Construction Technology_Concrete Mix Design_Project 1

Concrete Mix Design for M35 using Flyash

Mix proportion concrete using Fly ash as a part of replacement of OPC

• Stipulations for proportioning

1. Grade Designation – M35
2. Type of cement – OPC 43 grade confirming to IS8112
3. Type of Mineral admixture- Fly ash grade confirming to IS 3812 (part 1)
4. Maximum Nominal Size of Aggregate-20 mm
5. Minimum Cement Content-340kg/m^3(from Table 5-IS456:2000-Exposure condition)
6. Maximum water cement ratio- 0.45(from Table 5-IS456:2000-Exposure condition)
7. Workability -100mm (slump value for pump able concrete)
8. Exposure condition- severe (for reinforced concrete)
9. Method of concrete placing-Pumping
10. Degree of supervision-Good
11. Type of aggregate-Crushed angular aggregate
12. Maximum cement content-450kg/m^3
13. Chemical admixture type- super plasticizer

• Test data for materials

1. Cement used- OPC 43 grade confirming to IS8112
2. Specific gravity of cement-3.15
3. Fly ash- confirming to IS 3812 (part 1)
4. Specific gravity of fly ash-2.2
5. Chemical admixture-Super plasticizer conforming to IS 9103
6. Specific gravity of:

• Coarse aggregate-2.74
• Fine aggregate -2.74

1. Water absorption:

• Coarse aggregate-0.5%
• Fine aggregate -1.0%

1. Free surface moisture:

• Coarse aggregate-Nil
• Fine aggregate -Nil

1. Sieve Analysis:

• Coarse aggregate-
• Fine aggregate –conforming to grading zone II of Table 4 of IS 383

• Target strength for mix Proportioning:

f’ck=fck+1.65s

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

fck=Characteristic compressive strength at 28 days

S= Standard deviation

From Table 1 standard deviation,(S)=5n/mm^2

Therefore Target strength=35+1.65(5)

=43.25N/mm^2

• Selection of water-cement ratio:

From table 5 of IS 456:2000 for sever exposure, Maximum Water cement ratio =0.45

Adopted water cement ratio =0.45

• Selection of water content:

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

Estimated water content for 100mm slump =186+ (6/100) X186

=197 litre

As super plasticizer is used the water content can be reduced up to 20% and above

Water content requirement after SP=197-(0.20X197)

=157.70 = 160

Hence the arrived water content=160 litres

• Calculation of Cement content:

Water –cement ratio=0.45

Cement Content =160/0.45

=355.55kg/m^3

=356kg/m^3

From Table 5 of IS 456:2000 minimum cement content for severe exposure condition=340kg/m^3

356kg/mm^3> 340 kg/mm^3

Hence ok.

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

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 materials can be warrented.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 =356x1.10=391.1kg/mm^3

Water content=160kg/m^3

Fly ash @30%total cementitious material content=391.1x0.30=117.8=118kg/m^3

Cement (OPC)=391.1-117.8=274.12kg/m^3

Saving of cement while using fly ash=391.1-274.8=117kg/m^3

Fly ash being utilized=118 kg/m^3

Calculation of Super Plasticizers @ 0.6 percent to the mass of cementitious content = = 391.6*(0.6/100) = 2.35 kg

• 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 II) for water-cement ratio =0.62

In the present case the water cement ratio is 0.45

-Therefore, the volume of coarse aggregate needs to be increased to decrease the fine aggregate content.

-As water-cement ratio is lower by 0.10, 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 volume of coarse aggregate for the water-cement ratio of 0.45=0.63

Volume of coarse aggregate=0.63

Volume of fine aggregate=1-0.63=0.37

• Mix calculations:

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

• Volume of concrete=1m³
• Volume of cement = Mass of concrete x 1 .

Specific gravity of cement 1000

=275/(3.15*1000)

=0.087m³

• Volume of fly ash = Mass of fly ash x 1 .

Specific gravity of fly ash 1000

= 118/(2.5*1000)

=0.041m³

• Volume of Water = Mass of Water x 1 .

