THUMB RULE OF MAKING A MIX DESIGN.

THUMB  RULE   OF MAKING  A   MIX   DESIGN

It is very simple to understand:

for example we need to making of mix design of grade M40 for severe conditions. 

So in this case first we start from cement content 

AS PER INDIAN STANDARD 456:2000 MINIMUM CEMENT CONTENT FOR M40 GRADE FOR SEVERE CONDITION IS  : ( 320 KG/M3)

AND MAXIMUM WATER CEMENT RATIO IS : ( 0.45)

So here we got cement content and water cement ratio. 

w/c  = weight of water/weight of cementitious content

HERE WE DESIGN MIX FOR PURE OPC

Than we arrive weight of water just put value of cement and water in formula above.

we got weight of water  :  144 kg

If we convert weight of cement and water into volume than we get:

volume of cement  =  320/3.15  = 101.58 

volume of  water    =  144/ 1      =  144 

Than volume of Aggregate:  1000 - (101.58+144)

                                                :   754.42

Let specific gravity of 20mm: 2.90

       specific gravity of 10mm: 2.86

       specific gravity of c/sand: 2.70

THAN weight of aggregate :

for 20 mm= 754.42/ (% of 20mm/ specific gravity )

for 10 mm= 754.42/ (% of 10mm/ specific gravity )

for c / sand = 754.42/ (% of sand/ specific gravity ) 

We derive % of aggregate by combined grading of aggregate which is explain in my previous blog check this if you miss this 

Let % of 20mm  :   40%

       % of 10mm  :   25%

       % of c/ sand :   35%

IF WE PUT THIS IN ABOVE FORMULA WE GET :

754.42÷(0.40/2.90)+ 754.42÷(0.25/2.86)+754.42÷(0.35/2.7) = 2180 KG 

Here 2180kg is the weight of All aggregate. 

so weight of 20mm :  0.40×2180 = 872 kg

      weight of 10mm : 0.25× 2180= 545 kg

      weight of c / sand : 0.35 × 2180= 763 kg

THAN THE MIX DESIGN IS  :

CEMENT :  320 KG ( MINIMUM)

WATER    :  144 KG ( ACCORDING TO CEMENTITIOUS     CONTENT)

20 MM     : 872 KG

10MM      :  545 KG

C / SAND :   763 KG

FOR CUBIC METER CONCRETE.

This mix design is only for knowledge purpose not applicable for high grade concrete.

THIS IS ONLY THUMB RULE TO MAKE A MIX DESIGN FASTLY OTHER WISE WE MAKE MIX DESIGN ACCORDING TO INDIAN STANDARD 10262:2019