Birla 53 grade "cement:sand :aggragate : ratio"

[civil88]

Let me clarify the confusion regarding the kinds of mixes recommended for different RCC works. These are the ratios we have been following for residential buildings since a long period.

Use M15 grade concrete for Footings, Beams and Slab and
Use M20 grade concrete for Columns.

M15 in theory means, 1 part of cement, 2 parts of sand and 4 parts of stone. But in practice, it is advisable to go for 1 part of cement, 3 parts of sand and 4 parts of stone.
In terms of pots it would be 4 pots of cement, 12 pots of sand and 16 pots of stone.

M20 in theory means, 1 part of cement, 1.5 parts of sand and 3 parts of stone. But in practice, it is advisable to go for 1 part of cement, 2 parts of sand and 3 parts of stone.
In terms of pots it would be 4 pots of cement, 8 pots of sand and 12 pots of stone.

As Mr.Praveen, told adding sand helps in reducing honeycombs in concrete, which are very common if vibrator is not used.

While concreting, the best practice is to use water reducing agent like conplast(Fosroc) to maintain water:cement ratio, and using a pin vibrator for columns, footings, beams and pin as well as plate vibrator for slabs. Many contractors use only plate vibrator for slabs, as putting pin vibrator across the whole slab area is a cumbersome process. But if we can stand at the site, and insist on using pin for slab, it does make the RCC slab very compact and strong. One can easily see the amount of compaction a pin vibrator brings in a slab visually, as it reduces the height of the concrete poured on to the slab substantially, while a plate vibrator simply levels and gives a smoother finish to the roof. I am not saying plate vibrator is not effective - I am only saying both have their roles to play in the slab concreting.

[jult]

if the mix is designed it will give strength as per the design requirement with economic. if it is not done properly it may be over designed or under designed which is not correct. Members are requested to get input from professional ( Structural engineer) and arrive conclusion on mix design. if they need Quality as well as Economic.