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 Quality Control Manual

CHAPTER - XII

IMPORTANT SPECIFICATIONS

EARTH WORK

(IS CODES : 2720, 4701, 8237, 9481, 4081, 1200 and 9451)

The procedures to be adopted while doing earth work excavation for various jobs and the precautions to be taken are prescribed in the IS specified above. The important Do's and Don'ts are given below for ready reference.

A) EXCAVATION OF CANALS

DO'S

DO NOTS

1. Fixup the centreline and set the curves correctly.

1. Do not avoid approval of the deviation statement.


2. Avoid over break and loosening of canal

3. .Do not mixup usefull soils with other soil of cutting.

 

2. take working leves, real variation in ground levels and classification of soils.

3. Get top soil vegetation etc., removed

4. Form spoil bank as per drawing and away from the side drain with suitable gaps for drainage into the valley.  
5. Form Dowel Bank, as per drawing .  
6. Form Inspection path to a uniform longitudinal gradient and with gentle transvrse slope towards drains.  
7. Compact over excavation/ breakage portion with suitable soils. gravel, spalls.  
8. Provide CNS treatment in expansive black cotton soils.  

DO'S

DO NOTS

B) FORMATION OF EMBANKMENTS

1. Get the top spoil, vegetation and sand patches removed to complete depth.

1. Soil required for embankment to be obtained from borrow area should be got tested for proctor density & O.M.C. before start of work.

2. Do not raise the bank in piecemeal.

2. Scarify the ground and wet properly.

3. Do not allow new layer without scarification and wetting of old layer.

DO'S

DO NOTS

3. Obtain Proctor density OMC for the useful soils and borrow soils.

4. Do not allow new layer unless the old layer compacted up to required density.

5. Don't leave any loose layer un-rolled at the end of the day in rainy season.

4. Raise embankment to full width with uniform horizontal layer of 15 cm to 22.5 cm thickness.

6. Don't allow compacted layer to be more than 150mm.

5. Break clods, remove roots, big boulders other materials etc. larger than 75mm form the soils used in embankment.

7. No new layer to be laid unless the over moistured layer is either completely removed or allowed to dry.

6. Supplement deficit moisture whenever required.

8. Don't dump soils in heaps

7. Compaction with 8 to 10 tones power roller or Fuel - operated vibratory plate compactors.

9. Don't dump the soils in water and slush.

8. Conduct field compaction tests and determine compaction efficiency.

11. Do not forget to provide settlement allowance of 2 cm/mtr. Height of bank.

9. Check embankment profiles periodically.


SPECIFICATIONS OF PLAIN AND REINFORCED CONCRETE

1. Proportioning & batching:

Design mix concrete (controlled concrete) shall be used for concrete of grade M10 and higher. Nominal mix concrete (as per table) may be used for lean concrete mix (viz. concrete mix of grade lower than M10 viz. M5, M7.5). In proportioning concrete, the quantity of both cement and aggregate shall be determined by mass. Water shall be either measured by volume in calibrated tanks or weighed. Concrete shall be manufactured in mechanical mixers either in batching mixing plants or mechanical mixers of various capacities (14/10 or 10/7). Alternatively, mobile self-loading weight batching-mixing and transporting mixers of suitable drum capacity, can be used, both for mixing and transporting concrete. The mix proportions shall be such as to ensure the workability of the fresh concrete and when concrete is hardened, it shall have the required strength, durability, and surface finish.

Proportions for Nominal Mix Concrete

Grade of concrete

Total quantity of dry aggregates by mass per 50 kg. of cement to be taken as the sum of the individual masses of fine and coarse aggregate (kg.)

Proportion of fine aggregate to coarse aggregate (by mass)

1

2

3

M5

800

Generally 1:2 but subject to an upper limit of 1:1.5 and a lower limit of 1:2.5

M7.5

625

M10

480

Notes:

i) Graded aggregates shall be used.

ii) Water cement ratio should be as per mix design.

2. Design Mix concrete:

The mix shall be designed to produce the grade of concrete having the required workability and characteristics strength not less than appropriate values given below:

Grade of Designation of concrete

Specified characteristic compressive Strength of 150mm cube at 28 days in N/mm2

M10

10

M15

15

M20

20

M25

25

The concrete mix shall be designed for the `target mean strength'. The target mean strength of concrete mix should be equal to characteristic strength plus 1.65 times the standard deviation.

Where sufficient test results for a particular grade of concrete are not available, the value of standard deviation given below shall be assumed for design mix of concrete in the first instance. As soon as the results of samples are available, actual standard deviation shall be used and the mix designed accordingly.

