Project on Concrete Mix Design for various grades of Concrete

1. Aim : To calculate concrete mix design for M35 grade concrete without fly ash.

Introduction :

• Concrete is a complex material and has the right mix of constituents of concrete, which if not done properly will have adverse effects on the properties of concrete.
• Concrete mix design is a systematic process of choosing economical relative proportion of various ingrdients from available material that gives the concrete of desired workability.
• The process of selecting suitable ingredients for producing concrete of required strength durability and workability as economical as possible is known as concrete mix design.
• The compressive strength of the concrete depends on the quality and quantity of cement, water and aggregates.

Concrete mix design for M35 grade

Target mean strength of concrete

f'ck = fck + 1.65S

f'ck = 35 + 1.65*5

f'ck = 43.25 N/mm^2

maximum nominal size of aggregate is 20 mm

minimum cement content = 320 kg/mm^3 (from table 5 IS 456:2000)

exposure condition is severe

Maximum water cement ratio is 0.45 (from table 5 IS 456 :2000)

Maximum water content is 186 kg ( from table 2 of IS 10262 : 2009 )

Workability : 100 mm slump (Slump value for pumpable concrete)

cement used : OPC 43 grade

specific gravity of cement is 3.15

Sepcific gravity of coarse aggregate is 2.74

specific gravity of fine aggregate is 2.74

Water absorption of coarse aggregate is 0.5%

Water absorption of fine aggregate is 1.0%

Selection of water cement ratio :

Maximum water cement ratio is 0.45

for 25mm to 50 mm slump range water content is 186 kg

for 100 mm adding 3% per each additional 25 mm : 186 + 12 = 197 kg

so water content is 197 lit

Caluclation of cement content

cement content = water content/water cemet ratio = 197/0.45 = 438 kg

438 > 320 (minimum cement content ) hence ok

Calculating proportion of volume of coarse and fine aggregate

From table 3 of IS 10262 : 2009 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone 1 ) for water cement ratio 0.5 = 0.6

In the present case the water cement ratio is 0.45, therefor volume of coarse aggregate needs to be increased so as to decrease the volume of fine aggregate. As the water cement ratio is less by 0.05 we will increase the volume of coarse aggregate by 0.01, Hence volume of coarse aggregate for w/c ratio 0.45 is 0.61

for pumpable concrete the value has to be decreased by 10%

coarse aggregate = 0.61 * 0.9 = 0.549 = 0.55

fine aggregate = 1-0.55 = 0.45

Mix calculations

Volume of concrete = 1m^3

Volume of cement = mass of cement /specific gravity * 1/1000

= 438/3.15 * 1/1000

= 0.139 m^3

Volume of water = mass of water/specific gravity of water * 1/1000

= 197/1 * 1/1000 = 0.197 m^3

Volume of aggregate ( FA + CA) = 1- (0.139+0.197)=1-0.336 = 0.664

Mass of coarse aggregate = 0.664 * 0.55 * 2.74 * 1000 = 1000.65 kg

mass of fine aggregate = 0.664 * 0.45 * 2.74 * 1000 = 818.72 kg

Mix proportions for trial number 1

cement = 438 Kg

water = 197 lit

coarse aggregate = 1000 kg

fine aggregate = 819 kg

Trial mix ratio is 1:1.87: 2.28

B. Aim : To calculate concrete mix design for M35 grade concrete with fly ash.

Introduction :

• Concrete is a complex material and has the right mix of constituents of concrete, which if not done properly will have adverse effects on the properties of concrete.
• Concrete mix design is a systematic process of choosing economical relative proportion of various ingrdients from available material that gives the concrete of desired workability.
• The process of selecting suitable ingredients for producing concrete of required strength durability and workability as economical as possible is known as concrete mix design.
• The compressive strength of the concrete depends on the quality and quantity of cement, water and aggregates.

Considerations:

1. Grade designation : M35
2. Type of cement : OPC grade 43 confirming to IS 8112
3. Type of mineral admixture : Fly ash confirming to IS 3812 (part 1)
4. Maximum nominal size of aggregate : 20mm
5. Minimum cement content : 320 Kg/m^3 (table 5 IS 456)
6. Maximum water cement ratio : 0.45 (table 5 IS 456)
7. Workability 100 mm (slump for pumpable concrete)
8. Exposure condition : severe (for reinforced concrete )
9. Specific gravity of fly ash is 2.2

10. specific gravity of cement is 3.15

11. Sepcific gravity of coarse aggregate is 2.74

12. specific gravity of fine aggregate is 2.74

13. Water absorption of coarse aggregate is 0.5%

14. Water absorption of fine aggregate is 1.0%

Concrete mix design for M35 grade

Target mean strength of concrete

f'ck = fck + 1.65S

f'ck = 35 + 1.65*5

f'ck = 43.25 N/mm^2

From table 5 of IS 456 : 2000 for severe exposure, maximum water cement ratio is 0.45

Maximum water content is 186 kg ( from table 2 of IS 10262 : 2009 )

for 25mm to 50 mm slump range water content is 186 kg

for 100 mm adding 3% per each additional 25 mm : 186 + 12 = 197 kg

so water content is 197 lit

Caluclation of cement content

cementitious content (cement + fly ash) = water content/water cemet ratio = 197/0.45 = 438 kg

438 > 320 (minimum cement content ) hence ok

Considerations for fly ash:

we are considering 5% increase in the cementitious material

Cementitious material content = 438 * 1.05 = 460 Kg

water content = 197Kg/m^3

water cement ratio = 197/460 = 0.4282 = 0.43

Fly ash is 30% of the total cementitious material = 460*0.3 = 138 kg

cement = 460 - 138 = 322 Kg

Fly ash utilized : 138 Kg

Cement saved by using fly ash : 438-322= 116 Kg

Calculating proportion of volume of coarse and fine aggregate

From table 3 of IS 10262 : 2009 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (zone 1 ) for water cement ratio 0.5 = 0.6

In the present case the water cement ratio is 0.43, therefore volume of coarse aggregate needs to be increased so as to decrease the volume of fine aggregate. As the water cement ratio is less by 0.07 we will increase the volume of coarse aggregate by 0.014, Hence volume of coarse aggregate for w/c ratio 0.43 is 0.614

for pumpable concrete the value has to be decreased by 10%

coarse aggregate = 0.614 * 0.9 = 0.549 = 0.553

fine aggregate = 1-0.553 = 0.447

Mix calculations

Volume of concrete = 1m^3

Volume of cement = mass of cement /specific gravity * 1/1000

= 322/3.15 * 1/1000

= 0.102 m^3

Volume of cement used = 0.102 m^3

Volume of fly ash = mass of fly ash/specific gravity *1/1000

= 138/2.2*1/1000 = 0.0627 m^3

Volume of fly ash used = 0.0627m^3

Volume of water = mass of water/specific gravity of water * 1/1000

= 197/1 * 1/1000 = 0.197 m^3

volume of water used = 0.197 m^3

Volume of aggregate ( FA + CA) = 1- (0.102+0.197+0.0627)=1-0.3617= 0.6383

Mass of coarse aggregate = 0.6383 * 0.553 * 2.74 * 1000 = 967 Kg

mass of fine aggregate = 0.6383 * 0.447 * 2.74 * 1000 = 781.75 kg

Mix proportions for trial number 1

cement = 322 Kg

fly ash = 138 Kg

water = 197 lit

coarse aggregate = 967 kg

fine aggregate = 781.75 kg

Trial mix ratio is 1:2.42: 3