Project on Concrete Mix Design for various grades of Concrete

AIM: To calculate the concrete Mix design for M35 grade concrete with flyash & M50 grade concrete without flyash.

Introduction: Concrete mix design is the metod of inding the precise proportion of cement, sand and aggregates for concrete to achieve the target strenght in structures, therfore concrete mix design can stated as concrete mix in terms of cement:sand:aggregates. The design is done according to the requirements of concrete strenght. so, we can achieve the desirable properties of concrete either it is in fresh stage orr in hardened stage. The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by its method. Use of additives like admixtures, retarders, etc. other than basic ingredients are used o improve the properties of mix. This project consist of two parts, the first part deals with the design of M35 grade cement with fly ash as a part of it and second part is the design of M50 garde concrete without flyash.

Mix Design for M35 Grade concrete with Fly ash

AIM: Mix Design for M35 grade concrete with Fly ash.

Procedure:

Step 1: Stipulation For proportioning

1. Grade designation : M35
2. Type of cement : OPC 43 grade confirming to IS 8112.
3. Type of Mineral Admixture : Fly Ash. conforming to IS 3812 (part 1)
4. Maximum nominal size of aggregate : 20 mm
5. Minimum cement content : 320 kg/cum. As per code IS 456:2000, (Table No 5 based no exposure condition)
6. Maximum water-cement ratio : 0.45.
7. Workability : 100 mm (slump).
8. Exposure condition : Severe (For Reinforced concrete)
9. Method of concrete placing: Pumping
10. Maximum Water content: 450 kg/cum
11. Chemical admixture type : Super Plasticizer
12. Degree of supervision : Good.

Step 2: Test Data for materials

1. Specific gravity of cement : 3.15
2. Specific gravity of Flyash: 2.2 (conforming to IS 3812 part )
3. Specific gravity of Coarse aggregate : 2.74
4. Specific gravity of Fine aggregate : 2.74
5. Water Absoption of Coarse aggregate: 0.5%
6. Water Absoption of Fine aggregate: 1.0%

Sieve analysis of Coase aggregate: Conforming to Table 2 of IS 383

Sieve analysis of Fine aggregate: conforming to grading Zone 1 of table 4 IS 383.

Step 3: To find Target mean Strenght for Mix proportioning.

f_target = f_ck + 1.65 x s.

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

Target strength = 35 + 1.65 x 5.0 = 43.25 N/mm²

Step 4: Selection of water cement ratio,

From table: 5 of IS 456:2000, by exposure condition

Maximum water cement ratio= 0.45 (for severe condition , from table IS 456:2000)

Extreme water cement ratio is 0.4

0.4<0.45, Hence OK.

Step 5: Calculation of Water Content,

From Table 2 of IS 456:2000, 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 litres.

Based on trials with Super plasticizer, water content reduced upto 30%. Based on trial water content reduction of 29% is achieved with plasticizer, Hence the arrived water content = 197-[197 x (29/100)] = 140 litres.

Step 6: Calculation of Cement Content,

Water-cement ratio =0.40

Cementatious material ( cement + flyash) = 140/0.40 = 350 kg/m³

From Table 5 of IS 456:2000, minimum cement content for severe exposure condition = 320 kg/m³

350 kg/m³ > 320 kg/m³, Hence, OK.

Step 7:The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content,

From Table 3 of IS 456:2000, the volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for a water-cement ratio of 0.50 =0.60

In present case water cement ratio is 0.4, therfore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As the water cement ratio is lowered by 0.1, the proportion of volume of coarse aggregate is increased by 0.02 (at the ratio of +/- 0.01 for every +/- 0.05 change in water cement ratio)

Hence the corrected vlue of coarse aggregate for the water cement ratio=0.64.

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

Therefore, volume of coarse aggregate = 0.64 x 0.9 = 0.576.

Volume of fine aggregate content =1 – 0.576 =0.424.

Step 8: Mix Calculations,

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of Cement/Specific Gravity of Cement) X (1/1000)

= (270/3.15) X (1/1000)

= 0.086 m³

c) Volume of water = (Mass of Water/Specific Gravity of Water) X (1/1000)

= (140/1) X (1/1000)

= 0.140 m³

d) Volume of Flyash = ( Mass of Flyash / Specific gravity of Flyash) X (1/1000)

= (115/2.2) X (1/1000)

= 0.052 m³

d) Volume of chemical admixture = (Mass of Admixture / Specific Gravity of Admixture) X (1/1000)

= (7.6/1.14) X (1/1000)

= 0.006 m³

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

= 1 – (0.086 + 0.052+0.140+0.006)

= 0.716 m³

f) Mass of coarse aggregate = Volume of all Aggregate X Volume of coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.716 x 0.576 x 2.74 x 1000

= 1130 kg/m³

g) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.716 x 0.424 x 2.74 x 1000

= 831 kg/m³

Step 9: Concrete Mix Proportions,

• Cement = 270 kg/m³
• Water = 140 kg/m³
• Fly ash = 115 kg/m³
• Chemical Admixture = 7 kg/m³
• Fine aggregates = 831 kg/m³
• Coarse aggregate = 1130 kg/m³
• W/c = 0.364

Final Concrete Mix Ratio,

Mix ratio of M35 is 1 : 2.15 : 2.94

Step 10:

The slump shall be measured and the water content and dosage of admixture shal be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.

