Project on Concrete Mix Design for various grades of Concrete

1. M35 Mix design calculation:

• Grade designation : M 35
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 340 kg/m³
• Maximum water-cement ratio : 0.45
• Workability : 50-100 mm (slump)
• (g)Exposure condition : Very Severe (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m³
• Chemical admixture type : Super Plasticizer

a. test materials.

• Specific gravity of cement : 3.12
• Specific gravity of Coarse aggregate : 2.74
• Specific gravity of Fine aggregate : 2.56

b. required strength.

• (1) f_target = f_ck + 1.65 x S

As per the table I of IS: 10262-2009 , standard deviation, s = 5.0 N/mm²

Therefore, target strength = 35 + 1.65 x 5.0 = 43.25 N/mm²

^{c. water to cement ratio.}

From Table 5 of IS456:2000

Maximum water-cement ratio = 0.45

d. water content .

From Table 2 of IS456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 liter.

(Note: FOR adding Super plasticizer , the water content can be reduced upto 20% and above.)

water content = 197-[197 x (25/100)] = 147 litres.

e. cement content.

Water-cement ratio =0.45

Cement content = 147/0.45 = 350 kg/m³

From Table 5 of IS 456, minimum cement content for ‘Very Severe‘ exposure condition = 340 kg/m³

350 kg/m³ > 340 kg/m³, hence, O.K.

f.The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content.

From Table 3 of IS10262, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 = 0.62.

In the present case, the water-cement ratio is 0.45. Therefore, the volume of coarse aggregate is required to be increased to reduce the fine aggregate content.

As the water-cement ratio is lower by 0.10, the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.45 = 0.63.

NOTE – In case the coarse aggregate is not angular one. then also the volume of coarse aggregate may be required 10 be increased suitably, based on experience.

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.63 x 0.9 = 0.567.

Volume of fine aggregate content =1 – 0.567 =0.433

g. mix calucation.

• Volume of concrete = 1m³
• Volume of cement = (Mass of cement/Specific Gravity of Cement) X (1/1000)

= (350/3.12) X (1/1000)

= 0.112 m³

• Volume of water = (Mass of water/specific gravity of water) X (1/1000)

= (147/1) X (1/1000)

= 0.147 m³

• Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)

= (7/1.145) X (1/1000)

= 0.006 m³

• Volume of all aggregate = (a-(b+c+d))

= 1 – (0.112 + 0.147+0.006)

= 0.735 m³

• Mass of coarse aggregate = Volume of all aggregate X volume of coarse aggregate X Specific gravity of coarse aggregate X 1000

= 0.735 x 0.567 x 2.74 x 1000

= 1141.88 kg

• Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.735 x 0.433 x 2.56 x 1000

= 814.73 kg

h.Concrete Mix Proportions

• Cement = 350 kg/m³
• Water = 147 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 814.73 kg/m³
• Coarse aggregate = 1141.88 kg/m³
• W/c = 0.45

2. M50 mix calculation.

Grade Designation = M-50
Type of cement = O.P.C-43 grade
Brand of cement = Vikram ( Grasim )
Admixture = Sika [Sikament 170 ( H ) ]
Fine Aggregate = Zone-II

Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66

Minimum Cement (As per contract) =400 kg / m³
Maximum water cement ratio (As per contract) = 0.45

Mix Calculation: –

a. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa

b. Selection of water cement ratio:-
Assume water cement ratio = 0.35

c. Calculation of water: –
Approximate water content for 20mm max. Size of aggregate = 180 kg /m³ (As per Table No. 5 , IS : 10262 ). As plasticizer is proposed we can reduce water content by 20%.

Now water content = 180 -(180*20%) = 144 kg /m³

^{d. Calculation of cement content:-
Water cement ratio = 0.35
Water content per cum of concrete = 144 kg
Cement content = 144/0.35 = 411.4 kg / m3
cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3 )
Hence O.K.}

d.Calculation for C.A. & F.A.: [ Formula’s can be seen in earlier posts]-

Volume of concrete = 1 m³
Volume of cement = 412 / ( 3.15 X 1000 ) = 0.1308 m³
Volume of water = 144 / ( 1 X 1000 ) = 0.1440 m³
Volume of Admixture = 4.994 / (1.145 X 1000 ) = 0.0043 m³
Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 +0.0043 = 0.2791 m³

Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m³
Volume of F.A. = 0.7209 X 0.33 = 0.2379 m³ (Assuming 33% by volume of total aggregate )

Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m³

Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919 kg/ m³

weight of F.A. = 621 kg/ m³

Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365 kg/ m³

Say weight of C.A. = 1284 kg/ m³

Considering 20 mm: 10mm = 0.55: 0.45
20mm = 706 kg .
10mm = 578 kg .
Hence Mix details per m³
Increasing cement, water, admixture by 2.5% for this trial

Cement = 412 X 1.025 = 422 kg
Water = 144 X 1.025 = 147.6 kg
Fine aggregate = 621 kg
Coarse aggregate 20 mm = 706 kg
Coarse aggregate 10 mm = 578 kg
Admixture = 1.2 % by weight of cement = 5.064 kg.

Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043