for any highway work. 

  1. Scope of Work
  2. Reference Documents.
  3. Setting Out.
  4. Selection of Material & Borrow areas.
  5. Equipments.
  6. Methods of Operation.
  7. Quality Control.
  8. Work Safety
  9. Environmental Safety

 1.0 Scope of Work:-

The work shall consist of Construction of Sub-grade with approved and specified materials obtained from approved borrow areas or suitable material obtained from roadway excavation and drain excavation and in accordance with clause 305 of MORT&H specification.

2.0 Reference: –

Reference Documents:-

  1. Ministry of Road Transport & Highway Specifications.     
  2. Technical Specifications
  3. Relevant contract drawings.
  4. IS 2720 Codes.

3.0 Setting Out: –

After completion of site clearance/embankment the limits of sub-grade shall be marked by fixing pegs on both sides at regular intervals. The chainage boards and working bench mark shall be set outside the limits of construction areas.

4.0 Selection of Material and Borrow areas: –

4.1 Material:                              

The material used in Sub-grade shall be soil, moorum, gravel, a mixture of these or any other material approved by the Engineer. It shall be free from logs, stumps, roots, rubbish & any other material detrimental to the stability of structure. The material for sub-grade shall be obtained from the approved source with preference to the material becoming available from nearby roadway excavation or any other excavation under the contract. The material requirements shall be in accordance with clause 305.2 of MORT&H.

4.2 Borrow Material:

Samples should be taken from the known borrow area & to be tested as per IS 2720 for the suitability in use in embankment as per project specification. On confirmation of the suitability material the area shall be properly demarcated and satisfy the clause 305.2.2.2 or project specification

5.0 Equipments: –

The following equipments shall be carried out for the Sub-grade Construction. If desired the contractor shall demonstrate the efficacy of the type of equipment to be used, before commencement of work.

  1. Hydraulic Excavator
  2. Dozer
  3. Dumper (Tipper Trucks)
  4. Motor Grader
  5. Vibratory Roller
  6. Water Tanker
  7. Tractor Trolleys
  8. Survey Kit

6.0 Method of Operation: –

  • After completion of embankment, the limits of sub-grade shall be marked by fixing pegs at regular intervals  before commencing the earthwork. Construction toe line shall be more than the design toe line for proper construction of the edges.
  • The Embankment top shall be levelled to facilitate placement of first layer of Sub-grade, scarified, mixed with water and then compacted by rolling so as to achieve minimum dry density as specified in the modified Technical specification. Sub-grade treatment specified for Sub-grade shall be carried out as per approved drawing. Unsuitable material occurring in sub-grade foundation shall be removed as per direction and approval of the Engineer and replaced by approved materials laid in layers and suitably compacted to the required and specified degree of compaction. Excavation at approved borrow areas shall be carried out with excavator and transportation of excavated material shall be done by dumpers/ tractor trolley.
  • Maximum Dry density of borrow area soil shall be determined, and the soil shall be tested for dry density, if found less than 97% of M.D.D., the layer shall be scarified mixed with required quantity of water and compacted with soil vibratory roller to achieve minimum required specified dry density.
  • For construction adjacent to the existing embankment a continued, horizontal benching 300 mm wide or as per drawing shall be provided in the existing embankment.
  • The sub-grade material shall then be spread in layers not exceeding 250 mm compacted thicknesses or as per direction of the Engineer over the entire area with the dozer and finished by a motor grader. When the existing embankment to be widened continuous horizontal benches shall be cut out into the old slope to ensure adequate bond. Where water is required to be added the same shall be sprinkled from a water tanker fitted with sprinkler, uniformly on the surface but without flooding and shall be mixed thoroughly in soil by blending or harrowing until uniform moisture content is obtained throughout the depth of the layer. If the material delivered to the roadbed is too wet, it shall be dried by aeration and exposure to the sun till the moisture content is accepted for compaction.
  • The compaction shall be done with the help of Vibratory Roller of 8 – 10 Ton static weight with plain or pad foot drum or heavy pneumatic tyred roller of adequate capacity capable to achieve required compaction. Compaction trial shall be carried out on a suitable stretch to determine the no. of passes required for particular type of soil, dumped for sub-grade, to achieve densities specified in the table 300-2 of the Technical specification. Based on the trial actual compaction will be carried out with required no. of passes of Vibratory Roller until the specified density is achieved. Rolling shall progress parallel to the centerline of the road uniformly overlapping each preceding track by one-third width. Rolling shall be continued till the specified density is achieved as per table 300-2. In case specific compaction is not achieved the material in the soft area shall be removed and replaced with approved material. Densities shall be tested by sand replacement method / nuclear density gauge.
  • Subsequent layers shall be placed only after the finished layer has been tested as per the clause 903.2.2 and accepted. The top levels of the sub-grade shall be checked with reference to the longitudinal and cross profile of the road as per drawing to keep the variation within tolerance limit as per table 900-1. or as per standard specification.

7.0 Quality Control:-

Minimum compaction for sub-grade layers is 97% of modified proctor value of project specification.

8.0    Work Safety:-                   

8.1  During construction of widening works, adequate safety and traffic signs shall be installed adjacent to the road shoulders to protect the ongoing works as per location specific safety plan.

8.2  For locations where the dumping of embankment  materials by tippers are performed from the road shoulder, a minimum of 2 flagmen with reflective vests and holding a red  flag each be deployed to control the traffic which may be affected by the  unloading operation.

8.3  All locations adjacent to existing road where embankment construction is in progress shall be provided with safety and road signs.

8.4  No machines or equipment’s shall be permitted to remain on the existing road or shoulder unattended at all times unless it is properly protected and secured in a safe manner.              

8.5  The Safety Officer shall make frequent patrols along the highway to ensure that the safety equipment and signs are operational at all time.

8.6  Trucks sometimes fall over a tip head because the driver backs over the edge or the edge collapses under the weight of the truck. A protective berm or timber baulk should be used. Alternatively,  a signalman should be deployed in order to avoid this possibility.

8.7  When excavating trenches, place the excavated material at least 600 mm clear of the edge, where there is no danger of it falling back into or collapsing the side of the trench.

9.Environmental Safety: –

a.Nearby streams, water courses, lakes, reservoir shall be protected from contamination by the soil erosion from areas exposed during excavation by constructing temporary berms, dykes, sediment Basins, slopes, drains & by the use of temporary mulches, seeding or other control devices.

b.Vehicles tracks shall be kept moist to prevent flying of dust particles with the vehicle movement.

