Wednesday, August 26, 2020

Session 10 : RCC Work (RCC Column Work) (Free Online Quantity Survey and Estimation Course)

 RCC COLUMN WORK




1 Name of Work & Description

RCC (Reinforced Cement Concrete) Column: The vertical Member of any structure called as Column, Column is a very important member in any structure, this member is the main load transferring member, from building to the footing. All RCC Structure need to design RCC Designer, they are calculating all the details about the load calculation as well as per design the details of reinforcement steel.
 

Types of Column

1 Column
2 Y Columns
3. Inclined Columns
 
 

2 IS Code No.

Plain and Reinforced Cement Concrete IS Code: IS 456:2000
Methods of tests for aggregate for concrete: IS: 2386
Compressive strength test for cement mortar cubes: IS: 2250
Methods of sampling and analysis of concrete: IS: 1199
Specifications for fine & coarse aggregate from natural sources for concrete: IS: 383
 

3 The Drawing Needs to Read.

Following the drawing needs to study before start Column Work.
1 Column Section Drawing
2 Column Centre Line
3 Layout of Column Position
4 Column and Schedule.
5 Section (Floor to Floor Height)




 

4 Location of Work

The column is the important part of any structural work, as the column is started from Footing, Pile cap Foundation.
1 Column is Located at Footing Centre
2 Column is Located at as per centerline  drawing on Raft foundation.
3 Each and Every Floor Column Position is Different as per schedule
4 Stub columns on Cantilever Beam
5 Y Shape column is Located to support at cantilever position.




 

5 Standard Procedure of Work (Step by Step)

Following procedures need to follow before starting the Column Work.

1 Checking Column Centre as per Column Layout Drawing
2 Checking of Column Size as per Drawing
3 Checking of Column Position and alignment as per Drawing
4 Marking of Column Position on Slab, Footing, Beam Etc.
5 Checking of Steel Reinforcement as per schedule.
6 As per Marking of Column Position Fix the Starter properly
7 Fix and Binding of steel as per given schedule to column up to the middle of next floor as per drawing.
8 Concreting of Starter with given concrete grade with compaction.
9 Fixing the cover block to stirrups of the column and fix the shuttering.
10 Check the Supports of Columns, Size of Column at the top level.
 11 Check the Plumb Bob of Column as per Given Drawing.
12 Pour the Concrete as per given concrete grade with proper compaction, tamping, without disturbing the column position of the column. This may decenter the column or chances of bulging.
13 The next day remove shuttering and regular curing to be done.
14 The next day needs to hacking the column because after the final setting time completed hacking can not be more effective after 28 days.
 
 



6 Equipment and Machinery

Cast in situ Column Concreting required following Material
1 0.5 Bag/1 Bag Manual or Semi-Automatic Concrete Mixture.
2 Weight batcher
3 Wheel Borrow
4 Shovel & Ghamela
5 Trowel
6 Line Dori
7 Measurement Tape
7 Auto level and staff.
 
 

7 Measurements and Quantity Survey

Reinforced Cement Concrete is measuring in Cubic Meter.
Following are the procedures to take and write the measurements of Column Concreting.
If Size of Column is 600mm X 300mm and Height is given 3000mm (Floor to Floor),
If column height is given 3m Floor to Floor We need to calculate the Beam Depth which is resting on this column, suppose beam depth is 0.45m Then We need to cast Column up to 2.55m but standard plywood height is 1.22m X 2.44m i.e. We can do shuttering of column up to maximum 2.40m height, so we need to calculate the column concrete requirement as per the required height.
 
There are 2 points, If you are doing concrete you need to calculate the column height as per your requirement like if 1st stage of column concreting then column height need to calculate as per plywood height i.e 2.44m
 
If you are calculating the all over building quantities you need to calculate the column height in 2.55m because beam and slab need to consider separately.
 
 
1 Cubic Meter:
Size of column: 600mm X 300mm
Height: 2.44m
Concrete Quantity Column: 0.60m X 0.30m X 2.44: 0.439 Cubic Meters
 


 

8 Checklists

Checklist for Column Concrete is called Pour Card.
1 Excavation Level, Plinth Top Level, Column Size.
2 All Loose Material Removed and Cleaned the PCC base surface.
3 Marking is Done including offset to foundation
4 Formwork is cleaned and oiled
5 Formwork free from holes and gaps.
6 Formwork size is as per drawing.
7 Formwork is inline-level and plumb.
 

9 Quality Tests

Compression test of Cube
Testing of Cement
Testing of Aggregate
 



10 On-site Experiences

The column is the most important structure of any structure but when we actually execute the work, some of the engineers ignore the importance of this structure, due to this negligence lot of times may chance to bare huge cost to contractor, client, and time will require more to do rework if possible.


During the execution of column work, there are 3 steps

1.Reinforcement: 

Column shuttering should be checked carefully the checkpoint of the column are as follows like the diameter of steel, the spacing of bar as well as spacing of stirrups, link position,  and most important part is checking of lap length or if the lap is not possible need to check coupler joint done properly. After all the checking needs to check the position of the column as well as the position of a bar that the mean center is shifted or not. If the center is shifted please take advice from RCC consultant, do not joggle the bar, this is reducing the life and strength of the structure. Also, check the cover is placed or not, some covers are inserting in the bar, some covers are from the external side of the bar. So please check all the points of column reinforcement and do the actual bar bending schedule to claim in client bill.


2.Shuttering: 

Before shuttering of the column we need to check the quality of plywood, as well as please check the oil is applied to internal side or not, if not applied please apply it and the place and fix it as per size, please take precautions while supporting the column, like supporting by props, fixing of shikanja (MS Shuttering Clamp), anchor bolt, and tie rods, etc. while checking of column shuttering need to check the size of the column is proper or not, and line-level with the centerline of column, as well as most important part is checking of plumb bob of column this check is very very important to reduce the errors in the decentralization of the column on the next floor.  If you will put 5mm error while checking of column plumb bob, then next upper floor column will be shift 5mm from its position. So please take proper precautions while checking the column positions, the same criteria will be applicable to retaining wall, Pardi, shear wall, etc. internal side should be smooth, as well as oiled.  
 

3.Concreting: 

Before starting the concreting of the column we supposed to all above checks was done and found clear and rectified if found any error, after that we should make a proper scaffolding around the column to fill the concrete in it, do not apply more force of column shuttering because this is a temporary structure and all positions, size, plumb bob checking has been completed if we apply this more force on the column shuttering may chance to decentralize the column. This practice is not good. So please prepare the scaffold to do the concreting of the column. Also please check the concrete slump cone while concreting. Also, Fill the Concrete Cube for Compression test after 7 days, 15 days, and 28 days this is very good practice to know the concrete strength is achieved or not. If possible please keep a concrete cube near to the same column which is very useful, how may time actual curing was done to column and cube will know by the strength report.
Mr. Somnath
(Project Co-Ordinator)




Team
CBEC India

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