Project on Concrete Mix Design for various grades of Concrete

AIM: To Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash

Procedure :

PART 1:To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:

STEP 1: STIPULATIONS FOR PROPORTIONING

1. Grade designation : M35
2. Type of cement : OPC 53 Grade conforming IS 8112
3. Type of mineral admixture : Fly ash confirming to IS 3812 ( Part 1)
4. Maximum nominal size of aggregate : 20mm
   e. Minimum cement content : 320 kg/m³ (IS 456:2000)
   f. Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
   g. Workability : 100mm slump
   h. Exposure condition : severe (For Reinforced Concrete)
   i. Method of concrete placing : Pumping
   j. Degree of supervision : Good
   k. Type of aggregate : Crushed Angular Aggregates
   l. Maximum cement content : 450 kg/m³
   m. Chemical admixture type : Super Plasticizer

STEP 2 : TEST DATA FOR MATERIALS
a) Cement used : OPC 53 Grade conforming IS 8112

3. b) Specific gravity of cement : 3.15
4. c) Chemical admixture : Super Plasticizer conforming to IS 9103
5. d) Fly ash : confirming to IS 3812 (Part 1)
6. e) Specific gravity of

1) Coarse aggregate 20mm : 2.74
2) Fine aggregate : 2.74
3) Fly ash : 2.2

1. f) Water absorption:

1) Coarse aggregate : 0.5 %
2) Fine aggregate : 1.0%

1. g) Free (surface) moisture:

1) Coarse aggregate : Nil (Absorbed Moisture also Nil)
2) Fine aggregate : Nil

1. g) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
2) Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383

STEP -3 TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65 s
where
f’ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation.

From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm². Therefore, target strength = 35 + 1.65 x 5 = 43.25 N/mm².

STEP - 4 SELECTION OF WATER•CEMENT RATIO
Adopted maximum water-cement ratio = 0.45. From the Table 5 of IS 456 for Very severe Exposure maximum Water Cement Ratio is 0.44 0.44 < 0.45 Hence ok.

STEP -5 SELECTION OF WATER CONTENT
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range) Estimated water content for 100 mm slump = 186+ (6/186) = 197 litre.

(Note: If Super plasticizer is used, the water content can be reduced upto 20% and above.)

Based on trials with Super plasticizer water content reduction of 30% has been achieved, Hence the arrived water content = 197-[197 x (20/100)] = 158 litre.

STEP -6 CALCULATION OF CEMENT CONTENT
Adopted w/c Ratio = 0.44
Cement Content = 158/0.44 = 359 kg/m³

To proportion the mix containing flyash the following steps are suggested :

1. The percentage of flyash need to be decided based on project requirement and quality of materials.
2. In some cases increase in cementatious materials can be warrned . Increase in cementatious material content and its percentage may be based on experience and trial

In this increase of 10% cementatious material content is considered.

Final cementatious content = 359 *1.10 =395 kg

From Table 5 of IS 456, Minimum cement content for ‘Moderate’ exposure conditions 320kg/m³
= 359 kg/m³ > 340 kg/m³ hence ok

Cementitious material content = 395

New water cement ratio = 158/395 = 0.4

Fly ash content is taken as 30 % of the total cementitious content = 395 * .3 = 118.5 kg/m³

Cement required = 395 – 118.5 = 277 kg / m³

Cement quantity saved due to fly ash addition = 350 – 277 = 73 kg / m³

Cementitious material, cement and fly ash required is 395 kg/m3 , 277 kg/m3and 118 kg/m3 and the new water-cement ratio is 0.4 respectively

STEP-7 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 of 0.50 =0.62 .

In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. 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 proportion of volume of coarse aggregate for the water-cement ratio of 0.44 = 0.64

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

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate =0.64 x 0.9 =0.576.

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

Volume of fine aggregate & coarse aggregate is 0.424 and 0.576

STEP -8 MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m³

3. b) Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}
   = 277/{3.15 x 1000}
   = 0.087m³
4. c) volume of fly ash = [Mass of fly ash ] / {[Specific Gravity of fly ash ] x 1000}

= 118 / {2.2 x 1000 }

= 0.053 m³

1. d) Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}
   = 158/ {1 x 1000}
   = 0.158m³
2. e) Volume of chemical admixture = [Mass of admixture ] / {[Specific Gravity of admixture] x 1000}
   = 6 / {1.14 x 1000} =0.006 m³
3. f) Volume of all in aggregate = [a-(b+c+d+e)]
   = [1-(0.087+0.053+0.158+0.006)]
   = 0.696m³
4. g) Mass of coarse aggregate= f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
   = 0.696x 0.576 x 2.74 x 1000
   = 1098 kg/m³
5. h) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
   = 0.696 x 0.424x 2.74x 1000
   = 808 kg/m³

STEP -9 MIX PROPORTIONS
Cement = 277 kg/m³
Fly ash = 118 kg/m³
Water = 158 l/m³
Fine aggregate = 808 kg/m³
Coarse aggregate 20 mm =1098 kg/m³
Chemical admixture = 7.18 kg/m³
Water-cement ratio = 0.4
Mix Proportion By weight = 1:2.04:2.77

Step 10 :

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

Step 11 :

Two or more trials having variation of 10 % of water-cement ratio in Clause 10( Step 10) 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 feild trials .However durability shall be met.