 

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CONCRETE MIX DESIGN OF M25 GRADE – AS PER IS 10262:2019

1.STIPULATIONS FOR PROPORTIONING

a) Grade designation : M 25 RCC

b) Type of cement : 43 grade Ordinary Portland Cement conforming IS 8112

c) Maximum nominal size of coarse aggregate : 20 mm

d) Minimum amount of cement  : 300 kg/m³ as per IS 456

e) Maximum water-cement ratio : 50 as per Table 5 of IS 456:2000

f) Workability : 75-125 mm slump

g) Exposure condition : Moderate (For Reinforced Concrete)

h) Method of concrete placing : Pumping

j) Degree of supervision : Good

k) Type of aggregate : Crushed Angular Aggregates

l) Chemical admixture type : Super Plasticizer Normet

2.TEST DATA FOR MATERIALS

a) Cement used : Sagar 43 grade Ordinary Portland cement conforming IS 8112

b) Specific gravity of cement : 3.14

c) Chemical admixture : Super Plasticizer conforming to IS 9103 

d) Specific gravity of

1) Coarse aggregate 20 mm : 2.799

2) Coarse aggregate 10 mm: 2.789

3)Combined Specific Gravity of aggregate ( 20 mm- 60% & 10 mm 40 % )=2.795

4) Fine aggregate : 2.517

e) Water absorption:

1) Coarse aggregate 20 mm : 0.41 %

2) Coarse aggregate 10 mm  : 0.59 %

3) Fine aggregate           : 1.87 %

f) Aggregate Impact Value : 20.52%

g) Combined Flakiness & Elongation Index : 27.57 %

h) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383

2) Fine aggregate : Conforming to Grading Zone III of Table 4 of IS 383

3 TARGET STRENGTH FOR MIX PROPORTIONING

f’ck =fck + 1.65 s   Or  f’ck = fck + X  where

f’ck = average target compressive strength of concrete at 28 days,

fck = characteristics compressive strength of concrete at 28 days,

X   = Factor based on grade of concrete

S = standard deviation. From table 2 of IS 10262-2019  S = 4 N/mm² & from table 1 , X=5.5

Therefore target strength of concrete using both equation

.

a) f’ck= fck+ 1.65 S  = 25 + 1.65 x 4 = 31.60 N/mm²

b) f’ck = fck+ X        = 25 +  5.5 =  30.5 N/mm².

The higher value to be adopted , therefore target strength will be 31.60 N/mm². Can adopt  this value while doing the concrete mix design those who are working other than highway project.

But as per MORT&H Table 1700.5 required target mean compressive strength = 25 + 11 = 36.00 N/mm²  where 11 is the current margin. Adopt this value those who are working in highway project.

4. APPROXIMATE AIR CONTENT

From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained) concrete is 1.0 percent for 20 mm nominal maximum size of aggregate.

5 SELECTION OF WATER-CEMENT RATIO

From Fig. 1 of IS 10262 -2019, the free water-cement ratio required for  the target strength  of  31.60 N /mm²  is 0.48 may be used for OPC 43 grade curve. (For other than MORT&H)

Maximum water cement ratio required for the target strength of 36.00 N /mm²(As per MORT&H requirement)  is 0.44  from figure 1 of IS 10262-2019.

My suggestion & experience , never adopt higher water cement ratio  because it is the main reason for cube failure at site. In IS code , suggestion has been given for adopting the water cement ratio but concrete designer has to take the decision what to keep water cement ratio.

Based on trial & experience adopted 0.44 water cement ratio.

 This is lower than the maximum value of 0.50 prescribed for from the Table 3 of IS 456 maximum Water Cement Ratio for moderate condition

As per MORT&H, maximum water cement ratio is 0.45 for moderate condition  so 0.44 is satisfying  all codal provision  whether it is  IS 456 or MORT&H

0.44 < 0.50 < 0.45 hence ok.

6. SELECTION OF WATER CONTENT

From Table 4 of IS 10262:2019, maximum water content for 20 mm aggregate = 186 liter (for 25 to 50 mm slump range)

but for an increase by about 3 percent for every additional 25 mm slump so here estimated water content for 125 mm slump

= 186+(9/100) x 186

= 202 liter.       

Based on trials with Super plasticizer water content reduction of 23.76 % has been achieved . How it comes ,

We will see the back calculation

(Water requirement , if  we intended to keep cement 350 kg  &  w/c ratio 0.44 for our concrete mix design  calculated water will be 154 liter ,  so required reduction in water when using superplaticizer  = 100 – (154/202 x 100) = 23.76 %.)

Net required water = 202 – (202 x 23.76) % = 202 – 48 = 154.0 litre

Note :For 75 mm slump increase 3% , for 100 mm increase 6% , increase 9 % for 125 mm slump, increase 12 % for 150 mm slump & increase 15 % for 175 mm slump

7 CALCULATION OF CEMENT CONTENT

As discuss earlier adopted  based on trial w/c Ratio = 0.44

Cement Content = 154/0.44 = 350 kg/m³

,from Table 5 of IS 456, minimum cement content for ‘moderate’ exposure conditions is 300 kg/m³  but taken  350 kg/m³ > 300 kg/m³ hence ok.

As per MORT&H 5th revision for moderate exposure  with reference to Table number 1700-2  maximum water cement ratio 0.45 & minimum cement 340 kg/m³ is specified but we had taken 350 kg/m³ , hence ok

but we had taken 350 kg/m³ > 340 kg/m³ hence ok. 

8 PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

As per table number 5 of IS 10262:2019 volume of coarse aggregate for 20 mm nominal size aggregate and fine aggregate (Zone III) for having water-cement ratio of 0.50 =0.64 (a)

20 mm aggregate and fine aggregate (Zone III) for having water-cement ratio of 0.50 =0.64 (a)

In the present case water-cement ratio is 0.44. Therefore. volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. the proportion of volume of coarse aggregate is increased by 0.012 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).

= (0.06/0.05) = 1.2 times of 0.01 so  0.01 x 1.2 = 0.012 (b)

=  a+b = 0.64 + 0.012 =0.65  (at the rate of -/+ 0.01 for every ± 0.05 change in w/c ratio).

Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 = 0.65

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate =0.65 x 0.9 =0.585 or say 0.59

Volume of fine aggregate content = 1 – 0.59 = 0.41

9 MIX CALCULATIONS

The mix calculations per unit volume of concrete shall be as follows:

a)Volume of concrete = 1 m³

b)Volume of the entrapped air in wet concrete =0.01m³ 

c) Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}

= 350/{3.15 x 1000} = 0.111 m³

d) Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}

= 154/{1 x 1000} = 0.154 m³

e) Base on trial we had kept admixture 50 percentage by weight of cement(You can increase % admixture dosage as per requirement)

 Volume of admixture  = [Mass of admixture ] / {[Specific Gravity of admixture ] x 1000}

= 1.75 /{1.090 x 1000}

= 0.0016 m³

f) Volume of all in aggregate = [(a-b)-(c+d+e)]

= [(1-0.01)-(0.111+0.154+0.0016)]= 0.99-0.250

= 0.723 m³

g) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000

= 0.723 x 0.59 x 2.795 x 1000

= 1192.26 kg/m³

h) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

= 0.723 x 0.41 x 2.517 x 1000

= 746.11 kg/m³

10  MIX proportion

Cement = 350 kg/m³

Water = 154 l/m³

Fine aggregate = 746.11 kg/m³

Coarse aggregate 20 mm = 1192.26 x 60 %= 715.36 kg/m³

Coarse aggregate 10 mm  = 1192.26 x 40 %= 476.90 kg/m³

Chemical admixture = 1.75 kg/m³ 

Water-cement ratio = 0.44

11 CALCULATION

1.Aggregate 20 mm  = 715.26/ (1+(0.41/100)}           = 712.0 kg

2. Aggregate 10 mm = 476.90/ (1+(0.59/100)}         = 474.0 kg       

3.Sand                            = 746.11/ (1+(1.87/100)}           = 732.0 kg

4.Water                        = 2444 – 350 – 1.75 -732 -712 – 474  = 174.25 kg 

Can  say 174 kg  alternatively can calculate in the following manner.

