Project on Concrete Mix Design for various grades of Concrete

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

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 process of preparation of concrete with suitable proportion of ingredients to meet the required strength and durability of concrete structure. Every ingredient of concrete consists different properties so, it is not an easy task to get economical and good concrete mix.
• Concrete is a complex material and has the right mix of constituents of concrete, which if not done properly and will have adverse effect on the properties of concrete
• 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 ingredients for producing concrete of required Strength, durability and workability as economical as possible is known as concrete mix design
• The compressive strength of the concrete depends on the quality and quantity of cement, water and aggregates
• It also depends on the mixing, batching, placing, compaction and curing   
• Minimum Compressive Strength required for structural considerations
• Adequate workability
• Maximum water cement ratio to attain adequate durability
• Maximum Cement content to avoid shrinkage

Procedure:

1.Calculate the Concrete Mix Design for M35 grade concrete with fly ash

I.Stipulations for proportioning

1. Grade designation : M35
2. Type of cement : OPC 43 grade conforming to IS 8112
3. Type of material admixture:Fly ash conforming to IS3812(part1)
4. Maximum nominal size of aggregate : 20mm
5. Minimum cement content : 320 kg/m^3 (From Table 5 of IS 456: 2000 — Exposure condition)
6. Maximum water-cement ratio : 0.45 (From Table 5 of IS 456: 2000 — Exposure condition)
7. Workability :75 mm (slump value for pumpable concrete)
8. Exposure condition : Severe (for reinforced concrete)
9. Method of concrete placing : Pumping
10. Chemical admixture type : Superplasticizer
11. Degree of supervision : Good
12. Type of aggregate : Crushed angular aggregate
13. Maximum cement content : 450 kg/m^3

II.Test data for materials:

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

b)Specific gravity of cement : 3.15

c)Chemical admixture : Superplasticizer conforming to IS 9103

d)Fly ash  conforming to IS3812(part1)

e)specific gravity of fly ash:2.2

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: from table 2 IS 383
• Fine aggregate: Conforming to grading Zone I of Table 4 of IS 383

III. Target Strength for Mix proportioning:

f'ck = fck+1.65 S

Where, f'ck = Target average compressive strength at 28 days

               fck =characteristic compressive strength at 28 days

                   S= standard deviation

From Table 4 of IS 10262: 2019, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 35 + 1.65 X 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

Based on experience, adopted water-cement ratio is 0.42 from graph

0.42 < 0.45, hence O.K

V.Selection of Water content

 From Table-4 of IS 10262: 2019,

The maximum water content for 25mm to 50mm slump = 186 kg = 186 litre

{For additional slump 3% may be added for every 25mm slump}

Estimated water content for 75mm slump = 186 + 3/100x186

= 192 litre

As superplasticizer is us , the water content can be reduced up to 20% and above

Based on trials water content reduction of 30% is achieved with plasticizer.

Hence the arrived water content = 197x0.7= 135 litre

VI.Calculation of Cement Content:

Water-cement ratio = 0.42

Water content= 135 litre

Water content / cementitious(cement+flyash) content= 0.42

Cementitiouse content= 135/0.42 = 338 kg/m^ 3

From Table 5 of IS 456 minimum cement content for 'severe' exposure condition = 320 kg/m ^A 3

338 kg/m^3 > 320 kg/m^ 3 , Hence OK.

