Project on Concrete Mix Design for various grades of Concrete

Project on Concrete Mix Design

• Calculate the Concrete Mix Design for M35 grade concrete with fly ash

Mix Proportioning of Concrete using Fly ash as part of replacement of OPC

1. Stipulations for proportioning

1. a) Grade designation: M35

1. b) Type of cement: OPC 43 grade conforming to IS 8112

1. c) Type of mineral admixture: Fly ash conforming to IS 3812 (Part 1)

1. d) Maximum nominal size of aggregate: 20 mm

1. e) Minimum cement content: 340 kg/m³ (From Table 5 of IS 456: 2000- Exposure condition)

1. f) Maximum water-cement ratio: 0.45 (From Table 5 of IS 456: 2000 - Exposure condition)

1. g) Workability: 100 mm (slump value for pumpable concrete)

1. h) Exposure condition: Very Severe (for reinforced concrete)

1. i) Method of concrete placing: Pumping

1. j) Degree of supervision: Good

1. k) Type of aggregate: Crushed angular aggregate

1. l) Maximum cement content: 450 kg/m³

m) Chemical admixture type: Superplasticizer

Test data for materials:

a) Cement used: OPC 43 grade conforming to IS 8112

b) Specific gravity of cement: 3.15

c) Fly ash: Conforming to IS 3812 (Part 1)

d) Specific gravity of fly ash: 2.2

e) Chemical admixture: Superplasticizer conforming to IS 9103

f) Specific gravity of:

• Coarse aggregate: 2.74
• Fine aggregate: 2.74

g) Water absorption:

• Coarse aggregate: 0.5%
• Fine aggregate: 1.0 %

h) Free Surface moisture: Nil

• Coarse aggregate: Nil
• Fine aggregate: Nil

i) Sieve Analysis:

• coarse aggregate:

IS sieve sizes in mm	Analysis of C.A fraction		Percentage of different fraction			Remarks
	I.	II.	I	II	Combined
			percent	percent	percent
20	100	100	60	40	100
10	0	71.20	0	28.5	28.5	Conforming to Table 2 of IS 383
4.75		9.40		3.7	3.7
2.36		0

• Fine aggregate: Conforming to grading Zone I of Table 4 of IS 383

III. Target Strength for Mix proportioning:

f'_ck = f_ck + 1.65 S

Where, f'_ck = Target average compressive strength at 28 days

F_ck Characteristic compressive strength at 28 days

S = Standard deviation

From Table 1 of IS 10262: 2009, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 35+1.65 x 5 = 43.25 N/mm^2

1. Selection of Water-cement ratio:

From Table 5 of IS 456: 2000 for very severe exposure, maximum water-cement ratio = 0.45 water cement ratio of

Based on experience, adopt water-cement ratio as 0.40

0.40 < 0.45, Hence O.K

1. Selection of Water content:

From Table 2 of IS 10262: 2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range)

Estimated water content for 100mm slump = 186 + 6/100 X186= 197 litre

As superplasticizer is used, the water content can be reduced up to 30% Based on trials water content reduction of 29% is achieved with plasticizer. Hence the arrived water content = 197X0.71 = 140 litre

1. Calculation of Cement Content:

Water-cement ratio = 0.4

Cementitious material (cement + fly ash) content = 140/0.4 = 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 OK.

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

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

Cementitious material content= 350 x 1.10 = 385 Kg/m³

Water content = 140 litre

So, Water-cement ratio= 140/385= 0.363

Fly ash @ 30% total cementitious material content = 385 x 30% = 115 Kg/m³

Cement (OPC)= 385-115 = 270 Kg/m³

Saving of cement while using fly ash= 350-270 = 80 Kg/m³ and

Fly ash being utilized= 115 Kg/m³

VII. Proportion of Volume of coarse aggregate and Fine aggregate content:

From Table 3 of IS 10262: 2009, Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water-cement ratio of 0.5 = 0.6

In the present case the water cement ratio is 0.40

Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As water-cement ratio is lower by 0.10, 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).

