proposed genrl instructions cement concrete allied works jp 03,04,05,07

7/29/2019 Proposed Genrl Instructions Cement Concrete Allied Works Jp 03,04,05,07

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General Instructions for Concreting Works:

1. At least one week before commencing the construction of any massive concrete section the SiteEngineer has to consider all aspects so as to prevent concrete cracking or loss of strength

of concrete due to release of heat of hydration and drying shrinkage behavior etc., and on

satisfaction only casting massive concrete sections are to be taken up as noted on the

drawings or as identified by Client Engineers.

2. All concrete is to be mixed in mechanically operated batch mixers complying to IS: 1791 andshall be of approved make with suitable provision for correctly controlling the water delivered

to the drum. Weigh batchers shall conform to IS:2722 and shall be capable of controlling the

weights to within one percent of the desired value. Batching Plants shall conform to IS: 4925.The mixers, weigh batchers and batching plant etc. shall be maintained in clean and serviceable

condition. Accuracy of all equipment is to be periodically checked and recorded by the QC

Lab.

3. Materials: All materials such as Coarse and Fine Aggregates, Water and Cement conform torespective Specifications. Method of Procurement, Storage of materials and quality procedures

are subjected to periodical checks record of which are to be maintained in the QC Lab.

3.1.Aggregates

Any or All Tests for Aggregates as required by Client as per IS:2386 Parts-I to VIII. shall becarried out for the aggregates. The acceptance criteria of the samples tested shall be as per

the relevant IS.

For reinforced concrete work, coarse aggregates having a nominal maximum size of 20mm

shall be used. For reinforced concrete works with large pours with no restriction to the flow of

concrete, at such locations/sections aggregates having a nominal maximum size of 40mm or

above may be used with the permission of the Client Engineers. And In concrete elements with

sections of thickness less than 100mm, closely spaced reinforcement or small cover, aggregate

with maximum nominal size of 10mm is to be used.

For heavily reinforced concrete members such as in the case of ribs of main beams, the nominalmaximum size of the aggregate shall usually be restricted to 5mm less than the minimum clear

distance between the main bars or 5mm less than the minimum clear cover to reinforcement,

whichever is smaller.

3.2 Cement

Ordinary Portland cement of 43 grade or 53 grade as per IS: 8112 or IS: 12269 respectively

shall be used in concrete. For mix design, water cement ratio shall generally be as per Table 5

of IS:456, but would not exceed 0.45. The minimum cement content shall also be be as per

Table 5 of IS: 456. Chloride free sulphonated melamine based super plasticizer conforming to

IS: 9103 would be used as per mix design and manufacturers instructions to improve

workability


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3.3 Water

Water for use in concrete shall be clear and free from injurious oils, acids, alkalis, organic

matter, salt, silts or other impurities. Normally potable water is found to be suitable. Generally,

IS: 3550 will be followed for routine tests. In case of doubt, the acceptance test for water shall

be as per IS: 3025 and Table-I of IS:456.

3.4 Admixture

Quality admixtures as directed or permitted by the Engineer-in-Charge will be used. The

admixture shall conform to requirements of IS: 9103. Chloride free sulphonated melamine

based super plasticizer conforming to IS: 9103 would be added as per mix design and

manufacturers instructions to improve workability.

3.5

Nominal Mix Concrete

a) Nominal mix concrete shall be used only for plain cement concrete works and as indicatedin the drawings or as approved specifically by the Client Engineer. No trial mixes are done

for this concrete other than mixing in a mechanical mixer.

b) While proportioning concrete, the cement is to be measured by weight and Aggregates maybe determined by volume (for corresponding weight) but preferably by weight. Fine

aggregates if moist, the amount of surface water shall be determined and allowance shall be

made for bulking in case of volume batching, in accordance with IS:2386 (Part III). Moisture

correction is to be made for surface water present in the aggregates and recorded data is to

be recorded and maintained by the Field QC Lab to the satisfaction of the Engineer.c) The recommended proportions for Nominal Mix Concrete are specified in Table 1.

Table 1

Recommended Proportions for Nominal Mix Concrete

Grade of

Concrete

Total Quantity of Dry

Aggregates by Mass

per 50 Kg of Cement

Proportion of Fine Aggregate to

Coarse Aggregate (by Mass)

Quantity of

water per

50 Kg of

Cement,

M 5 800Generally 1:2 but subject to an

upper limit of 1:1.5 and a lower

limit of 1:2.5

60 ltrs.M 7.5 625 45 l

M 10 480 34 l

M 15 330 32 l

M 20 250 30 l

Note: The proportion of fine to coarse aggregates shall be adjusted from upper limit to lower

limit progressively as the grading of fine aggregates becomes finer and the maximum size of

coarse aggregate becomes larger. Graded coarse aggregate shall be used.

e) If nominal mix concrete made in accordance with specified proportions does not yield thespecified strength of the corresponding grade and fails to satisfy the requirements of"Acceptance Criteria for Concrete" as specified in IS:456 is to be mutually agreed upon with

Client Engineers.


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f) Nominal mix proportion shall not be classified as higher grade proportion on the ground thatthe test strengths are higher than the minimum specified.

4.3.2 Design Mix Concrete

a) Design Mix Concrete shall be used on all concrete works, except where specified otherwise

or specially permitted by the Engineer. The mix shall be designed for all grades of concrete

(except those specified under Nominal Mix Concrete) to obtain required characteristic

strength not less than the appropriate values given in Table 2. Using standard deviation

specified in IS: 456, the minimum value of target strength of design mix of various grades of

concrete shall be as per Table 2.

Table 2

Grades of Concrete

Note: The above values correspond to site having essential pre requisites such as proper

storage of cement;-weigh batching of all materials, ;Controlled addition of water; Regular

checking of all materials;-Provisions for aggregate gradings; and moisture content checks and

periodic checking of workability and strength etc., Deviation to above Preliminary Test strength

asterisk marked values are to be adopted.

b) In proportioning the concrete, the quantities of both cement and aggregates is to be determinedby mass. At the discretion of the Engineer quantity of aggregates may be allowed to be

determined by an equivalent volume basis after establishing the relationship between weightand volume after several trials and the same being verified periodically. Water shall either

be measured by volume in calibrated tanks or weighed. All measuring equipment, at site, is to

be maintained in a clean, serviceable condition, with their accuracy duly calibrated.

c) To keep the water-cement ratio to designed value, allowance are to be made for the moisturecontents to both fine and coarse aggregates and determined in accordance with IS: 2386 (Part

III). Daily recording of the same or as directed by the Engineer. Trial mix as required shall be

carried out accordingly.

d) Water quantity may be increased to any of the concrete grades with prior permission of

Engineer. Cement quantity, in such cases, shall also be increased pro rata to maintain thewater cement ratio constant as adopted during preliminary tests to that of the corresponding

grade of concrete.

