concrete

METHOD STATEMENT FOR CONCRETE WORKS

1. Materials 1) Cement2) Sand3) Aggregates (Metal)4) Water5) Admixtures

1.1 Consumable materials (All details to be in appendix) a. Admixture b. Accelerator c. Super plasticizers d. Air entrained

2. Tools and Machineries

I). Mason trowel II). Masonry level bar

III). Power trowel IV). Finishing trowel

V). Poker & vibrator sets VI). Mortar span

VII). Pump car VIII). Truck mixture

IX). Concrete mixture X).Boom truck

XI). Air compressor machine XII). Crane (bucket method)

XIII). Fork lift machine XIV). Dumper & wheel barrow

4. Work norms

• Pump machine – 18m3/hr [3M+4L]

• Crane & bucket method – 12m3/hr [3M+4L]• Manual mixing &

pouring - 2.5m3/hr [3M+4L]

5. For successful execution of the work following selection shall be communicated

• Survey gang – check the concrete leveling• Materials suppliers with store keeper – to

maintain adequate stock • Concrete gang with concrete foreman –

mixing ,pouring, compacting & leveling the concrete

• Q/A/,Q/C Engineer – check the concrete mixes

6. Rate Breakdown

7. Calculation Calculation relative to concrete volume

• Concrete Volume = Length (x) Width (x)

Height (m3)

• Reduction = Steel Volume (Nearly 0.5% to

2.5%of concrete volume)

• Addition = Yield Volume (can be find during

the Trail mixing test)

• Addition = 0.25 m3 for pump car wastage

8. Procedure for concrete work

1). Mix design trial mix Mix proportion of concrete shall be designed for

each grade of concrete specified in the technical specification and trial mix shall be carried out for each mix design. (pl . see trail mix Method statement)

a. Quality of following materials used for concrete shall be checked by testing or manufacturer’s certificate in order to assure the quality of concrete.• Cement• Coarse aggregates• Fine aggregates• Water• Admixture b. Compressive strength test for each trial mix shall be

carried out at following curing days.

• At 7 days• At 28 days

c. Reports of tests mentioned above shall be submitted to Engineer, and each mix design shall be approved by Engineer prior to concrete work.

2). Preparation

a. Concreting plan.

Method and procedure of concreting shall be planned prior to concrete casting in consideration of following items.(see attached example drawing)

• Method of casting (pump or crane w/hopper)• Layout of pump car & piping, or crane• Required concrete volume per hour• Casting sequence or layout with quantity• Temporary access or platform for concrete

place

b. Following equipment shall be prepared in stand-by condition prior to casting concrete.

• Pump car & piping , or crane & hopper• Vibrator and other tools for concrete

compaction• Tools for concrete pouting such as

hoe/level/bar/ trowel/Power travel machine• Level machine & staff• Lighting for night time work

c. Temporary access/plat form for casting concrete shall be provided prior to casting concrete.

d. Inside form shall be thoroughly cleaned by pressured air prior to casting concrete.

e. Watering to form surface shall be carried out prior to casting concrete.

f. When using pump car in order to cast concrete, the motor (cement : sand = 1:1½) can be used for initial pumping purpose. So we have to prepare that mixture at least in one bags

3) Batching & delivery

Ready mix concrete shall be batching plant and delivered to site by truck mixer with delivery sheet.

Following items mentioned in delivery sheet shall be checked at

site.

• Time of departure (Concrete shall be cast within

three hours after the time of departure)

• Nominal strength• Designed• Max . size of coarse aggregate• Type of cement 4) Casting

a. Slump test shall be carried out at the commencement of casting and for each 100 m3 of concrete (this volume can varied with specification ).Acceptable slump shall be _+

2.5 cm of designed slump.

b. Test cube for compressive strength test One set test cubes shall be prepared for each 30 m3 of concrete and at least one set on each day. A set of test cubes shall consist of 9nos. of test cube.(3 nos. For 7 day test , 3 nos. For 28 days test and 3 nos. for form removal)

c. Pouring & Compaction

Pouring shall be carried out by taking care of following items.

Concrete shall not be poured from high place that causes segregation .(Height not more than 1.5m ,If exceed put pocket or connect trimly pipe to pump car)

Concrete shall not be poured at one

place intensively.Concrete shall be poured

layer by layer with proper compaction.

d. Compaction shall be carried out by taking care of following items.

