Project on Concrete Mix Design for various grades of Concrete

Concrete Mix Design for M35 grade concrete with fly ash.

1. Concrete grade – M35
2. Type of cement – OPC 43 grade.
3. Type of mineral admixture – Fly ash (confirming from IS 3812 part 1)
4. Nominal size of aggregate - 20mm
5. cement content - 320 kg/m3 (From table 5 of IS456:2000- Exposure condition)
6. water cement ratio – 0.45 (From Table 5 of IS 456:2000 – Exposure condition)
7. Workability – 100 mm (Slump value for pumpable concrete)
8. Exposure condition – Severe (For reinforcement concrete)

Method of concrete placing – pumping

1. Degree of supervision: Good
2. Type of aggregate – Crushed angular aggregate.
3. cement content – 450kg/m3
4. Chemical admixtures type – Superplasticizer

TEST DATA FOR MATERIAL:

1. Cement used – OPC 43 grade confirming to IS 8112
2. Specific Gravity of cement – 3.15
3. Fly ash – confirming to IS 3812 – part 1
4. Specific gravity of Flyash – 2.2
5. Chemical admixture – Super plasticizer (confirming to IS 9103)
6. Specific gravity of Coarse aggregate – 2.74

Specific gravity of Fine aggregate – 2.74

1. Water absorption : Coarse aggregate – 0.5%

Fine Aggregate – 1.0%

1. Free Surface Moisture

Coarse aggregate – NIL

Fine aggregate – NIL

1. Sieve Analysis

Coarse aggregate Confirming to Table -2 of IS 383

Fine aggregate confirming to grading Zone I of table 4 of IS383

TARGET STRENGTH FOR THE MIX PROPORTIONING

Fck’ = fck +1.65s

Where fck’ – target average compressive strength @28days

Fck – characteristic compressive strength @28 days

s – standard deviation.

From table 1 of IS10262:2019

Std. Deviation, s = 5 N/mm2

Target strength = 35 + 1.65*5

= 43.25 N/mm2

SELECTION OF WATER – CEMENT RATIO:

FROM TABLE 5 of IS456:2000 for severe exposure, Max. W/C ratio = 0.45

Based on experience, adopt W/C ratio as 0.40

0.40 < 0.45 .

Hence OK.

SELECTION OF WATER CONTENT

From Table 2 of IS 10262:2019, Max. water content for 20 mm aggregate = 186 ltr (for 25mm to

50mm slump range)

Estimated water content for 100mm slump = 186 +((6/100)*186)

197 lts.

As Super plasticizer is used, the water content can be reduced upto 30%

Based on trials, water content reduction of 29% is achieved with plasticizer.

Hence the arrived water content = 197 * 0.71 = 140ltrs.

CALCULATION OF CEMENT CONTENT

Water cement ratio – 0.4

Cementitious material (cement+flyash) content = 140/0.4 = 350kg/m3

From Table 5 of IS456 minimum cement content for severe exposure condition = 320kg/m3

350 kg/m3 > 320 kg/m3

Hence OK.

The following steps are considered to proportion a mix containing Fly ash

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 its percentage may be based on experience and trial. ( This is example with increase of 10 % cementitious material content)

Cementitious material content = 350*1.10 = 385 kg/m3.

Water content = 140 kg/m3.

So water cement ratio = 140/385 = 0.364

Fly ash @ 30% total cementitious material content = 385 * 30% = 115.5 Kg/m3.

Therefore, Cement (OPC) = 385 – 115 = 270 Kg/m3

Saving of cement using Fly ash = 350-270 = 80 kg/m3

Fly ash being utilized = 115 kg/m3

PROPOTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

From table 5 of IS 10262:2019, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone 1) for Water cement / water cementitious Material Ratio of 0.50 = 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 coarse 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 w/c ratio)

Therefore, Corrected volume of coarse aggregate for w/c ratio of 0.40 = 0.62.

For pumpable concrete these values are reduced by 10%.

Therefore, Vol of Coarse aggregate = 0.62 *0.9 = 0.56.

Vol of Fine aggregate content = 1-0.56 = 0.44.

MIX CALCULATION

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

1. Vol of cement -= 1 m3
2. Vol of cement = (Mass of cement / sp. Gr of cement ) x (1/1000)

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

= 0.086 m3

1. Vol of Fly ash = (Mass of Fly ash / sp. Gr of Fly ash ) x (1/1000)

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

= 0.052 m3

1. Vol of Water = (Mass of water / sp. Gr of water ) x (1/1000)

= (140/1) x (1/1000)

= 0.140 m3

1. Vol of chemical admixture = (Mass of chemical admixture / sp. Gr of chemical admixture ) x

(1/1000)

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

= 0.0067 m3

1. Vol of aggregates ( Coarse aggregate & Fine aggregate)

= 1 – ( 0.086+0.052+0.14+.0067) = 0.716 m3

1. Mass of coarse aggregate = e x Vol of CA x sp. Gr x 1000 = 0.716*0.56*2.74*1000 = 1098 kg/m3
2. Mass of Fine aggregate = e x Vol of FA x sp. Gr x 1000 = 0.716 *0.44*2.74*1000 = 863.2096 kg/m3.