Assumed standard deviation (as per IS : 456 - 2000)

Grade of concrete

Assumed standard deviation

M10

3.5

M15

3.5

M20

4.0

M25

4.0

Water cement ratio(W/C):

Water cement ratio is one of the key elements for a durable and sound concrete of adequate strength. Accordingly, Water cement ratio shall be maintained at correct value. The water contents in both fine and coarse aggregate shall be determined regularly. The amount of added water shall be adjusted to compensate for any observed variation in moisture content. The amount of surface water may be estimated from the following table in the absence of exact data:

S.No.

Aggregate

Approx. quantity of surface water

% by mass

Litre/m3

1.

Very wet sand

7.5

120

2.

Moderately wet sand

5.0

80

3.

Moist sand

2.5

40

4.

Moist sand/crushed rock

1.25 to 2.5

20 to 40

Durability of concrete:

It is essential that the concrete be durable viz., it should perform satisfactory in the working environment during its anticipated exposure conditions during service. The materials and mix proportions are to be such as to maintain its integrity, and (where ever applicable), to protect embedded metal/reinforcement from corrosion.

The different environmental exposure conditions are given below:

Environmental exposure conditions(as per Table 3 of IS 456 : 2000)

S. No.

Environment

Exposure condition

1.

Mild

Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal area.

2.

Moderate

           Concrete surfaces sheltered from severe rain or freezing whilst wet.

           Concrete exposed to condensation and rain.

           Concrete continuously under water.

           Concrete in contact or buried under non-aggressive soil/ground water.

           Concrete surfaces sheltered from saturated salt air in coastal area.

3.

Severe

           Concrete surfaces exposed to severe rain, alternate wetting and drying, or occasional freezing whilst wet or severe condensation.

           Concrete completely immersed in sea water.

           Concrete exposed to coastal environment.

4.

Very Severe

           Concrete surfaces exposed to sea water spray, corrosive fumes or severe freezing conditions whilst wet.

           Concrete in contact with or buried under aggressive subsoil/ground water; concrete exposed to alternate wetting & drying.

5.

Extreme

           Surface of members in tidal zone.

           Members in direct contact with liquid/solid aggressive chemicals.

The severity level in the RWSRP works may be assumed moderate to severe only, except in such environment which is associated with corrosive fumes or where the concrete work is to be in contact with or buried under aggressive sub-soil/ground water.

Workability of concrete:

The concrete mix proportions chosen shall be such that the concrete is of adequate workability for the placing conditions of the concrete and can be properly compacted. Slump for good workability of concrete shall be as per mix design / as per IS code 456 - 2000

Mixing :

Concrete ingredients shall be mixed thoroughly in the mechanical mixer and the mixing shall be continued until there is a uniform distribution of the ingredients and the mass is uniform in colour and consistency. Minimum mixing time shall be 2 minutes or as determined by the Engineer-incharge. The accuracy of the measuring equipment shall be within + 2 percent of the quantity of cement being measured and within + 3 percent of the quantity of aggregate and water being measured.

Transporting :

Concrete shall be transported from the mixer to the form work/site of placement as quickly as possible by methods, which shall prevent the segregation and maintain the requisite workability. Transportation of concrete in ordinary open tippers or trucks shall not be allowed as it causes segregation. Transit concrete mixers can be used for transportation. Self loading, batching, mixing & transporting mixers can also be used both for mixing and transporting concrete.

Placing:

The concrete shall be placed and compacted with vibrators (Immersion/needle) and plate vibrators in case of lining before initial setting of concrete commences and shall not be subsequently disturbed. Methods of placing shall be such as to avoid segregation. Strict and meticulous care shall be taken to avoid displacement of reinforcement or movement of form work and concrete. Concrete shall be fully worked around reinforcement and in the corners of form work. Over vibration resulting into bleeding of concrete shall be strictly avoided. Spare vibrator shall be kept by the contractors as stand by. Temperature of concrete, as placed, shall preferably be restricted to about 32 Degree C (90DegreeF)

Curing :

Curing shall commence as soon as possible after concrete is placed and initial set has occurred but before it has hardened. Curing with water shall be continued for at least 14 days. Exposed surfaces of concrete shall be kept continuously in a damp/wet condition by pounding or by covering with a layer of sacking, canvas, hessian, or similar materials and kept continuously wet for 14 days.

