Challenge

Project on Concrete Mix Design for various grades of Concrete

SShahid Afaridi11 May 2023

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 finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures.
Therefore concrete mix design can be stated as concrete mix in terms of cement: sand: aggregates.
The design is done according to the requirements of concrete strength.
So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage.
The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by this method.
Use of additives like admixtures, retarders etc. other than basic ingredients are used to improve the properties of mix.
This project consist of two parts, the first part deals with the design of M35 grade cement with fly ash and second part is the design of M50 grade concrete without fly ash.

Formulae Used :-

1) 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.

And, S = standard deviation.

The value of standard deviation "S" is obtained from Table I of IS 10262:2009.

2) Cement content :-

Cement content = water content / water-cement ratio

Minimum cement criteria can be checked by Table 5 of IS 456 : 2000.

3) Volume calculation :-

(a) Volume of concrete = Assume or Given.

(b) Volume of cement = [(Mass of cement) ÷ (Specific Gravity of Cement x 1000) ].

(d) Volume of water = [(Mass of water) ÷ (Specific Gravity of water x 1000) ].

(e) Volume of chemical admixture = [(Mass of admixture) ÷ (Specific Gravity of admixture x 1000)].

(f) Volume of aggregate =[a-(b+c+d+e)]

(g) Mass of coarse aggregate = f x Volume of Coarse Aggregate x Specific Gravity of Coarse Aggregate x 1000.

(h) Mass of fine aggregate = f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000.

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

STEP - 1:- Stipulations for proportioning
Grade designation	M35
Type of mineral admixture	Fly ash confirming to IS 3812 (Part 1)
Maximum nominal size of aggregate	20 mm
Minimum cement content	320 kg/m³ (Table 5 of IS 456:2000- Exposure condition)
Maximum water-cement ratio	0.45 (Table 5 of IS 456:2000 Exposure condition)
Workability	100 mm (slump value for pumpable concrete)
Exposure condition	Severe (For Reinforced Concrete)
Method of concrete placing	Pumping
Degree of supervision	Good
Type of aggregate	Crushed Angular Aggregates
Maximum cement content	450 kg/m³
Chemical admixture type	Super Plasticizer

STEP - 2:- Test data for materials
Cement used	OPC 43 Grade conforming IS 8112
Specific gravity of cement	3.15
Fly ash	confirming to IS 3812 (Part 1)
Specific gravity of Fly ash	2.2
Chemical admixture	Super Plasticizer conforming to IS 9103
Specific gravity of coarse aggregate	2.74
Specific gravity of fine aggregate	2.74
Water absorption of coarse aggregate	0.5%
Water absorption of fine aggregate	1.0%
Free surface moisture of Coarse aggregate	Nil
Free surface moisture of Coarse aggregate	Nil
Sieve analysis: Coarse aggregate	Conforming to Table 2 of IS 383
Sieve analysis: Fine aggregate	Conforming to Grading Zone 1 of Table 4 of IS 383

Procedure :-

Step - 1. Target mean strength for mix proportioning -

f'ck = fck + 1.65 x S

Where, f'ck - target mean strength at 28 days,

fck - Characteristics compressive stregth at 28 days

And S - Standard deviation value is obtained from Table 1 of IS 10262 : 2009

So, f'ck = 35 + 1.65 x 5

Hence f'ck = 43.25 N/mm^2.

Step - 2. Selection of water cement ratio -

From table 5 of IS 456 : 2000 for severe exposure

Maximum water cement ratio = 0.45

Based on experience adopted value of water-cement ratio = 0.35

Since, maximum value of w/c is greater than adopted value of w/c ( i.e. 0.45 > 0.35 )

Hence, Adopted value is ok.

Step - 3. Selection of water content -

From table 2 of Is 10262 :2009 , Maximum water content for 20 mm aggregate = 186 litre ( For slump value of 25 mm - 50 mm ).

Estimated water content for 100 mm slump = 186 + 186 x 6 % ( Since for additional 50 mm slump, 3% may be added for every 25 mm slump ).

Estimated water content for 100 mm slump = 197 litre.

As superplasticizer is used, the water content can be reduced upto 20% and above.

Based on trials water content reduction of 20% is achieved with plasticizer.

Hence arrived water content = 197 x 0.80

Hence arrived water content = 158 litre.

Step - 4. Calculation of cement content and Fly ash required -

Since, adopted water cement ratio = 0.35

Hence, cement content = w ÷ 0.35

= 158 ÷ 0.35

cement content = 451 Kg/m^3.

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%.

Final cementitious content = 451 x 1.10

Final cementitious content = 496 Kg/m^3.

