Project on Concrete Mix Design for various grades of Concrete
PROJECT-I:
AIM:
To Estimate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash.
INTRODUCTION:
Concrete mix design is the process of selecting suitable ingredients for producing concrete of the required strength, Durability, and workability of the structures. Finally, the mix design is calculated as the required proportion of Cement: Fine aggregate: Coarse aggregate. The concrete mix design depends on mixing, batching, placing, compaction and curing. The Design is done for the proper requirements for material properties for Fresh concrete and Hardened concrete. The use of additives like admixtures, and retarders other than basic ingredients are used to improve the properties of the mix. The guidelines used for concrete mix proportioning are IS 10262:2019 and the recommended guidelines for IS 10262:2009. This project consists of two parts, the first part deals with the design of M35-grade cement with fly ash as a part of it and the second part is the design of M50-grade concrete without fly ash.
OBJECTIVE:
To the main objective of this project is to produce a design mix for M35-grade concrete with fly ash and M50-grade concrete without fly ash.
EQUATIONS USED:
1. Target mean strength:
f’ck =fck + 1.65s
Where
f’ck = Target mean strength of concrete at 28 days.
fck = characteristics compressive strength at 28 days, and
S = standard deviation
2. Cement content:
Cement content =( water content / water-cement ratio)
3. Volume Calculations:
(a) Volume of concrete=1 m^3.
(b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x (1/1000)
(c) Volume of water = [Mass of water] / [Specific Gravity of water] x (1/1000)
(d)Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x (1/1000)
(e) Volume of all in aggregate =[a-(b+c+d)]
(f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
(g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
PART 1:To Estimate the Concrete Mix Design for M35 grade of concrete with fly ash:
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STEP 1: STIPULATIONS FOR PROPORTIONING |
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A) Grade of designation |
M35 |
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B) Type of cement |
OPC 43 Grade confirming to IS 8112 |
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C) Maximum nominal size of aggregate |
20 mm |
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D) Type of mineral admixture |
Fly ash confirming to IS 3812 (Part 1) |
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E) Minimum cement content |
320 kg/m3 (Table 5 of IS 456:2000- Exposure condition) |
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F) Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000 Exposure condition) |
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G) Workability |
100 mm (slump value for pumpable concrete) |
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H) Exposure condition |
Severe (For Reinforced Concrete) |
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I) Method of concrete placing |
Pumping |
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J) Degree of supervision |
Good |
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K) Type of aggregate |
Crushed Angular Aggregates |
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L) Maximum cement content |
450 kg/m3 |
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M) Chemical admixture type |
Super Plasticizer |
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STEP 2: TEST DATA FOR MATERIALS |
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A) Cement used |
OPC 43 Grade conforming IS 8112 |
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B) Specific gravity of cement |
3.15 |
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C) Fly ash |
Confirming to IS 3812 (Part 1) |
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D) Specific gravity of fly ash |
2.2 |
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E) Chemical admixture |
Super Plasticizer conforming to IS 9103 |
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F) Specific gravity of coarse aggregate |
2.74 |
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G) Specific gravity of fine aggregate |
2.74 |
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H) Water absorption of coarse aggregate |
0.5% |
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I) Water absorption of fine aggregate |
1.0% |
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J) Free surface moisture of Coarse aggregate |
Nil |
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K) Free surface moisture of Coarse aggregate |
Nil |
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L) Sieve analysis: Coarse aggregate |
Conforming to Table 2 of IS 383 |
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M)Sieve analysis: Fine aggregate |
Conforming to Grading Zone II of Table 4 of IS 383 |
STEP 3: TARGET MEAN STRENGTH FOR MIX PROPORTIONING:
f’ck =fck + 1.65 s
As per IS 10262:2019 Table Number:1,
s= 5 N/mm2. (M35 grade of concrete)
fck=35 N/mm2.
f'ck=35+1.65 x 5 = 43.25 N/mm2.
Therefore,
Target Mean strength of concrete= 43.25 N/mm2.
STEP 4: SELECTION OF WATER-CEMENT RATIO:
The maximum water-cement ratio to design M35 grade concrete can be found in Table 5 of IS 456-2000.
Condition: Severe( Reinforced concrete)
Maximum water-cement ratio:0.45
Based on Experience, Adopted water-cement ratio:0.42
0.42<0.45, Hence it's ok.
Therefore,
Adopted water-cement ratio=0.42
STEP 5: SELECTION OF WATER CONTENT:
From Table 4 of IS 10262:2019,
Nominal maximum size of aggregate=20 mm
Maximum water content = 186 kg.(for 25 mm to 50 mm slump)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So 6% is to be added to it.
Estimated water content for 100 mm slump = 186+(186 x 6/100) = 197 lit or kg.
AS Superplasticizer is used, the water content can be reduced up to 20% and above.
Based on trials with Super plasticizer water content reduction of 20% has been achieved.
Hence, Arrived water content = 197-(197 x 20/100) = 157.6 ≈ 158 lit or Kg.
