What is redosing in RMC and is there any IS recommendation

Dnyan Deshmukh

Staff member
Re-dosing in RMC generally means to dosing concrete with admixture.

This happens when, the concrete need to be made wait for more than time for which it was initially design.
You can imagine all situation for delays, ultimate resultant is re-dosing of admixture.

What happen after re-dosing

The workability regain observed after re-dosing.

The designer of concrete should know about the limitation of use of admixture in his / her design.

He / She should check for maximum dosage of admixture which can handle without hangover by concrete and it remembers all his properties.

as said by @K Kiran , you can refer IS guide lines as mentioned by him.
 

K Kiran

Senior Member
Many Standards states that concrete should be placed within 90 min. after batching. Nowdays many brands of admixtures are available in markets .i.e third generation admixtures (PCE based), Which are formulated to meet required slump retention time.

My suggestion is Concrete designer should carry out the trials or mock ups on re-dosing without deviating the required fresh and hardned concrete properites meanwhile you have take approval of customer.
 

Pawan Dhagate

Staff member
Many Standards states that concrete should be placed within 90 min. after batching. Nowdays many brands of admixtures are available in markets .i.e third generation admixtures (PCE based), Which are formulated to meet required slump retention time.

My suggestion is Concrete designer should carry out the trials or mock ups on re-dosing without deviating the required fresh and hardned concrete properites meanwhile you have take approval of customer.
One small correction is PCE based admixtures are 5th generation admixtures not 3rd.
 
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Re-dosing in RMC generally means to dosing concrete with admixture.

This happens when, the concrete need to be maid wait for more than time for which it was initially design.
You can imagine all situation for delays, ultimate resultant is re-dosing of admixture.

What happen after re-dosing

The workability regain observed after re-dosing.

The designer of concrete should know about the limitation of use of admixture in his / her design.

He / She should check for maximum dosage of admixture which can handle without hangover by concrete and it remembers all his properties.

as said by @K Kiran , you can refer IS guide lines as mentioned by him.
Thanks
 
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P.GOKUL

Apprentice
Dear all,
I have one doubt,What will be the maximum time to unload the Concrete from RMC , When its batching time...?

Distance from my site to RMC plant is approximately it takes 1 hours (in non-traffic Time)
 

Dnyan Deshmukh

Staff member
Dear all,
I have one doubt,What will be the maximum time to unload the Concrete from RMC , When its batching time...?

Distance from my site to RMC plant is approximately it takes 1 hours (in non-traffic Time)

It completely depends on the admixture used and its retention time.

The retention of admixture need to checked along with setting properties by doing trials at plant to avoid issues in concrete transport and placement.

We can get concrete from RMC which can be consumed even after 6 hours.

To understand the actual retention time you should ask RMC supplier about it.

There is no general term like concrete should be consumed within 3 hours but in most of the cases admixture do perform up to 3 hours in favourable conditions.

When buying concrete from RMC.
Ensure no water is being added at site.
Also do check performace od admixture by taking trial with same mix proportion and do check retention.

Most of the RMC's (Local RMC's + Some reputed RMC's) fail to give retension time due to negotiation in rate by a purchaser which does not allow manufacturer to batch concrete as per mix and to make a profit they do compromise.

What the engineer should do at site.
On receiving RMC concrete at site, must check a batch report for correct ingredients quantities, do not allow water addition and do cross check the poured quantity vs theoretical quantity.

RMC need to be handle with more care, if you work in company where purchasing is done only on lowest rate basis, as you dont know what criminal act might RMC supplier does to just ensure completion of order and getting profits from it.
 

Dnyan Deshmukh

Staff member
can you please attach the screenshot or position of location in pages in IS 456:2000 because I can not find the clause no. in book. So please update here.
Thank you.
is 456 4th amendment.jpg

You can also download 4th amendment from below thread.

 

Valmiki

Senior Member
What is redosing in RMC and is there any IS recommendation.
Hi,
Please avoid Re dosage of admixture at site during pour, once the Admixture added during batching with all correction including mostiure in raw material the only way to increase are decrease the dosage is depending on weather of the day during batching. inbound8650939255717491564.jpg