# Concrete Mix Design Calculation for M15 Grade as per IS 10262-2009 Reading time: 1 minute

M15 concrete mix has a mix proportion of 1:2:4 of cement, fine aggregate, and coarse aggregate respectively. M15 – M represents Mix and 15 N/mm2 is the characteristic compressive strength of concrete cube at 28 days.

### Required Data M15 Grade Concrete

• Characteristic compressive strength of concrete at 28days = 15N/mm2
• Nominal maximum size of aggregate = 20mm
• Specific Gravity of cement = 3.15
• Specific gravity of fine aggregate = 2.6
• Specific gravity of Coarse aggregate = 2.65

### Step 1: Calculation of Target Strength

Target mean strength of concrete is derived from the below formula

ft = fck + 1.65 s

Where S = standard deviation which is taken as per below table= 3.5

Characteristic compressive strength after 28 days fck = 15N/mm2
ft = 15 + 1.65 x 3.5
Therefore, target mean strength ft = 20.775 N/mm2

### Step 2: Selection of Water-Cement Ratio

Water- cement ratio is selected from the graph plotted between 28-day compressive strength and water-cement ratio which is as per IS10262-2009

So, W/C ratio = 0.57

From table 5 of IS 456-2000, the maximum free water-cement ratio for moderate exposure is
W/C Ratio = 0.60

The final water-cement ration will be taken as the minimum of the above two values,
Therefore, W/C ratio = 0.57

### Step 3: Air Content Calculation

Nominal maximum size of aggregate taken is = 20mm

So, from the table entrapped air content in % of the volume of concrete = 2%

### Step 4: Water Content Calculation

For nominal maximum size of aggregate of 20mm, the required water content is selected form the table-

The aggregate nominal maximum size is 20mm and they belong to zone 2. So, Adjustment for compacting factor is to be applied.

Therefore, water content = 186 + (186 x 3/100) = 191.6 lit / m3 of concrete.

### Step 5: Cement Content Calculation

From step 2, Water cement ratio = W/C = 0.57
From step 4, Water content W = 191.6 liters = 191.6kg
191.6 / C = 0.57
Finally, C = 336.14 Kg / m3 of concrete

But from table 5 of IS456-2000, Minimum cement content required for moderate exposure condition for M15 grade concrete is = 240 Kg/m3 of concrete.
Greater of above two values will be the cement content.
Hence, C = 336.14Kg

### Step 6: Aggregate Ratio for Concrete

From the table, ratio of volume of coarse aggregate to volume of total aggregate, for 20mm nominal maximum size aggregate and zone-2 fine aggregate is

Therefore, P = 0.62

### Step 7: Aggregate Content Calculation

Volume of concrete (with entrapped air) = 1 m3
From step 3, Entrapped air % = 2% = 0.02
Therefore, volume of concrete (without air content) = 1-0.02 = 0.98m3

Fine aggregate content F.A is determined from below formula,

V = [W + C/Gc + (1/ (1-P) X (F.A)/Gf)] x 1/1000

0.98 = [191.6 + 336.14/3.15 + (1/ (1-0.62) X (F.A)/2.6)] x 1/1000
Therefore, amount of fine aggregate F.A = 673.52kg
Similarly, Coarse aggregate content C.A is derived from

Therefore, amount of coarse aggregate C.A = 1120kg

### Step 8: Final Mix Proportions of Ingredients

W/C ratio = 0.57
Cement quantity = 336.14Kg = 337kg
Fine aggregate quantity = 673.52kg = 674kg
Coarse aggregate Quantity = 1120 kg

Mix proportion for M15 Concrete = Cement : F.A : C.A = 1 : 2 : 3.3