Grade

Designation

of

Compressive strength of a 150 mm cube at 28 days

in ( N/mm2)

Preliminary Test Strength

(target strength of trial mix)

Characteristic

strength

on works cubes

M 15

M 20

M 25

M 30M 35

21 /

22*

27 /

28*32 /

1

5

20


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e) Suitable admixture shall be used to improve cohesion & workability, without compromising onthe quality of concrete.

4.3.3 Mix Design

a) Prior to actual commencement of the work Preliminary tests/ trial mix, as specified or as

required by the Engineer, to arrive at the grading of aggregates, for different grades of

concrete is to be made from representative samples of aggregates and cement that are

expected to be used on the works. The water-cement ratio, workability and the quantity of

cement required to give Preliminary (target)compressive strengths as specified in Table 2 are

arrived at. The mix so designed (and not the method of design) shall be approved by the

Engineer.

Type of cement and minimum cement contents for different exposures and sulphate attack

shall be as per IS: 456. However, if higher value is obtained due to strength consideration

from trial mix, minimum cement content shall be as per the requirement of trial mix.

b) At least three trial mixes shall be made and a minimum of six test cubes taken for each trialmix. Slump for each type of mix shall be checked. Three cubes from each mix, after proper

curing, shall be tested in a laboratory (approved by the Engineer) after 7 days and balance

three cubes checked after 28 days to obtain the compressive strength. Over wet mixes are to

be avoided while preparing for the design mixes

c) The Test reports of mix design are submitted to Client Engineers for his review, indicatingdesign criteria, analysis and proportioning of materials etc. The reports shall also include

design mix particulars, graphs and curves etc., indicating the permissible variation in the

grading of aggregates. These test reports shall form the basis for finalisation of mixproportion by mass and the water-cement ratio indicating achieving desired characteristic

strength and workability. The approved proportions for different grades of concrete shall not

change during all concreting operations unless there is a change in quality of the materials.

In case of change in the quality of materials or characteristic strength of concrete or water

cement ratio or workability, arrangements are made for carrying out similar trial mixes and

Preliminary tests and the revised mix proportions and water-cement ratio are ascertained

afresh.

d) At locations, where compaction of concrete is not possible by

vibration, e.g. casting of piles, the method of compacting concrete cubes for preliminary / trialmixes and work tests shall be in the similar manner to that of the compaction method

proposed to be that as used at site actually during concreting.

4.3.4 Workability of Concrete

a) At frequent intervals the workability of concrete shall be subjected to checking. Theworkability of concrete is measured in accordance with IS:1199 for every sample taken

for testing and recorded with corresponding cube test result.

b) The degree of workability depends on type and nature of the structure and is to be based onexperience and tests. Ranges of workability for different placing conditions of concrete shallconform to IS: 456. This is essential to to know about how well the concrete is

compacted and worked into the corners of formwork and around the reinforcement and

renders to achieve the required surface finish.


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4.3.5 Mixing of Concrete

a) Concrete may be mixed in a mechanical mixer conforming to IS: 1791. However, mixingpreferably may be done at a single central batching plant, conforming to IS: 4925, located

within the Project area allocated. The plant shall have a mechanically operated mixer of an

approved size and type, capable of ensuring a uniform distribution of the materials throughoutthe mass. The mass shall be uniform in colour and consistency.

b) Water shall not be added into the drum of the mixer, until all the cement and aggregatesconstituting the batch are already in the drum and dry mixed for at least one minute and are

uniformly distributed. Water added subsequently and mixing of each batch is continued

until there is a uniform mixing of the materials takes place the mass becomes uniform in

colour and consistency. In no case mixing is done for less than two minutes and less than 40

revolutions. Despite, this if there is segregation after unloading from the mixer, the concrete

shall be remixed. When absorbent aggregates are used or when the mix is very dry the

mixing time shall be extended as directed by the Engineer,.Do not over load the Mixers

beyond its rated capacity as this prevents thorough mixing of the batch.

The accuracy of measuring equipment shall be within 2 percent of the quantity of cement

being weighed and within 3 percent of the quantity of aggregate, admixtures and water

being weighed.

c) The entire contents of the drum are to be discharged before ingredients for e next batch arefed into the drum. No partly set or remixed or excessively wet concrete shall be used and it

shall be immediately removed from site. Each time if the work stops for more than 30

minutes, the mixer shall be thoroughly cleaned and when the next mixing commences, the

first batch shall have 10% additional cement.

d) Dosages of retarders, plasticizers and super plasticizers shall generally be restricted to 0.5, 1.0and 2.0 percentages respectively by weight of cementitious materials. However,

recommendations of manufacturer are also to be considered in this regard.

4.3.6 Concrete Conveying

a) Concrete shall be handled and conveyed as rapidly as practicable, from the place of mixing tothe place of final laying, by approved means, before the initial setting of the cement starts.

Concrete shall be conveyed in such a way that there is no segregation or loss of any of the

ingredients or ingress of foreign matter or water and the required workability is maintained.

During very hot or cold weather, as directed by the Engineer, concrete shall be transported in

deep containers so as to reduce the rate of water loss by evaporation in hot weather and heat

loss in cold weather.

b) Conveying equipment for concrete shall be mortar tight, well maintained andthoroughly cleaned before commencement of concrete mixing. Such equipment shall be kept

free from set concrete. Chutes shall not be used for transport of concrete without the written

permission of the Engineer. The chute, in case permitted , Chutes shall be of such size and

design which ensures practical continuous flow. Slope of the chute is to be so adjusted that

the concrete flows with out the use of excessive quantity of water and without segregation of

its ingredients. Chutes, on approved for use, shall have slopes not flatter than 1 vertical: 3horizontal. The delivery end of the chute shall be as close as possible to the point of deposit.