Sampling and strength of designed mix concrete:

Sampling of concrete:

A random sampling procedure shall be adopted to ensure that each concrete batch shall have a reasonable chance of being tested, viz. the sampling should be spread over the entire period of concreting and cover all mixing units (concrete production units).

Frequency of sampling:

The minimum frequency of sampling of concrete of each grade shall be in accordance with the following:

 

Quantity of concrete in the work, m3

Number of samples

Remarks

Upto 50 cum.

One set of 3 samples

 

51 and above

One additional set of 3 sample for each additional 50 m3 or part thereof.

 

At least one sample shall be taken from each shift.

Test specimen:

Three test specimens shall be made for each sample for testing at 28 days. Additional specimens may be taken to determine the strength of concrete at 7 days. Test results of the sample shall be the average of the strength of 3 specimens. The individual variation should not be more than + 15% of the average strength of 3 specimens. If more, the test results of the sample are considered invalid.

Acceptance criteria of compressive strength:

The concrete shall be deemed to comply with the strength requirement when both the following conditions are met, as per IS: 456-2000:

(a) The mean strength determined from any group of 4 non-overlapping consecutive test results complied with the appropriate limits in columns 2 of the following table.

(b) Any individual test results complied with the appropriate limits in column 3 of the following table.

Table

Characteristics compressive strength compliance requirements

Specified grade

Mean of the group of 4 non-overlaping consecutive test results in N/mm2

Individual test results in N/mm2

M15

> fck + 0.825 x established standard deviation (rounded off to nearest 0.5N/mm2)
Or
fck + 3 N/mm2 whichever is greater

> fck - 3 N/mm2

M20 or above

> fck + 0.825 x established standard deviation (rounded off to nearest 0.5N/mm2)
Or
fck + 4 N/mm2 whichever is greater

> fck - 4 N/mm2

In the absence of established value of standard deviation the following value may be assumed in the first instance and there after established values based on the requisite number of test results.

Grade of concrete

Assumed standard devotion

M10 and M15

3.5N/mm2

M20 and M25

4.0N/mm2

fck = Characteristic compressive strength of 150mm cube at 28 days in N/mm2. For M15 & M20 grades, fck is 15N/mm2 and 20N/mm2 respectively.

For M10 concrete, fck is 10N/mm2. In respect of CC lining with a minimum cement level of 250 Kg./m3, minimum fck envisaged is 13.5N/mm2. Based on the assumed standard of deviation values of 2N/mm2 and 2.5N/mm2 for M10 and M13.5 respectively their acceptance criteria of compressive strength can envisaged as;

 

Specified grade

Mean of the group of 4 non-overlaping consecutive test results in N/mm2

Individual test results in N/mm2

M10

> fck + 0.825 x established standard deviation

> fck - 2 N/mm2

M13.5 (CC lining with minimum cement level of 250 Kg/m3)

> fck + 0.825 x established standard deviation

> fck - 4 N/mm2

Note : The minimum cement level of 250kg/m3 for plain cement concrete lining is from the durability consideration and not on the 28 day characteristic strength basis alone.

Standard Deviation : IT is calculated from the following equation:

   

 

N= No. of samples (30 samples are generally considered)

`X = Sum of the mean value of 3 test specimens of each sample divided by the number of samples, viz. overall average strength.

X = Difference between overall average strength and the mean strength of 3 test specimen of each sample.

 

CONCRETE

(IS CODES 383, 269, 2116, 2386, 456, 516, 1199, 3878, 9103)

CONSTRUCTION JOINTS & TECHNIQUE OF GREEN CUTTING:

 

CONSTRUCITON JOINTS:

Concrete shall be placed in massive structures in lifts, which are generally 1.5 m high. To develop proper bond between the lifts, the concrete surface shall be freed of all laitance, coating stains, defective concrete and all foreign material and the surface shall be roughened. This can be achieved by green-cutting. For lining work the construction joint where ever required is to be adopted as per the sketch in Annexure-III.

 

GREEN CUTTING:

The surface of the joint shall be thoroughly green-cut with an air-water jet. Green cutting is usually done 8 to 12 hours after the top surface of a concrete lift has been completed and sufficiently hardened. The actual time for taking up the green cutting operation shall depend upon the following factors:

a) Concrete placement temperature:

b) Atmospheric temperature

c) Concrete mix; and

d) Slump

The air-water jet will remove the thin surface film of laitance and grout to expose clean surface.

