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Concrete mix proportioning at site.

 
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desai_1960
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PostPosted: Mon Sep 03, 2018 2:30 pm    Post subject: Concrete mix proportioning at site. Reply with quote

Dear Sefians,


Proper concrete mix proportioning at site plays a vital role towards achieving desired strength and workability.


Nominal nix proportioning is getting slowly phased out, but it still prevails. cement, sand and coarse aggregates will be mixed in the specified proportions by volume in case of nominal concrete mixes..


In case of a design mix concrete, we are expected to follow weigh batching. But the contractors have a tendency to convert proportions by weight into proportions by volume and start volume batching.


In this regard, I have the following two questions.


1) Whether the contractor can be permitted to adopt volume batching for design mix concrete also?


2) Whether we are prohibited from using volume batching for design mix concrete?


I request Sefians to kindly clarify my doubts.


Regards,


R.K.Desai

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SATYAPAUL
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PostPosted: Tue Sep 11, 2018 5:30 am    Post subject: Concrete mix proportioning at site. Reply with quote

ask him to add 10% more cement.rough test is to make a hand ball from finished concrete mix and squeeze  with full force.no water or paste shall come out.other wise reduce water.thumb rule 142.5 cu ft of dry  material gives 100 cu.ft of ready mix concrete.ignore volume of cement.this was practiced for years. regards satya pal   On Tue, 11 Sep 2018 08:59:49 +0530 "desai_1960"  wrote >                   Dear Sefians, >  >  > Proper concrete mix proportioning at site plays a vital role towards achieving desired strength and  workability. >  >  > Nominal nix proportioning is getting slowly phased out, but it still prevails. cement, sand and coarse  aggregates will be mixed in the specified proportions by volume in case of nominal concrete mixes.. >  >  > In case of a design mix concrete, we are expected to follow weigh batching. But the contractors have a  tendency to convert proportions by weight into proportions by volume and start volume batching. >  >  > In this regard, I have the following two questions. >  >  > 1) Whether the contractor can be permitted to adopt volume batching for design mix concrete also? >  >  > 2) Whether we are prohibited from using volume batching for design mix concrete? >  >  > I request Sefians to kindly clarify my doubts. >  >  > Regards, >  >  > R.K.Desai >       > >  >  > --

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bkkk
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PostPosted: Tue Sep 11, 2018 9:06 am    Post subject: Volmetric batching Reply with quote

Dear sefian,

Volumetric batching is not allowed for design mix  concrete.However if situation demands, weight  proportios may be converted to volume based on the unit weight of your constituents

Er.venkat
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Rohinton Bhathena
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PostPosted: Tue Sep 11, 2018 12:30 pm    Post subject: Concrete mix proportioning at site. Reply with quote

Once the weight to volume ratio is established for a given batch of materials there should be no problem. If one goes to reserve bank to fetch coins, they will not count but weigh it for you. It more to do with percentage error that is acceptable. 

On Mon, 10 Sep 2018, 23:29 desai_1960, <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
           Dear Sefians,


Proper concrete mix proportioning at site plays a vital role towards achieving desired strength and workability.


Nominal nix proportioning is getting slowly phased out, but it still prevails. cement, sand and coarse aggregates will be mixed in the specified proportions by volume in case of nominal concrete mixes..


In case of a design mix concrete, we are expected to follow weigh batching. But the contractors have a tendency to convert proportions by weight into proportions by volume and start volume batching.


In this regard, I have the following two questions.


1) Whether the contractor can be permitted to adopt volume batching for design mix concrete also?


2) Whether we are prohibited from using volume batching for design mix concrete?


I request Sefians to kindly clarify my doubts.


Regards,


R.K.Desai
     



     



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SATYAPAUL
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PostPosted: Thu Sep 13, 2018 1:30 pm    Post subject: Concrete mix proportioning at site. Reply with quote

if volume mix is used conforming to design mix(by conversion).the result may vary up to  10%,provided water is controlled. MinImum six reshuffles shall be done.three dry and  three with water mix. regards satya pal  On Thu, 13 Sep 2018 18:15:28 +0530 "SATYAPAUL"  wrote >                   ask him to add 10% more cement.rough test is to make a hand ball from finished  concrete mix and squeeze with full force.no water or paste shall come out.other wise  reduce water.thumb rule 142.5 cu ft of dry material gives 100 cu.ft of ready mix  concrete.ignore volume of cement.this was practiced for years. regards satya pal On  Tue, 11 Sep 2018 08:59:49 +0530 "desai_1960" wrote >            Dear Sefians, >  > > Proper concrete mix proportioning at site plays a vital role towards achieving  desired strength and workability. > > > Nominal nix proportioning is getting slowly  phased out, but it still prevails. cement, sand and coarse aggregates will be mixed in  the specified proportions by volume in case of nominal concrete mixes.. > > > In case  of a design mix concrete, we are expected to follow weigh batching. But the contractors  have a tendency to convert proportions by weight into proportions by volume and start  volume batching. > > > In this regard, I have the following two questions. > > > 1)  Whether the contractor can be permitted to adopt volume batching for design mix concrete  also? > > > 2) Whether we are prohibited from using volume batching for design mix  concrete? > > > I request Sefians to kindly clarify my doubts. > > > Regards, > > >  R.K.Desai >       > > > > -- >       > >  >  > --

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suraj
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PostPosted: Sun Sep 16, 2018 7:13 am    Post subject: Structural Concrete-No volume batching Reply with quote

Structural Concrete-No volume batching


Use calibrated site mixer & adopt weight batching
Produce not more than 50 kg cement mix
If equipment permits, use 2 bags cement mix
Keep hopper's beneath space (space between hipper external surface & ground) clear frequently, so that no aggregate is pushed into that annular space
Such trapped aggregate would result on dial erroneously, which consequences in reactionary force impact dial reading

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IntPE(India)Suraj Singh FIE Civil
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