Project on Concrete Mix Design for various grades of Concrete

1. Calculation of concrete mix design for M35 concrete with fly ash:

Introduction:

The concrete mix design is a systematic process of choosing economical relative proportion of various ingredients from available material that gives the concrete of desired workability.

The process of selecting suitable ingredient for producing concrete of required strength, durability, workability as economical as possible is known as concrete mix design.  

 This mix design covers the calculation of M35 Grade Concrete with Fly ash admixture, as per Indian Standard Codebooks IS10262(2009), IS 456-2000, IS10262- 2019 – Guidelines for Concrete Mix Proportioning.

Aim:

To achieve the designed/ desired workability in the plastic stage.

To achieve the desired minimum strength in the hardened stage.

To achieve the desired durability in the given environment conditions.

To produce concrete as economically as possible.

I.Stipulation for proportioning:

a) Grade of concrete: M35

b) Type of cement: OPC 43 grade conforming to IS 8112

c) Type of mineral admixture: Fly ash conforming to IS 3812 (part 1)

d) Maximum nominal size of aggregate: 20mm

e) Exposure condition: severe (reinforced concrete)

f) Minimum cement content:320kg/m^3 (from table 5 of IS 456:2000- exposure condition)

g) Maximum cement content: 450 kg/m^3 as per IS 456:2000

h) Maximum water-cement ratio: 0.45 (from table 5 of IS 456:2000- exposure condition)

i) Method of concrete placing: Pumping

j) Degree of supervision: Good

k) Type of aggregate: Crushed angular aggregate

l) Chemical admixture type: Super plasticizer conforming to IS 9103

m) Workability: 100mm (slump for pumpable concrete) 

II.Test data for material:

a) Cement used: OPC 43 grade conforming to IS 8112

b) Specific gravity of cement: 3.15

c)Fly ash: Conforming to IS 3812 (Part 1)

d)Specific gravity of fly ash: 2.2

e) chemical admixture: Super plasticizer conforming to IS 9103

f) Specific gravity of: 

Coarse aggregate: 2.74

Fine aggregate: 2.74

g) Water absorption:

coarse aggregate: 0.5%

Fine aggregate: 1.0%

h) Free surface moisture: 

coarse aggregate: Nil

Fine aggregate: Nil

i) Sieve analysis:

coarse aggregate: conforming to grading zone 1 of table 3 of IS 383

Fine aggregate: conforming to grading zone 1 of table 4 of IS 383

Calculation procedure:

III. Target strength for mix proportioning:

Target strength of the concrete, f'ck= fck+1.65s

Where, s is the standard deviation.

From the table 1 of IS10262:2009, standard deviation for M35 concrete, s=5 N/mm^2

Target strength f'ck=35+1.65*5=43.25 N/mm^2

IV. Selection of water-cement ratio:

From table 5 of IS 456:2000 for severe exposure, maximum water-cement ratio= 0.45

From the graph of IS 10262:2019, adopted water-cement ratio is 0.39

0.39<0.45, so water-cement ratio is 0.39.

V. Selection of water content:

From table 2 of IS 10262:2009, maximum water content for 20mm aggregate =186 liters (for 25 to 50 mm slump range)

But for 100mm slump as per specification, the water-content needs to be increased to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence, the increase of water content by 6% to get an additional 50mm slump for the concrete.

Estimated water content for 100mm slump= 186+( 6/100*186) =197 liters.

Based on trails water content reduction is 29% is achieved with plasticizers

The arrived water content = 197* 0.71= 140 liters

VI. Calculation of cement content:

Water-cement ratio, w/c= 0.39

cement content= W/ (w/c) = 140/0.39

                         = 358.97 kg/m^3

From table 5 of IS 456:2000 the minimum cement content for severe exposure condition is 320 kg/m^3.

358.97 kg/m^3 > 320 kg/m^3, Hence ok.

Now, to proportion a mix containing fly ash the following steps are followed:

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

Cementitious material content = 358.97 * 1.10 = 394.867 kg/m^3

Water content = 140 kg/m^3

So, Water-cement ratio = 140/ 394.867 = 0.354

Fly ash at 30% total cementitious material content = 394.867*(30/100)

                                                                          = 118.460 kg/m^3

Cement content = 394.867-118.460 = 276.407 kg/m^3.