 

GREEN CUTTING, IF DONE AT THE PROPER TIME, SHALL YIELD VERY GOOD RESULTS:

When started too early, it shall result in over-cutting and removing too much mortar. It is also liable to loosen the aggregate particle and leaving too poor a surface to bind the fresh concrete. On the other hand, if green-cutting is delayed too long, the cutting action of the air and water jet would be ineffective for proper removal of laitance. It, therefore requires much greater care and judgement for proper use at the proper time.

 

SKILL OF JET OPERATOR

Besides determining the proper time for initiating green-cutting, the process will require constant attention on the part of the air-water jet operator. By correct manipulation of the high velocity air-water jet, a trained operator can ensure the removal of the thin surface film of laitance and grout effectively and at the same time leaving the aggregate stones, already embedded in the mortar, undisturbed.

 

PROPER AIR-WATER GUN

In addition to the skill of the jet operator, a proper air-water gun is also a vital requirement for effective green - cutting. The issuing nozzle must be about 460 mm(18 inches) long to ensure the requisite cutting force close to the concrete surface. A dimensioned sketch of an air-water gun is enclosed as Annexure -VI.

 

QUANTUM OF COMPRESSED AIR AND WATER:

for effective green-cutting, it is essential that the air pressure should be around 6.33 to 7.03 kg/cm2 (90 to 100 lbs. Per square inch.) It should not be allowed to fall below 90 lbs. per square inch. The water pressure, of course, should be sufficient to bring the water into effective influence of the air pressure. As an approximate estimate, the quantity of compressed air required by the green-cutting gun is 2 cubic meters per minute (70 cfm) and the quantity of water 60 gallons (273 liters) per minute

 

SAND BLASTING:

Sand blasting is the process of roughening and cleaning the surface of old and set concrete by means of coarse sand and air applied under pressure of 90 to 100 pounds per square inch (6.33 to 7.03 kilograms per square centimeter) through a nozzle, so as to erode the laitance and grout from the old and fresh concretes monolithic. Sand blasting of rock is also done so that concrete may be placed on or against a clean surface as required according to specifications.

There are two types of sand blasting, namely "wet sand blasting" and "dry sand blasting". In wet sand blasting water is also used along with sand and air under pressure, while in the latter, only sand and air under pressure are used. Normally the concrete and rock surface etc., are wet sand blasted to keep down the dust.

The percentage of different sizes of sand particles for efficient sand blasting shall be as follows:

 

Size

Percentage

8 mesh per inch (25.40 millimeters)...

26

16 mesh per inch (25.40 millimeters)...

30

30 mesh per inch (25.40 millimeters)...

23

50 mesh per inch (25.40 millimeters)...

21

For effective sand blasting it is essential that pressure of air should be between 90 to 100 pounds per square inch (6.33 to 7.03 kilograms per square centimeter). If pressure falls below 90 pounds per square inch (6.33 kilograms per square centimeter), sand blasting becomes in effective. If sand having large percentage of fines is used, it will not provide the requisite cutting power and the whole effort goes waste. A good quality well graded "sand -blast-sand" is needed for achieving the objective of sand blasting.


A) FOR FOUNDATION: (CONCRETE WORK) 

DO'S

DO NOTS

1. Verify dimensions and foundation levels as per drawing.

1. Do not forget to compare bearing capacity of actual soils met with design strength.

2. Wet the foundation surface to a depth of 150 mm or to impermeable material.

2. Don't lay the foundation concrete without wetting the surface.

3. Compact with suitable bedding materials in case of over excavations and with M-5 grade concrete in case of rock.

3. Don't allow admixtures, which will harm the strength of concrete.

4. Ensure the rock surface free from oil, objectionable coating unsound fragments.

4. Do not lay the concrete under water and over slush.

5. Check-up correct batching of ingredients.

5. The minimum mixing time should not be less than 2 min.

6. Check the batch of cements and its make.

6. Do not forget to keep stand by vibrator and needles.

7. Check-up water cement ratio and slump test.

7. Do not place concrete in raw in sufficiently heavy to wash mortar from concrete.

8. Ensure uniform mixing in a mixer for at least 2 minutes

8. Do not forget to cast the cubes

9. Ensure proper compaction with vibrators and keep stand-by vibrator and needles.

9. Do not allow segregation of concrete

10. Operate immersion type vibrators nearly in vertical position to vertical drain.

10. Do not use unsatisfactory mix.

11. Cure with water for 28 days.

 

B) FOR SUPER STRUCTURE

 

DO'S

DO NOTS

1. Check the form work

1. Avoid abrupt surface irregularities.

2. Apply cement slurry after cleaning the surface at vertical joints.

2. Do not deviate from specified dimensions of cross section from -6mm to +12 mm.

3. Clean and cover with a layer of 10 to 15 mm thick mortar of the same proportion of concrete mix for horizontal joints.

