METHODOLOGY / PROCEDURE OF CONCRETING WORK

 METHODOLOGY / PROCEDURE FOR CONCRETING WORK

        Concrete Mix Proportion

     

Ø  The Mix Design shall be established for various grade of concrete to determine proportion of cement, aggregate, water and Admixtures to attain the required strength shall be either preparation of design Mix.

Ø  For Design Mix concrete proportion of raw material shall be finalized as per IS 10262 “Recommended guidelines for concrete mix design”.

Ø  Minimum Cement content, Water cement ratio shall be followed as per specification & IS standards.

Ø  The compliance of a design mix for structural concrete shall be done as per the required  strength of hardened concrete in comparison with the specified characteristic strength.

Ø  Final Mix design of concrete shall be submitted to for approval.

 

Batching of Concrete.

 

Ø  Availability of all approved material shall be ensured by approved RMC Vendor. 

Ø  In proportioning concrete, the quantity of both cement and aggregate shall be determined by weight and as per approved Mix Design.

Ø  The water-cement ratio shall be maintained as a constant at its correct value. As per approved Mix design

Ø  Determination of moisture content in both fine and coarse aggregate shall be done on daily basis for required water correction.

Ø  The concrete shall be thoroughly mixed to achieve required workability at the point of pouring.

Ø  Approved admixture shall be used in required quantity to achieve workability and longer setting time. Dosage shall be as per approved Mix Design.

                                    

Transportation

 

Ø  Concrete transportation shall be done by Transit Mixer from batching plant to the point of place to ensure that there shall not be any segregation.

Ø  With every load of concrete delivery slip (Batch Sheet) shall be issued mentioning dispatch date & time, Grade of Concrete, Location, Quantity, Slump & Temperature of concrete.

Ø  Concrete shall be transported from the mixer to the formwork as rapidly as possible by    methods that will prevent the segregation, loss of any ingredients

or ingress of foreign matter or water and will maintain the required workability.

Ø  Concrete shall be deposited as close as possible to its final position to avoid segregation & re-handling of the concrete.

 

Placement & Compaction of Concrete.

  

Ø  Concrete Pour shall be commenced after getting approval (Pour card) as per approved ITP.

Ø  Before placing concrete, all equipment for mixing and transporting the concrete shall be cleaned.

Ø  The face of construction joint shall be roughened and all loose material shall be removed & approved bonding agent shall be applied prior to concrete.

Ø  Sweet water shall be sprinkled on soil, PCC, shutter prior to concrete.

Ø  Concrete shall be placed as nearly as practicable in its final position to avoid segregation due to re-handling or flowing.

Ø  Concrete shall be placed while it is sufficiently workable for full compaction. It shall be worked around reinforcements and embedded items.

Ø  The Concrete Shall be Placed and compacted before initial setting of concrete.

Ø  Free fall of concrete shall not be more than 2.0 m or as per IS code guideline.

Ø  Chutes, hopper gates & other points of discharge shall be so designed or fitted with suitable baffles that concrete passing from them will not segregate during its free fall into place.

Ø  As concrete is placed, it shall be adequately vibrated with internal vibrators to the point of consolidating into a dense homogeneous mass thoroughly embedding the reinforcement and filling all corners and angles.

Ø  Concrete shall not be moved horizontally by vibration. (Vibration will be in controlled manners)

Ø  Concrete shall be properly worked around the reinforcement, the embedded fixtures and into the corners of formwork, so as to achieve finished surface of concrete.

 

Finishing & Curing of Concrete

  

Ø  All exposed concrete surfaces shall be left reasonably smooth and free of excessive form marks and honeycombing.

Ø  Top surfaces of concrete in walls, beams and floors shall be finished to the proper level. No holes or rough patches shall remain.

Ø  Newly placed concrete shall kept wet by the continuous application of water for the first 7 days.

Ø  Casting date shall be marked on all concrete elements for having track of curing period.

Ø  All vertical faces shall be covered with Hessian cloth and kept wet.

Ø  For Horizontal surface like slab, foundation etc. shall be cured by ponding water.

Ø  Curing compound shall also be used after prior approval and shall be immediately applied after de-shuttering of the concrete element.

Ø  Proper Construction joint shall be provided for the further lift.

Ø  For construction joint shear key shall be provided throughout length of wall, at center of column & foundation.

Ø  Construction joint in slab & beam shall not be at center of its span it should be at 1/3rd length of span and should be vertical as per consultant or Client approval.

       

        a. Pond Curing                             b. Curing by Water Spraying

Precautions to avoid Cracks in Mass Concrete

Ø  Plant mixed concrete shall have a temperature between 5 deg. C to 40 deg. C.

Ø  Thickness of freshly laid concrete layer shall not exceed 450 mm.

Ø  Good compaction of the concrete shall be secured. Slump of concrete shall be maintained to the minimum possible to avoid possible shrinkage cracks.

Ø  Mass concrete shall be protected from excessive heating and premature drying by covering it with wet hessian cloth, as soon as the concrete gets a set, enough to avoid disturbance of finished surface.

Ø  Curing shall be done for a minimum period of seven days.

 

Inspection & Testing

        

Fig. Checking of Fresh Concrete

Ø  Testing shall include compressive tests of molded concrete cubes and slump tests for consistency, according to IS 516 & IS 1199.

Ø  For Sampling of Compressive Testing set (6 Specimen) of cubes shall be prepared, which include 3 specimens each for 7 days & 28 days as per IS 456.

Ø  The fresh concrete shall be sampled in accordance with IS 1199.

Ø  Rate of sampling shall be as per project specification.

Ø  Slump test shall be carried out to check the consistency of concrete.

Ø  Inspection shall be carried out as approved ITP and Acceptance criteria shall be as per applicable codes and specification.

        

Fig. Casting & Testing of Concrete Cubes

Reference Documents

IS CODE	DOCUMENT TITLE
IS 383 -1970	Specification of coarse and fine aggregate from  natural sources  for concrete
IS  2386 -1963	Methods of test for aggregate for concrete
IS 10262 -1982	Recommended guidelines for concrete mix design
IS 456 -2000	Plain and Reinforced Concrete - Code of Practice
IS  1489 -1911	Specification for Portland pozzolana cement
IS 455 -1989	Specification for Portland slag cement
IS 4926 -2003	Specification for Ready-Mixed Concrete
IS 516 -1959	Method of test for strength of concrete
IS 1199  -1959	Methods of sampling and analysis of concrete
IS 3025 -1964	Methods of Sampling and Test
	Contract documents and drawings