MIX DESIGN FOR M35 GRADE CONCRETE

• Design Stipulations for Proportioning
  1. Grade Designation : M35
  2. Type of cement : OPC 43 grade confirming to IS 8112
  3. Maximum nominal size of aggregate : 20mm
  4. Exposure condition : Very severe
  5. Minimum cement content : 360 kg/m3 (From Tabl 5 IS 456-2000)
  6. Maximum water-cement ratio : 45
  7. Workability : 100mm (slump)
  8. Method of concrete placing : Pumping
  9. Degree of supervision : Good
  10. Type of aggregate : Crushed angular aggregate
  11. Maximum cement content : 450 kg/m3 (Cl 8.2.4.2 of IS 456-2000)
  12. Chemical admixture type : Superplasticizer Ceraplast 400
  13. Specific gravity of chemical admixture : 100

2 Test Data for Materials

1. Cement used : OPC 43 grade confirming to IS 8112
2. Specific gravity of cement : 120
3. Chemical admixture type : Superplasticizer

Fosroc Cornplast SP 430

2. Specific gravity of coarse aggregate : 820

Specific gravity of fine aggregate : 2.690

Specific gravity of chemical admixture : 1.180

1. Water absorption of coarse aggregate : 380 % Water absorption of fine aggregate : 1.400 %
2. Free moisture of coarse aggregate : Nil Free moisture of fine aggregate : Nil
3. Sieve analysis of fine aggregate : Confirming to Zone II of IS 383 Sieve analysis of coarse aggregate : Confirming to Table 7 of IS 383

3 Target Strength

f'ck	=	fck + 1.65 S
	or
f'ck	=	fck + X

From Table 2 IS 10262 2019 standard deviation, S=4

From Table 1 standard IS 10262 2019 deviation, X=5.5

f'ck	= =	fck + 1.65s 35+1.65X4 = 41.60 N/mm2
f'ck	= =	fck + X 35+5.5 = 40.50 N/mm2

Therefore, target strength = 41.60 N/mm²

4 Approximate air content

From table 3 IS 10262 2019 the approximate amount of entrapped air is 1.0% for 20mm nominal maximum size of aggregate

5 Water Cement Ratio

From Table 5 of IS 456, maximum water-cement ratio = 0.40 From Fig 1 of IS 10262 2019 water cement ratio = 0.45

Based on experience water cement ratio taken as 0.38

6 Selection of Water Content

From Table 4 of IS 10262-2019 maximum water content = 186litre (for 50mm slump) Estimated water content for 150 mm slump as per IS 10262 -2019 clause 5.3 water content to be increased by 12%

So water content = 186+(12*186/100) = 208 litre

As superplasticizer is used, the water content can be reduced

Based on trials with superplasticizer water content reduction of 21% has been achieved Hence arrived water content = 208*0.79 = 165 litre

7 Calculation of Cement Content

Water cement ratio = 0.38

Water content = 165 litre

So cement content = 433 kg/m3

Minimum cement content : 360 kg/m3 (As per Table 5 of IS 456)

Maximum cement content : 450 kg/m3 (Cl 8.2.4.2 of IS 456-2000) 360 kg/m3 < 432 kg/m3 < 450kg/m3

Hence OK

8 Proportion of Volume of Coarse Aggregate and Fine Aggregate Content

From Table 5 of IS 10262-2019 corresponding to 20mm size aggregate and fine aggregate (Zone II) volume of coarse aggregate per unit volume of total aggregate for water cement ratio of 0.50 = 0.620

As the water cement ratio is lowered the proportion of volume of coarse

aggregate is changed at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio

(0.12*0.01/0.05)	=	0.024
So volume of coarse aggregate	=	0.644
For pumpable concrete these values to be reduced by 10%
Therefore Volume of coarse aggregate = 0.640 *0.9	=	0.580
Volume of fine aggregate = 1-0.580	=	0.420

9 Mix Calculations

The mix calculations per unit volume of concrete shall be as follows :

1. Volume of concrete = 000 m3
2. Volume of entrapped air in wet concrete = 010 m3
3. Volume of cement = mass of cement /(sp. Gravity of cement *1000)

= 432/(3.12*1000) = 0.139 m3

1. Volume of water = mass of water/(sp. Gravity of water*1000)

=164/(1*1000) = 0.165 m3

1. Volume of chemical admixture (@ 1% of Cement ) = mass of CA /(sp.gravity of CA * 1000)

=432*1/(1.10*1000*100) = 0.004 m3

1. Volume of all in aggregate f = (a-b)-(c+d+e)

= 0.683 m3

1. Mass of coarse aggregate = f * Vol of CA * Sp gravity of CA *1000

= 1116 kg

1. Mass of fine aggregate = f * Vol of FA * Sp gravity of FA *1000

= 772 kg

10 Adjustment on water, fine aggregate and coarse aggregate

1. Fine aggregate (Dry)

=Mass of FA in SSD condition/(1+Water absorption/100)

=772/(1+1.4/100) = 761.00

1. Coarse aggregate (Dry)

=Mass of CA in SSD condition/(1+Water absorption/100)

=1116/(1+0.38/100) = 1112.00

Extra water to be added for absorption by fine aggregate and coarse aggregate

=(772-761)+(1116-1112)	=	15
So estimated water becomes 164+15	=	179
11 Mix Proportions Cement	=	433 kg/m3
Water	=	179 litre
Fine aggregate	=	761 kg/m3
Coarse aggregate	=	1112 kg/m3
Chemical admixture	=	4.33 kg/m3
Free Water Cement ratio	=	0.380