PART 2 :To Calculate the Concrete Mix Design for M50 grade :

Procedure :

STEP 1: STIPULATIONS FOR PROPORTIONIN

1. a) Grade designation : M50
2. b) Type of cement : OPC 53 Grade conforming IS 8112
3. c) Maximum nominal size of aggregate : 20mm
   d) Minimum cement content : 320 kg/m³ (IS 456:2000)
   e) Maximum water-cement ratio : 0.45 (Table 5 of IS 456:2000)
   f) Workability : 100mm slump
   g) Exposure condition : severe (For Reinforced Concrete)
   h) Method of concrete placing : Pumping
   i) Degree of supervision : Good
   j) Type of aggregate : Crushed Angular Aggregates
   k) Maximum cement content : 450 kg/m³
   l) Chemical admixture type : Super Plasticizer

STEP 2 : TEST DATA FOR MATERIALS
a) Cement used : OPC 53 Grade conforming IS 8112

3. b) Specific gravity of cement : 3.15
4. c) Chemical admixture : Super Plasticizer conforming to IS 9103
5. d) Specific gravity of

1) Coarse aggregate 20mm : 2.74
2) Fine aggregate : 2.74

1. e) Water absorption:

1) Coarse aggregate : 0.5 %
2) Fine aggregate : 1.0%

1. f) Free (surface) moisture:

1) Coarse aggregate : Nil (Absorbed Moisture also Nil)
2) Fine aggregate : Nil

1. g) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383
2) Fine aggregate : Conforming to Grading Zone II of Table 4 of IS 383

STEP -3 TARGET STRENGTH FOR MIX PROPORTIONING
f’ck =fck + 1.65 s
where
f’ck = target average compressive strength at 28 days,
fck = characteristics compressive strength at 28 days, and
s = standard deviation.

From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm². Therefore, target strength = 50 + 1.65 x 5 = 58.25 N/mm².

STEP - 4 SELECTION OF WATER•CEMENT RATIO
Adopted maximum water-cement ratio = 0.45. From the Table 5 of IS 456 for Very severe Exposure maximum Water Cement Ratio is 0.44 0.44 < 0.45 Hence ok.

STEP -5 SELECTION OF WATER CONTENT
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range) Estimated water content for 100 mm slump = 186+ (6/186) = 197 litre.

(Note: If Super plasticizer is used, the water content can be reduced upto 30%

Based on trials with Super plasticizer water content reduction of 29% has been achieved, Hence the arrived water content = 197-[197 x (29/100)] = 140 litre.

STEP -6 CALCULATION OF CEMENT CONTENT
Adopted w/c Ratio = 0.44
Cement Content = 140/0.44 = 350 kg/m³

From Table 5 of IS 456, Minimum cement content for ‘Moderate’ exposure conditions 320kg/m³
= 350 kg/m³ > 340 kg/m³ hence ok

STEP-7 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 of 0.50 =0.62 .

In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. 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 proportion of volume of coarse aggregate for the water-cement ratio of 0.44 = 0.64

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

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate =0.64 x 0.9 =0.576.

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

Volume of fine aggregate & coarse aggregate is 0.424 and 0.576

STEP -8 MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Volume of concrete = 1 m³

3. b) Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000}
   = 350/{3.15 x 1000}
   = 0.111m³

1. c) Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}
   = 140/ {1 x 1000}
   = 0.140m³

7. d) Volume of chemical admixture = [Mass of admixture ] / {[Specific Gravity of admixture] x 1000}
   = 6 / {1.14 x 1000} =0.006 m³
8. e) Volume of all in aggregate = [a-(b+c+d)]
   = [1-(0.111+0.140+0.006)]
   = 0.743m³
9. f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
   = 0.743 x 0.576 x 2.74 x 1000
   = 1173 kg/m³
10. g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
    = 0.743 x 0.424x 2.74x 1000
    = 863 kg/m³

STEP -9 MIX PROPORTIONS
Cement = 350 kg/m³
Water = 158 l/m³
Fine aggregate = 863 kg/m³
Coarse aggregate 20 mm =1173 kg/m³
Chemical admixture = 7.18 kg/m³
Water-cement ratio = 0.4
Mix Proportion By weight = 1:2.46:3.35

Step 10 :

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

Step 11 :

Two or more trials having variation of 10 % of water-cement ratio in Clause 10( Step 10) 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 feild trials .However durability shall be met.

Result : The mix ratio for M 50 grade concrete is 1:2.46:3.35