CONSTRUCTION JOINTS IN IN-SITU CONCRETE METHOD STATEMENT

CONSTRUCTION JOINTS IN IN-SITU CONCRETE METHOD STATEMENT

1.    SCOPE

 The scope of this procedure outlines methods to be used for constructing effective and durable construction joints in accordance with the contract specifications.

 2.    PROCEDURE

.1    In some cases CLIENT shall have to prepare shop drawings proposing location and type of construction joints and obtain approval from the Consultant’s representative before proceeding with the work.

.2    Horizontal Surfaces:

     Laitance on the surface must be removed from the concrete in order to ensure that a good bond will be achieved when fresh concrete will be placed against it. Following methods may be used for removing laitance from the top of walls and columns unless specified otherwise in the contract:

 i)    Washing and Brushing:

 The easiest way is to brush off the laitance while the concrete is still fresh but has stiffened slightly. Brushing shall be commenced between one to two hours after placing of concrete. Site operatives shall have brushes with soft and hard bristles so that it can be used depending upon stiffness of concrete. Care shall be taken that the brushing shall not be harsh which will dislodge the coarse aggregates. In case laitance has hardened but is still green, a wire brush should be used.

 ii)    Air and Water Jet:

 Laitance can be removed by directing a jet of air and water onto it. This method can be used up to six hours after placing or possible longer but the site operative must make his own judgement while adopting this method. This operation must not start too soon because it might dislodge coarse aggregate particles.

 iii)    Mechanical Scabbling:

 If laitance is too hard to be removed by wire brushing, mechanical scabbling can be tried using small percussion power tools. This method can be applied after 3 days when concrete has hardened sufficiently. Care shall be taken not to weaken the coarse aggregates.

iv)    Abrasive Blasting:

 Wet or dry abrasive blasting can be used to expose the aggregate but special safety precautions shall be taken while using sand.

.3    The most appropriate time for treating the joints is a matter of judgement, because it depends on the rate of setting and hardening (which is itself dependent on the temperature of the concrete).

.4    Where there is likely to be even a short delay before placing the next concrete pour, protruding reinforcement should be protected. Before the next pour is placed, rust, loose mortar or other contamination should be removed from the bars.

.5    Vertical Surfaces:

i)    Stop Ends/Expanded Metal Mesh:

Vertical joints in walls, beams and slabs are usually formed at a stop end in the formwork. Stop ends shall be located where the reinforcement is least dense. Holes for reinforcement in stop-ends are a potential weakness because grout loss can occur. In lightly reinforced sections and where starter bars are acceptable, this problem is frequently avoided by bending bars so that they run along the inner face of the stop-end. When the stop-end is removed, the bars are cut out and straightened. However, the cutting out and straightening can damage the concrete and cause local loss of bond with the bar, especially if this is carried out within 48 hours of placing the concrete.

 Proprietary stop-ends have been developed which overcome this problem by encasing the bent bars in expanded plastic foam. The foam can easily be removed and the bars strengthened by means of a steel tube. Take particular care not to use impact to straighten bent steel at stop-ends as this can cause brittle fracture.

 Permanent forms of expanded metal are increasingly employed, particularly in deep slabs. The concrete surface produced by such system is very irregular and does not normally require any surface preparation. Where a very high workability mix is being used (slump greater than 200mm) with expanded metal formwork, care should be taken to avoid over – vibration at the joint as this may cause grout loss.

 ii)    Formwork:

 Formwork for subsequent concrete pours must be accurately aligned and well fixed so that there is no grout leak which results into discoloration and honey combing. Strips of foam rubber or polyurethane unless specified otherwise can be fixed around the edge of the hardened prepared joint.

 .6    The methods explained previously i.e. washing and brushing, mechanical scabbling and abrasive blasting can also be used in case of vertical joints. However special care shall be taken not to damage the leading edges (leave a margin).