 154+(746.11-732.0) +(715.26-712) +(476.90-474) = 154 + 14.11 + 3.26 + 2.90 = 174.27  or say 174 kg

Note 1.Do the trial in dry position as in practical in batching plant you can cot use aggregate in SSD condition.

2.Do the number of trials with variation of ± 10 percent of water-cement ratio & different cement content,

3.Do the surface moisture correction whenever required.

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EMBANKMENT CONSTRUCTION METHODOLOGY

Embankment are the main part of the any  earth work .They are widely used, e.g. as embankment dams for reservoirs,  as road, railway and airport runway embankments in transportation but here we are discussing sequence wise working methodology for the earthwork in embankment for highway work.

  1. Scope of Work 
  1. Reference Documents. 
  1. Setting Out. 
  1. Selection of Material & Borrow areas. 
  1. Equipments. 
  1. Methods of Operation. 
  1. Quality Control. 
  1. Work Safety 
  1. Environmental Safety 

1.0 Scope of Work:

The work shall consist of Construction of embankment with approved and specified materials obtained from approved borrow areas or suitable material obtained from roadway excavation and drain excavation and in accordance with clause 305 of MORT&H specification.

2.0 Reference: 

Reference Documents:

  1. Ministry of Road Transport & Highway Specifications for Road & Bridges.5th Revision
  2. IRC SP-87
  3. Technical Specification
  4. Relevant contract drawings.
  5. IS 2720 Codes

3.0  Setting Out: 

After completion of site clearance, the limits of embankment shall be marked by fixing pegs on both sides at regular intervals. The chainage boards and working bench mark shall be set outside the limits of construction areas.

4.0  Selection of Material and Borrow areas: 

4.1  Material:                                

The material used in Embankment shall be soil, moorum, gravel, a mixture of these or any other material approved by the Engineer. It shall be free from logs, stumps, roots, rubbish & any other material detrimental to the stability of structure. The material for embankment shall be obtained from the approved source with preference to the material becoming available from nearby roadway excavation or any other excavation under the contract. The material requirements shall be in accordance with clause 305.2 of MORT&H.

4.2  Borrow Material:

Samples should be taken from the known borrow area & to be tested as per IS 2720 for the suitability in use in embankment as per project specification. On confirmation of the suitability material the area shall be properly demarcated and satisfy the clause 305.2.2.2

5.0  Equipments: 

The following equipments shall be carried out for the Embankment Construction. If desired the contractor shall demonstrate the efficacy of the type of equipment to be used, before commencement of work.

  1. Hydraulic Excavator
  2. Dozer
  3. Dumper (Tipper Trucks)
  4. Motor Grader
  5. Soil Compactor
  6. Water Tanker
  7. Tractor Trolleys
  8. Survey Kit / instrument

6.0  Method of Operation: 

  • After completion of site clearance, the limits of embankment shall be marked by fixing pegs at regular intervals before commencing the earthwork. Construction toe line shall be more than the design toe line for proper construction of the edges .
  • The original ground shall be levelled to facilitate placement of first layer of embankment, scarified, mixed with water and then compacted by rolling so as to achieve minimum dry density as specified in the modified Technical specification. Foundation treatment specified for embankments shall be carried out as per approved drawing. Unsuitable material occurring in embankment foundation shall be removed as per direction and approval of the Engineer and replaced by approved materials laid in layers and suitably compacted to the required and specified degree of compaction.  Excavation at approved borrow areas as per clause 305.2.2.2 shall be carried out with excavator and transportation of excavated material shall be done by dumpers/ tractor trolley.
  • Natural ground soil shall be tested for its suitability. If found unsuitable it shall be replaced with the permission of the Engineer.
  • Dry Density of natural ground soil shall be determined, and natural ground shall be tested for dry density, if found less than 95% of M.D.D., the original ground shall be scarified and mixed with the required quantity of water and then compacted by vibratory roller to achieve minimum specified dry density.
  • For construction adjacent to the existing embankment, a continuous horizontal benching 300 mm wide or as per drawing shall be provided in the existing embankment.
  • The embankment material shall then be spread in layers not exceeding 250 mm compacted thicknesses when using vibratory roller over the entire area with the dozer and finished by a motor grader. When the existing embankment to be widened continuous horizontal benches shall be cut out into the old slope to ensure adequate bond. Where water is required to be added the same shall be sprinkled from a water tanker fitted with sprinkler, uniformly on the surface but without flooding and shall be mixed thoroughly in soil by harrowing until uniform moisture content is obtained throughout the depth of the layer. If the material delivered to the roadbed is too wet, it shall be dried by aeration and exposure to the sun till the moisture content is accepted for compaction. At the time of compaction the moisture content should be in the range of +/- ½ of OMC.
  • The compaction shall be done with the help of Vibratory Roller of 8 – 10 Tonne static weight. Compaction trial shall be carried out on a suitable stretch to determine the no. of passes required for particular type of soil, dumped for embankment, to achieve densities specified in the table 300-2 of the Technical specification. Based on the trial actual compaction will be carried out with required no. of passes of Soil Compactor until the specified density is achieved. Rolling shall progress parallel to the center line of the road uniformly overlapping each preceding track by one-third width. Rolling shall be continued till the specified density is achieved as per table 300-2.  In case specific compaction is not achieved the material in the soft area shall be removed and replaced with approved material. Densities shall be tested by sand replacement method / nuclear density gauge.
  • Subsequent layers shall be placed only after the finished layer has been tested as per the clause 903.2.2 and accepted. The top levels of the embankment shall be checked with reference to the longitudinal and cross profile of the road as per drawing to keep the variation within tolerance limit as per table 900-1.
  • Different layers of embankment will be marked on pillars fixed outside the toe-line.

7.0 Quality Control:

Minimum compaction for embankment layers is 95% of modified proctor value.

8.0    Work Safety:                

8.1   During construction of widening works, adequate safety and traffic signs shall be installed adjacent to the road shoulders to protect the ongoing works as per location specific safety plan.

8.2   For locations where the dumping of embankment  materials by tippers are performed from the road shoulder, a minimum of 2 flagmen with reflective vests and holding a red  flag each be deployed to control the traffic which may be affected by the  unloading operation.

8.3 All locations adjacent to existing road where embankment construction is in progress shall be provided with safety and road signs.

8.4 No machines or equipment’s shall be permitted to remain on the existing road or shoulder unattended at all times unless it is properly protected and secured in a safe manner.   

8.5 The Safety Officer shall make frequent patrols along the highway to ensure that the safety equipment and signs are operational at all time.

8.9  Trucks sometimes fall over a tip head because the driver backs over the edge or the edge collapses under the weight of the truck. A protective berm or timber baulk should be used. Alternatively,  a signalman should be deployed in order to avoid this possibility.