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c) Concrete shall be conveyed and placed by mechanically operated equipment e.g. Concretepumps or pneumatic placers with due permission of the Engineer, who shall also review

the entire scheme for which comprehensive details as required is to be furnished by the SiteEngineers..

4.3.7 Concrete Placing

a) Concrete shall be placed and compacted in its final position prior to onset of initial setting ofthe concrete and it shall be compacted in its final position within minutes of discharge from

the mixer.

b) Where ever direct placement is not possible, suitable arrangements such as chutes, tremie,elephant trunks etc. to confine the movement of concrete as directed by the Engineer are to be

made by the Site Engineers. Concrete shall not be dropped from a height or handled in a

manner causing segregation. As a general guidance, the maximum permissible free fall for

the concrete shall be limited to 1.0m.

c) Concrete placed by pumping, minimum for conveyance shall be ensured .As a generalguideline, clause 7.0 of IS: 456 is to be followed.

Prior to commencing regular pumping, the pipeline is to be lubricated by cement mortar

(1:2) and once pumping commences, stoppages shall be avoided. Care is be taken to see that

cement mortar does not get discharged in the structure being concreted.

d) Concrete shall not be placed in foundations on soft areas or where there is stagnant water ordebris is present. Such soft areas shall be removed and filled with M10 nominal mix concrete

(1:3:6) or as directed by the Engineer.

e) When ever concrete is to be laid on or in the vicinity / adjacent to rock surfaces, rock is to bechecked for its soundness. On sloping rock faces, rough steps or benches are to be made and

concrete placed.. Prior to pouring concrete, the rock surface is to be thoroughly cleaned with

a high pressure water and air jet and kept wet for three hours. Excess water if any from

depressions is to be dried and the rock surface dried and a 10 mm thick cement-sandmortar (1:6) layer shall be placed and worked into all crevices, cracks, depressions etc.,

f) The placing of concrete shall be a continuous operation with no interruptionof more than 30 minutes between the placement of continuous portions of concrete. Concrete

shall be placed in continuous horizontal layers of 150 mm or higher thickness as directed by

the Engineer and layer shall be thoroughly compacted before placing next layer. The thickness

of each layer shall be such that it is deposited before the previous layer has stiffened. When

placing concrete through reinforcing steel, care shall be taken to prevent segregation of the

coarse aggregates.

g) Slots, openings, holes, pockets etc. are to be provided in the concrete as per drawings or asdirected by the Engineer.

h) Slabs, beams and similar concrete members shall normally be poured in one operation. Inspecial circumstances, with the approval of the Engineer, these can be poured in horizontal

layers, but care must be taken to ensure that the under layer is not hardened. Bleeding of


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under layer, if any, shall be effectively removed. Moulding, throating, drip course etc. shall be

poured as indicated on the drawings or as directed by the Engineer.

j) After the concrete has been placed, it shall be spaded and thoroughlycompacted by approved mechanical vibrators conforming to IS: 2505, IS: 2506, IS: 2514 and

IS: 4656 to a maximum subsidence without segregation and thoroughly worked around

reinforcement or other embedded fixtures into the correct form and shape. Care must be taken

to ensure that the inserts, fixtures, reinforcement and formwork are not displaced or disturbed

during placing of concrete.

k) Vibrators shall penetrate both the layer poured and the under layer to ensure good bond andhomogeneity and prevent the formation of cold joints. Immersion vibrators shall not be

allowed to come in contact with steel reinforcement after start of initial set. Also, they shall

not be allowed to come in contact with forms or finished surfaces.

l) Immersion vibrators shall have a 'no load' frequency, amplitude and

acceleration as per IS: 2505 depending upon the size of the vibrator. Immersion vibratorsshall be operated by experienced personnel. These vibrators shall be immersed not more than

450 mm apart and withdrawn when air bubbles cease to come to the surface. Such vibrators

shall always be immersed vertically into the concrete and in no case these shall be used to

push concrete inside the forms and vibrators shall be withdrawn slowly.

m) For vibrations to be applied externally, the design of formwork and the disposition ofvibrators shall receive special consideration to ensure efficient compaction and to avoid

surface blemishes. Surface vibrators and form attached vibrators shall be permitted only for

pre-cast elements. These are used with written approval of the Engineer.

n) No concrete shall be placed in wet weather or on a water covered surface. If there has beenany sign of washing of cement or sand, the entire concrete shall be removed immediately.

Suitable precautions shall be taken in advance to guard against possible rains before leaving

the fresh concrete unattended.

o) Mass concrete shall be poured in lifts not exceeding 1.0 m in height unless otherwise indicatedon drawings or directed by the Engineer.

4.3.8 Protection and Curing of Concrete

a) Newly placed concrete is to be protected by approved means from rain, sun and wind.Concrete placed below ground level is to be protected from falling earth, during post placing

operations. Concrete placed on ground containing any deleterious substances is to be kept

free in the vicinity. All seepages of water in the vicinity of such ground should be

maintained dry during and post placing of concrete for a period of at least seven days or as

otherwise instructed by the Engineer.

b) The ground water around newly poured concrete shall be kept down to an approved level bypumping or other approved means of drainage. Adequate steps are to be taken to prevent

floatation or flooding. Steps, as approved by the Engineer, are to be taken to protect

immature concrete from damage by debris, excessive loading, vibration, abrasion, mixing

with earth or other deleterious materials etc. that may impair the strength and durability of the

concrete.


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c) As soon as the concrete is hardened sufficiently for the surface not to be marked, it shall bekept in a damp or wet condition by ponding or by covering with a layer of sacking, canvas,

hessian or similar materials and kept continuously wet for at least seven days after final setting

in case of Ordinary Portland Cement and at least for 10 days where mineral admixtures or

blended cements are used. The curing period shall not be less than 10 days for concrete

exposed to dry and hot weather conditions in case of Ordinary Portland Cement and at least 14

days where mineral admixtures or blended cements are used. Curing of horizontal surfaces

exposed to drying winds shall begin immediately after the concrete has hardened. Concrete

slabs and floors shall be cured for the periods mentioned above by flooding / ponding water

to minimum 25 mm deep

d) Approved curing compounds may be used in lieu of moist curing only with the permission ofthe Engineer. Such compounds shall be applied to all exposed surfaces of the concrete, as

soon as possible after the concrete has set.

e) Quantity of water applied shall be such as to prevent erosion of freshly placed concrete.