3. Do not allow concreting until all form work installation of items to be embedded and preparation of surface involved are approved.

4. Place the concrete, preferable at temperature not exceeding about 90o F.

 

5. The concrete shall be discharged with in half an hour after introduction of the mix water and cement.

 

 

C. REINFORCED CEMENT CONCRETE SLABS

(I.S. CODES 2502, 1786)

 

DO'S

DO NOTS

1. Check the reinforcement as per drawing and I.S. Code with particular reference to concrete cover.

1. Do not pass without specified cover.

2. Provide asphaltic pad and water stopper as per drawing.

2. Do not allow less lengths in over laps.

3. Ensure lightning arrangement if the work is to be carried out during night.

 

4. Ensure stand by vibrator & mixer in working condition at site before start of work.

 

5. Fill up the cubes of concrete samples for testing.

 

REGISTERS TO BE MAINTAINED

1. Load Register

2. Cement Day book

3. Sieve analysis for sand and metal.

4. Slump for consistency.

5. Compressive strength of concrete.

PREPARATION OF SUB-GRADE FOR C.C. LINING

(I.S. CODES : 2720, 4701, 3873

PREPARATION OF SUB-GRADE

Preparation of sub-grade is a factor on which depends much of the successful performance of lining. Failure or cracking of lining in many cases can be attributed to poor preparation of sub-grade. Due emphasis is, therefore to be laid on control and proper preparation of sub-grade for lining. Sub-grade indifferent soil reaches shall be prepared based on IS : 3873-1978. Whereas the work of trimming the canal section up to underside of lining shall be carried out well in advance, the trimming of proud section equivalent to the thickness of lining (for base preparation of lining) should be carried out immediately prior to laying of lining but in no case the time interval shall exceed 3 days in normal weather and 2 days in adverse condition.

Preparation of Sub-grade consisting of Earth :

1. The sub-grade should be prepared, dressed and rolled true to level according to the required cross-section of the canal to form a firm compacted bed for the lining. Sample

profiles true to the cross section of the canal should be made at suitable intervals to ensure correct formation of the sub-grade. If at any point material of sub-grade has been excavated beyond the neat lines required to receive lining, the excess excavation should be filled with material compatible with sub-grade material and thoroughly compacted.

2. When partial filling of existing canal sections is necessary to reduce the cross sectional area to that required for lined canal, the fill shall be paced and suitably compacted by rolling / compactors/mechanical tampers to form firm foundation for placing the lining to avoid its settlement. Slope compactors shall also be used as required for effective compaction of sub grade to the specified density.

3. The consolidation of bed in sandy reaches shall be done by saturating the bed with water before lining is placed. The consolidation of side slopes in such reaches shall be done by over cutting the sub grade in slopes by 15 cm and refilling it with earth and compacting by vibro-compactors/ appropriate mechanical compactors.

4. The compaction of sub grade in other than predominantly sandy reaches shall be done at optimum moisture content in layers not more than 15 cm-20 cm thick to obtain a dry bulk density of 95% of the density at optimum moisture content obtained in accordance with IS:2720 (Part VII)-1965. Consolidation shall be done by power rollers/pneumatic or fuel-powered tampers/suitable compactors. In the sandy reaches, compaction shall be governed by `relative density test' and the relative density shall not be less than 70% Compaction by manual labour shall not be permitted.

5. Where placing and compacting bedding material is on sloping foundation, the layers shall be placed parallel to the surface of the foundation. If at any point the foundation material is disturbed or loosened, it shall be moistened if necessary and thoroughly compacted to form firm foundation for placing the lining.

6. All along the canal alignment, the rain cuts on the inner slopes of the banks shall be filled up with approved soil and shall be compacted thoroughly to required lines, dimensions, and levels.

7. If at any place, placement of bedding material below the proposed lining is required, due care shall be taken to place the bedding material on scientifically approved surface adequately moistened (to be wet to a depth of 15 cm or to depth up to impermeable layer below, whichever is less) in layers not exceeding 15 cm in depth in a single operation and thoroughly compacted.

8. All loose materials likely to be present at the end panel of existing lining adjacent to which lining is to be placed shall be removed and all voids beneath the existing lining shall be refilled and compacted thoroughly.

 

Preparation of Sub grade consisting of Rock

1. The sub grade shall be prepared and dressed true to level and according to the required cross-section of the canal.

2. Final cutting for 300mm-450mm in hard rock shall be carried out by wedging, barring, controlled blasting or trimming with pavement breakers etc.