8.10  When excavating trenches, place the excavated material at least 600 mm clear of the edge, where there is no danger of it falling back into or collapsing the side of the trench.

9.Environmental Safety: 

a.Nearby streams, water courses, lakes, reservoir shall be protected from contamination by the soil erosion from areas exposed during excavation by constructing temporary berms, dykes, sediment Basins, slopes, drains & by the use of temporary mulches, seeding or other control devices.

b.Vehicles tracks shall be kept moist to prevent flying of dust particles with the vehicle movement.

 

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Methodology For Clearing & Grubbing

Clearing means the removal of all vegetation, while grubbing is the removal of roots that may remain in the soil.
This includes the removal of all logs, brush, and debris, further as grinding and removal of stumps.

We can divide all work sequence wise into 8 sections and discuss one by one:

  1. Scope of Work 
  1. Reference 
  1. Preservation of Property / Amenities 
  1. Equipment 
  1. Method Statement 
  1. Disposal of Material 
  1. Work Safety 
  1. Environment Safety 
  1. Scope of Work

The work shall consist of cutting, excavation, removing and disposing of all materials such as trees of girth up to 300 mm, bushes, shrubs, stumps, roots, grass weeds, rubbish etc. and top soil up to 150mm declared unsuitable by the Engineer, including draining out stagnant water if any from the area of road land, drain, cross drainage structure and other area as specified in the drawing or instructed by Engineer. It shall include necessary excavation & back filling of the pits, by suitable soil, resulting from uprooting of trees & stumps and making the surface levelled by suitable equipment and compacted by the power roller to required compaction as per Clause 305.3.4 of the Technical specification.  The work also includes handling, salvaging and disposal of cleared material. Clearing and grubbing shall be done well before starting the   earthwork operation and in accordance with requirement of project specification.

2. Reference

Reference Documents:-

I) Ministry of Road Transport & Highway Specifications

II) Technical Specifications.

3. Preservation of Property / Amenities

Suitable safeguards shall be ensured with the approval of Engineer to protect the road side amenities, erosion & water pollution by the exposed surface of slopes & cut formed during the clearing & grubbing operations, shall be prevented through the use of berms, dykes, sediment basins, slope drains, grasses or other suitable devices as per Clause 201.2 of MORT&H.

4. Equipments

The following equipments shall be used to carry out the Clearing & Grubbing operation.

  1. Grader
  2. Excavator / J.C.B.
  3. Tipper / Tractor Trolley.
  4. Rollers
  5. Water tankers
  6. Survey Kit / Instrument
  7. Dozer with all attachments.
5.0 Method of Operation

5.1 The toe line shall be jointly (both by contractor & consultant) established, with reference to the alignment based on the levels taken earlier. The area for clearing & grubbing shall be jointly identified, covering areas of road embankment, drains, cross drainage structures and such other areas as specified.

5.1 a.  Enumeration of Trees girth more than 300 mm falling within the Toe line shall be prepared and got approved for measurement prior to cut. Modes of measurement shall be done according to clause 201.5.

5.2   Trees up to 300 mm in girth and stumps and roots shall be removed by the suitable equipment or by manual labour means.

5.3   The Grader / Excavator / Dozer shall be deployed to remove all shrubs, bushes, vegetation, grass, weeds, rubbish and top organic soil not exceeding 150 mm in thickness, which in the opinion of Engineer is unsuitable for  incorporation in the work.

5.4.  The above machines & tools shall be deployed to carry out the Clearing & Grubbing operation and the bushes, stumps falling with in the excavation and fill lines shall be cut to the depth below ground level that in no case these fall within 500 mm of the sub grade, also all vegetation and deleterious matters unsuitable for use in the embankment & sub -grade should be removed between fill lines .

5.5  All branches of the trees extending above the highway shall be trimmed.

5.6  All excavation below the general ground level done to remove the trees shall be filled with suitable approved material and compacted to the density as required by the contract specification.

5.7   The existing soil of natural ground shall be tested for its suitability. In the event of the material nonconforming to the MORT&H specifications, it shall be removed and replaced with the approved material & compacted with Vibratory Roller to achieve the required density of 95%. In case where ground level is less than 0.5 M required density shall be 97%.

5.8  OGL will be taken after clearing and grubbing and compaction.

 6.Disposal of the Materials

6.1   Materials collected from Clearing and Grubbing is disposed off to the specified places as per the Engineer’s instruction.

6.2   Stacking of cleared stumps, branches & boulders shall be done neatly at the approved location up to a lead of 1000 M.

7. Work Safety

Safety aids shall be mobilized in required number to take care of the workers & of the adjoining road users.

7.1     Minimum of two flagmen with reflective vests holding a red flag each shall be deployed to control the traffic which may be affected by clearing & grubbing operations.

7.2   All locations adjacent to the existing road where clearing & grubbing is progressing shall be provided with visible safety & road signs.

7.3   No machines or equipments shall be permitted to remain on the existing road or shoulder unattended at all times unless it is properly protected & secured in a safe manner.

7.4  The safety Officer shall make frequent patrols along the highway to ensure the safety of equipment & signs are operational at all time.

7.5  Borrow pits shall not be dug in the right-of-way of the road. Also it has to be ensured that the borrow area is being placed in the prescribed zone at the site and also ensure about the soil characteristics of the borrow area like slope, ground water level etc.

8.Environmental Safety

1.Deleterious matters detrimental to the environment shall be disposed off at the designated locations as per direction of the Engineer.

2.Vehicles tracks shall be kept moist to prevent flying of dust particles with the vehicle movement.

 

 

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QUALITY CONTROL ENGINEER INTERVIEW QUESTION & ANSWER

In this competitive market , facing interview is very difficult , if you’re trying to find employment that is expounded to Quality Control Engineer in highway project & you wish to organize for the 2020 highway project Quality Control Interview queries. it’s true that each interview is completely different as per the various job profiles. Here, we’ve got ready the necessary Quality Control Interview question and answers which is able to assist you get success in your interview.

In this article, we have a tendency to shall gift fifty two  most vital and often asked Interview question in big and reputed organization like L&T , Afcons & Tata consultancy etc. These interview can be in the following trend:

  • Q 1 . Tell me about yourself in brief ?
  • Ans: “Hello, my name is XYZ. I am a professional with a degree/diploma in Civil Engg in 20xx . My qualifications include xyz years of experience in infrastructure project especially in Highway Project & deals with quality control aspect.
  • I started my carrier with building project with XXX(Name of First company) as a Diploma / Degree Trainee Engineer and after that gone to YYY (Name of second company) as Quality Control Engineer ; after 2017 , I engaged in highway project and joined in ZZZ (Name of third company) & successfully completed one/two National /State highway project.
  • At present, I am responsible for Soil/Concrete/ GSB/Bituminous work & assisting my boss to doing concrete /GSB /CTB /Bituminous mix design.

Q 2. What is the name of your Material Engineer?

Ans : The name of my material Engineer is Mr xyz

Q 3. What is the minimum CBR of subgrade soil ?

