In this series we are looking at the various stages in the construction of a building.
So far we have covered from land acquisition up to mobilization and from mass excavation up to columns of the first floor.
This article brings you the intricacies and steps in casting the roof slab.
For the purpose of clarity, the tasks have been grouped under:
A. Pre-concreting care: B. During concreting care: C. Post -concreting care:
All the Activities ,however, have been sequenced in a continuous serial nos from 1 to 47.
The activities sequence:
1.Columns up to beam bottom
2.Curing of columns
3.marking of beam bottom on columns
4.fixing of runner blocks on columns
Beam bottoms & sides:
5.Fixing of beam bottom
6.Supports below beam bottom
7.Inside face of beam: side fixing
8.Slab centering in plates
9.Gaps fixing with planks & closing of gaps qith iron strips or masking tape.
10.Fixing of Accrow spans
11.Levelling of centering plates
12.Keeping camber in the slab
13.laying of beam reinf.
14.Laying of slab reinf.
15.placing chairs below bent up bars
Electrical conduits/ fixtures:
16.Laying electrical conduits/ fan hooks/ down pipes from beams
17.Keeping pipe sleeve in the sunk portion for drainage pipe
18.Placing cover blocks for beams & slabs
19. Fixing clamps for beams
20.Fixing tie bars in sleeves for deep beams
21.Steel measurement and checking
( jointly with clients engineer)
23.Extra bars counting
Arrangement for casting:
24.Installing the concrete pump
25.Fixing the pipes for concrete
26.scheduling the transit mixer ( TM)
27.Final checking by consultant
28.pour card approval
B. Care during concreting :
30.Compaction by needle vibrator
32.slab thickness verification
34.Removing excess debris from slab
C.Post concreting care:
35.casting of specimen cubes
36.providing mortar bunds for curing
37.ponding with water
38.striking off beam sides
39. striking off slab centering
40. striking off beam bottom
41.Hacking the concrete surface
42.Sunk portions cleaning
44.ponding with water
45.Testing of cubes on 7th & 28th days
46.Reconciliation of materials
Ready mix concrete or RMC is the secret behind many of today’s fast paced and technologically advanced construction projects.
RMC means getting a timely supply of concrete at your site in desired quantities as per agreed schedule, with assured quality without having to bother for operational details like materials procurement , design mix, weigh batching, mixing etc.
This article is aimed to take the reader on interesting journey through the wonderland of ready mix concrete so that no one can dare say ” You mean you don’t know RMC ? “
If concrete is proportioned & mixed at a central location under
strict quality controls and if it can be delivered to the customers on just-in-time basis, it shall be quite useful , economical and reliable.
When we say RMC , which elements doesitinclude?
For manufacturing of the ready mix concrete , a RMC plant is needed .
RMC plant is the entire set up required to produce ,test & deliver the ready mix concrete of different grades.
A RMC plant shall essentially need the following :
1.A batching plant: This is a collective term for :
1.1 Bulk Material storage yard :
Open storage for Natural sand, Crushed sand, Aggregates of different sizes, Plasticizers.
Storage sheds & silos for cement ( OPC & PPC ). 1.2 Conveyor arrangement : From open storage to bins 1.3 Storage bins 1.4 WeighBatcher 1.5 Conveyor from Weigh Batcher to mixer 1.7 Rotary Mixer 1.6 Water tank 1.8.Loading arrangements 1.9 Excavator with front loader.
2. Material Testinglaboratory:
This could be a small lab minimum of these arrangements : 2.1.Slump cone 2.2 Cubesmoulds 2.3 Cubes vibrationtable 2.4 Curingpondforspecimencubes 2.5 Compressiontestingmachine
2.6.Sieves for sand & aggregates
2.6.Flakiness testing kit for aggregates
2.7.Silt measurement jar for sand
If it is an advanced lab it may also have facilities for cement & water testing.
3. Computerized controls for all operating systems.
Deployed at the site.This pumps the concrete to the desired location through pipes.
5. Necesary administrative facilities.
6. Competent Staff
Note : There could also be RMC plants which integrate a stone crusher in the same premises.
In this case, the stone aggregates are produced in the same or adjoining campus and suitably shifted to the storage yard.
This is done with transit mixers. A transit mixer is a mixer which is mounted on a heavy truck .
1.A heavy capacity truck
2.A drum of capacity 6 to 7.5 cum.
3.A hopper for filling concrete inside drum at the batching plant
4.A gear operated rack & pillion arrangement for rotating the drum.
5.There are helical shaped blades mounted on the inside surface of the drum.
6.A chute for taking out concrete at the site
The key to this question is in the direction in which drum is rotated.
During the transit ,the drum rotates in a clockwise motion whereas when the concrete is to be poured out ,the rotation is reversed.
When the drum moves clockwise, the helical blades pull the concrete downwards ( away from its outlet).
When the drum moves anti-clockwise, the helical blades pull the concrete towards the drum outlet and hence the concrete starts pouring out.
What is the process of pumping concrete ?
Pipe line is laid from the receiving point upto the exact location of placing the concrete.
The transit mixer delivers the concrete directly in the hopper of the concrete pump.
The rotating screw pushes the concrete in the pump from where it is pushed across the connected pipe. Concrete gets delivered to the desired location where it is properly vibrated, compacted and levelled.
What are the advantages of using concrete pump ?
The entire set up for transportation of concrete from the receiving or mixing location upto the point of use is eliminated.
In short we don’t need the concrete lift or buckets , the trolleys and the workers tom transport the trollies back & forth.
What is needed is the set of pipes, connectors, bends and stands for the pipes.
Thus main advantage is elimination of all scaffolding .Dependence on labour is reduced.