3. The bed and side slopes of the canal excavation profile over which the bedding material, under-drainage and pressure relief arrangements (where ever so required) are to be placed and over laid with lining shall be furnished accurately to true and even surfaces and to the dimensions shown on the drawings.

4. All excavation including over breakage below the lines of underside of lining shall be back-filled completely up to the lines of the underside of lining with suitable bedding material as under or as directed by the Engineer-incharge.

The bedding material shall be lean concrete (1:5:10) in bed and sides for thickness of filling less than 15 cm; and RR masonry in cement mortar (1:5) if thickness is more than 15 cm.

OR

In Slopes : In slopes, the selected material shall be suitable semi-previous material/gravely soil and a layer of pea gravel as binding material duly moistened and compacted by appropriate compactors/tampers to form a firm backing for the lining.

In Bed: In bed, the selected bedding material shall be rock spalls and chips to form a firm backing.

Selected bedding material to be used over fractured rock or rubble shall be such as would resist piping and consequent washing of fines into the sub grade voids and thus losing support. The material shall be approved by the Engineer-incharge for its impermeability and care of placement.

Tolerance in Surface Irregularities in Preparation of Final Subgrade

Surface irregularities shall be tested by the use of a long template consisting of a straight edge or the equivalent there-of for curved surfaces and shall not exceed the following limits:

i) 6.25mm for sub grade in bed.

ii) 12.50 mm for sub grade in the side slopes.

Preparation of subgrade consisting of expansive soils (IS:9451-1994)

Field and laboratory tests shall be carried out to determine the physical, textural, engineering, and chemical properties of expansive soils and evaluate the swelling pressures of soils in various reaches to establish the thickness of CNS (Cohesive non-swelling soils) layer required so that the resulting deformation is within the permissible limit of 2 cm. The thickness of CNS layer to be provided normal to the sub grade shall be governed by the Indian Standard IS :9451-1994, out lined below. CNS material shall be non-swelling with a maximum swelling pressure of 10KN/m2 when tested in accordance with IS 2720(Part-41) : 1977 at optimum moisture content and minimum cohesion. Some of the soils which may be considered as cohesive non-swelling soils are all adequately compacted clayey soils, silty clays, sandy clays, gravelly sandy clays, etc. exhibiting cohesive properties and containing predominately non-expanding type clay minerals with liquid limit not exceeding 50 percent.

Expansive soils are inorganic or organic plastic clays characterized by shrinkage, high compressibility, and swelling properties. To counter act the swelling pressure and prevent deformation of lining, a CNS material of required thickness is sandwiched between the soil and lining. The thickness of CNS material is normal (perpendicular) to the sub grade. Guidelines for choosing the thickness of CNS materials (Cohesive Non-Swelling) required for balancing the different swelling pressures.

Specification of CNS Soils :

(i) Gradation of CNS Soil

Clay (less than 0.002 mm) 15 to 20%

Silt (0.06mm - 0.002mm) 30 to 40%

Sand (2mm-0.06mm) 30 to 40%

Gravel (grater than 2mm) 0 to 10%

ii) The CNS materiel shall be non-swelling, with a maximum swelling pressure of 10 KN/m2 when tested in accordance with IS: 2720 (part -41) 1977 at optimum moisture content and minimum cohesion.

Liquid limit Greater than 30, but less than 50%

Plasticity Index Greater than 15 but less than 30%

If given CNS material is not available, designed soils mix to produce artificial CNS may be used. The artificial CNS shall broadly satisfy all the requirements of CNS outlined above.

In respect of the provisions of CNS layer in the bed, it shall be as worked out from consideration of swelling pressure. However, the thickness of CNS layer to be provided on slopes shall, in addition, be governed by the construction consideration viz. from the Power Roller rollable width consideration for achieving effective compaction. CNS layers shall be compacted to 98% proctor density.

Note : During construction, it shall be ensured that :

(i) Serrations/steps/benches shall be provided in the side slopes of canal in cutting to provide a good bond between the CNS layers and expansive soil and to also prevent contact slides between CNS materials and expansive soil.

(ii) Proper moisture shall be added to CNS material and expansive soil.

(iii) CNS material shall be laid in layers (+ 20cm thickness) and compacted to requisite proctor density, preferably, by Power Roller.

(iv) To avoid slipping and rain cuts during the rainy season, it shall be advisable to provide CNS right up to the ground level.