Ans : As per IRC 58-2015 Clause 5.7.3.6 , a minimum CBR of 8 % is recommended for 500 mm of selected soil used as subgrade.

Q 4.What is code reference from which you are performing CBR test with 3 energy level as per MORTH 5 revision ?

Ans : AASHTO Designation: T 193-99 -2003

Q 5. What is the limit of Air Voids , flow & VFB in Dense Bituminous Macadam mix design ?

Ans : The limit of Air voids , flow & VFB is 3 -5% , 2- 4 mm & 65-75% simultaneously.

Q 6.How much staff is working under you , draw the organization chart & show your position ?

Ans : Total xyz staff is working under me is xyz , draw a diagram on your own & make practice.

Q 7.What should be the minimum required density of Subgrade soil as per MORT&H 5th revision ?

Ans : 17.5 KN/m³ or 1.78 gm /cc

Q 8 What is the softening point of VG 30 & VG40 grade bitumen ?

Ans : The softening point of VG30/VG 40 grade bitumen is 47 ºC / 50ºC

Q 9. What will be the maximum allowable size of granular material for subgrade soil as per MORT&H specification ?

Ans : Allowable size of granular material in subgrade is 50 mm

Q 10. What is the maximum Liquid Limit & Plasticity Index allowed in earth work in embankment/subgrade soil ?

Ans :Clay should have Liquid Limit less than 50 % & PI should always be less than 25 %.

Q 11. What is the frequency of taking core for BM/DBM/BC for checking of compaction & thickness of laid layer as per MORT&H 5th revision ?

Ans : One core at 700 m²

Q 12.What is the maximum Aggregate Impact Value of aggregate allowed for Bituminous concrete(BC) work in flexible pavement ?

Ans : AIV should not be more than 24%.

Q 13. What is the minimum cement content & maximum W/C ratio for M 25 RCC concrete for moderate condition as per MORT&H 5TH Revision ?

Ans : Minimum Cement Content 340 Kg & Maximum W/C ratio is 0.45

Q 14. What is the density frequency of compacted layer in Embankment & subgrade/Shoulder ?

Ans : 1 set of 10 test for 3000 m² of Embankment / 1 set of10 test for 2000 m² of Subgrade/Shoulder.

Q 15. What is difference between Specific Gravity & Density ?

Ans :Bulk density is the ratio between soil weight to the total volume of the soil  but Specific Gravity (G) is the ratio of the weight in air of a given volume of soil solids at a stated temperature to the weight in air of an equal volume of distilled water at that temperature . Specific gravity has no unit and it is generally used in design of concrete/bituminous mix.

Q 16. What is the maximum Aggregate Impact Value of aggregate for concrete work ?

Ans : 45%

Q 17 .What is the rate of spray of Prime Coat over WMM ?

Ans : 0.7 -1.0 kg/m²

Q 18.Which IS code specified the specification of aggregates ?

Ans : IS 383-2016

Q 19. How much Kinetic Viscosity of VG 40 bitumen is ?

Ans : The Kinematic Viscosity of VG 40 grade bitumen is 400 cst minimum at 135 º C.

Q 20. What is the dry density of WMM & GSB material in your project ?

Ans : The density of WMM/GSB in our project is 2.23 /2.24 gm/cc

Q 21.What is the minimum cement content & maximum W/C ratio for Pile concrete as per IRC 78 -2014 Cl 709.1.9 ?

Ans : Minimum amount of cement  content 400 kg/m³ & maximum W/C ratio is 0.40

Q 22.What will be the minimum cement content as per IRC SP 49 2014 for DLC mix design ?

Ans : 140 kg / m³

Q 23 .How many samples you take for 900 m² of DLC laying ?

Ans : 3 samples (9 Cubes)

Q2 4. What is the Nominal size of aggregate for grade 1 Bituminous Concrete?

Ans : 19 mm

Q 25.What is the maximum limit of FI+EI for Dense Bituminous Macadam as per MORT& H 5th revision ?

Ans: Maximum FI+EI limit is 35%

Q 26.What is setting time RS1 & SS1 Emulsion?

Ans: 15 to 30 minutes for RS1  & 24 hours for SS1  

Q 27. How many cube mould required for 110 m³ concrete ?

Ans: 4 +1+1=6 samples means 18 cubes as IS 456-2000

Q 28. As per MORT&H 5th revision how many grades of GSB are there?

Ans : Six grades are there.

Q 29. From which IS code  concrete mix design is being done ?

Ans: IS 10262 -2009 now the latest revision introduced IS 10262-2019

Q 30. On what temperature  Kinetic Viscosity test of any bitumen is being done ?

Ans = At 135 º C

Q 31. What is minimum bitumen content as per MORT&H 5th revision in DBM & BC for grade 1 mix ?

Ans : DBM 4.0 % & BC 5.2 % Minimum for the aggregate having specific gravity below 2.7.

Q 32. What is Compaction parameter of Bituminous Concrete ?

Ans : Relative density minimum 92% of Gmm of that day

Q 33. How much water can reduce the Superplasticizer ?

Ans : Practically more than 30 %

Q 34 What is the relation between Air Voids & Density ?

Ans : Air voids is inversely proportional to Density i.e If Air Voids are increasing density will be decreasing & reverse versa

Q 35.In tack coat which type of emulsion is used?

Ans : RS1

Q 36. What is the minimum rolling & laying temperature for VG grade 30 DBM/BC mix ?

Ans : Minimum laying temperature for laying is 140 º C & minimum rolling temperature is 90 º C.

Q 37.In prime coat what type emulsion is used as per MORT&H 5th revision in Indian condition ?

Ans : SS1

Q 38. What is the minimum sand equivalent value of crusher dust if to be used in Bituminous work ?

Ans : 50 %

Q 39.What does mean by VG 40 Bitumen ?

Ans : . Kinematic viscosity at 135º C, is 400 cSt, min.

Q 36. What is the minimum rolling & laying temperature for VG grade 30 DBM/BC mix ?

Ans : Minimum laying temperature for laying is 140 º C & minimum rolling temperature is 90ºC.

Q 37.In prime coat what type emulsion is used as per MORT&H 5th revision in India ?

Ans : SS1

Q 38. What is the minimum sand equivalent value of crusher dust if to be used in Bituminous work ?

Ans : 50 %

Q 39.What does mean by VG 40 Bitumen ?

Ans :  Kinematic viscosity at 135 º C, is 400 cSt, min

Q 45.Can you tell the name of IRC SP guide line for Quality System for road construction highway & Road bridge  ?

Ans: IRC SP 57 – 2000 but now latest revision with change the name also is IRC SP 112 -2017 & IRC SP 47-1998 for Road Bridge

Q 46. Which apparatus is used for softening point ?

Ans : Ring & ball apparatus

Q 47. What is the Rate of spread of Prime coat/Tack Coat ?

Ans: Three test per day

Q 48.Why you want to leave your present company?

1.I’d really love to be part of your project from beginning to end, and I know I’d have that opportunity here.

2. In my current role, I’ve learned many new skills. I’m looking for a position in which I can continue to grow that skill set in new circumstances.”.

