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.
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 :
1.2 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
1.9 Excavator with front loader.
2. Material Testing laboratory:
This could be a small lab minimum of these arrangements :
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
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
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 .
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
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.
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.
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.