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JollyRogers wrote:During the RCC roofing recently my contractor was using 9 pots of sand and 10 pots of 20 mm Jalli for 1 bag of Cement. Going through the post, I see that its not the optimal mix.
I just saw this inormation in the Bharti Cement Technical support section: "Concrete: The ideal ratio of the concrete mixture should be 1:1½:3 (1 cement: 1½ sand:3 aggregate)." which might be incorrect as everywhere else I see the ratio as 1:1.5 Stones and 3 Sand, and also as indicated by Ar.Praveen.N..
For RCC I was using ACC Concrete Plus cement. Is the mixing ratio different for different brands of cement? Can anyone please shed some more light on this topic?

Hi JollyRogers,
Did you find out the correct mixing ratio? We are constructing the house and we are also confused on the ratio. Our engineer says 1:1.5:3 for cement:Jelly:Sand
However, my contractor is going by cement bag as reference. He is mixing 1 bag of birla Super 53 grade, 9 pots of sand and 12 pots of jelly. I think he is mixing too much of jelly looking at the finish and settlement of jelly at the bottom of the colums. Please share the info if you have any.

Please refer to the URL for more details, authenticated:

http://www.engineeringcivil.com/concret ... -code.html

The cement ratio will increase depending on quality of sand. Hence, it is very important to have the right kind of sand for the RCC purpose.

Hi BengaluruBoy,

To be very honest, we cannot keep counting the exact ratio if they have mixed during every mix. I noticed this randomly, and they were doing it correctly, but at times I noticed they would put 1 or 2 additional quantity of Sand or Jelly if the person mixing in the concrete machine would tell them.

sam_m400 wrote:I am not getting clear as it states we need to use M20 mix for RCC, but about others like

1. Columns mix + with size of steel to use
2. Beams mix + with size of steel to use)
3. lintel concrete + steel size to use:
4 .roof concrete : Already mentioned (M20 proportion) but can anybody mention the size of steel to use -
5.Chajja Mix :
6.internal flooring (Any steel to use)
7.External flooring. (any steel to use)
8.Belt mix for foundation with size of steel to use ( if brick foundation is not used only Belt foundation)

Anybody please give the same as it would help everybody to propose this model

Hi,Sam
Rcc is always designed for every project by structural engineer depending up on the column spans,slab type,load factors etc...
We are only discussing about M20 mix ( very commonly used mix).Steel details are not common that can be fixed .

Regards
Ar.Praveen.N
Ardes Architects and Interior Designers
ardesarchitects@gmail.com
www.ardesarchitects.com

Hi All
I am in the moulding stage and the M20 proportion is a debate. I have asked for 1:1.5:3 to masory ,and it will 4 Pots of cement:6 Pots of sand: 12 Pots of jelly , but one masory suggesting to add 4:7:6 more sand and less jelly. I am not sure which is right proportion as they all suggests to for more sand and less jelly but M20 suggests less sand and more jelly i.e double the jelly of sand as per proportion of 1.5 to 3. Anybody can share there experience.

Hi,
The M20 concrete grade is of ratio as described by you 1:1.5:3.

Now 1.5 of sand is 50% of medium and 50% of coarse river sand or FULL of ROBO SAND
and 3 is 20mm and down size aggregates.

now 3 of 20mm down size aggregates means, you may have to bring 20mm jelli, 12mm jelli and 6mm jelli. which is definetely available in the market.

If you now mix as below, you don't need to change the ratio and may stick to the same ratio of 1:1.5:3

1 cement
0.75 medium river sand
0.75 coarse river sand
1 20mm jelli
1 12mm jelli
1 6mm jelli.

Don't put more than 0.50 water cement ratio and if the mason wants more workability use fosroc brand conplast admixture.
and DEFINITELY USE CONCRETE VIBRATOR WITH THE ABOVE MIX.

All the very best.

thanks. but here the confusion is on the pots they used. I bag of cement is 4 pots,so others need to be mixed at 6 pots and 12 pots of jelly. but mason saying we should use 4:7:6 where they normally use everywhere as they need to add more sand than jelly. here 1 pots more sand than jelly (7 and 6). Here it won;'t become 1:1.5:3 ,it would be 1:2:1.5 which is coming. Is this right proportion?????.

sam_m400
most labours or gangmen are like this. They are plain lazy to bring the required number of pots (baandlis) into mix. If you want to be sure of the proportion, you have to stand and monitor if your contractor/labour is not reliable.

For RCC footing concrete, my contractor initially quoted 1:1.5:3. Today in actual construction I saw them doing 1:1.5:2 (i.e. for every 4 trays of cement, 6 trays of sand and 8 trays of jelly). Contractor says 12 trays is too much jelly and it wont mix fully. Is this right ?

My architect visited the site during mixing and suggested 2 pots of cement topped up: 6 pots of sand: 7 pots of jelly for footer. He mentioned that this is fine since cement is topped up (and made a cone) and hence volumes are different. He was happy with the final mixture of concrete that came out using this mix.

During manual mixing for columns, this was recommended to be 1 sack cement: 8 pots of sand mixed well. The resultant mixture is mixed in 1:1 ratio with jelly.