Project on Concrete Mix Design for various grades of Concrete

Aim :

To prepare mix design for M35 grade concrete with fly ash content and M50 grade concrete without fly ash as per Indian standards.

Introduction :

• Design mix is more scientific than the nominal mix.
• Mix design is widely used for more extensive and important concrete works.
• Mix design is based on the actual available material to be used in construction works.
• Locally available material can satisfy the standard criteria and can be used for making mix design concrete, so that the cost can be reduced for importing material from outside.
• In this design mix we are taking guidelines from Indian Standard codes such as –IS 10262– 2019 and recommended guideline for concrete mix design – IS 10262 – 1982 & 2009, IS 456- 2000.

1. THE CONCRETE MIX DESIGN FOR M35 WITH FLY ASH CONTENT :
2. DATA FOR MIX PROPORTIONING :

Grade of designation = M35

Type of cement = OPC

Grade of cement =43 grade conforming to IS 8112

Minimum cement = 340 kg/ m³ (as per IS 456 in table 5)

Maximum fly ash content = 30% weight of cement

Maximum water cement ratio = 0.45 (as per IS 456 in table 5)

Admixture = Super plasticizer

Exposure condition = very severe (for reinforced cement concrete)

Max. nominal size of aggregate = 20mm

Maximum cement content = 450 kg/ m³

Type of aggregate = crushed angular stone

Fine aggregate = Zone II

Method of placing = Pumping

Workability = 100mm (slump value)

Degree of supervision = Good

2. TEST DATA FOR MATERIALS :

Specific gravity of cement = 3.15

Specific gravity of fly ash = 1.0

Specific gravity of fine aggregate = 2.65

Specific gravity of coarse aggregate = 2.72 (20mm)

Specific gravity of Super plasticizer = 1.145

Water absorption of coarse aggregate = 0.5%

Water absorption of coarse aggregate = 1.0%

3. MIX CALCULATIONS :
4. Target mean strength ft’ = fck +1.65s

= 35 + (1.65x5)

= 43.25 N/mm²

ft’ - target average compressive strength at 28 days

fck– characteristic compressive strength at 28 days

s - Assumed standard deviation from IS 10262-2019 in table 2 for M35 grade s = 5 N/mm²

1. Selection of water cement ratio :

From table 5 of IS 456-2000 maximum water cement ratio for very severe exposure condition

w/c = 0.45

As per IS 10262-2019 in fig.1 gives water cement ratio for a target strength

w/c = 0.39

0.45 > 0.39

therefore w/c = 0.39

• Calculation of water :

From table 4 of IS 10262-2009

Water content for 20mm size aggregate = 186 kg/m³ (50mm slump)

Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it

Estimated water content For 100mm slump = 186 + (0.06 x 186) = 197 liters/m³

Based on trials with Super plasticizer water content reduction of 20% has been achieved,

Arrived water content = 197 x 0.80 = 158 liters/m³

1. Calculation of cement and fly ash content :

Water cement ratio = 0.39

Water content = 158 liters/m³

Cement content = 158 /0.39 = 405.13 kg/m³

From table 5 of IS 456-2000 minimum cement content is 340 kg/m³

405.13kg/m³ > 340 kg/m³

Cement content = 405.130kg/m³,Hence OK

Now to proportion a mix containing fly ash as the following steps are suggested :

1. The percentage of fly ash needs to be decided based on project requirement and quality of materials
2. In some cases increase in cementitious material can be warranted. Increase in cementitious material content and it’s percentage may be based on experience and trial ( This example is with increase of 10% cementitious material content )

Cementitious material content = 1.10 x 405.130 = 445.643 kg/m³

Water content = 158 liters/m³

So, water Cement ratio = 158 / 445.643 = 0.355

Fly ash @ 30% of cementitious material content = 445.643 x 0.3

= 134 kg/m³

Revised OPC cement content = 445.643 – 134 = 311.643 kg/m³

Saving of cement while using fly ash =405.13–311.643= 93.487 kg/m³

Fly ash being utilized = 134 kg/m³

Weight of admixture = 2% of weight of cement

Therefore the weight of admixture =405.13 x 0.02 = 8.102 kg/m³

1. Calculation of coarse aggregate and fine aggregate :

From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 is 0.62

In the present case water-cement ratio is 0.39. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).

Volume of coarse aggregate for zone II = 0.62

For w/c 0.5 = 0.62

For w/c 0.39 = ?

X = [((0.5-0.39) x 0.01 / 0.05]

X = 0.022

Volume of coarse aggregate = 0.62 + 0.022 = 0.642

If pumping, the volume of coarse aggregate should be reduced by 10%

Therefore volume of coarse aggregate = 0.642 x 0.9 = 0.578

Volume of fine aggregate = 1 – 0.578 = 0.422

1. Mix calculation :

1. Volume of concrete = 1 m³
2. Volume of cement = (weight of cement / specific gravity) x(1/ 1000 )

= (311.643 / 3.15) x(1/ 1000 ) = 0.099 m³

3. Volume of fly ash = (134 / 1) x(1/ 1000 ) = 134 m³
4. Volume of water = (158 / 1) x(1/ 1000 ) = 158 m³
5. Volume of admixture = (8.102 / 1.145 ) x (1/ 1000 ) = 0.007 m³
6. Total volume of other material except aggregates = 0.099+ 0.134 + 0.158 + 0.007 = 0.398 m³
7. Volume of coarse aggregate and fine aggregate = 1 – 0.398 = 0.602 m³