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

1. a) The percentage of fly ash needs to be decided based on project requirement and quality of materials
2. b) In some cases increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial (This example is with increase of 10% cementitious material content)

Cementitious material content= 338 x 1.10 = 372 Kg/m^3

Water content= 135 Kg/m^ 3

So, Water-cement ratio= 135/372= 0.362

Fly ash @ 30% total cementitious material content =372x30%=112 Kg/m^3

Cement (OPC)=372-112=260  Kg/m^3

Saving of cement while usingfly ash=338-260=78  Kg/m^3

Fly ash being utilized=112  Kg/m^3

VII. Proportion of Volume of coarse aggregate and Fine aggregate content:

From Table 3 of IS 10262: 2019, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone l) for water-cement ratio = 0.6

In the present case the water cement ratio is 0.42

Volume of coarse aggregate content =(0.5-w/c)/0.05)x0.01)+ Proportion of Volume of coarse aggregate

                                             =0.5-0.42/0.05x0.01+0.6

                                            =0.616

Volume of fine aggregate content =1- Volume of coarse aggregate

                                         =1-0.616

                                             =0.384

VIII. Mix Calculations:

The mix calculation per unit volume of concrete shall be as follows:

a)Volume of Concrete = 1 m^3

b)Volume of Cement =(Mass of cement/ Specific gravity of cement)x1/1000

                                    =(260/3.15)x1/1000

                                    =0.0825 m^3

c) Volume of Fly ash=(mass of Fly ash/Specific gravity of fly ash)x1/1000

                               =(112/2.2)x1/1000

                                = 0.0509 m^3

d) Volume of water= (Mass of water/ Specific gravity of water)x1/1000

                               =(135/1)x1/1000

                               =0.135m^3

 e) Volume of chemical admixture=(Mass of chemical admixture/ Specific gravity of chemical admixture)x1/1000

 Mass of chemical admixture=2% of cementitious material

                                              =(338x2/100)

Mass of chemical admixture =6.76kg

Volume of chemical admixture=(6.76/1.145)x1/1000

                                                   =0.0059m^3

f) volume of aggregate= (Volume of Concrete-( Volume of Cement+ Volume of Fly ash+Volume of water+ Volume of chemical admixture))

                                 =(1-(0.0825+0.0509+0.135+0.0059))

                                  =0.7257

g)Mass of Coarse aggregate= volume of aggregate x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000

                                        =0.7257x0.616x2.74x1000

                                          =1225 kg/m^3

 h) Mass of fine aggregate = volume of aggregate x volume of fine aggregate x specific gravity of fine aggregate x1000

                                      =0.7257x0.384x2.74x1000

                                    =764 kg/m^3

 IX.Mix proportions for  Number :

Cement=260 kg/m^3

Fly ash=112 kg/m^3

Water=135 kg/m^3

Fine aggregate=764 kg/m^3

Coarse aggregate=1225 kg/m^3

chemical admixture=6.76 kg/m^3

water cement ratio =0.42

Concrete mix design for M35 grade concrete with fly ash:

Mix Ratio= 1 : 2.05: 3.29

X.The slump shall be measured and 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

XI.Two more trials having variation of 10% of water-cement ratio in Clause X 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 field trials. However, durability shall be met.

2.Calculate the Concrete Mix Design for  M50 grade concrete without Fly ash 

I.Stipulations for proportioning

1. Grade designation : M50
2. Type of cement : OPC 43 grade conforming to IS 8112
3. Maximum nominal size of aggregate : 20mm
4. Minimum cement content : 320 kg/m^3 (From Table 5 of IS 456: 2000 — Exposure condition)
5. Maximum water-cement ratio : 0.45 (From Table 5 of IS 456: 2000 — Exposure condition)
6. Workability 75 mm (slump value for pumpable concrete)
7. Exposure condition : Severe (for reinforced concrete)
8. Chemical admixture type : Superplasticizer
9. Method of concrete placing : Pumping
10. Degree of supervision : Good
11. Type of aggregate : Crushed angular aggregate
12. Maximum cement content : 450 kg/m^3

II.Test data for materials:

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

b)Specific gravity of cement : 3.15

c)Chemical admixture : Superplasticizer 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

d) Sieve Analysis:

• Coarse aggregate: from table 2 IS 383
• Fine aggregate: Conforming to grading Zone I of Table 4 of IS 383

