Concrete Mix Design Calculation for M15 Grade as per IS 10262-2009

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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

• Grade of concrete =M15
• 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

f_t = f_ck + 1.65 s

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

Grade of concrete	Standard deviation (N/mm2)
M10	3.5
M15	3.5
M20	4.0
M25	4.0
M30	5.0
M35	5.0
M40	5.0
M45	5.0
M50	5.0

Characteristic compressive strength after 28 days f_ck = 15N/mm²
f_t = 15 + 1.65 x 3.5
Therefore, target mean strength f_t = 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

Nominal maximum size of aggregate	Air content (% of the volume of concrete)
10mm	5%
20mm	2%
40mm	1%

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-

Nominal maximum size of aggregate	Maximum water content
10mm	208
20mm	186
40mm	165

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

Read More:
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