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.40 = 0.62

(Note: If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.62X0.9 = 0.56

Volume of fine aggregate content = 1-0.56 = 0.44

VIII. Mix Calculations:

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

1. a) Volume of Concrete = 1 m³

1. b) Volume of Cement =Mass of cement/Specific gravity of cementX1/1000

= 270/3.15 x 1/1000= 0.0857 m³

1. c) Volume of Fly ash = Mass of fly ash /Specific gravity of fly ash X 1/ 1000

= 115/2.2 x 1/1000= 0.052 m³

1. d) Volume of water = Mass of water / Specific gravity of water X 1/1000

= 140/1 x 1/1000= 0.140 m³

1. e) Volume of chemical admixture = Mass of chemical admixture/Specific gravity of admixture X 1/1000

= 7.7/1.145 x 1/1000 = 0.0067 m³

Note: Mass of chemical admixture = 2% of Cementous material

1. f) Volume of aggregate (FA & CA) = (a- (b+c+d+ e)) = (1-(0.0857+0.052+0.140+0.0067))

= 0.715 m³

1. g) Mass of Coarse aggregate = (f) X Volume of coarse aggregate x Specific gravity of coarse aggregate X 1000

= 0.715 x 0.56 x 2.74 x 1000 ≈ 1097 Kg/m³

1. h) Mass of fine aggregate= (f) X Volume of fine aggregate x Specific gravity of fine aggregate X1000

= 0.715 x 0.44 x 2.74 x 1000 = 862 Kg/m³

1. Mix proportions for Trial Number 1: for 1 m³

Cement= 270 kg

Fly ash = 115 Kg

Water= 140 Kg

Fine aggregate = 862 Kg

Coarse aggregate = 1097 Kg

Chemical admixture = 7.7 Kg (2% of Cementous material)

Water-cement ratio = 0.364

Trial Mix Ratio = 1:2.23: 2.84 (This mix ratio is only trail and error method so that the correct mix ratio obtained in laboratory)

1. The slump shall be measured and the water content and dosage of admixture shall 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

1. Two more trials having variation of 10% of water-cement ratio in Clause X shall be carried out and a graph between three water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.

• Calculate the Concrete Mix Design for M50 grade concrete without fly ash.

Ans:

1. Stipulations for proportioning

1. a) Grade designation: M50

1. b) Type of cement: OPC 53 grade conforming to IS 12269

1. c) Maximum nominal size of aggregate: 20 mm

1. d) Minimum cement content: 320 kg/m³ (From Table 5 of IS 456: 2000- Exposure condition)

1. e) Maximum water-cement ratio: 0.45 (From Table 5 of IS 456: 2000 - Exposure condition)

1. f) Workability: 175 mm (slump value for pumpable concrete)

1. g) Exposure condition: Severe (for reinforced concrete)

1. h) Method of concrete placing: Pumping

1. i) Degree of supervision: Good

1. j) Type of aggregate: Crushed angular aggregate

1. k) Maximum cement content: 450 kg/m³

1. L) Chemical admixture type: Superplasticizer (30% reduction)

1. Test data for materials:

1. a) Cement used: OPC 53 grade conforming to IS 12269

3. b) Specific gravity of cement: 3.15

1. c) Fly ash: Conforming to IS 3812 (Part 1)

2. d) Specific gravity of fly ash: 2.2

1. e) Chemical admixture: Superplasticizer conforming to IS 9103 (30% reduction)

1. f) Specific gravity of:

• Coarse aggregate: 2.72
• Fine aggregate: 2.72

1. g) Water absorption:

• Coarse aggregate: 0.6%
• Fine aggregate: 1.3 %

1. h) Free Surface moisture: Nil (surface saturated dry condition)

• Coarse aggregate: Nil
• Fine aggregate: Nil

1. i) Sieve Analysis:

• coarse aggregate: Ratio of C.A 20mm and 10mm is (60:40)

