Category Archives: ready mix concrete

Free Video for you on Concrete. [Grade from Ratio and vice versa]

Hello Friends ,

Enjoying the day ?

Every construction person needs to know these :

  1. How to find out the grade of concrete if the ratio is known
  2. How to find the ratio if the grade is given.

Right ?

Just spend 12 minutes of your busy time in watching the following video and you shall know the trick. Learn through the simple to follow steps and master the technique.

Concrete : Grade to Ratio 

By the way , if you want to know more knowledge on construction , why not join the

On Line Courses for Civil Engineers ?

You learn many difficult topics from the comfort of your home.

easy to follow video leactures are available in each module.

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Working Knowledge about concrete

Dear Friends ,

Good afternoon.

If you study this article, you can certainly discuss about concrete with the construction persons. This is the beginning of the vast and detailed science of concrete technology.
Read on

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Yeah..the Slab is finally cast

Overview:
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:

A.Pre-concreting care:

Columns:
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

Slab centering:
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

Reinforcement laying:
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

Sunk portion:
17.Keeping pipe sleeve in the sunk portion for drainage pipe

Securing:
18.Placing cover blocks for beams & slabs
19. Fixing clamps for beams
20.Fixing tie bars in sleeves for deep beams

Joint inspection:
21.Steel measurement and checking
( jointly with clients engineer)
22.Laps counting
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 :

29.Placing concrete
30.Compaction by needle vibrator
31.levelling
32.slab thickness verification
33.finishing
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
43.waterproofing
44.ponding with water
45.Testing of cubes on 7th & 28th days
46.Reconciliation of materials
47.Bills

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You mean you don’t know RMC ?

Overview:

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 ? “

What’s the idea behind it ?
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.

THE RMC PLANT : A long shot
THE RMC PLANT :
A long shot

When we say RMC , which elements does it include ?

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  Weigh Batcher
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.
a long shot of another RMC plant
a long shot of another RMC plant
Open yard storage of aggregates . [ On the right side you can see the Cement silo ]
Open yard storage of aggregates .
[ On the right side you can see the Cement silo ]

2. Material Testing laboratory:
This could be a small lab minimum of these arrangements :
2.1.Slump cone
2.2 Cubes moulds
2.3 Cubes vibration table
2.4 Curing pond for specimen cubes
2.5 Compression testing machine
2.6.Sieves for sand & aggregates
2.6.Flakiness testing kit for aggregates
2.7.Silt measurement jar for sand

REPLENISHMENT OF MATERIAL STOCK WITH DUMPERS.
REPLENISHMENT OF MATERIAL STOCK WITH DUMPERS.

If it is an advanced lab it may also have facilities for cement & water testing.
3. Computerized controls for all operating systems.

4.Transit mixers.
5.Concrete pump:
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.
MOULDS for casting the concrete cubes.Cubes are tested in the in-house testing facility.
MOULDS for casting the concrete cubes.Cubes are tested in the in-house testing facility.
CONCRETE CUBES CAST FOR TESTING THE COMPRESSIVE STRENGTH
CONCRETE CUBES CAST FOR TESTING THE COMPRESSIVE STRENGTH
COMPRESSION TESTING MACHINE FOR THE CONCRETE CUBES. Left : Cube clamping mechanism  Right : Dial indicators to note down the crushing load.
COMPRESSION TESTING MACHINE FOR THE CONCRETE CUBES.
Left : Cube clamping mechanism
Right : Dial indicators to note down the crushing load.

How is the concrete transported to different sites ?
This is done with transit mixers. A transit mixer is a mixer which is mounted on a heavy truck .

TRANSIT MIXER  [ CAPACITY 6 CUM ]
TRANSIT MIXER
[ CAPACITY 6 CUM ]

The transit mixer comprises of which elements ?

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

TRANSIT MIXER  look at the drum , the chute and the ladder .
TRANSIT MIXER
look at the drum , the chute and the ladder .

Why the concrete does not spill out during transit although the drum is kept rotating ?

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.

CONCRETE PUMP This can deliver 40 CUM of concrete per hour
CONCRETE PUMP
This can deliver 40 CUM of concrete per hour
CONNECTOR FROM CONCRETE PUMP TO PIPE LINE
CONNECTOR FROM CONCRETE PUMP TO PIPE LINE
PIPE LENGTHS KEPT READY FOR CONNECTION.
PIPE LENGTHS KEPT READY FOR CONNECTION.

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.
PIPE LINE LAID ON STANDS from concrete pump upto the point of placing concrete.
PIPE LINE LAID ON STANDS from concrete pump upto the point of placing concrete.
COLUMN CASTING IS IN PROGRESS WITH CONCRETE PUMP. Location : AT THE 9TH FLOOR OF A HIGH RISE BUILDING
COLUMN CASTING IS IN PROGRESS WITH CONCRETE PUMP.
Location : AT THE 9TH FLOOR OF A HIGH RISE BUILDING