Project on Concrete Mix Design for various grades of Concrete

Aim: - Calculate the Concrete Mix Design for M35 grade concrete with fly-ash

I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE

a) Grade designation: - M35

b) Type of cement: OPC 53 grade conforming to IS 8112

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

d) Maximum nominal size of aggregate: 20 mm

e) Minimum cement content: 340 kg/m^3 (From Table 5 of IS 456: 2000-Exposure condition).

f) Maximum water-cement ratio: 0.45 (From Table 5 of IS 456: 2000-Exposure condition)

g) Workability: 100 mm (slump value for pumpable concrete)

h) Exposure condition: Very Severe (for reinforced concrete)

i) Partial replacement of cement by Fly ash = 30% as per requirement

j) Chemical Admixture = PCS Type

Procedure: -

II. TEST DATA FOR MATERIALS

Materials should be tested in the laboratory as per tests given in the codebook and their properties should be found. Values of the material properties will be used in the design process and to check the quality of the material with the help of codebook standards. Standard values are taken here for calculation purpose.

A] Cement Used = OPC 53 Confirming to IS8112

B] Specific Gravity of Cement = 3.15 Test – IS: 2720

C] Mineral Admixture = Fly-ash Confirming to IS12089

D] Specific Gravity of Fly ash = 2.90

E] Chemical Admixture = @0.6% IS9103

F] Specific Gravity of Test – IS 2386

Coarse Aggregate = 2.74

Fine Aggregate = 2.74

Admixture PCE based = 1.12

G] Water Absorption Test – IS 2386

Coarse aggregate = 0.5 %

Fine aggregate = 1 %

H] Sieve Analysis Test – IS 2386

Coarse aggregate = Confirming to Table 2-IS383

Fine aggregate = Zone II Confirming to Table 4-IS383

III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE

Fck = fck+1.65s “S” from Table1-IS10262

Fck = 35+1.65×5

Fck = 43.25 N/mm2

IV. SELECTION OF WATER-CEMENT RATIO

The maximum water-cement ratio for different grade of concrete is given in Table 5-IS456. You can reduce the water-cement ratio based on your requirements. Water-cement ratio directly affects the strength of the concrete.

Maximum W/C ratio =0.45 Table 5-IS456

Adopted W/C ratio =0.45

V. SELECTION OF WATER CONTENT

Maximum Water Content =186 L Table 2-IS1026

Above water-content is for 25 to 50mm slump but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.

Water-content for 100mm Slump =186+(0.06*186) =197.16 L

Since superplasticizers are used water content can be reduced to get good strength of concrete. Percentage of reduction of water depends on the type of superplasticizers used in the concrete.

Percentage of Reduction in water content =20%

Water content requirement after SP =198 – (0.20*198) =157.73

Adopted Water Content =160 L

VI. CALCULATION OF CEMENT AND FLY ASH CONTENT

Adopted Water Cement Ratio =0.45

Total Cementitious (Cement +Fly ash) requirement = Water Content / Water-Cement ratio

=160/0.45 =355.55 kg

Since Fly ash is used the amount of Cementitious content (Cement + Fly-ash) shall be increased to get good workability and strength. the percentage of increase depending on experience and research. Here we increased the cementitious content by 1.1 %.

Final Cementitious

Content (Cement + Fly ash) = 356*1.1 =391.6 kg

Minimum Cement Content required for ‘severe’ exposure =340kg [Table 5-IS456]

Adopted Cementous content =391.6 kg > 340kg

Fly ash content requirement = 391.6 * 0.30 30% replacement = 117.48 ~ 118 kg

Cement Content requirement = Cementous content – Fly ash =391.6-117.48 = 274.12

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

VII COARSE AND FINE AGGREGATE

Coarse Aggregate ratio = 0.62 Table3-IS10262 (For W/C =0.5)

Coarse Aggregate ratio for 0.45 w/c ratio = 0.63 (adding 0.01 for every decrease .05 and vice versa)

Final Fine Aggregate ratio = 0.37 (1-0.63) = 0.37

VIII MIX CALCULATIONS OF M35 GRADE CONCRETE

A Volume of Concrete = 1 cu.m

B Total Volume of Cement = Cement/(S.G*1000) = 275/(3.15*1000) = 0.087 cu.m

C Total Volume of Fly ash = Flyash/(S.G*1000) = 118/(2.5*1000) = 0.041 cu.m

D Volume of Water =Water /(S.G*1000) = 160/(1*1000) = 0.160 cu.m

E Volume of Superplasticizers = Superplasticizers /(S.G*1000) = 2.35/(1.12*1000) = 0.002 cu.m

F Total Aggregates requirement = A – (B+C+D+E) =1 -(0.087 +0.041+0.160+0.002) =0.71 cu.m

G Coarse Aggregate (C.A) = F * C.A ratio * S.G * 1000 = 0.71*0.63 *2.74 *1000 `= 1225.6 kg

I Fine Aggregate (F.A) = F * F.A ratio * S.G * 1000 = 0.71*0.37*2.74 *1000 =719.8 kg

Cement Fly-ash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete

Sr.No. MATERIALS QUANTITY

1 Cement = 275 kg

2 Fly-ash = 118 kg

3 Fine Aggregate = 720 kg

4 Coarse Aggregate (20mm) = 1226 kg

5 WATER = 160 L

6 PCE based Super-Plasticizer = 2 L

To find the design mix ratio divide the calculated value of all materials by the weight of cement.

Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Fly-ash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58

Aim: - Calculate the Concrete Mix Design for M50 grade concrete without Fly-ash

Data required: -

I. Stipulations for proportioning

a) Grade designation: - M50

b) Type of cement: OPC 53 grade conforming to IS 8112

c) Maximum nominal size of aggregate: 20 mm

d) Minimum cement content: 360 kg/m^3 (From Table 5 of IS 456: 2000-Exposure condition).

e) Maximum water-cement ratio: 0.35 (From Table 5 of IS 456: 2000-Exposure condition

f) Workability: 75 mm (slump value for pumpable concrete)

g) Exposure condition: Extreme (for reinforced concrete)

h) Chemical admixture type : Super Plasticizer

Procedure: -

II. Test Data for Materials

The following data are collected by performing standard tests in a laboratory.

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

1. Target Strength for Mix Proportioning

f_target = fck + 1.65 x s

f_target denotes the Target Average Compressive Strength at 28 days,

fck denotes the Characteristic Compressive Strength at 28 days,

‘s’ stands for 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

2. Selection of Water/Cement Ratio

From Table 5 of IS 456: 2000,

Maximum water-cement ratio = 0.35

3. Selection of Water Content

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

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

(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)] = 143litres.

4. 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.

5. 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 pumpable 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

6. 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 Superplasticizer = (Mass of Superplasticizer / 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

f) 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

g) 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

7. 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