.7    Watertight Construction:

i)    In watertight construction unless specified otherwise, flexible waterbars of specified details can be used. Care shall be taken while concreting so that all waterbars are securely tied to avoid its folding during concreting.

 .8    Cold Joints:

 i)    Cold joints normally occur during the concreting operation when a delay in placing adjacent concrete has occurred and earlier concrete placed has stiffened.

 ii)    A simple test can be used to determine whether concreting can proceed. Embed the poker vibrator into the existing concrete to examine the condition of concrete. Where the action of the poker has left a distinct hole, concreting operations should not continue. In this case the joint face can be prepared by one of the methods described above for horizontal construction joints.

 .9    Placing the Fresh Concrete:

 i)    Particular care as explained below shall be taken while placing and compacting new concrete on or against the old:

ii)    Any dirt or dust from the surface of the hardened concrete shall be removed preferably with a compressed air hose. As a safety precaution site operatives must wear safety goggles. This cleaning shall be done before new formwork is fixed because not only access be easier than but also dirt might otherwise stick to the new formwork.

iii)    While fixing a new formwork extra dirt is created which can be cleaned after removing a stop end – which will make it easy to be swept or blown away.

.10    Joint Sealing:

 i)    Where the structural component containing the joint is to be exposed to the external environment, the joint has to be sealed to prevent ingress of water. For type and method of application refer to the contract specifications and/or manufacturer’s instructions.

  3.    DOCUMENTATION

 Following documentation and forms may be maintained as a minimum pending on Project Quality Plan requirements and contract specification.

 i)    Contract and/or approved workshop drawings.

i)    Manufacturer’s test certificates (in case of sealants and

waterbars).

iii)    Request for Consultant’s consent/approval.

 The above referenced documentation where appropriate will be retained in the HEE archive for the prescribed period of time.

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CONSTRUCTION JOINTS IN IN-SITU CONCRETE METHOD STATEMENT

Batching Of Concrete Method Statement

Batching Of Concrete Method Statement

The scope of this procedure covers checks required to be carried out prior to and during the site batching of concrete.

PROJECT: PROJECT NAME	Ref No. CONC/09
	PAGE 1 OF 4
SECTION: CONCRETING	DATE OF ISSUE Dec. 2012
SUBJECT:
Batching Of Concrete Method Statement	APPROVED BY: QEHS MANAGER
	ACTION	VERIFY
1.    SCOPE The scope of this procedure covers checks required to be carried out prior to and during the site batching of concrete. 2.    PROCEDURE .1    Checks Prior to Commencement of Activity: i)    Basic constituents of concrete viz. cement, coarse and fine aggregates shall comply with the contract specifications. In case of large projects and where specified, a laboratory will be set up at site for conducting tests on materials and ensured product. Refer Work Procedure CONC/13. ii)    Availability of potable water and power shall be ensured. In case of supply failure alternative arrangements shall also be planned. iii)    Verify the type of admixture if required, to be added. If required, receive approval from Consultant’s representative. .2    Handling and Storage of Materials: Special care shall be taken for proper storage of basic materials in order to avoid contamination. Unless otherwise specified, the following measures shall be taken for proper handling and storage of these materials: .3    Cement (in bulk): i)    The silos shall be weatherproof and the mechanism will be cleaned regularly in accordance with manufacturer’s manual. ii)    The air filter will be cleaned after every delivery. iii)    Care shall be taken to use stored cement in the order of delivery. iv)    Care shall be taken to minimise the contact of cement with air. v)    The silo shall be painted white and wherever possible, shaded from sun.	Project Engineer Site Engineer Plant Operator	Source Certificates Analysis Report Approval Operation Manual, Supplier’s instructions Manufactu- rers manual