Water content = 158 kg or lit.
STEP 6: CALCULATION OF CEMENT AND FLY ASH CONTENT
Adopted water-cement ratio = 0.42
Water content = 158 lit or kg
Cement content = 158/ 0.42 = 376.13 ≈ 376 kg/m3.
To increase cementitious material content and its percentage may be experienced and trials, Here we are increasing cementitious content by 10%.
Final Cementitious material content = 376 x 1.10 = 413.6 ≈ 414 kg/m3.
From Table 5 of IS 456, the Minimum cement content for ‘Severe’ exposure conditions = 320 kg.
414 kg/m3> 320 kg/m3 , Hence ok.
Water content = 158 kg
New water cement ratio = 158/ 414 = 0.38
So, Flyash content is taken as 30% of total cementitious material content,
= 414 x 30 % = 124.2 ≈ 124 kg/m3
Therefore,
Cement required = 414-124 = 290 kg/m3
Flyash being utilized = 124 kg/m3
Cement quantity saved due to fly ash addition = 350 - 290 = 60 kg/m3
Cementitious material, cement and fly ash required is 414 kg/m3, 290 kg/m3and 124 kg/m3 and the new water-cement ratio is 0.38 respectively.
STEP 7: PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
From table number 5 of IS 10262:2019,
The volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone III ) for water cement ratio = 0.64
In the present case, the water-cement ratio = 0.42, Therefore, the 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 the 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, the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.42 is,
= 0.64+0.02 = 0.66
For pumpable concrete, these values should be reduced up to 10%.
Therefore, the volume of coarse aggregate = 0.66-(0.66 x 10/100) = 0.594
the volume of Fine aggregate = 1-0.594 = 0.406
The volume of fine aggregate and coarse aggregate is 0.594 and 0.406
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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) The volume of concrete |
1 m3 |
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b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x (1/1000) |
(290/3.15) X (1/1000) = 0.092 m3 |
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c) Volume of fly ash = [Mass of fly ash] / [Specific Gravity of fly ash] x (1/1000) |
(124/2.2) X (1/1000) =0.056 m3 |
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d) Volume of water = [Mass of water] / [Specific Gravity of water] x (1/1000) |
(158/1) X (1/1000) = 0.158m3 |
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e) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x (1/1000) |
(7.52/1.145) X (1/1000) =0.006 m3 |
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f) Volume of all in aggregate = [a-(b+c+d+e)] |
[1-(0.092+0.056+0.158+0.006)] = 0.688 m3 |
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g) Mass of coarse aggregate= f x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000 |
0.688 x 0.594 x 2.74 x 1000 =1120 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 |
0.688 x 0.406 x 2.74 x 1000 = 765 kg/m3 |
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STEP 9: MIX PROPORTIONS |
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1.Cement |
290 kg/m3 |
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2.Fly ash |
124 kg/m3 |
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3.Water |
158 kg or lit |
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4.Fine aggregate |
765 kg/m3 |
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5.Coarse aggregate 20mm |
1120 kg/m3 |
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6.Chemical admixture |
7.52 kg/m3 |
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Water-cement ratio (lowest W/C ratio is selected) |
0.38 |
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Mix Proportion By weight |
Cement : FA: CA 414 : 765: 1120 1: 1.84: 2.70 |
STEP-10:
The slump shall be measured, and the water content and dosage of admixture shall be adjusted for achieving the required slump on trials. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
STEP 11:
Two more trials having a variation of 10% of the 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 of concrete without Fly ash:
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STEP 1: Stipulations for Concrete design mix |
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A) Grade designation |
M50 |
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B) Type of cement |
OPC 53 Grade confirming to IS BIS 12269 - 1987 |
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C) maximum nominal size of aggregate |
20 mm |
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D) Minimum cement content |
20 kg/m3 (Table 5 of IS 456:2000- Exposure condition) |
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E) Maximum water-cement ratio |
0.45 (Table 5 of IS 456:2000 Exposure condition) |
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F) Workability |
100 mm (slump value for pumpable concrete) |
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G) Exposure condition |
Severe (For Reinforced Concrete) |
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H) Method of concrete placing |
Pumping |
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I) Degree of supervision |
Good |
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J) Type of aggregate |
Crushed Angular Aggregates |
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K) Maximum cement content |
450 kg/m3 |
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L) Chemical admixture type |
Super Plasticizer |
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STEP 2: TEST DATA FOR MATERIALS |
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A) Cement used |
OPC 53 Grade conforming IS 12269-1987 |
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B) Specific gravity of cement |
3.15 |
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C) Chemical admixture |
Super Plasticizer conforming to IS 9103 |
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D) Specific gravity of coarse aggregate |
2.74 |
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E) Specific gravity of fine aggregate |
2.74 |
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F) Water absorption of coarse aggregate |
0.5% |
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G)Water absorption of fine aggregate |
1.0% |
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H) Free surface moisture of Coarse aggregate |
Nil |
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I) Free surface moisture of Coarse aggregate |
Nil |
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J) Sieve analysis: Coarse aggregate |
Conforming to Table 2 of IS 383 |
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K)Sieve analysis: Fine aggregate |
Conforming to Grading Zone II of Table 4 of IS 383 |
STEP 3: TARGET MEAN STRENGTH FOR MIX PROPORTIONING:
f’ck =fck + 1.65 s
As per IS 10262:2019 Table Number:1,
s= 5 N/mm2. (M50 grade of concrete)
fck=50 N/mm2.
f'ck=50+1.65 x 5 = 58.25 N/mm2.