Fly ash being utilized = 118.460 kg/m^3.

VII. Proportion of volume of coarse aggregate and fine aggregate:

From table 3 of IS 10262:2009, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone- 1) for water-cement ratio= 0.60

Obtained water cement ratio from the calculation of cement content is 0.354, which is <0.39

Hence, In the present case the water-cement ratio is 0.354

The corrected volume of coarse aggregate for the water-cement ratio of 0.35= 0.6292

For pumped concrete these values are reduced by 10%

Volume of coarse aggregate= 0.6292*0.9= 0.56628

Volume of fine aggregate content = 1-0.56628= 0.43372

VIII. Mix calculation:

The mix calculation per unit volume of concrete shall be as follow,

a)Volume of concrete = 1m^3

b)Volume of cement  = Mass of cement/ specific gravity of cement* (1/1000)

                                  =276.407 /3.15*(1/1000) = 0.0877 m^3.

c)Volume of water = mass of water/ specific gravity of water*(1/1000)

                              =140/1*(1/1000)

                              = 0.140m^3

d)Volume of chemical admixture,

 superplasticizer of 2% by

 mass of cementitious material              = Mass of admixture/ specific gravity of admixture*(1/1000)

                                                          =7.897/1.145*(1/1000)

                                                          =0.00689m^3

e) Volume of aggregate (fine aggregate and coarse aggregate) =(a-(b+c+d))

                                                                                               = (1-(0.0877+0.140+0.00689))

                                                                                                =0.7654m^3

f) Mass of coarse aggregate = e* volume of coarse aggregate*specific gravity of coarse aggregate*1000

                                             =0.7654*0.56628*2.74*1000

                                             =1187.600 kg/m^3

g) Mass of fine aggregate =e*volume of fine aggregate* specific gravity of fine aggregate* 1000

                                          =0.7654*0.43372*2.74*1000

                                          =909.595 kg/m^3

Result:

IX. Mix proportions:

Cement= 276.407 kg/m^3

Fly ash = 118.460 kg/m^3.

Water= 140 kg/m^3

Fine aggregate= 909.595 kg/m^3

Coarse aggregate= 1187.600 kg/m^3

Chemical admixture= 7.897 kg/m^3

water-cement ratio=0.354

Hence, the mix ratio of M35 grade concrete with fly ash is 1: 3.29: 4.29.

The mix consist of 1 part of cement and 3.29 parts of fine aggregate and 4.29 parts of coarse aggregate for the above trail.

2.Calculation of concrete mix design for M50 concrete without fly ash:

Introduction:

The concrete mix design is a systematic process of choosing economical relative proportion of various ingredients from available material that gives the concrete of desired workability.

The process of selecting suitable ingredient for producing concrete of required strength, durability, workability as economical as possible is known as concrete mix design.  

 This mix design covers the calculation of M50 Grade Concrete, as per Indian Standard Codebooks IS10262(2009), IS 456-2000, IS10262- 2019 – Guidelines for Concrete Mix Proportioning.

Aim:

To achieve the designed/ desired workability in the plastic stage.

To achieve the desired minimum strength in the hardened stage.

To achieve the desired durability in the given environment conditions.

To produce concrete as economically as possible.

I.Stipulation for proportioning:

a) Grade of concrete: M50

b) Type of cement: OPC 43 grade conforming to IS 8112

c) Maximum nominal size of aggregate: 20mm

d) Exposure condition: severe (reinforced concrete)

e) Minimum cement content:320kg/m^3 (from table 5 of IS 456:2000- exposure condition)

f) Maximum cement content: 450 kg/m^3 as per IS 456:2000

g) Maximum water-cement ratio: 0.45 (from table 5 of IS 456:2000- exposure condition)

h) Method of concrete placing: Pumping

i) Degree of supervision: Good

j) Type of aggregate: Crushed angular aggregate

k) Chemical admixture type: Super plasticizer conforming to IS 9103

l) Workability: 100mm (slump for pumpable concrete) 

II.Test data for material:

a) Cement used: OPC 43 grade conforming to IS 8112

b) Specific gravity of cement: 3.15

c) chemical admixture: Super plasticizer conforming to IS 9103

d) Specific gravity of: 