8. Mass of coarse aggregate = volume of coarse aggregate x specific gravity x 1000
9. Mass of coarse aggregate = 0.602 x 0.578 x 2.72 x 1000 = 946.424 kg/m³
10. Mass of fine aggregate = 0.602 x 0.422 x 2.65 x 1000 = 673.205 kg/m³

• Results :

Cement = 311.643 kg/m³

Fly ash = 134.000 kg/m³

Water = 158.000 kg/m³

Admixture = 8.102 kg/m³

Fine aggregate = 673.205 kg/m³

Coarse aggregate = 946.424 kg/m³

Water-cement ratio = 0.355

Mix proportion by weight = 1 : 2.16 : 3.04

1. THE CONCRETE MIX DESIGN FOR M50 WITHOUT FLY ASH :
2. DATA FOR MIX PROPORTIONING :

Grade of designation = M35

Type of cement = OPC

Grade of cement =53 grade conforming to IS 12289-1987

Minimum cement content = 320 kg/ m³ (as per IS 456 in table 5)

Maximum water cement ratio = 0.45 (as per IS 456 in table 5)

Admixture = Super plasticizer

Exposure condition = Severe (for reinforced cement concrete)

Max. nominal size of aggregate = 20mm

Maximum cement content = 450 kg/ m³

Type of aggregate = crushed angular stone

Fine aggregate = Zone II

Method of placing = Pumping

Workability = 125mm (slump value)

Degree of supervision = Good

2. TEST DATA FOR MATERIALS :

Specific gravity of cement = 3.15

Specific gravity of fine aggregate = 2.65

Specific gravity of coarse aggregate = 2.72 (20mm)

Specific gravity of Super plasticizer = 1.145

Water absorption of coarse aggregate = 0.5%

Water absorption of coarse aggregate = 1.0%

3. MIX CALCULATIONS :
4. Target mean strength ft’ = fck +1.65s

= 50 + (1.65x5)

= 58.25 N/mm²

ft’ - target average compressive strength at 28 days

fck– characteristic compressive strength at 28 days

s - Assumed standard deviation from IS 10262-2019 in table 2 for M35 grade s = 5 N/mm²

1. Selection of water cement ratio :

From table 5 of IS 456-2000 maximum water cement ratio for very severe exposure condition

w/c = 0.45

As per IS 10262-2019 in fig.1 gives water cement ratio for a target strength

w/c = 0.34

based on experience adopted water cement ratio is 0.44

0.45 > 0.44

therefore w/c = 0.44

• Calculation of water :

From table 4 of IS 10262-2009

Water content for 20mm size aggregate = 186 kg/m³ (50mm slump)

Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 9% is to be added to it

Estimated water content For 100mm slump = 186 + (0.09 x 186) = 202.74 liters/m³

Based on trials with Super plasticizer water content reduction of 20% has been achieved,

Arrived water content = 202.74 x 0.80 = 162 liters/m³

1. Calculation of cement content :

Water cement ratio = 0.44

Water content = 162 liters/m³

Cement content = 162 /0.44 = 359 kg/m³

From table 5 of IS 456-2000 minimum cement content is 320 kg/m³

359 kg/m³ > 320 kg/m³

Cement content = 359 kg/m³,Hence OK

Weight of admixture = 2% of weight of cement

Therefore the weight of admixture =3593 x 0.02 = 7.180 kg/m³

1. Calculation of coarse aggregate and fine aggregate :

From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 is 0.62

In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).

Volume of coarse aggregate for zone II = 0.62

For w/c 0.5 = 0.62

For w/c 0.39 = ?

X = [((0.5-0.44) x 0.01 / 0.05]

X = 0.012

Volume of coarse aggregate = 0.62 + 0.012 = 0.632

If pumping, the volume of coarse aggregate should be reduced by 10%

Therefore volume of coarse aggregate = 0.632 x 0.9 = 0.569

Volume of fine aggregate = 1 – 0.569 = 0.431

1. Mix calculation :

1. Volume of concrete = 1 m³
2. Volume of cement = (weight of cement / specific gravity) x(1/ 1000 )

= (359 / 3.15) x(1/ 1000 )

= 0.144 m³

3. Volume of water = (162 / 1) x(1/ 1000 ) = 162 m³
4. Volume of admixture = (7.180 / 1.145 ) x (1/ 1000 ) = 0.007 m³
5. Total volume of other material except aggregates = 0.144 + 0.162 + 0.006 = 0.282 m³
6. Volume of coarse aggregate and fine aggregate = 1 – 0.282 = 0.718 m³

7. Mass of coarse aggregate = volume of coarse aggregate x specific gravity x 1000
8. Mass of coarse aggregate = 0.718 x 0.569 x 2.72 x 1000 = 1110.864 kg/m³
9. Mass of fine aggregate = 0.718 x 0.431 x 2.65 x 1000 = 819.791 kg/m³

• Results :

Cement = 359.000 kg/m³

Water = 162.000 kg/m³

Admixture = 7.180 kg/m³

Fine aggregate = 819.791 kg/m³

Coarse aggregate = 1110.864 kg/m³

Water-cement ratio = 0.44

Mix proportion by weight = 1 : 2.28 : 3.09