Project on Concrete Mix Design for various grades of Concrete
Q. Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash.
Ans:-
AIM: To calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash.
INTRODUCTION:
Concrete mix design is the method of selecting suitable ingredients of concrete and determining their relative proportions with objective of producing concrete of certain minimum strength and durability as economically as possibly. The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability, etc. are attained by this method. Use of additives like admixtures, retarders, etc. other than basic ingredients are used to improve the properties of the mix.
OBJECTIVE:
The objective of this project is to produce a Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash. The mix will be prepared as per IS 10262:2009
PART 1]: To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:
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M35 grade concrete with Fly ash |
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STEP 1: DATA STIPULATION FOR CONCRETE DESIGN MIX |
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Grade of concrete |
M35 |
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Type of cement |
OPC 43 Grade |
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Type of mineral admixture |
Fly ash confirming to IS 3812 (Part 1) |
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Maximum nominal size of aggregate |
20 mm |
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Minimum cement content |
320 kg/m3 (Table 5 of IS 456:2000- Exposure condition) |
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Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000 Exposure condition) |
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Workability |
100 mm (slump value for pumpable concrete) |
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Exposure condition |
Severe (For Reinforced Concrete) |
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Method of concrete placing |
Pumping |
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Degree of supervision |
Good |
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Type of aggregate |
Crushed Angular Aggregates |
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Maximum cement content |
450 kg/m3 |
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Chemical admixture type |
Super Plasticizer |
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STEP 2: TEST DATA FOR MATERIALS |
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Cement used |
OPC 43 Grade conforming IS 8112 |
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Specific gravity of cement |
3.15 |
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Fly ash |
confirming to IS 3812 (Part 1) |
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Specific gravity of fly ash |
2.2 |
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Chemical admixture |
Super Plasticizer conforming to IS 9103 |
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Specific gravity of coarse aggregate |
2.78 |
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Specific gravity of fine aggregate |
2.70 |
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Water absorption of coarse aggregate |
0.5% |
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Water absorption of fine aggregate |
1% |
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Free surface moisture of Coarse aggregate |
Nil |
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Free surface moisture of Coarse aggregate |
Nil |
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Sieve analysis: Coarse aggregate |
Conforming to Table 2 of IS 383 |
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Sieve analysis: Fine aggregate |
Conforming to Grading Zone I of IS 383 |
STEP 3: CALCULATION OF TARGET MEAN STRENGTH
f’ck = fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days
- s = standard deviation
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.
f'ck = fck + 1.65s = 35 + 1.65 x 5 = 43.25 N/mm2
Therefore, target mean strength = 43.25 N/mm2
STEP 4: SELECTION OF W/C RATIO
From Table 5 of IS 456:2000 for severe exposure condition, maximum water-cement ratio = 0.45
Based on experience, adopt w/c ratio as 0.44
0.44 < 0.45, hence OK
Adopted w/c ratio = 0.44
STEP 5: SELECTION OF WATER CONTENT
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From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate |
186 litre (for 25 to 50 mm slump range) |
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Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it Estimated water content for 100 mm slump |
186+ (6/100)*186 = 197 litre. |
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As Super plasticizer is used, the water content can be reduced by up to 25% and above. Based on trials with Super plasticizer water content reduction of 25% has been achieved. Hence the arrived water content |
197*0.75 = 148 litres |
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Water required 148 litres |
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STEP 6: CALCULATION OF CEMENT AND FLY ASH CONTENT REQUIRED
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Adopted w/c Ratio |
0.44 |
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Total cementitious (Cement + fly ash) requirement = Water content/ Water Cement ratio |
148/0.44 = 336 kg/m3 |
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The cementitious content has to be increased in order to attain good workability and strength. The increment required is determined on the basis of experience and research. Here we are increasing cementitious content by 10% |
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Final cementitious content |
336 X 1.10 = 370 kg |
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From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions |
320 kg |
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370 kg/m3 > 320 kg/m3 hence ok. |
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Cementitious material content |
370 kg |
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New water cement ratio |
148/370 =0.4 |
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Fly ash content is taken as 30% of the total cementitious content |
370 X 0.3 = 111 kg/m3 |
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Cement required (OPC) |
370 – 111 = 259 kg/m3 |