4.3.9 Construction Jointsa) When ever work is required to be interrupted, the concrete shall be rebated and/ or keyed at

the joint to such shape and size as required by the Engineer or as shown on the drawings. All

vertical construction joints shall be made with stop boards, which are rigidly fixed and

slotted to allow passage to reinforcing steel. In the case of water retaining structures,

basements, tunnels etc. water stops of approved material is to be provided, as per clause

12.4 of IS:456 and as specified on the drawings or as directed by the Engineer.

b) Construction joints shall be located as indicated the approved drawings. Where ever not

specified/indicated, the joints shall be in accordance with the following guidelines:

i) In a column, the joints shall be formed about 75 mm below the lowest soffit of thebeams framing into it, including haunches, if any. In flat slab construction, the joint

shall be 75 mm below the soffit of the column capital.

ii) Concrete in a beam shall be placed throughout without a joint. If unavoidable, the jointshall be vertical and within the middle-third of the span. When a beam intersects a

girder, the joints in the girder is to be l be given an offset equal to a distance twice the

width of the beam and additional reinforcement provided for shear. The joint shall bevertical throughout the full thickness of the concrete member.

iii) A joint in a suspended floor slab shall be vertical at one quarter points of the span andat right angle to the principal reinforcement.

iv) Construction joints in equipment foundations are to be avoided.

v) Vertical construction joints in water retaining structures is not permitted unlessindicated on the drawings.

vi) Construction Joints shall are to be placed at accessible locations to permit cleaning outof laitance, cement slurry and unsound concrete, in order to create rough / uneven

surface.


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However, any adjustments in the location of construction joints ( suiting site conditions)

from those shown on drawings or from those explained above, prior approval from

Engineer is to be taken.

c) Before fresh concrete is placed, the cement skin of the partially hardened concrete pouredearlier is to be thoroughly removed and surface made rough and aggregate exposed, by wire

brushing, hacking, water jetting, air jetting or any other method as directed by the Engineer.The exposed rough surface is to be thoroughly wetted for about 1/2 hour, allowed to dry and

then coated with 5 to 10 mm thick layer of freshly mixed cement sand slurry. The ratio of sandto cement and water to cement in this slurry shall be same as that of new concrete to be

placed. Special care is to be taken to see that the first layer of concrete placed after a

construction joint is thoroughly rammed against the existing layer.

d) In forming a joint, concrete should not be allowed to slope away to a thin edge. The location ofconstruction joints is to be planned by the Site Engineer well in advance of pouring. These

joints are to be approved by the Engineer. The Site Engineers proposals include the location of

construction joints, the sequence of pouring, formwork details and their stripping times.

f) Where ever the concrete is not fully hardened, all laitance is to be removed by scrubbing thewet surface with wire or bristle brushes, care being taken to avoid dislodgement of particles of

aggregate. The exposed surface wetted thoroughly and all free water is removed. The

exposed surface is to be coated with neat cement slurry. On this surface, a layer of concrete

not exceeding 150 mm in thickness is to be placed first and rammed well rammed against old

work, particular attention being paid to corners and close spots. Thereafter, proceed in normalmanner .

g) Suitable time gap is to be maintained between the setting of the earlier

placed concrete and the commencement of next concrete pour for multiple lift work. The timegap shall be a minimum of 4 hours for columns, piers or walls and 24 hours for beams, girders

or slabs.

h) A construction joint should preferably be placed in a low stress zone and at right angle to thedirection of the principal stress.

4.3.10 Work in Extreme Weather Conditions

During hot weather (atmospheric temperature above 40C) or cold weather (atmospheric temp

at 5C and below) the concreting shall be done as per the procedures and precautions set out in

IS: 7861 (Parts I and II).

Temperature during pouring of Concrete shall be in the range < not less than 5 degreesCentigrade and not more than> 38 degree Centigrade.

When pouring concrete in very hot weather, precautions are to be taken to maintain

temperature of wet concrete below 38 degrees Centigrade. This shall be achieved by stacking

aggregates under the shade and keeping them moist by constant spraying of chilled water and

using ice flakes, reducing the time between mixing and placing to the minimum, cooling the

formwork by sprinkling water, starting curing before concrete dries out etc. However, before

mixing/ placing concrete, when conditions vary to specified temperatures on either sides,

approval of Engineer is to be obtained for execution methods.


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4.3.11 Inspection, Cleaning and Finishing of Concrete

a) All concrete surfaces shall have even and clean finish free from honeycombs, air bubbles, finsor other blemishes, unmarred and reasonably smooth. Panels and form linings shall be of

uniform size and be as large as practicable and installed with closed joints. The formwork joint

marks on concrete work exposed to view are to be rubbed with carborandum stone and defects

repaired with a paste of cement-sand mortar (1:2) and cured. The finish shall be made to the

satisfaction of the Engineer. Concrete surfaces are to be subsequently plastered or brick work

as required is to be taken up after adequate hacking to ensure proper bonding.

b) Immediately after removal of forms, the concrete is to be inspected and defective areas aspointed out by the Engineer are to l be removed and replaced by sound concrete as directed

by the Engineer. Holes, left by form bolts etc. are to be filled up and made good with cement

sand mortar of approved mix. All superficial defects such as honeycombing, rough patches

etc. are to be made good. If the defective area is at a vulnerable location. e.g. at the ends of

beams & columns etc. then it may be necessary to cut out the member completely or in part

and reconstructed as per directions of the Engineer.

c) Epoxies are to be used on approval of Engineer. Poured concrete affected by faultyformwork is to be removed totally and replaced. As per directions of the Engineer grouting /

shotcreting is to be resorted for repairs of the area / element .

d) Proper care is to be taken to avoid rejection of Concrete subsequent to pouring. Visiblepresence of porous or honey-combed mix, or wherever the placing has been interrupted

without providing a proper construction joint, or the reinforcement got displaced beyond

specified tolerances or construction tolerances have not been met, the concreting is liable for

rejection.

e) Generally, repair work shall consist of any or all of the following operations:-

i) Sack rubbing with mortar and stoning with caboundum stone.ii) Cutting away the defective concrete to the required depth and shape.iii) Cleaning of reinforcement and embedments.iv) Roughening by sand blasting or chipping.v) Installing additional reinforcement/welded mesh fabric.vi) Dry packing with stiff mortar.vii) Plastering, guniting, shotcreting etc.

viii) Placing and compacting concrete in the void left by cutting out defective concreteix) Grouting with cement sand slurry of 1:1 mix. .