From table 5 of IS 456 minimum cement content for "severe" exposure comdition = 320 Kg/m^3.

Since minimum cement criteria is full filling hence final cement content = 451 Kg/m^3 is OK.

Now, Cementitious material content = 496.

And water content = 158 Kg.

New water cemet ratio = Weight of water / Weight of cement

water cemet ratio = 158 / 496

water cemet ratio = 0.32

Fly ash may be takent as 30% of total cementitious material content

Hence Fly ash = 496 x 30%

Fly ash = 149 Kg/m^3.

Cement required ( OPC ) = 496 - 149

Cement required ( OPC ) = 347 Kg/m^3.

Cement quantity saved due to fly ash addition = 451 - 347

Cement quantity saved due to fly ash addition = 104 Kg.m^3.

And fly ash being utilized = 149 Kg/m^3

Step - 5. Proportion of volume of coarse aggregate and fine aggregate content -

From table 3 of Is 10262 : 2009, volume of coarse aggegate corresponding to 20 mm size aggergate and fine aggregate ( Zone 1 ) for W/C ratio of 0.5 is 0.6

In the present case water-cement ratio is 0.35.

Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.25. 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 0.35 = {0.6 + (0.02 ÷ 0.05) x (0.6 - 0.35)}

= 0.7

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate = 0.7 x 0.9

volume of coarse aggregate = 0.63

Hence, volume of fine aggrgate = 1 - 0.63

volume of fine aggrgate = 0.37

Step - 6. Mix calculation -

(a) Volume of concrete = 1 m^3.

(b) Volume of cement = [(Mass of cement) ÷ (Specific Gravity of Cement x 1000) ].

= [(347) ÷ (3.15 x 1000) ].

= 0.110 m^3.

= [(149) ÷ (2.2 x 1000) ].

= 0.068 m^3.

(d) Volume of water = [(Mass of water) ÷ (Specific Gravity of water x 1000) ].

= [(158) ÷ (1 x 1000) ].

= 0.158 m^3.

(e) Volume of chemical admixture = [(Mass of admixture) ÷ (Specific Gravity of admixture x 1000)].

= [(2% of cementitous materials) ÷ (Specific Gravity of admixture x 1000)].

= [(10) ÷ (1.145 x 1000)].

= 0.009 m^3.

(f) Volume of aggregate =[a-(b+c+d+e)]

= 1 - (0.110 + 0.086 + 0.158 + 0.009)

= 0.637 m^3.

(g) Mass of coarse aggregate = f x Volume of Coarse Aggregate x Specific Gravity of Coarse Aggregate x 1000.

= 0.637 x 0.63 x 2.74 x 1000

= 1099 Kg.

(h) Mass of fine aggregate = f x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000.

= 0.637 x 0.37 x 2.74 x 1000

= 646 Kg.

Step - 7. Mix proportion for trial 1 -

Cement = 347 Kg/m^3.

Fly ash = 149 Kg/m^3.

Water = 158 Kg/m^3.

Coarse aggregate = 1099 Kg/m^3.

Fine aggregate = 646 Kg/m^3.

Chemical Admixture = 10 Kg/m^3.

W/C ratio = 0.32

Trial -1 Mix ratio = Cement : fine aggregate : coarse aggregate

= 347 : 464 : 1099

= 1 : 1.86 : 3.17

Step - 8. The slump may shall be measured and shall be adjusted and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be rewareded for the actual water content and checked for durabilty requirements.

Step - 9. Two more trials having variation of 10% of w/c ratio in clause 8 shall be carried out and a graph between three w/c ratio and corresponding strength shall be plotted to work out the mix proportion for the given target strength for field trials. However, durability shall be met.

Part - 2:- To Calculate the Concrete Mix Design for M50 grade concrete without fly ash -

STEP - 1:- Stipulations for proportioning
Grade designation	M50
Maximum nominal size of aggregate	20 mm
Minimum cement content	320 kg/m³ (Table 5 of IS 456:2000- Exposure condition)
Maximum water-cement ratio	0.45 (Table 5 of IS 456:2000 Exposure condition)
Workability	100 mm (slump value for pumpable concrete)
Exposure condition	Severe (For Reinforced Concrete)
Method of concrete placing	Pumping
Degree of supervision	Good
Type of aggregate	Crushed Angular Aggregates
Maximum cement content	450 kg/m³
Chemical admixture type	Super Plasticizer