Specific gravity of water 100

= 160/(1*1000)

=0.16 m³

• Volume of Chemical admixture = Mass of Chemical admixture x 1 .

Specific gravity of Chemical admixture 1000

=2.35/(1.12*1000)

=0.002m³

• Volume of aggregates(FA&CA) = a – (b+c+d+e)

=1 - (0.087 +0.041+0.160+0.002)

=0.71m³

• Mass of coarse aggregate = f x Volume of coarse aggregate x specific gravity of coarseaggregate x 1000

= 0.71*0.63 *2.74 *100

= 1225.6 kg

• Mass of fine aggregate= f x Volume of coarse aggregate x specific gravity of fineaggregate x 1000

= 0.71*0.37*2.74 *1000

=719.8 kg/m³

• Mix proportion for Trial number 1:

Cement =275kg/m³

Fly ash =118kg/m³

Water = 160 L

Fine aggregate =720kg/m³

Coarse aggregate =1226kg/m³

Chemical admixture =2 L

Trial Mix Ratio =1:2.6:4.46

The slump shall be measured and the water content and dosage of admixture shall be adjusted for achieving the required slump on trail. The mix proportion shall be reworked for the actual water content and checked for durability requirements.

MIX DESIGN FOR M50 GRADE

• Stipulations for Concrete Mix Design

• Grade designation : M 50
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 360 kg/m³
• Maximum water-cement ratio : 0.35
• Workability : 50-75 mm (slump)
• Exposure condition : Extreme (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m³
• Chemical admixture type : Super Plasticizer

• Test Data for Materials

• Specific gravity of cement : 3.12
• Specific gravity of Coarse Aggregate : 2.74
• Specific gravity of Fine Aggregate : 2.56
• Procedure for Concrete Mix Design of M 50 Concrete

• Target Strength for Mix Proportioning

f_’ck = f_ck + 1.65 x s

f_’ck = Target Average Compressive Strength at 28 days,

f_ck = Characteristic Compressive Strength at 28 days,

‘s’ = Standard Deviation

According to the table 1 of IS :10262-2009,

standard deviation, s = 5.0 N/mm²

Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm²

• Selection of Water/Cement Ratio

From Table 5 of IS 456:2000,

Maximum water-cement ratio = 0.35

• Selection of Water Content

From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

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

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)

Based on trials with Super plasticizer water content reduction of 27% has been achieved, Hence the arrived water content = 197 – [197 x (27/100)] = 143 litres.

• Calculation of Cement Content

Water-cement ratio = 0.35

Cement content = 143/0.35 = 410 kg/m³

From Table 5 of IS 456, minimum cement content for ‘Extreme exposure’ condition = 360 kg/m³

410 kg/m³ > 360 kg/m³, hence, O.K.

• Proportion of Volume of Coarse Aggregate and Fine Aggregate Content

From Table 3 of IS 10262 . volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.

In the present case, the water-cement ratio is 0.35. 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 0.10. 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 the water-cement ratio).

Therefore, the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.

NOTE – In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience.

For pump able concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.

Volume of fine aggregate content =1 – 0.585 =0.415

• Mix Calculations

a) Volume of concrete = 1m³

b) Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

= (410/3.12) X (1/1000)

= 0.131 m³

c) Volume of Water = (Mass of water/specific gravity of water) X (1/1000)

= (143/1) X (1/1000)

= 0.143 m³

d) Volume of Super plasticizer = (Mass of Super plasticizer / Specific gravity of admixture) X (1/1000)

= (8.2/1.145) X (1/1000)

= 0.007 m³

e) Volume of all aggregate = (a – (b + c + d))

= 1 – (0.131 + 0.143+0.007)

= 0.719 m³

e) Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000

= 0.719 x 0.585 x 2.74 x 1000

= 1152.48 kg

f) Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine aggregate X 1000

= 0.719 x 0.415 x 2.56 x 1000

= 763.86 kg

Concrete Mix Proportions

• Cement = 410 kg/m³
• Water = 143 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 763.86 kg/m³
• Coarse aggregate = 1152.48 kg/m³
• W/c = 0.35

Trial mix ratio =1:1.86:2.81