III. Target Strength for Mix proportioning:

f'ck = fck+1.65 S

Where, f'ck = Target average compressive strength at 28 days

               fck =characteristic compressive strength at 28 days

                   S= standard deviation

From Table 4 of IS 10262: 2019, standard deviation, S = 5 N/mm^2

Therefore, Target strength = 50 + 1.65 X 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

Based on experience, adopted water-cement ratio is 0.35 from graph

0.35 < 0.45, hence O.K

V.Selection of Water content

 From Table-4 of IS 10262: 2019,

The maximum water content for 25mm to 50mm slump = 186 kg = 186 lit

{For additional slump 3% may be added for every 25mm slump}

Estimated water content for 75mm slump = 186 + 3/100x186

                                                             = 192 litre

As superplasticizer is us , the water content can be reduced up to 20% and above

Based on trials water content reduction of 30% is achieved with plasticizer.

Hence the arrived water content = 197x0.7= 135 litre

VI.Calculation of Cement Content:

Water-cement ratio = 0.35

Water content= 135 litre

Water content / cement content= 0.35

Cement content= 135/0.35 = 385 kg/m^ 3

From Table 5 of IS 456 minimum cement content for 'severe' exposure condition = 320 kg/m ^A 3

385 kg/m^3 > 320 kg/m^ 3 , Hence OK.

VII. Proportion of Volume of coarse aggregate and Fine aggregate content:

From Table 3 of IS 10262: 2019, Volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (Zone l) for water-cement ratio = 0.6

In the present case the water cement ratio is 0.35

Volume of coarse aggregate content =((0.5-w/c)/0.05)x0.01)+ Proportion of Volume of coarse aggregate

                                             =0.5-0.35/0.05x0.01+0.6

                                            =0.63

Volume of fine aggregate content =1- Volume of coarse aggregate

                                         =1-0.63

                                             =0.37

VIII. Mix Calculations:

The mix calculation per unit volume of concrete shall be as follows:

a)Volume of Concrete = 1 m^3

b)Volume of Cement =(Mass of cement/ Specific gravity of cement)x1/1000

                                    =(385/3.15)x1/1000

                                    =0.122m^3

c) Volume of water= (Mass of water/ Specific gravity of water)x1/1000

                               =(135/1)x1/1000

                               =0.135m^3

d) Volume of chemical admixture=(Mass of chemical admixture/ Specific gravity of chemical admixture)x1/1000

Mass of chemical admixture=2% of cementitious material

                                              =(385x2/100)

Mass of chemical admixture =7.7kg

Volume of chemical admixture=(7.7/1.145)x1/1000

                                                   =0.0068m^3

e) volume of aggregate= (Volume of Concrete-( Volume of Cement+ Volume of water+ Volume of chemical admixture))

                                 =(1-(0.122+0.135+0.0068))

                                  =0.7362

f)Mass of Coarse aggregate= volume of aggregate x Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000

                                        =0.7362x0.63x2.74x1000

                                          =1270kg/m^3

 g) Mass of fine aggregate = volume of aggregate x volume of fine aggregate x specific gravity of fine aggregate x1000

                                      =0.7362x0.37x2.74x1000

                                    =746kg/m^3

 IX.Mix proportions for  Number :

Cement=385kg/m^3

Water=135 kg/m^3

Fine aggregate=746 kg/m^3

Coarse aggregate=1270 kg/m^3

chemical admixture=6.76 kg/m^3

water cement ratio =0.35

Concrete mix design for M50 grade concrete:

Mix Ratio= 1 : 1.93: 3.29

X.The slump shall be measured and 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

XI.Two more trials having variation of 10% of water-cement ratio in Clause X 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 field trials. However, durability shall be met.

Result:

Concrete mix design for M35 grade concrete with fly ash:

Mix Ratio= 1 : 2.05: 3.29

Concrete mix design for M50 grade concrete:

Mix Ratio= 1 : 1.93: 3.29