Step 11:

Two or more trials having variations of 10% of water cement ratio in clause 10 shall be carried out and a graph between three water cement ratio and corresponding strenghts shall be plotted to work out the mix proportions for the given target strength for field trails. however durability shall be met.

Result: The mix design for M35 grade of concrete with flyash is 1:2.15:2.94

Mix design of M50 grade concrete without Fly Ash:

Aim: Mix design of M50 grade concrete

Procedure:

Step 1:

• Grade designation : M5o
• Type of cement : OPC 43 grade confirming to IS 8112.
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 320 kg/cum.
• Maximum water-cement ratio : 0.45 As per code IS 456:2000, (Table No 5 based no exposure condition)
• Workability : 100 mm (slump).
• Exposure condition : Severe (For Reinforced concrete)
• Method of concrete placing: Pumping
• Maximum Water content: 450 kg/cum
• Chemical admixture type : Super Plasticizer
• Degree of supervision : Good.
• Type of aggregtae: Crushed Angular Aggregates.

Step 2: Test Data for materials

1. Specific gravity of cement : 3.15
2. Specific gravity of Coarse aggregate : 2.74
3. Specific gravity of Fine aggregate : 2.64
4. Water Absoption of Coarse aggregate: 0.5%
5. Water Absoption of Fine aggregate: 1.0%

Sieve analysis of Coase aggregate: Conforming to Table 2 of IS 383

Sieve analysis of Fine aggregate: conforming to grading Zone 1 of table 4 IS 383.

Step 3: To find Target mean Strenght for Mix proportioning.

f_target = f_ck + 1.65 x s.

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

Target strength = 50 + 1.65 x 5.0 = 58.25 N/mm²

Step 4: Selection of water cement ratio,

From table: 5 of IS 456:2000, by exposure condition

Maximum water cement ratio= 0.45 (for severe condition , from table IS 456:2000)

Based on experience, adopted water cement ratio is 0.44

0.44<0.45, Hence OK.

Step 5: Calculation of Water Content,

From Table 2 of IS 456:2000, 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 litres.

Based on trials with Super plasticizer, water content reduction of 20% has been achieved, Hence the arrived water content = 197-[197 x (20/100)] = 158 litres.

Step 6: Calculation of Cement Content,

Water-cement ratio =0.44

Cementatious material ( cement + flyash) = 158/0.44 = 359 kg/m³

From Table 5 of IS 456:2000, minimum cement content for severe exposure condition = 320 kg/m³

350 kg/m³ > 320 kg/m³, Hence, OK.

Step 7:The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content,

From Table 3 of IS 456:2000, the volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for a water-cement ratio of 0.50 =0.60

In present case water cement ratio is 0.4, therfore the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As the water cement ratio is lowered by 0.1, the proportion of volume of coarse aggregate is increased by 0.02 (at the ratio of +/- 0.01 for every +/- 0.05 change in water cement ratio)

Hence the corrected value of coarse aggregate for the water cement ratio=0.632.

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

Therefore, volume of coarse aggregate = 0.632 x 0.9 = 0.568

Volume of fine aggregate content =1 – 0.576 =0.431

Step 8: Mix Calculations,

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of Cement/Specific Gravity of Cement) X (1/1000)

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

= 0.114 m³

c) Volume of water = (Mass of Water/Specific Gravity of Water) X (1/1000)

= (158/1) X (1/1000)

= 0.158 m³

d) Volume of chemical admixture = (Mass of Admixture / Specific Gravity of Admixture) X (1/1000)

= (7.6/1.145) X (1/1000)

= 0.006 m³

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

= 1 – (0.114 + 0.158+0.006)

= 0.722 m³

f) Mass of coarse aggregate = Volume of all Aggregate X Volume of coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.722 x 0.568 x 2.74 x 1000

= 1123 kg/m³

g) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000

= 0.722 x 0.431 x 2.64 x 1000

= 821 kg/m³

Step 9: Concrete Mix Proportions,

• Cement = 359 kg/m³
• Water = 158 kg/m³
• Chemical Admixture = 7.18 kg/m³
• Fine aggregates = 821 kg/m³
• Coarse aggregate = 1123 kg/m³
• W/c = 0.44

Final Concrete Mix Ratio,

Mix ratio of M50 is 1 : 2.28 : 3.12

Step 10:

The slump shall be measured and the water content and dosage of admixture shal be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.

Step 11:

Two or more trials having variations of 10% of water cement ratio in clause 10 shall be carried out and a graph between three water cement ratio and corresponding strenghts shall be plotted to work out the mix proportions for the given target strength for field trails. however durability shall be met.

Result: Mix proportion by weight of M35 grade of concrete with fly ash is 1:2.15:2.94 and its water cement ratio was found to be 0.364.

Mix proportion by weight of M50 grade of concrete without fly ash is 1 : 2.28 : 3.12 and its water cement ratio was found to be 0.44.