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Saving of cement by using fly ash |
336 - 259 = 77 kg/m3 |
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Cementitious material, cement and fly ash required is 370 kg/m3 , 259 kg/m3and 111 kg/m3 and the new water-cement ratio is 0.4 respectively |
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STEP 7: PROPORTION OF VOLUME OF COARSE AND FINE AGGREGATE CONTENT
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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 is = 0.62 |
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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). |
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Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 is = 0.62 +0.02 = 0.64 |
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For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate = 0.64 x0.9 = 0.576 |
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Volume of fine aggregate content = 1 - 0.576 = 0.424 |
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Volume of fine aggregate and coarse aggregate is 0.424 and 0.576. |
STEP 8: MIX CALCULATIONS
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The mix calculations as per unit volume of concrete shall be as follows: |
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a) Volume of concrete |
1 m3 |
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b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000 |
(259/3.15) X (1/1000) =0.082m3 |
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c) Volume of fly ash = [Mass of fly ash] / [Specific Gravity of fly ash] x 1/1000 |
(111/2.2) X (1/1000) =0.05 |
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d) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 |
(148/1) X (1/1000) = 0.148m3 |
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e) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000 (Assuming dossage of 2% by weight of cementitious material and sp. gr. of 1.1, mass of admixture = [2/100]x370 = 7.4kg) |
(7.4/1.1) X (1/1000) =0.007 m3 |
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f) Volume of all in aggregate = [a-(b+c+d+e)] |
[1-(0.082+0.05+0.148+0.007)] = 0.713m3 |
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g) Mass of coarse aggregate= [f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate] x 1000 |
0.713 x 0.576 x 2.78 x 1000 = 1142 kg/m3 |
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h) Mass of fine aggregate= [f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate] x 1000 |
0.713 x 0.424 x 2.70 x 1000 = 816 kg/m3 |
STEP 9: MIX PROPORTIONS
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Cement |
259 kg/m3 |
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Fly ash |
111 kg/m3 |
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Water |
148 kg/m3 |
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Fine aggregate |
816 kg/m3 |
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Coarse aggregate 20mm |
1142 kg/m3 |
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Chemical admixture |
7.4 kg/m3 |
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Water-cement ratio (lowest W/C ratio is selected) |
=0.4 |
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Mix Proportion By weight |
1:3.02:4.23 |
STEP 10:
For the above mix, batch properly, mix properly and slump shall be measured. Dosage of admixture to be adjusted as per workability condition.
Two mix trials having variation of 10% of water-cement ratio 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 for field trials.
[PART 2]: To Calculate the Concrete Mix Design for M50 grade concrete without fly ash:
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M50 grade concrete without Fly ash |
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STEP 1: DATA STIPULATION FOR CONCRETE DESIGN MIX |
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Grade of concrete |
M50 |
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Type of cement |
OPC 43 Grade |
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Maximum nominal size of aggregate |
20 mm |
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Minimum cement content |
320 kg/m3 (Table 5 of IS 456:2000- Exposure condition) |
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Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000 Exposure condition) |
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Workability |
100 mm (slump value for pumpable concrete) |
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Exposure condition |
Severe (For Reinforced Concrete) |
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Method of concrete placing |
Pumping |
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Degree of supervision |
Good |
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Type of aggregate |
Crushed Angular Aggregates |
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Maximum cement content |
450 kg/m3 |
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Chemical admixture type |
Super Plasticizer |
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STEP 2: TEST DATA FOR MATERIALS |
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Cement used |
OPC 43 Grade conforming IS 8112 |
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Specific gravity of cement |
3.15 |
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Chemical admixture |
Super Plasticizer conforming to IS 9103 |
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Specific gravity of coarse aggregate |
2.74 |
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Specific gravity of fine aggregate |
2.65 |
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Water absorption of coarse aggregate |
0.5% |
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Water absorption of fine aggregate |
1% |
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Free surface moisture of Coarse aggregate |
Nil |
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Free surface moisture of Coarse aggregate |
Nil |
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Sieve analysis: Coarse aggregate |
Conforming to Table 2 of IS 383 |
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Sieve analysis: Fine aggregate |
Conforming to Grading Zone I of IS 383 |
STEP 3: CALCULATION OF TARGET MEAN STRENGTH
f’ck = fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days
- s = standard deviation
From Table I of IS 10262:2009, Standard Deviation, s = 5 N/mm2.