3. I’ve learned a lot in my current role, but I’m looking for an opportunity that provides more challenges as I continue developing my skills and abilities.”

Q 49.Tell me your 5 strong point?

Ans: 1.Flexibility to handle any situation

2. Good Communication

3.Work under pressure

4.Dedication

5.Honesty

Q 50.Tell me your achievement in your carrier?

1.Re-organized something to make it work better

2.Identified a problem and solved it

3.Developed or implemented new procedures or systems

4.5.Worked on special projects

Received awards/Certificate

Q 51.What is your salary expectation?

Ans: This is your most important negotiation. Never lie about what you currently make, but feel free to include the estimated cost of all your fringes, which could well tack on 25 -30% more to your present “cash-only” salary.

Q 52.How much time you required to join ?

Ans: Always says one month but handle this situation very calmly. if you are ideal & have no job , can say within 7 days.

 

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Concrete Mix Design Of M35 Grade(Pile) as per IS 10262:2009

1.STIPULATIONS FOR PROPORTIONING

a) Grade designation : M35 RCC (Pile)

b) Type of cement :53 grade Ordinary Portland Cement conforming IS 12269

c) Maximum nominal size of coarse aggregate : 20 mm

d) Minimum amount of cement  : 400 kg/m³ as IS 2911-Part 1/Sec 2 & IRC 78-2014.

e) Maximum water-cement ratio : 0.40 as per IRC 78 -2014 ,Cl  709.1.9

f) Workability : 150-200 mm slump as per IRC 78-2014 , Cl  709.1.9

g) Exposure condition : Moderate (For Reinforced Concrete)

h) Method of concrete placing : Trieme

j) Degree of supervision : Good

k) Type of aggregate : Crushed Angular Aggregates

l) Chemical admixture type : Super Plasticizer Normet

2.TEST DATA FOR MATERIALS

a) Cement used : Sagar 53 grade Ordinary Portland cement conforming IS 12269

b) Specific gravity of cement : 3.14

c) Chemical admixture : Super Plasticizer conforming to IS 9103 

d) Specific gravity of

1) Coarse aggregate 20 mm : 2.799

2) Coarse aggregate 10 mm: 2.789

Combined Specific Gravity of aggregate ( 20 mm-45% & 10 mm 55% )=2.792

2) Fine aggregate : 2.517

e) Water absorption:

1) Coarse aggregate 20 mm : 0.41 %

2) Coarse aggregate 10 mm  : 0.59

3) Fine aggregate           : 1.87 %

f) Aggregate Impact Value : 20.52

g) Combined Flakiness & Elongation Index : 27.57 %

h) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383

2) Fine aggregate : Conforming to Grading Zone III of Table 4 of IS 383

3 TARGET STRENGTH FOR MIX PROPORTIONING

f’ck =fck + 1.65 s    where

f’ck = average target compressive strength of concrete at 28 days,

fck = characteristics compressive strength of concrete at 28 days,

S = standard deviation.From table 1 of  IS 456 & IS 10262  assumed Standard Deviation, s = 5 N/mm² ; therefore target strength of concrete = 35 + 1.65 x 5 = 43.25 N/mm². Can adopt  this value while doing the concrete mix design those who are working other than highway project.

But as per MORT&H Table 1700.5 required target mean compressive strength = 35 + 12 = 47.00 N/mm²  where 12 is the current margin. Adopt this value those who are working in highway project.

4 SELECTION OF WATER•CEMENT RATIO

Based on the trial , adopted water cement ration 0.40

From the Table 5 of IS 456 maximum Water Cement Ratio for moderate condition is 0.50

As per Section 709.1.9 of IRC 78, maximum water cement ratio is 0.40 

so 0.40 is satisfying  all codal provision  whether it is  IS 456 or MORT&H

0.40 < 0.50 = 0.40 hence ok.

 5 SELECTION OF WATER CONTENT

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)

but for an increase by about 3 percent for every additional 25 mm slump so here estimated water content for 175 mm slump

= 186+(15/100) x 186

= 213.9 or 214 liter.

Based on trials with Super plasticizer water content reduction of 21.50% has been achieved.How it comes , see below calculation:

Water requirement , if  we intended to keep cement 420 kg for &  w/c ratio 0.40 for our concrete mix design  calculated water will be 168.0 liter ,  so required reduction in water when using superplaticizer  = 100 – (168/214 x 100) = 21.50 %.

Net required water = 214 – (214 x 21.50) % = 214 –46.1 = 167.99 liter say 168 liter.

Note :For 75 mm slump increase 3% , for 100 mm increase 6% , increase 9 % for 125 mm slump, increase 12 % for 150 mm slump & increase 15 % for 175 mm slump

6 CALCULATION OF CEMENT CONTENT

As discuss earlier adopted  based on trial w/c Ratio = 0.40

Cement Content = 168.0/0.40 = 420 kg/m³

As per IS 2911-Part 1/Sec 2 minimum cement content for tremie concrete is 400 kg/m³.

(As per Section 709.1.9 of IRC 78 – 2014 minimum cement content  400 kg & maximum water cement ratio is 0.40 specified)

but we had taken 420 kg/m³ > 400 kg/m³ hence ok.

7 PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

As per table number 3 of IS 10262:2009 volume of coarse aggregate for 20 mm nominal size aggregate and fine aggregate (Zone III) for having water-cement ratio of 0.50 =0.64 (a)

In the present case water-cement ratio is 0.40. Therefore. volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio). As the water-cement ratio is lower by 0.10. The proportion of volume of coarse aggregate is increased by

= (0.10/0.05) = 2.0 times of 0.01 so  0.01 x 2.0= 0.020 (b)

=  a+b = 0.64 + 0.020 =0.66

(at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).

Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.40 = 0.66

NOTE – In case the coarse aggregate is not angular one, then also volume of coarse

aggregate may be required to be increased suitably based on experience & Site conditions.

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate =0.66 x 0.9 =0.59.

Volume of fine aggregate content = 1 – 0.59 = 0.41.

8 MIX CALCULATIONS

The mix calculations per unit volume of concrete shall be as follows:

a) Volume of concrete = 1 m³

b) Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}

= 420/{3.15 x 1000} = 0.133 m³

c) Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}

= 168.0/{1 x 1000} = 0.168 m³

d) Base on trial we had kept admixture 1.0 percentage by weight of cement

 Volume of admixture  = [Mass of admixture ] / {[Specific Gravity of admixture ] x 1000}

= 4.2 /{1.090 x 1000}

= 0.0039 m³

e) Volume of all in aggregate = [a-(b+c+d)]

= [1-(0.133+0.168+0.0039)]

= 0.695 m³

f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of  coarse Aggregate x 1000

= 0.695 x 0.59 x 2.792 x 1000

= 1144.86 kg/m³

g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

= 0.695 x 0.41 x 2.517 x 1000

= 724.22 kg/m³

9 MIX PROPORTIONS

Cement = 420 kg/m³

Water = 168.0 l/m³

Fine aggregate = 724.22 kg/m³

Coarse aggregate 20 mm = 1144.86 x 45 %= 515.19 kg/m³

Coarse aggregate 10 mm  = 1144.86 x 55%= 629.67 kg/m³

Chemical admixture = 4.2 kg/m³ 

Water-cement ratio = 0.40

Calculation :

1. Aggregate 20 mm= 515.99/ (1+(0.41/100)}      = 514.0 kg

2. Aggregate 10 mm = 629.67/ (1+(0.59/100)}    = 725 kg  

3. Sand                           = 724.44/ (1+(1.87/100)}    = 626.0 kg

3. Water                         =  2460-420-711-514-626  = 189          

NOTE 

1.Do the trial in dry position as in practical in batching plant you can cot use aggregate in SSD condition.