• Compaction must be done as concrete placed,• Put the poker into the concrete QUICKLY. Take

the poker out very SLOWLY otherwise a hole, or weak spot , may be left in the concrete.

• Always compact in a definite pattern so the radius of action overlap and covers the whole area of the concrete.

• The poker should be long enough to reachand enter into the layers

of concrete under theone being compacted.

• Never touch the form with the poker as it can damage the formwork and alignment.

• Never touch the reinforcement with the poker.

• Never spread or move concrete sideways

with the poker, always use a shovel.• Never leave the

poker running when not in use.

• For concrete of average workability( i.e.. Slump of 80 mm) with a poker size between 25-75 mm, concrete should usually be vibrated for between 5 and 15 seconds. It worse to UNDER - VIBRATE than to OVER- VIBRATE concrete.

e. Level & Finishing• Level of concrete

shall be checked by level machine at 2m interval.

• Surface finishing shall be carried out as per

architectural requirement. No final finishing

can begin until the bleed water has dried up. Mixing bleed water with the surface paste will weaken it , possibly resulting in a dusty surface.

• Excess bleed water can be removed by dragging an ordinary garden hose across the surface of the concrete.

• Never try to dry up the bleed water using stone dust or cement

as this will weaken the concrete surface in the long run.

• Floating can be done by hand or with a power float.

Submit QA/QC check sheet to main contractor5) Curing

Curing is done just after finishing the concrete surface ,as soon as it will not be damaged.

The simplest method of APPLYING WATER is to put a continuous fine, misty spray of water over the concrete . The spray must be a very fine mist or else it will damage the surface of the concrete.

Another way of curing is, cover with PLASTIC SHEET or GUNNEY BAGS to slow down water loss. This method is easy and cheap. The only problem is that the sheets may cause concrete become darker in places. To avoid this keep concrete EVENLY moist. For better strength and durability, cure concrete for 7 DAYS. The concrete is cured LONGER ; it will have its best possible strength and durability. Other method of curing1) Pounding method2)Spary waste timber dust and apply water3)Spary chemicals

6) Compressive strength testOne set (3 cubes) shall be tested at 7 days and one set 28 days after casting.Average strength of 3 cubes shall be equal or greater than design strength and individual test result shall be greater than 85% of design strength.Each test report shall be submitted to Engineer.

07) Flow Chart of concrete worka). Lean concrete

Lean concrete

Mark the locations on the Lean concrete

Fixing of reinforcement & cover blocks

R/f inspection by contractor

R/f Inspection by consultant

Erection of formwork

Inspection by Contractor

Final inspection by consultant

Concreting

Curing

Removal of formwork

Not satisfied Satisfied

Do rectification as per Structural Engineers

instructionsCarry out further

works

NOOK

OK

OKNO

NO

NOOK

Inspection

b). Columns

Mark the locations on the foundation or floor slab

Fixing of reinforcement & cover blocks and (anchor bolts for base plates of steel columns)






Concreting

Removal of formwork

Inspection



instructions

Carry out further works

Curing

NO

NO

NO

NO

OK

OK

OK

c). Beams

Mark the location and level

Erection of bottom form work with adequate supports






Concreting

Removal of supports and bottom form

Inspection


Do rectification as per Structural Engineers instructions


Curing

NO

NO

NO

NO

OK

OK

OK

Fixing of reinforcement & cover blocks

Removal of side formwork

d). Ground slab

Lay gauge 1000 polythene layerOn the compacted earth

Mark the stud column starter bar as per the drawings

Fix stop board where necessary to hold concrete

Inspection by contractor

Inspection by consultant

Concreting

Removal of supports and bottom formwork

Inspection


Do rectification as per Structural Engineers instructions


Curing

NO

NOOK

Lay R/F and Fix column starter bar as per details given in the drawings

Removal of side formwork

e). Suspended slab

Mark the location and levels

Erection of slab bottom formwork with supports

Inspection by contractor

Inspection by consultant

Fixing of side board

Concreting

Removal of formwork and support

Inspection



instructions


Curing

NO

NO

NOOK

Laying of R/F and cover blocks and M&E services

OK

Cleaning

Inspection by contractor & Consultant

concrete

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