Therefore,
Target Mean strength of concrete= 58.25 N/mm2.
STEP 4: SELECTION OF WATER-CEMENT RATIO:
The maximum water-cement ratio to design M50 grade concrete can be found in Table 5 of IS 456-2000.
Condition: Severe( Reinforced concrete)
Maximum water-cement ratio:0.45
Based on Experience, Adopted water-cement ratio:0.42
0.42<0.45, Hence it's ok.
Therefore,
Adopted water-cement ratio=0.42
STEP 5: SELECTION OF WATER CONTENT:
From Table 4 of IS 10262:2019,
Nominal maximum size of aggregate=20 mm
Maximum water content = 186 kg.(for 25 mm to 50 mm slump)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So 6% is to be added to it.
Estimated water content for 100 mm slump = 186+(186 x 6/100) = 197 lit or kg.
AS Superplasticizer is used, the water content can be reduced up to 20% and above.
Based on trials with Super plasticizer water content reduction of 20% has been achieved.
Hence, Arrived water content = 197-(197 x 20/100) = 157.6 ≈ 158 lit or Kg.
Water content required = 158 kg or lit.
STEP 6: CALCULATION OF CEMENT CONTENT:
Adopted water-cement ratio = 0.42
Water content = 158 lit or kg
Cement content = 158/ 0.42 = 376.13 ≈ 376 kg/m3.
From Table 5 of IS 456, the Minimum cement content for ‘Severe’ exposure conditions = 320 kg.
376 kg/m3> 320 kg/m3 , Hence ok.
Cement content required = 376 kg/m3
STEP 7: PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
From Table number 5 of IS 10262:2019,
The volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone III ) for water cement ratio = 0.64
In the present case, the water-cement ratio = 0.42, Therefore, the 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 the 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, the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.42 is,
= 0.64+0.02 = 0.66
For pumpable concrete, these values should be reduced up to 10%.
Therefore, the volume of coarse aggregate = 0.66-(0.66 x 10/100) = 0.594
the volume of Fine aggregate = 1-0.594 = 0.406
The volume of fine aggregate and coarse aggregate is 0.594 and 0.406
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STEP 8: MIX CALCULATIONS: |
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The mix calculations 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) |
(376/3.15) X (1/1000) =0.119m3 |
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c) Volume of water = [Mass of water] / [Specific Gravity of water] x (1/1000) |
(158/1) X (1/1000) = 0.158m3 |
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d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x (1/1000) |
(7.58/1.145) X (1/1000) =0.006 m3 |
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e) Volume of all in aggregate = [a-(b+c+d)] |
[1-(0.119+0.158+0.006)] = 0.717m3 |
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f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000 |
0.717x 0.594 x 2.74 x 1000 = 1167 kg/m3 |
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g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000 |
0.717x 0.406x 2.74 x 1000 = 798 kg/m3 |
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STEP 9: MIX PROPORTIONS |
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Cement |
376 kg/m3 |
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Water |
158 kg or lit |
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Fine aggregate |
798 kg/m3 |
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Coarse aggregate 20mm |
1167 kg/m3 |
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Chemical admixture |
7.58kg/m3 |
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Water-cement ratio |
0.42 |
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Mix Proportion By weight |
Cement : FA :CA 376: 798: 1167 1 : 2.12: 3.10 |
STEP-10:
The slump shall be measured, and the water content and dosage of admixture shall be adjusted for achieving the required slump on trials. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
STEP 11:
Two more trials having a variation of 10% of the 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 Proportions by its weight of M35 grade of concrete with fly ash is 1: 1.84: 2.70 and its water-cement ratio was found to be 0.38.
- Mix Proportions by its weight of M50 grade of concrete without fly ash is 1 : 2.12: 3.10 and its water-cement ratio was found to be 0.42.
APPENDIX
1. PHYSICAL CHARACTERISTICS OF DIFFERENT TYPES OF OPC CEMENT
2. Table – 5 Minimum Cement Content, Maximum Water-Cement Ratio, and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregate of 20 mm Nominal Maximum Size IS: 456-2000
3. Table 2 of IS 383: Grade size distribution for different nominal sizes of coarse aggregate
4. Table 4 of IS 383: Grading of fine aggregate
5.Table I of IS 10262:2019: Assumed standard deviations
6. Table 2 of IS 10262:2009: maximum water content for 20 mm aggregate