2.Batch for trial is given in dry position.

3.Do the number of rials with variation of ± 10 percent of water-cement ratio & different cement content

4.Do the surface moisture correction whenever required.

 

 

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Concrete Mix Design for M25 grade as per IS 10262:2009

1.STIPULATIONS FOR PROPORTIONING

a) Grade designation : M25 RCC

b) Type of cement :53 grade Ordinary Portland Cement conforming IS 12269

c) Maximum nominal size of coarse aggregate : 20 mm

d) Minimum amount of cement  : 300 kg/m³ as per IS 456:2000

e) Maximum water-cement ratio : 0.50 as per Table 5 of IS 456:2000

f) Workability : 100 – 125 mm slump

g) Exposure condition : Moderate (For Reinforced Concrete)

h) Method of concrete placing : Pumping

j) Degree of supervision : Good

k) Type of aggregate : Crushed Angular Aggregates

l) Chemical admixture type : Super Plasticizer Normet

2.TEST DATA FOR MATERIALS

a) Cement used : Sagar 53 grade Ordinary Portland cement conforming IS 12269.

b) Specific gravity of cement :3. 15

c) Chemical admixture : Super Plasticizer conforming to IS 9103.

d) Specific gravity of

1) Coarse aggregate 20 mm : 2.799

2) Coarse aggregate 10 mm: 2.789

3) Combined Specific Gravity of aggregate

( 20 mm-45% & 10 mm -55% )=2.792.

4) Fine aggregate : 2.517

e) Water absorption:

1) Coarse aggregate 20 mm : 0.41 %

2) Coarse aggregate 10 mm  : 0.59 %

3) Fine aggregate                      : 1.87 %

f) Aggregate Impact Value : 20.52 %

g) Combined Flakiness & Elongation Index : 27.57 %

h) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383

2) Fine aggregate : Conforming to Grading Zone III of Table 4 of IS 383

3 TARGET STRENGTH FOR MIX PROPORTIONING

f’ck =fck + 1.65 s

where

f’ck = average target compressive strength of concrete at 28 days,

fck = characteristics compressive strength of concrete at 28 days, and

s = standard deviation.

From table 1 of  IS 10262 assumed Standard Deviation, s = 4 N/N/mm². Therefore, target strength of concrete = 25 + 1.65 x 4 = 31.6 N/mm².

But as per MORT&H 5th revision Table 1700.5 required target mean compressive strength = 25 + 11 = 36.00 N/mm²  where 11 is the current margin.

4 SELECTION OF WATER•CEMENT RATIO

Based on the trial , adopted water cement ratio 0.38

From the Table 5 of IS 456 maximum Water Cement Ratio is 0.50

0.38 < 0.50 Hence ok.

As per MORT&H 5th revision Maximum Water Cement Ratio water cement ratio for moderate exposure is 0.45 , hence it is ok

 5. SELECTION OF WATER CONTENT

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 liter for 25 to 50 mm slump range but for an increase by about 3 percent for every additional 25 mm slump so here estimated water content for 125 mm slump = 186+(9/100) x 186 = 202 liter.

Water requirement if we are considering cement 360 kg & w/c ratio o.38 for concrete mix design ; calculated water will be  136.8 so net  reduction in water while using super plasticizer = 100 – (136.8/202 x 100) = 32.28 %.

Now we had got  reduction percentage of water , calculate of the required water = 202 – (202 x 32.28) % = 202 – 65.20 = 136.80 (For 75 mm slump increase 3% , for 100 mm increase 6% & increase 9 % for 125 mm slump) 

6. CALCULATION OF CEMENT CONTENT

Adopted w/c Ratio = 0.38   then Cement Content = 136.80/0.38 = 360 kg/m³ ,from Table 5 of IS 456, minimum cement content for ‘moderate’ exposure conditions is 300 kg/m³  but taken  360 kg/m³ > 300 kg/m³ hence ok.

As per MORT&H 5th revision for moderate exposure  with reference to Table number 1700-2  maximum water cement ratio 0.45 & minimum cement 340 kg/m³ is specified but we had taken 360 kg/m³ , hence ok

7. CALCULATION OF COARSE AGGREGATE AND FINE AGGREGATE PROPORTION

From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone III) for water-cement ratio of 0.50 =0.64 (a)

In the present case water-cement ratio is 0.38 therefore, volume of coarse aggregate is required to be increased to decrease the fine  aggregate content.

As the water cement ratio is lower by 0.12 , the proportion of volume of  coarse aggregate  is increased by= (0.12/0.05) = 2.4 times of 0.01 ,so  0.01 x 2.4= 0.024 (b)

Net required water cement ratio= a+b = 0.64 + 0.024 =0.66(at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.38 = 0.66

NOTE – In case the coarse aggregate is not angular one, then also volume of coarse aggregate may be required to be increased suitably based on experience & Site conditions.

If we are doing concrete with pump , reduce upto 10% these value ,therefore volume of coarse aggregate =0.66 x 0.9 =0.59.

Actual reduced volume of fine aggregate content = 1 – 0.59 = 0.41.

8. MIX CALCULATIONS

Determination of mix calculation will be as under:

a)Volume of concrete = 1 m³

b)Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}  = 360/{3.15 x 1000} = 0.115 m³

c)Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}

= 136.80/{1 x 1000} = 0.136 m³

d) Base on trial we had kept admixture 0.45 percentage by weight of cement

 Volume of admixture  =  [Mass of admixture ] / {[Specific Gravity of admixture ] x 1000}

= 1.62 /{1.090 x 1000} = 0.00149 m³

e)Volume of all in aggregate = [a-(b+c+d)]

= [1-(0.115+0.134+0.00149)] = 0.750 m³

f)Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000

= 0.750 x 0.59 x 2.792 x 1000 = 1235.46 kg/m³

g)Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

= 0.750 x 0.41 x 2.517 x 1000 = 773.98 kg/m³

9. MIX PROPORTIONS

Cement = 360 kg/m³

Water = 136.80 l/m³

Fine aggregate = 834 kg/m³

Coarse aggregate 20 mm = 1235.46 x 45 %= 555.96 kg/m³

Coarse aggregate 12 mm  = 1235.46 x 55%= 679.50 kg/m³

Chemical admixture = 1.62 kg/m³ 

Water-cement ratio = 0.38

   

1.Aggregate 20 mm  = 555.96/ (1+(0.41/100)}                     = 554.0 kg

2. Aggregate 10 mm = 679.50/ (1+(0.59/100)}                   = 676.0 kg

3.Sand                            = 834.0/ (1+(1.87/100)}                      = 819.0 kg

4.Water                         = 2568 -360 – 819 -554 – 676      = 160.0 kg       

NOTE

1.Do the trial in dry position as in practical in batching plant you can cot use aggregate in SSD condition.