IS sieve sizes in mm	Analysis of C.A fraction		Percentage of different fraction			Remarks
	III.	IV.	I	II	Combined
			percent	percent	percent
20	100	100	60	40	100
10	0	71.20	0	28.5	28.5	Conforming to Table 2 of IS 383
4.75		9.40		3.7	3.7
2.36		0

• Fine aggregate: Conforming to grading Zone II of Table 4 of IS 383

III. Target Strength for Mix proportioning:

f'_ck = f_ck + 1.65 S

Where, f'_ck = Target average compressive strength at 28 days

F_ck Characteristic compressive strength at 28 days

S = Standard deviation

From Table 1 of IS 10262: 2009, standard deviation, S = 5 N/mm²

Therefore, Target strength = 50+1.65 x 5 = 58.25 N/mm²

1. Selection of Water-cement ratio:

From Table 5 of IS 456: 2000 for severe exposure, maximum water-cement ratio = 0.45 water cement ratio of

Based on experience, adopt water-cement ratio as 0.42

0.42 < 0.45, Hence O.K

1. Selection of Water content:

From Table 2 of IS 10262: 2009, maximum water content for 20mm aggregate = 186 litre (for 25mm to 50mm slump range)

Estimated water content for 100mm slump = 186 + 15% of 186= 213.9 litre ≈ 214 litre

As superplasticizer is used, the water content can be reduced up to 30% Based on trials water content reduction of 25% is achieved with plasticizer. Hence the arrived water content = 214-25% of 214 = 160.5 litre

1. Calculation of Cement Content:

Water-cement ratio = 0.42

Cementitious material (cement) content = 160.5/0.42 = 382 kg/m³

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

382 kg/m³> 320 kg/m³, Hence OK.

VII. Proportion of Volume of coarse aggregate and Fine aggregate content:

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 = 0.62

In the present case the water cement ratio is 0.42

Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

As water-cement ratio is lower by 0.10, 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).

Therefore, corrected volume of coarse aggregate for the water-cement ratio of 0.42 = 0.63

(Note: If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be increased suitably, based on experience)

For pumpable concrete these values are reduced by 10%

Therefore, volume of coarse aggregate = 0.63X0.9 = 0.567

Volume of fine aggregate content = 1-0.567 = 0.433

VIII. Mix Calculations:

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

1. a) Volume of Concrete = 1 m³

1. b) Volume of Cement =Mass of cement/Specific gravity of cementX1/1000

= 382/3.15 x 1/1000= 0.121 m³

1. c) Volume of water = Mass of water / Specific gravity of water X 1/1000

= 160.5/1 x 1/1000= 0.1605 m³

1. d) Volume of chemical admixture = Mass of chemical admixture/Specific gravity of admixture X 1/1000

= 7.64/1.145 x 1/1000 = 0.0066 m³

Note: Mass of chemical admixture = 2% of Cementous material

1. e) Volume of aggregate (FA & CA) = (a-(b+c+d)) = (1-(0.121 +0.1605 +0.0066))

= 0.712 m³

1. f) Mass of Coarse aggregate = (f) X Volume of coarse aggregate x Specific gravity of coarse aggregate X 1000

= 0.712 x 0.567 x 2.72 x 1000 =1098 Kg/m³

1. g) Mass of fine aggregate= (f) X Volume of fine aggregate x Specific gravity of fine aggregate X1000

= 0.712 x 0.433x 2.72 x 1000 = 838.5 Kg/m³

1. Mix proportions for Trial Number 1: for 1 m³

Cement= 382 kg

Water= 160.5 litre

Fine aggregate = 838.5 Kg

Coarse aggregate = 1098 Kg

Chemical admixture = 7.64 Kg (2% of Cementous material)

Water-cement ratio = 0.42

Trial Mix Ratio = 1:2.46:3.16 (This mix ratio is only trail and error method so that the correct mix ratio obtained in laboratory)

1. The slump shall be measured and the water content and dosage of admixture shall 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

1. Two more trials having variation of 10% of water-cement ratio in Clause X shall be carried out and a graph between three water-cement ratios and corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.