f'ck = fck + 1.65s = 50 + 1.65 x 5 = 58.25 N/mm2
Therefore, target mean strength = 58.25 N/mm2
STEP 4: SELECTION OF W/C RATIO
From Table 5 of IS 456:2000 for severe exposure condition, maximum water-cement ratio = 0.45
Based on experience, adopt w/c ratio as 0.44
0.44 < 0.45, hence OK
Adopted w/c ratio = 0.44
STEP 5: SELECTION OF WATER CONTENT
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From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate |
186 litre (for 25 to 50 mm slump range) |
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Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it Estimated water content for 100 mm slump |
186+ (6/100)*186 = 197 litre. |
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As Super plasticizer is used, the water content can be reduced by up to 25% and above. Based on trials with Super plasticizer water content reduction of 25% has been achieved. Hence the arrived water content |
197*0.75 = 148 litres |
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Water required 148 litres |
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STEP 6: CALCULATION OF CEMENT AND FLY ASH CONTENT REQUIRED
Adopted w/c ratio = 0.44
Cement content = [148/0.44] = 336 kg/m3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions = 320 kg/m3
336 kg/m3 > 320 kg/m3, hence OK
Cement required is 336 kg/m3
STEP 7: PROPORTION OF VOLUME OF COARSE AND FINE AGGREGATE CONTENT
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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 is = 0.62 |
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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). |
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Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 is = 0.62 + 0.02 = 0.64 |
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For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate = 0.64 x0.9 = 0.576 |
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Volume of fine aggregate content = 1 - 0.576 = 0.424 |
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Volume of fine aggregate and coarse aggregate is 0.424 and 0.576. |
STEP 8: MIX CALCULATIONS
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The mix calculations as per unit volume of concrete shall be as follows: |
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a) Volume of concrete |
1 m3 |
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b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000 |
(336/3.15) X (1/1000) =0.082m3 |
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c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000 |
(148/1) X (1/1000) = 0.148m3 |
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d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000 (Assuming dossage of 2% by weight of cementitious material and sp. gr. of 1.1, mass of admixture = [2/100]x370 = 7.4kg) |
(7.4/1.1) X (1/1000) =0.007 m3 |
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e) Volume of all in aggregate = [a-(b+c+d)] |
[1-(0.082+0.148+0.007)] = 0.763m3 |
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f) Mass of coarse aggregate= [f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate] x 1000 |
0.763 x 0.576 x 2.74 x 1000 = 1204 kg/m3 |
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g) Mass of fine aggregate= [f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate] x 1000 |
0.763 x 0.424 x 2.65 x 1000 = 857 kg/m3 |
STEP 9: MIX PROPORTIONS
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Cement |
336 kg/m3 |
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Water |
148 kg/m3 |
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Fine aggregate |
857 kg/m3 |
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Coarse aggregate 20mm |
1204 kg/m3 |
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Chemical admixture |
7.4 kg/m3 |
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Water-cement ratio |
0.44 |
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Mix Proportion By weight |
1:2.55:3.58 |
STEP 10:
The slump shall be measured, 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.
Two mix trials having variation of 10% of water-cement ratio 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 for field trials.
RESULTS:
Mix Proportion by weight of M35 grade of concrete with fly ash is 1:3.02:4.23 and its water-cement ratio was found to be 0.4
Mix Proportion by weight of M50 grade of concrete without fly ash is 1:2.55:3.58 and its water-cement ratio was found to be 0.44