(v) The sub grade on which CNS layer is to be laid shall, generally, be not kept exposed for more than 4 days prior to the placement of CNS layer.

(vi) Effective compaction of sub grade for side lining on slopes is very important in cutting or embankments. In addition to the designed thickness of CNS, 20 cm or more (perpendicular to side slope) of extra thickness (called proud) shall be provided and compacted. This proud shall be removed only just prior to the placement of lining (a time interval of, say, about one day), thus making a fresh and well-compacted surface available for bedding. IN small section channels, it shall be appropriate to over excavate the section, and fill the entire section with CNS material (laid in successive layers and compacted to 98% proctor density), and, thereafter, scoop this section to the designed section for placement of lining. This PAD method ensures effective compaction by 8-10 T power rollers or equivalent power vibratory rollers. The CNS material so scooped out is utilized in the next reach through re-handling.

(vii) To avoid slipping and rain cuts during the rainy seasons, the CNS shall be provided right up to ground level in cutting reaches.

(viii)Under drainage arrangement, as per provisions in the agreement.

Sub-grade Density and Moisture Control :

A sound dense earth foundation, carefully trimmed and pre-moistened before lining placement are critical steps, prerequisite to a good lining construction. Required foundation density of embankment and preparation coupled with moisture control are the key requirement. At the time, concrete is placed the sub-grade is required to be thoroughly moist (but not muddy) for a depth of about 12 to 15 cms and 20 to 22 cm in case of sand as else the concrete would extract moisture from the sub-grade. Compliance of these requirements must be recorded by the execution, QC staff in the OK card. Photographic record showing the actual use of very fine spray nozzles instead of hose (for moistening the compacted sub-grade) should also be kept.

 

Lining Preparation of Subgrade 

DO'S

DO NOTS

1. Check the model section to the canal profile i.e., bottom or lining viz side slopes, bed width, top width, slant length, smoothness of slant length.

1. Do not allow concrete lining on loose sub-grade.

2. Check the canal profile with reference to model section. Profile be prepared at 15 M intend in case of tile lining.

2. Do not allow any root or stumps to be on sub-grade.

3. Remove roots and stumps completely from the sub-grade

3. Do not allow lining in expansive soils without treatment with C.N.S. soils.

4. Compact over-excavation in soils with earth gravel duly wetted.

4. Do not place the porous plug below the surface of the lining.

5. Compact over-excavation in rocky area or fill up with not concrete as per specification.

5. Do not allow lining without wetting the sub-grade suitably.

6. Provide treatment with C.N.S. soils in expansive soils.

6. Do not allow movement of labourers after preparation of subgrade.

7. Provide porous plugs of specified size in each panel with specified local filters of graded metal and sand.

 

8. Check whether porous plugs are freely draining or not.

 

 

C.C. LINING

(I.S. CODES, 353, 269, 2116, 456, 516)

CONCRETE CORES FROM CANAL LINING AND OTHER STRUCTURE

 

A specimen to be tested for strength shall not be removed from the structure until the concrete has become hard enough to permit its removal without disturbing the bond between the mortar and the course aggregate. In general the concrete shall be 28 days old before the specimens are removed. Specimens that show abnormal defects or that have been damaged in removal shall not be used. (IS: 457-1997).

Core Drill: A core drill shall be used for securing cylindrical core specimens. For specimens taken perpendicular to a horizontal surface, a diamond drill shall be used.

Specimens: A core specimen for the determination of pavement thickness shall have a diameter of at least 10 cm. A core specimen for the determination of compressive strength shall have a diameter of at least three times the maximum nominal size of the course aggregate used in concrete and in no case shall the final diameter of the specimen be less than twice the maximum size of the course aggregate. The length of the specimen, when capped, shall be, as nearly as practicable, twice its diameter. The curve enclosed Annexure - VIII should be used to correct the indicated strengths so that they will be comparable with those obtained from standard specimens (having L/D ratio as 2).

Core Drilling:

A core specimens shall be taken perpendicular to a horizontal surface, so that its axis is perpendicular to the bed of the concrete as originally placed.

Frequency of drill cores could be one core each from bed and side lining per 2000 square meter of insitu lining. The cores should be inspected for

a) Segregation b) Honey-combing and c) Thickness of lining.

The cores should be tested for

a) Density b) Compressive strength and c) Water absorption.

Compressive Strength:

End Preparation: Core specimen to be tested in compression shall have ends that are essentially smooth. Perpendicular to the axis and of the same diameter, as the body of the specimen.