MIX PROPORTION

Cement = 270 kg/m3

Fly ash = 115 kg/m3

Water = 140 kg/m3

Coarse aggregate = 1098 kg/m3

Fine aggregate = 863 kg/m3

W/c ratio = 0.364

Chemical admixture = 7 kg/m3

Mix ratio CEMENT FINE AGG COARSE AGG.

270+115 863 1098

1 2.24 2.85

Therefore , the mix ratio = 1:2.24:2.85

II .Concrete Mix Design for M50 grade concrete without fly ash.

1. Grade of concrete - M50
2. Type of cement – OPC 43 grade confirming to IS8112
3. nominal size of aggregate – 20mm
4. Minimum cement content - 320 kg/m3 (From table 5 of IS 456:2000 – exposure condition)
5. W/c ratio = 0.45 (From table 5 of IS 456:2000 – exposure condition)
6. Workability – 100 mm (Slump value for pumpable concrete)
7. Exposure condition – Severe (For reinforcement concrete)

Method of concrete placing – pumping

1. Degree of supervision: Good
2. Type of aggregate – Crushed angular aggregate.
3. cement content – 450kg/m3
4. Chemical admixtures type – Superplasticizer

TEST DATA FOR MATERIAL:

1. Cement used – OPC 43 grade confirming to IS 8112
2. Specific Gravity of cement – 3.15
3. Chemical admixture – Super plasticizer (confirming to IS 9103)
4. Specific gravity of Coarse aggregate – 2.74

Specific gravity of Fine aggregate – 2.74

1. Water absorption : Coarse aggregate – 0.5%

Fine Aggregate – 1.0%

1. Free Surface Moisture

Coarse aggregate – NIL

Fine aggregate – NIL

1. Sieve Analysis

Coarse aggregate Confirming to Table -2 of IS 383

Fine aggregate confirming to grading Zone I of table 4 of IS383

TARGET STRENGTH FOR THE MIX PROPORTIONING

Fck’ = fck +1.65s

Where fck’ – target average compressive strength @28days

Fck – characteristic compressive strength @28 days

s – standard deviation.

From table 1 of IS10262:2019

Std. Deviation, s = 5 N/mm2

Target strength = 50 + 1.65*5

= 58.25 N/mm2

SELECTION OF WATER – CEMENT RATIO:

FROM TABLE 5 of IS456:2000 for severe exposure, Max. W/C ratio = 0.45

Based on experience, adopt W/C ratio as 0.40

0.40 < 0.45 .

Hence OK.

SELECTION OF WATER CONTENT

From Table 2 of IS 10262:2019, Max. water content for 20 mm aggregate = 186 ltr (for 25mm to

50mm slump range)

Estimated water content for 100mm slump = 186 +((6/100)*186)

197 lts.

As Super plasticizer is used, the water content can be reduced upto 30%

Based on trials, water content reduction of 29% is achieved with plasticizer.

Hence the arrived water content = 197 * 0.71 = 140ltrs

CALCULATION OF CEMENT CONTENT

Water cement ratio – 0.4

Cement content = 140/0.4 = 350kg/m3

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

350 kg/m3 > 320 kg/m3.

PROPOTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

From table 5 of IS 10262:2019, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone 1) for Water cement / water cementitious Material Ratio of 0.50 = 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 coarse 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 w/c ratio)

Therefore, Corrected volume of coarse aggregate for w/c ratio of 0.40 = 0.62.

For pumpable concrete these values are reduced by 10%.

Therefore, Vol of Coarse aggregate = 0.62 *0.9 = 0.56.

Vol of Fine aggregate content = 1-0.56 = 0.44.

MIX CALCULATION

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

1. Vol of cement -= 1 m3
2. Vol of cement = (Mass of cement / sp. Gr of cement) x (1/1000)

= (350/3.15) x (1/1000)

= 0.111 m3

1. Vol of Water = (Mass of water / sp. Gr of water) x (1/1000)

= (140/1) x (1/1000)

= 0.140 m3

1. Vol of chemical admixture = (Mass of chemical admixture / sp. Gr of chemical admixture ) x

(1/1000)

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

= 0.006 m3

1. Vol of aggregates ( Coarse aggregate & Fine aggregate)

= 1 – ( 0.111+0.14+.006) = 0.743 m3

1. Mass of coarse aggregate = e x Vol of CA x sp. Gr x 1000 = 0.743*0.56*2.74*1000 = 1140 kg/m3
2. Mass of Fine aggregate = e x Vol of FA x sp. Gr x 1000 = 0.743 *0.44*2.74*1000 = 896 kg/m3

MIX PROPORTION

Cement = 350 kg/m3

Water = 140 kg/m3

Coarse aggregate = 1140 kg/m3

Fine aggregate = 896 kg/m3

W/c ratio = 0.4

Chemical admixture = 7 kg/m3

Mix ratio CEMENT FINE AGG COARSE AGG.

1 2.56 3.26

Therefore , the mix ratio = 1:2.56:3.26