4.4 Sampling and Testing

4.4.1 General

a) Concrete cubes for work tests are to l be cured under laboratory conditions, except when inthe opinion of the Engineer, extreme weather conditions prevail, at which time, these may

require curing under job conditions.

b) For the purposes of statistical analysis, any substandard cube result, which in the opinion ofthe Engineer is due to improper sampling, moulding or testing, is to be discarded and a

dummy result shall be substituted. The value of a dummy result shall be equivalent to the

average value of the cubes from the same grade of concrete tested immediately before and


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floor. However, the reservoir shall be retested and the walls shall also be treated if required

by the Sub-contractor.

v) The reservoir/ tank shall be retested as described above or asdirected by the Engineer for water tightness after rectification. The reservoir / tank shallbe treated and tested again, if leakage is observed during retesting.

g) For basement type structures like track-hopper tunnel, neutralising pit etc. the test for ingress

of sub-soil water shall be carried out and leakages shall be rectified.

4.4.2 Sampling of Concrete

a) Sampling Frequency

i) Trial Mixes: At least three trial mixes are to be made with min. 6 testcubes for each mix.

ii) Works tests: The minimum frequency of sampling of concrete of each grade shall beaccording to IS: 456. However, after getting continuous satisfactory results and in case

of voluminous concrete work, the Engineer may at his discretion reduce the frequency

of sampling as follows:

For each grade of concrete, and for each 8 hours (shift) of work or part thereof, at least

one sample consisting of six specimens shall be taken from each 100 cum of concrete

or part thereof. 3 specimens shall be tested at 7 days and remaining 3 shall be tested at

28 days. However, in all cases, the 28 days compressive strength shall be the criterion

for acceptance or rejection.

b) To control the consistency of concrete from every mixing, slump tests and compaction factor

tests in accordance with IS: 1199 are to be carried out every two hours or as directed by the

Engineer. Slumps corresponding to the test specimens are to be recorded for reference.

Concrete sampling for te, making test specimens, curing and testing procedure etc. shall be as

per IS:516 and IS:1199 with specimen size being 15 cm cubes. Normally, only compression

tests are to be performed apart from other tests as per IS: 516. Sampling procedure, frequency

of sampling and test specimen shall conform to clause 15 of IS: 456. Acceptance criteria for

the concrete shall be in accordance with clause 16 of IS: 456. Concrete work found unsuitable

for acceptance is to be dismantled and replaced/redone as per approved specification. During

dismantling, care is to be taken to avoid damages to embedded items or adjacent structures.

Despite precautions if any damages takes place the same are to be made good to the

satisfaction of the Engineer.

4.4.3 Acceptance Criteria

a) The acceptance criteria of concrete shall be in accordance with IS: 456. The concrete shall be

deemed to comply with the strength requirements when both the following conditions are

satisfied:

i) The mean strength determined from any group of four consecutive test results complies

with the appropriate limits in column 2 of Table 3.

ii) Any Individual test result complies with the appropriate limits in column 3 of Table 3b) Unacceptable concrete work shall be dismantled and replaced by fresh work, meeting the

specification requirements. In the course of dismantling, if any damage is done to the


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embedded items or adjacent structures, the same shall be made good, to the satisfaction of

the Engineer.

Table 3

Characteristic Compressive Strength Compliance Requirements

Specified

Grade

Mean of the Group of 4 Non Overlapping

Consecutive test results N/sqmm)

Individual Test

Results (N/sqmm)

M 15 fck + 0.825 X established standard deviation

(rounded off to nearest 0.5 N/sqmm)

or fck+3 whichever is greater

fck - 3

M 20 or

above

fck + 0.825 X established standard deviation

(rounded off to nearest 0.5 N/sqmm)

or fck+4 whichever is greater

fck - 4

Note: In the absence of established value of standard deviation, the values given in Table

4 may be adopted and attempt shall be made to obtain result of 30 samples as early as

possible.

Table 4

Assumed Standard Deviation

Grade of Concrete Assumed Standard Deviation(N/sqmm)

M10, M15 3.5M20, M25 4.0

M30 to M50 5.0

Note: The above values correspond to the site control having proper storage of cement,

weigh batching of all materials, controlled addition of water, regular checking of all

materials, aggregate gradings and moisture content; and periodic checking of workability

and strength. Where there is a deviation from the above the values given in Table 4 shall

be increased by 1 N/sqmm.

4.4.4 Load Test

If any work is found unacceptable whereupon the Engineer requires its removal and

reconstruction, and if requests for retesting is made, the same shall be load tested in

accordance with the provision of IS:456 as given below :

a) Load tests shall be carried out as soon as possible after expiry of 28 days from the time ofplacing of concrete. The structure shall be subjected to load equal to full dead load of the

structure plus 1.25 times the imposed load for a period of 24 hours and then the imposed load

shall be removed. Dead load includes self weight of the structural members plus weight of

finishes and walls or partitions, if any, as considered in design. Struts strong enough to take

the entire superimposed, dead and imposed loads are to be placed in position, leaving a smallgap under the members.


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b) The maximum deflection shall be measured after the test load is in position for 24 hours.Thereafter, the test load shall be removed.

c) 24 hours after removal of the load, if the structure does not show a recovery of at least 75percent of the maximum deflection, registered as in (b) above, the test shall be repeated after

a lapse of 72 hours. The structure shall be considered to have failed to pass the test if the

recovery after the second test is less than 80% of the maximum deflection during the second

test.

d) If the maximum deflection in mm, shown during 24 hours under load, is less than 40 l2/D,where l is the effective span in m and D is overall depth of the section in mm, it is not

necessary for the recovery provision of the above mentioned clauses to be applied.

e) If the member shows evident failure, changes as necessary to make the structure adequatelystrong, are to be undertaken as per directions of the Engineer. Under Statutory Regulations

and as per discretion of the Engineer, the structure under test or a portion thereof may be

retained as such without any modification also by de rating its load bearing capacity,

provided the design criteria allows such de rating.

f) A reinforced concrete beam, floor or roof shall be deemed to have passed the test, if themaximum deflection at the end of 24 hours does not exceed the deflection given in clause

16.5 of IS: 456. If a portion of the structure is found to be unacceptable, it shall be dismantled

and replaced by a new structure as specified. If, in the course of dismantling, any damage

done to the embedded items and or other adjacent structures, is to be made good, to the

satisfaction of the Engineer.