Coarse aggregate: 2.74

Fine aggregate: 2.74

e) Water absorption:

coarse aggregate: 0.5%

Fine aggregate: 1.0%

f) Free surface moisture: 

coarse aggregate: Nil

Fine aggregate: Nil

g) Sieve analysis:

coarse aggregate: conforming to grading zone 1 of table 3 of IS 383

Fine aggregate: conforming to grading zone 1 of table 4 of IS 383

Calculation procedure:

III. Target strength for mix proportioning:

Target strength of the concrete, f'ck= fck+1.65s

Where, s is the standard deviation.

From the table 2 of IS10262:2019, standard deviation of M50 concrete, s=5 N/mm^2

Target strength, f'ck=50+1.65*5=58.25 N/mm^2

IV. Selection of water-cement ratio:

From table 5 of IS 456:2000 for severe exposure, maximum water-cement ratio= 0.45

From the graph of IS 10262:2019, adopted water-cement ratio is 0.34

0.34<0.45, Hence water-cement ratio is 0.34.

V. Selection of water content:

From table 2 of IS 10262:2009, maximum water content for 20mm aggregate =186 liters (for 25 to 50 mm slump range)

But for 100mm slump as per specification, the water-content needs to be increased to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence, the increase of water content by 6% to get an additional 50mm slump for the concrete.

Estimated water content for 100mm slump= 186+( 6/100*186) =197 liters.

Based on trails, water content reduction is 29% is achieved with plasticizers.

The arrived water content = 197* 0.71= 140 liters

VI. Calculation of cement content:

Water-cement ratio, w/c= 0.34

cement content,C = W/ (w/c) = 140/0.34

                                            = 411.764 kg/m^3

From table 5 of IS 456:2000 the minimum cement content for severe exposure condition is 320 kg/m^3.

411.764 kg/m^3 > 320 kg/m^3, Hence ok.

VII. Proportion of volume of coarse aggregate and fine aggregate:

From table 3 of IS 10262:2009, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone- 1) for water-cement ratio= 0.60

In the present case the water-cement ratio is 0.34

The corrected volume of coarse aggregate for the water-cement ratio of 0.34= 0.632

For pumped concrete these values are reduced by 10%

Volume of coarse aggregate= 0.632*0.9= 0.5688

Volume of fine aggregate content = 1-0.5688= 0.4312

VIII. Mix calculation:

The mix calculation per unit volume of concrete shall be as follow,

a) Volume of concrete = 1m^3

b) Volume of cement = Mass of cement/ specific gravity of cement* (1/1000)

                                     =411.764/3.15*(1/1000) = 0.1307 m^3.

c)Volume of water = mass of water/ specific gravity of water*(1/1000)

                                 =140/1*(1/1000)

                                 = 0.140m^3

d)Volume of chemical admixture:

 superplasticizer of 2% by

 mass of cementitious material    = Mass of admixture/specific gravity of admixture*(1/1000)

                                                =8.235/1.145*(1/1000)

                                                =0.00719m^3

e) Volume of aggregate (fine aggregate and coarse aggregate) =(a-(b+c+d))

                                                                                               = (1-(0.1307 +0.140+0.00719))

                                                                                               = 0.72211m^3

f) Mass of coarse aggregate = e* volume of coarse aggregate*specific gravity of coarse aggregate*1000

                                           =0.72211*0.5688*2.74*1000

                                            =1125.417 kg/m^3

g) Mass of fine aggregate= e* volume of fine aggregate* specific gravity of fine aggregate* 1000

                                     =0.72211*0.4312*2.74*1000

                                     =853.164 kg/m^3

Result:

IX. Mix proportions:

Cement= 411.764 kg/m^3

Water= 140 kg/m^3

Fine aggregate= 853.164 kg/m^3

Coarse aggregate= 1125.417 kg/m^3

Chemical admixture= 8.235 kg/m^3

water-cement ratio=0.34

Hence, the mix ratio of M50 grade concrete is 1: 2.07: 2.73.

The mix consist of 1 part of cement and 2.07 parts of fine aggregate and 2.73 parts of coarse aggregate for the above trail.