Moisture Conditioning:

Test specimens shall be completely submerged in water at room temperature for 40 to 48 hours immediately prior to the compression test. Specimens shall be tested promptly after removal from water storage. The testing shall be done in accordance with the guide lines laid down in I.S.: 516-1959 complete data and test results of cores should be meticulously recorded as per format enclosed (Annexure - IX).

Concrete in the member represented by a core test shall be considered accepted if the average equivalent cube strength of the cores is equal to at least 85% of the cube strength of the grade of concrete specified for the corresponding age and no individual core has strength less than 75 percent.


 

DO'S

DO NOTS

1. Check the canal prism and verify the bed levels.

1. Do not allow concrete lining on loose sub-grade.

2. Check the gradation analysis of fine and coarse aggregate to the requirement of mix at batching plant.

2. Do not allow lining without wetting sub-grade

3. Allow the ingredients of fine and coarse aggregate as per required mix by weigh batching.

3. Do not allow C.C. lining manually without vibration.

4. Check the calibration of weighing machine at batching plant.

4. Do not allow segregation of concrete while laying through discharge conveyor.

5. Check the water meter and its discharge.

5. Do not allow concrete directly on subgrade from transit mixer.

6. Check the batch of cement, its make and test results.

6. Do not form contraction joints over longitudinal drains.

7. Check the water cement ratio and record the slump.

7. Do not fill up contraction joints with sealing compound without cleaning with air water jet or sand blast.

8. Check whether any retarders and air entraining agents are added.

8. Do not allow any projections or contraction joint over the surface of the lining.

9. Maintain load register.

9. Do not allow the C.C lining without applying suitable primer to sides.

10. Record the No. CC cubes cast and its compressive strength.

10. Do not remove the channels immediately before setting of C.C.

11. Cure CC Lining with water for 28 days.

11. Do not use untested cement.

12. Ensure smooth surface with paver roller passes.

12. Do not allow to sink the porous plugs in the drains.

13. Form the contraction and construction joints as per approved drawing.

13. Do not allow lining without making proper arrangements for curing with water.

14. Check the thickness of C.C. lining for each panels.

14. The Co-efficient of variation in the compressive strength of cement should not be more than 8%.

15. Checking placing of mastic pad at structures of construction joints.

 

16. Allow concrete lining at temperature between 15o C and 32o C.

 

17. Check periodically the coefficient of variation in the compressive strength of cement.

 

18. The batching plant to be used shall confirmed to the required of IS 4925-1968.

 

 


MASONRY

I.S. CODES 1597, 1812, 1200 383, 269, 2116

DO'S

DO NOTS

1. The stone shall be of uniform colour, texture, strong, hard durable.

1. Do not use soft stones of crushing strength less than the specified strength.

2. Dress C.R.S. stone to a depth of 75 mm on all four sides.

2. Do not allow projections more than 40 mm on the face.

3. Wet the stones before placing in position clean and cover with fresh mortar.

3. Do not allow stones of length more than 3 times the height.

4. Place stones in layers to the line and plumb.

4. Do not allow stone of breadth less than height of of thickness of wall.

5. Provide weep holes at 2 mtrs interval staggered as per drawing.

5. Do not allow breaking of vertical joints less than 75 mm.

6. Chisel dress the corner stones.

6. Header shall not project not less than 10 cm beyond stretcher.

7. Face stones shall be laid alternately in headers and stretchers.

7. Do not place stones in position without cleaning and wetting.

8. Provide bond stones at 2 mtrs. Interval in each layer and mark.

8. Do not allow skin stones, weathered stones.

9. Place the heating stones on its broadest face.

9. Do not place stone in position without wetting.

10. Ensure perfect heating to make the masonry water tight.

10. Smaller stones shall not be placed in lower crores.

11. Mortar shall be used within 30 min. after discharge from mixer.

11. Joints thickness should not be more than 12 mm.

12. Sieve analysis for sand shall be done periodically.

12. Do not allow mixing less than 3 minutes for thorough mix.

13. For flush pointing the mortar shall be finished off flush and level with edges of the stones.

13. Do not add more water than required to have a consistency of 90 to 130 mm.

14. Joint shall be raked out to minimum depth of 12 mm when the mortar is green.

14. Avoid spreading of mortar over the surface of the masonry. Mortar should be spreaded over the stone just before laying the next layer.

15. Cure the masonry with water for 14 days.

15. No pointing to be commenced without washing and wetting the joints thoroughly.

16. Cure the plastered surface with water for 14 days.

 

17. Cure the pointing surface with water for 7 days.

 

 

 


 

 

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