5.0 GROUTING

Furnishing and placement of grout in block outs, foundation bolt holes and underpinningof base plates with proper side shuttering.

5.1 General Requirements

5.1.1 The space between the top surface of the foundation, the underside of the base plate,

pockets, etc are to be filled with appropriate grout by providing proper side form work to

retain the grout.

5.1.2 Crushing strength of grout shall be at least one grade higher than the foundation concrete.

The minimum crushing strength of grout shall be 25 N/mm2. The grout strength for

machine bases shall be based on the recommendations of equipment manufacturer.

5.1.3 The contact area between the grout and base plate shall not be less than 90%.

5.2 Grout Materials shall be in accordance with Technical specification

5.2.2 For flow able grout, clean and well graded sand conforming to grade zone-4 shall be used.

5.2.3 Admixtures

Non-shrink grouting admixtures of approved make shall be used.


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5.3 Mixing and Placing

5.3.1 Ready mixed non-Shrink cementitious grouts

Mixing and placing of Ready mixed non-Shrink cementitious grouts shall be according to

manufacturers recommendations.

5.3.2 Type of Mix for other grouts

Generally following two types of grout mix are used:

a) Cement-Sand Grout: The proportion of cement to sand shall generally be 1:2, unless

otherwise specified.

b) Cement Aggregate Grout: The approximate proportions of cement, sand and coarse

aggregate shall be 1:1.25:2, with a maximum size of aggregate as 10mm. This mix shall be

used for grout thickness above 40 mm.

5.3.3 Mixing

Depending upon the case of placement and method of application, following shall be thegrout consistencies.

a) Fluid mix: Water-cement ratio shall be between 0.5 and 0.6. Plasticizer conforming to IS:9103 may be added to increase workability, wherever required. This grout mix shall be

suitable for application with low pressure grouting equipment like pressure grout pump of

adequate capacity or self flowing and suitable for grouting of pockets / blackouts, etc.,

b) Plastic Mix: Water-cement ratio shall be about 0.5. This grout mix shall be suitable forapplication with trowel or rod.

c) Stiff Mix: Water-cement ratio shall generally be 0.4. This grout mix shall be suitable fordry-pack application. The consistency should allow pressurising into firm hard ball without

cracking.

5.3.4 Placing

a) The block outs, bolt holes etc. which are to be grouted, are to be cleaned thoroughly by use

of compressed air prior to taking up the grouting operations.

b) Cement, sand, aggregate and anti-shrinkage admixture of approved quality and of provenmake shall be first blended thoroughly in the required proportion as per manufactures

specifications. Grout shall then be prepared by mixing this admixture with water. Any

grout, which has been mixed for a period longer than half an hour shall not be used on the

work.

c) Immediately after preparation, the grout shall be poured into the block outs, pockets andbolts holes either from the sides or through the holes provided for the purpose in the base

plate, by using special equipment for pressure grouting. It shall be ensured by rodding

and by tapping of bolts that the block out is completely filled without leaving any voids.The pouring shall cease as soon as each hole is filled and any excess grout found on the

surface of the concrete foundation shall be completely removed and the surface dried.


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d) The space between the top surface of the foundation concrete and the underside of the baseplate shall be filled with appropriate grout type. Grouting, once commenced, shall be done

continuously. Grout shall be worked from one end to the other (to prevent air entrainment)

and continued till the grout oozes out through the grout holes provided in the base plates.

e) In case of stiff mix, the space between the top surface of foundation concrete and theunderside of the base plate shall be dry packed by firmly pressing or ramming into placeagainst fixed supports.

f) When it is clear that the centre of base has been properly filled, the grout outside the baseplate shall be briefly rammed to ensure compaction below the edges. Shims provided for

the alignment of plate bases shall be positioned at the edges of the base to permit

subsequent removal, if required; Shims shall not be removed before 7 days after the

grouting has been executed. The resulting cavities after removal of shim plates shall be

made good with the same grade of grout as has been used for grouting under the base plate.

g) The work shall be cured for a period of at least 7 days commencing 24 hours after thecompletion of the grouting. The curing shall be done by covering the surfaces with wet

gunny bags, constant water spraying and flooding.

6.0 ENCASEMENT OF STEEL STRUCTURES / ELEMENTS

This section of the specification deals with the requirement for encasement of steel work in

concrete with necessary formwork, placing, finishing and curing, complete as per drawings

and specifications.


6.1.1 All concrete work, reinforcement, formwork & staging work shall be done as per

stipulations of clause 3.0, 4.0 and 5.0 of this specification.

6.1.2 The reinforcement to be provided for encasement of steel elements shall be mild steel bars

or in the form of wire netting. The wire shall be at least 5 mm in diameter. The

reinforcement shall be in the form of stirrups with binding at not more than 150mm pitch

so arranged as to pass through the centre of the covering of the edges and outer faces of

the flanges and supported by longitudinal spacing bars not less than four in number. Such

reinforcement shall be kept 20 mm away from the steel member and held securely to it.

6.1.3 The minimum grade of concrete to be used for encasing shall be M15. The aggregate to be

used in concrete shall be 10 mm maximum size unless specified otherwise. Where the

clear cover to steel is more than 75mm, concrete with 20mm coarse aggregate shall be

used. In case of box type steel sections, encasement shall be done with cement-sand

plaster (1:4) with thickness of 50 mm over 0.9 mm size wire netting conforming to IS:

3150, or as shown on the drawings.

6.1.4 In the case encasement of beams with concrete, if the gap between the edge of the shuttering

and flange is insufficient for placing the concrete, the workability of the concrete shall be

increased suitably by increasing the water-cement ratio or adding admixtures as per

instruction of Engineer.