PROJECT: PROJECT NAME	Ref No. CONC/09
	PAGE 2 OF 4
SECTION: CONCRETING	DATE OF ISSUE Dec. 2012
SUBJECT:	BY: QA/QC ENGINEER
BATCHING OF CONCRETE	APPROVED BY: QHSE MANAGER
	ACTION	VERIFY
.4    Aggregates: i)    Storage of aggregates shall be on clean; permanent clean hard-standing laid to fall for drainage. ii)    Different sizes of aggregates shall be separated from each other in bins or compartments with rigid dividing walls extending high enough to prevent different aggregates from being mixed during batching. iii)    In hot climates either shading or sprinkling clean water is required to reduce that fines and dust have not built up at the lower levels. If this has occurred, contaminated aggregates shall be removed and washed or replaced with clean material. iv)    If aggregates are wet stockpiles shall be frequently inspected to make sure that fines and dust have not built up at the lower levels. If this has occurred, contaminated aggregates shall be removed and washed or replaced with clean material. .5    Admixtures: i)    Storage of admixture shall be as per the manufacturer’s recommendations. ii)    The containers shall be levelled to indicate the contents, batch number, date of manufacture, shelf life and any other requirements for storage. .6    Water: i)    Water shall be stored as cool as possible, particularly if it has been supplied by road tanker or shallow wells. ii)    Wherever possible, storage tanks shall be sited below ground. It this is not possible, they should be at least be shaded from the sun and painted white. iii)    Tank to be covered properly to prevent the growth of algae. iv)    For cooling of water even site cooling towers can be used which reduces the temperature up to 10OC or ice can be used.	Plant Operator Store- keeper Plant Operator	Manufactu- rer’s recom- mendation

PROJECT: PROJECT NAME	Ref No. CONC/09
	PAGE 3 OF 4
SECTION: CONCRETING	DATE OF ISSUE Dec. 2012
SUBJECT:	BY: QA/QC ENGINEER
BATCHING OF CONCRETE	APPROVED BY: QEHS MANAGER
	ACTION	VERIFY
.7    Plant: i)    Batching and mixing plant shall be pained white and kept clean. ii)    If possible, mixing and batching plant shall be shaded from the sun. iii)    Provision shall be made to prevent dust accumulating in the plant and immediately before it is used each day (or after any substantial interruption in concreting) it shall be flushed out with water. iv)    Feed belts and weigh batchers shall be protected from the wind so that cement can’t be blown away. v)    Ensure the accuracy of all weighing and measuring equipment falls within + 3% unless specified otherwise calibrate plant as necessary. .8    Batching by Volume: i)    Prepare gauge boxes or similar standard containers of a size such that complete filling is necessary when proportioning materials. ii)    Clear written instructions will be provided to the Plant operator on quantities of all materials to be batched and batching sequence for each mix required. iii)    Priming of internal drum of mixer to be done at the time of loading the first batch of materials. iv)    Mix ingredients for sufficient time as specified to ensure uniform distribution of materials. v)    Check the zero reading when hopper is empty. vi)    Check the speed of mixer drum once a week and adjust to that given in the manufacturer’s manual. vii)    Regular maintenance of moving parts shall be done in accordance with the manufacturer’s manual. viii)    Transport the concrete with minimum delay so that it is placed before it comes hardened and difficult to place and compact.	Plant Operator Plant Operator

 Download the Batching Of Concrete Method Statement word format: Batching Of Concrete Method Statement

Batching Of Concrete Method Statement

PROJECT: PROJECT NAME	Ref No. CONC/09
	PAGE 4 OF 4
SECTION: CONCRETING	DATE OF ISSUE Dec. 2012
SUBJECT:	BY: QA/QC ENGINEER
BATCHING OF CONCRETE	APPROVED BY: QEHS MANAGER
	ACTION	VERIFY
3.    DOCUMENTATION .1    Following documents may be appropriate as a minimum requirement: i)    Test certificates of cement, aggregates, water and admixtures. ii)     Mix design details. iii)     Calibration record of all equipment of batching plant.	Project Engineer