STEP - 2:- Test data for materials
Cement used	OPC 53 Grade conforming IS 12269-1987
Specific gravity of cement	3.15
Fly ash	confirming to IS 3812 (Part 1)
Specific gravity of Fly ash	2.2
Chemical admixture	Super Plasticizer conforming to IS 9103
Specific gravity of coarse aggregate	2.74
Specific gravity of fine aggregate	2.74
Water absorption of coarse aggregate	0.5%
Water absorption of fine aggregate	1.0%
Free surface moisture of Coarse aggregate	Nil
Free surface moisture of Coarse aggregate	Nil
Sieve analysis: Coarse aggregate	Conforming to Table 2 of IS 383
Sieve analysis: Fine aggregate	Conforming to Grading Zone 1 of Table 4 of IS 383

Procedure :-

Step - 1. Target mean strength for mix proportioning -

f'ck = fck + 1.65 x S

Where, f'ck - target mean strength at 28 days,

fck - Characteristics compressive stregth at 28 days

And S - Standard deviation value is obtained from Table 1 of IS 10262 : 2009

So, f'ck = 50 + 1.65 x 5

Hence f'ck = 58.25 N/mm^2.

Step - 2. Selection of water cement ratio -

From table 5 of IS 456 : 2000 for severe exposure

Maximum water cement ratio = 0.45

Based on experience adopted value of water-cement ratio = 0.30

Since, maximum value of w/c is greater than adopted value of w/c ( i.e. 0.45 > 0.30 )

Hence, Adopted value is ok.

Step - 3. Selection of water content -

From table 2 of Is 10262 :2009 , Maximum water content for 20 mm aggregate = 186 litre ( For slump value of 25 mm - 50 mm ).

Estimated water content for 100 mm slump = 186 + 186 x 6 % ( Since for additional 50 mm slump, 3% may be added for every 25 mm slump ).

Estimated water content for 100 mm slump = 197 litre.

As superplasticizer is used, the water content can be reduced upto 20% and above.

Based on trials water content reduction of 20% is achieved with plasticizer.

Hence arrived water content = 197 x 0.80

Hence arrived water content = 158 litre.

Step - 4. Calculation of cement content and Fly ash required -

Since, adopted water cement ratio = 0.30

Hence, cement content = w ÷ 0.30

= 158 ÷ 0.30

cement content = 527 Kg/m^3.

Step - 5. Proportion of volume of coarse aggregate and fine aggregate content -

From table 3 of Is 10262 : 2009, volume of coarse aggegate corresponding to 20 mm size aggergate and fine aggregate ( Zone 1 ) for W/C ratio of 0.5 is 0.6

In the present case water-cement ratio is 0.30.

Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.30. 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 0.35 = {0.6 + (0.02 ÷ 0.05) x (0.6 - 0.30)}

= 0.72

For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate = 0.72 x 0.9

volume of coarse aggregate = 0.65

Hence, volume of fine aggrgate = 1 - 0.65

volume of fine aggrgate = 0.35

Step - 6. Mix calculation -

(a) Volume of concrete = 1 m^3.

(b) Volume of cement = [(Mass of cement) ÷ (Specific Gravity of Cement x 1000) ].

= [(527) ÷ (3.15 x 1000) ].

= 0.167 m^3.

= [(158) ÷ (1 x 1000) ].

= 0.158 m^3.

(d) Volume of chemical admixture = [(Mass of admixture) ÷ (Specific Gravity of admixture x 1000)].

= [(2% of cementitous materials) ÷ (Specific Gravity of admixture x 1000)].

= [(1) ÷ (1.145 x 1000)].

= 0.001 m^3.

(e) Volume of aggregate =[a-(b+c+d)]

= 1 - (0.167 + 0.158 + 0.001)

= 0.67 m^3.

(f) Mass of coarse aggregate = e x Volume of Coarse Aggregate x Specific Gravity of Coarse Aggregate x 1000.

= 0.674 x 0.65 x 2.74 x 1000

= 1200 Kg.

(g) Mass of fine aggregate = e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000.

= 0.674 x 0.35 x 2.74 x 1000

= 646 Kg.

Step - 7. Mix proportion for trial 1 -

Cement = 527 Kg/m^3.

Water = 158 Kg/m^3.

Coarse aggregate = 1200 Kg/m^3.

Fine aggregate = 646 Kg/m^3.

Chemical Admixture = 10 Kg/m^3.

W/C ratio = 0.30

Trial -1 Mix ratio = Cement : fine aggregate : coarse aggregate

= 527 : 646 : 1200

= 1 : 1.23 : 2.28

RESULTS:

Mix Proportion by weight of M35 grade of concrete with fly ash is 1 : 1.86 : 3.17 and its water-cement ratio was found to be 0.35.

Mix Proportion by weight of M50 grade of concrete without fly ash is 1 : 1.23 : 2.28 and its water-cement ratio was found to be 0.30.

Project on Concrete Mix Design for various grades of Concrete

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