6.1.5 Minimum cover for reinforcement in concrete encasement shall be 25 mm.


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6.2 Materials

The materials shall be in accordance with the relevant parts of technical specification

Common Civil Construction Material.

7.0 JOINTS IN CONCRETE

This section of the specification deals with the requirement of furnishing & installing of

joints including joint filler materials, water bars, resilient pad type

vibration damping materials in and around the sides of concrete works etc.


7.1.1 Details of joints shall be as approved by Engineer or as per approved drawings. Where

necessary or / and specified, joints shall be made water tight by use of water stops.

7.2 Classification of Joints

From the point of view of utility, the joints as provided may be classified as given below:

7.2.1 Construction Joints

Construction joints shall be introduced at locations where construction stops for any

reason and when this location is not the planned location of expansion or contraction

joint. Construction joints shall generally, but not necessarily, be vertical or horizontal.

Requirements of construction joints shall be as per Technical specifications/Approved

drawings.

7.2.2 Contraction Joints

These joints are provided to eliminate tensile stresses due to shrinkage and are

commonly used where temperature variations are small and there is no likelihood of

expansion, such as spaces below water and earth levels & unexposed to atmosphere. At

contraction joints, the reinforcement shall be discontinued and bond shall not be allowed

to develop between the joint faces, thereby introducing a structural discontinuity. A

contraction joint shall also serve as a construction joint so far as break in the pouring of

concrete is concerned. Dummy type contraction joints may be provided as directed by

the Engineer for thin sections. These shall be provided by forming a groove in either or

each of the surfaces of the concrete, the total depth of groove being one-third to one-fifth

of the thickness of the section.

7.2.3 Expansion Joints

These shall be provided either to completely eliminate or to significantly reducecompressive stresses in concrete that would otherwise result from thermal expansion and

might crush, buckle or crack part of the structure. Expansion joints serve the purpose of

contraction and also construction joints.

7.2.4 Control Joints

At places where cracking is inevitable, places of weakness shall be introduced by the

provision of control joints so that the cracking takes place along these joints instead of


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allowing it to develop in a haphazard manner.

7.2.5 Separation Joints

At places where the expansion of the structure is not expected but they are required to be

kept structurally separate so that stresses, vibrations etc. are not transferred to theadjoining structure, a separation joint shall be provided. Like expansion joint, a gap shall

be provided in separation joint also. The gap may be filled up by bitumen impregnated

fibre board or other resilient material. In case, no gap is required, the separation joint can

be obtained by using an approved alkathene sheet or equivalent stuck on the surface

against which concrete shall be placed.

7.2.6 Settlement Joints

Structures, which are likely to settle with respect to the adjacent structures, shall be

separated by a settlement joint so that the adverse effects of differential settlement are

obviated. It is like an expansion joint but with a different sealing arrangement.

7.3 Materials

The materials shall be in accordance with the relevant parts of technical specification

Common Civil Construction Material.

7.4 Installation

7.4.1 Bitumen Board / Expanded Polystyrene

The bitumen impregnated fibre board of approved manufacturer as per IS: 1838 may besecured to vertical concrete by nails in the first placed concrete. The joint filler shall be

coated on both faces with coal-tar pitch conforming to IS: 216 or bitumen of suitable grade

conforming to IS: 73 or IS: 702.

7.4.2 Resilient Pads

The resilient pads shall be installed around the foundations or at other locations as shown

on the drawings. The pads shall be installed in position by sticking the same to the

foundations by using approved glue.

7.4.3 Sealing Compound

When directed, the gap in joints shall be thoroughly cleaned and sealing compound laid as

per manufacturers specification and approved drawings. Primer shall be applied wherever

required.

7.4.4 Water Stops

a) Water stops shall be selected based on the recommendations of IS: 3414. Water stops shall

not have any longitudinal joints and shall be procured and installed in the largest

practicable lengths having a minimum number of transverse joints.

The PVC Water stop used for construction/expansion joint shall be 225 / 230 mm wideand 6 / 8 mm thick as per drawings or as per instruction of Engineer. If water table is


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above the base level of the trench, PVC water stop shall be provided at all construction

and expansion joints. The jointing procedure shall be as per the manufacturers

recommendations and shall be reviewed and approved by the Engineer. Suitable fieldsplicing kit including heater shall be used for this purpose. The edges shall be neatly

crimped and bent to ensure proper bond with the concrete.

b) As non-metallic water stops can be easily handled in very large lengths unlike metal strips,transverse joints will be allowed only under unavoidable circumstances and with the

specific approval of the Engineer. The method of forming these joints, laps etc. shall be as

specified by the Manufacturer and/ or approved by the Engineer, taking particular care to

match the centre and the edges accurately.

c) Particular care shall be taken for the correct positioning of the water stops to prevent anyfaulty installation, which may result in joint leakage.

Adequate provision shall be made to support the water stops during progress of work and

to ensure their proper embedment in the concrete. The symmetrical halves of the waterstops shall be equally divided between the concrete pours adjacent to the joints.

Maximum density and imperviousness of concrete shall be ensured by thoroughly working

in the vicinity of joints. However, particular care should be exercised in use of vibrators in

the proximity of joints to avoid dislodging of the water stops.

d) Splices

Splices in the continuity of intersections of runs of water stops shall be jointed as per

manufacturers stipulations. In case of a cross section, over lapping must not be done

but, instead factory made cross joint shall be used. It is essential that the material is notdamaged during the splicing operation and that the continuity of the entire water stops

across the section is maintained.

e) Inspection

All water stops installations shall be subject to inspection and approval by the Engineer,

before concreting operations encasing water stops are performed.

7.4.5 Metal Cover Strips

The metal cover strips shall be pinned at one end and slotted at the other end. Exposedsurface of mild steel shall be painted with two coats of approved anticorrosive paint and/

or bituminous paint over a coat of suitable primer. Welding of Aluminium shall be in

accordance with IS: 2812.

8.0 CEMENT ADDITIVES / ADMIXTURES IN CONCRETE

This section of the specification deals with the requirements of furnishing, placing and

mixing cement additives/ admixtures, in all kinds of cement concrete, (plain or reinforced) for

all kinds of structures at all levels.