2.Batch for trial is given in dry position.

3.Do the number of rials with variation of ± 10 percent of water-cement ratio & different cement content

4.Do the surface moisture correction whenever required.

 

 

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DETERMINATION OF RESIDUE BY EVAPORATION OF EMULSION AS PER IS 8887:2018

SCOPE:  This Indian standard covers the physical and chemical requirements of cationic bitumen emulsion for application in  road works.

APPARATUS

a. Glass Beakers :1 000 ml capacity .

b. Glass Rods : Polished 6.5 ± 0.5 mm in diameter and 175 ± 0.5 mm in length.

 c.Balance :500 g capacity accurate to 0.1 g. 

d.Oven :Thermostatically controlled at a temperature of 163 ± 2.8°C.

 PROCEDURE

1.Take 3 beaker & glass rod & weigh them with the glass rod. This will be in grams(B).

2.Now take 50 ± 0.1 g of well mixed emulsion into each of the 3 beakers as stated above .

3.Now keep this  beaker along with the glass rod in the oven at 163 ± 2.8°C for 2 hours.

4.After completing two hours , taken out all three beaker  and stir them thoroughly.

5.Keep all three beaker with glass rod for another 1 hour then withdraw from oven and let them cool at room temperature’

6.Now weigh each beakers along with the rods & residue. This will be in grams(A)

CALCULATION

Residue, percent = 2 (A – B)

where, A = mass of beaker, rod and residue, in g; and B = tare mass of beaker and rod, in g.

For the accuracy of the result take the average of them in %.

TESTS ON RESIDUE

From this emulsion residue we can perform the following test:

1.Penetration Determination accordance with IS 1203.

2.Ductility Determination according with IS 1208

3.Determination of Solubility in Trichloroethylene with IS 1216

 

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EMULSION STABILITY TO MIXING WITH CEMENT AS PER IS 8887 : 2018

Scope:  This Indian standard covers the physical and chemical requirements of cationic bitumen emulsion for application in  road works.

Apparatus

a.Sieve :A 1.40 mm IS Sieve approximately 100 mm in diameter and 40 mm in height and 150 micron IS Sieve approximately 200 mm in diameter.

b.Metal Dish : Round-bottomed about 500-ml capacity.

c.Steel Rod : A steel rod with rounded ends 13 mm in diameter.

d.Balance : 250 gram capacity with least count 0.1 g.

e.Cylinder : Graduated Cylinder of 100 ml capacity.

f.Pan :Shallow Pan of 100-mm diameter and of about 50-ml capacity.

g.Oven : A well-ventilated oven controlled at 110°C.

 Procedure:

1.Water content in testing emulsion shall be 50% if not ; add necessary extra water .

2.Now screen the cement through 150 micron IS Sieve and take 50 gram weigh  into the metal dish. Weigh the 1.40 mm IS Sieve and shallow pan to nearest 0.1 (W1).

3.Add 100-ml of emulsion to the cement in the dish and stir the mixture at once with the steel rod with a circular motion making about 60 revolution per minute.

4.At the end of the one minute mixing period add 150 ml freshly boiled distilled water at room temperature and continue stirring for 3 min.

5.During mixing keep temperature of approximately 25°C . Pour the mixture through the weighed 1.40 mm IS Sieve and rinse with distilled water.

6.Place the sieve in weighed pan, heat in the oven at 110°C until dry and weigh to nearest 0.1 g (W2).

Calculation :

Coagulation value = ( W2-W1) /W3X 100

 where, W1 = mass, in g, of weighed sieve and pan;

W2 = mass, in g, of sieve and pan and the material retained on them; and

W3 = mass, in g, of binder in 100 ml of diluted emulsion determined according to Annex J of IS 8887:2018

Report : Report the coagulation value as percentage the nearest whole number.

 Precision : If we perform duplicate test; result should not be differ by the following :

 a.Cement Mixing Mass Percent          0 to 2  

b.Percent Repeatability Mass                  0.2

c. Percent Reproducibility Mass             0.4

 

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ABSOLUTE VISCOSITY OF BITUMEN AS PER IS 1206 PART II

Scope

This standard (part II) covers the method for the determination of absolute viscosity of bitumens and cut-backs by vacuum capillary viscometers at any specified temperature. It is applicable to materials having a viscosity range of 42 to 200 000 Poises.

APPARATUS

a.Viscometer  – Cannon-Manning Vacuums Viscometer

b.Thermometer – The thermometer shall be of mercury in glass tube with cylindrical bulbs and made of suitable thermometer glass and shall conform to the following requirements:

c.Bath – A suitable bath for immersion of the viscometer so that the liquid reservoir or top of the capillary, whichever is uppermost is at least 20 mm below the upper bath level. The accuracy of the viscometer bath should be ± 0.1°C over the entire length of the viscometer

d.Vacuum System – A vacuum system capable of maintaining a vacuum to within ± 0.05 Cm of the desired level up to & 30 cm of mercury. The glass tubing of 6.35 mm diameter and all glass joints should be completely airtight and no loss of vacuum should be permitted till the experiment is on. A vacuum or aspirator pump is suitable for the vacuum source.

e.Timing Device – A stop watch or stop clock capable of being read up to half a second.

f.Oil  for Bath :  Silicon oil  

procedure

1.Preparation of the Sample – Heat the sample to a temperature not more than 60°C for the tars and pitches and not more than 90°C for bitumens above their softening point . Take about 20 gm of sample into a  container and maintain the temperature of 135 ± 5.5°C stirring in water bath or in thin film oven to allow the entrapped air to escape.

2. Charging of  viscometer -Charge the viscometer by pouring the prepared sample to within ± 2 mm of flll line E. Place the charged viscometer in an oven or bath maintained at 135 ± 5.5°C for a period of 10 ± 2 min to allow large air bubbles to escape.

3.Testing – Maintain the temperature of bath 60˚C ± 0.1°C & keep the charged viscometer vertical in position  into the water. Establish a vacuum of 30 ± 0.05 cm of mercury in the vacuum system and connect it to the viscometer with the valve closed. After the completion of  30 ± 5 min kept in bath , open the valve and allow the asphalt to flow into the viscometer. Measure to within ± 0.5 s the time required for the leading edge of the meniscus to pass between successive pairs of timing marks.

4.Test Completion – After the  completion of the test, remove the viscometer from the bath and place it in an inverted position in an oven maintained at 135 ± 5°C to drained off thoroughly from the viscometer. Clean by rinsing several times with benzine completely.

Calculation

Calculate the viscosity by the following equation:

Viscosity in  Poises = Kt

where K= calibration factor, in poise per second; and t = flow time, in seconds.

Always report the test temperature and vacuum with the viscosity test results. For example, viscosity at 60°C, 30 cm Hg Vacuum in poises.

PRECISION

The second test results of sample should not differ by more than the following:

1. Repeatability 7 % of their mean 

2. Reproducibility 10 % of their mean

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