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8.1.1 All essential resources such as Labour, Material and Equipments etc., shall be deployed to

place and mix cement additives / admixtures, water proofing cement additives, cement

plasticizer etc., in cement mortar & concrete of any grade. Works as specified earlier in

relevant clauses of this specification for concrete & cement mortar and complete the work as

indicated on the drawing and as per specifications shall be carried out thereafter.

8.1.2 Cement additives / admixtures shall be free from aggressive chemicals like Chlorides,

Sulphides etc., unless specified otherwise, which can cause corrosion of steel reinforcement

in RCC.

8.1.3 As per requirement and as indicated by the Engineer, the services of the manufactures

supervisor to supervise the work shall be arranged.

8.1.4 Admixtures in concrete for promoting workability, improving strength, entraining air or for

similar purposes may be used with prior permission of the Engineer. Addition of admixturesshall not reduce the specified strength or durability of concrete in any case. The admixtures

shall conform to IS: 9103 and shall be of proven make and from a reputed manufacturer.

Calcium chloride shall not be permitted to be used.

8.2 Materials

The materials shall be in accordance with the technical specification Common Civil

Construction Material.

8.3 Mixing

8.3.1 Admixtures/ water proofing additives shall be used as per dosage specified by the

manufacturer or as indicated on the drawings and shall be mixed with water, as required by

the Engineer.

8.3.2 Samples of concrete in which admixtures and/ or water proofing cement additive is added

shall be tested for waterproofness, workability, compressive strength, water absorption,

density, setting time etc. The results shall conform to relevant IS Specifications.

9.0 PRECAST CONCRETE

The specification for pre-cast concrete of grade M20 or M25 (as per construction drawing)shall be similar as for the cast-in-situ concrete described in clause no. 3.0. All pre-cast work

shall be carried out in a yard made for the purpose. This yard shall have a hard and levelled

platform made of concrete finished smooth with neat cement plaster overlaid by layer of G.I.

Plain sheets, curing tank and such other facilities. The moulds shall preferably be of steel or

of wood lined with G.I. sheet metal. The yard shall preferably be fenced.

Precast concrete elements shall be suitably marked for correct orientation and placement in

position. Precast concrete planks after 28 days of casting and curing shall be transported to

site by suitable means approved by the Engineer. Lifting hooks, protected with edge

protection angle of suitable size shall be embedded in correct position of the unit to

facilitate erection, even if not shown on the drawing, and shall be burnt off and finishedafter erection. All care shall be taken to ensure that no damage occurs during transportation.

All adjustments, levelling and plumbing shall be done as per the instructions of the

Engineer. Required help in instruments, materials and men to the Engineer for checking the


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be designed for the worst combination of loading as specified hereinafter.

e. GDCL shall submit design calculations and drawing to prove adequacy of the staging forapproval of the Engineer. On receipt of final approval, GDCL shall provide 3 copies of

approved drawings for distribution.

f. The staging shall be so designed that no load from platforms is passed on to the formwork atthe top.

g. All platforms, walkways etc., shall be clear of the formwork and at least 200mm above it.The width of platforms and walkways shall be at least 1.2 metres for easy movement of

workmen both ways.

h. The platforms shall be made of planks or bamboo mats (clamped with steel strips suitablystiffened to avoid springing).

i. The formwork and staging shall be designed for a live load of 1000 Kg/m2.

j. The staging shall be braced in both the directions.

k. The staging shall be supported on rigid surfaces at ground level.

l. The staging shall be sufficiently rigid to prevent any distortion in the formwork.

m. The Site Engineer shall take all precautions to ensure concreting of TG Raft, columns and TGDeck in one pour each. Concreting shall be continuous and no break in concreting shall be

permitted.

n. The Sub-contractor shall prepare a scheme for concreting giving details of number of mixers,labour, vibrators, pouring schedule and obtain prior approval of the same from the Engineer

before commencing concreting operations.

o. Site Engineer shall ensure that at no time the temperature of the green concrete exceeds 38degree C and take suitable precautions. If required, ice shall be added to control the

temperature.

11.1 Test for Soundness of Concrete

a. After completion of the construction of TG foundations, GDCL shall get the Deck andcolumn tested for soundness of concrete by ultrasonic wave nondestructive test method

from reputed research institutions as approved by Client.

b. If the test report calls for any rectification in the concrete works by way of pressure groutingor otherwise, the same shall be carried out by GDCL.

c. Further,any additional tests required to establish the adequacy of the rectification workscarried out shall also be done by GDCL. At mutually worked out costs..

12.0 DISMANTLING/ DEMOLISHING RCC AND/ OR PCC WORK

This section of the specification deals with the requirements of dismantling/ demolishing

RCC and/ or PCC work.


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12.1.1 General Requirements

12.1.1 The dismantling implies, carefully taking up or down and removing without damage. This

activity covers dismantling of one or more parts of a structure. This includes chipping work,

making holes/ opening etc. in concrete members, according to the required shape, size, and

profile at all elevations.

12.1.2 The term demolition implies, taking up or down or breaking up of a structure/ member, in

part or full, as specified or shown on drawings or as directed by the Engineer.

12.1.3 In a structure/ member, both dismantling and demolishing work may be involved. In such

case, the portion of work treated as demolishing shall be as shown on the drawing or as

decided by the Engineer.

12.1.4 The dismantling / demolishing operation shall be carried out in proper sequence so that the

serviceable material can be salvaged, without being damaged during

the process of work. All serviceable materials obtained from demolition / dismantling

work shall be separated out and stacked properly to avoid damage up to a lead of 500

metres or shall be returned to Clients stores and all unserviceable materials, rubbish etc.

shall be disposed of by GDCL beyond the project site.

12.1.5 Necessary propping, shoring and under pinning are to be provided for the safety of the

adjoining works or property which is to be left intact, prior to commencing dismantling/

demolishing work.

12.1.6 All demolition work shall be carried out in conformance with the local safety regulations,

extreme caution being exercised to avoid damage to the works and the equipment, whichare to be left intact. The dismantled/demolished materials shall be lowered to the ground

and not thrown and then properly stacked as directed by the Engineer. Necessary

precautions shall be taken to keep the dust nuisance down. Wherever required temporary

enclosures shall be erected to minimize the dust or moisture infiltration. Safety

requirements stipulated in IS: 4130 shall also be followed.

proposed genrl instructions cement concrete allied works jp 03,04,05,07

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