Project on Concrete Mix Design for various grades of Concrete

1.TO DETERMINE THE MIX DESIGN FOR M35 CONCRETE WITH FLY ASH CONSISTING OF THE FOLLOWING PROPERTIES:

• Grade of designation:M35
• Types of mineral admixtures FLY ASH
• Maximum nominal size of aggregate :20
• Minimum water-cement ratio:0.45
• Workability:100-120mm slump
• Exposure condition: moderate
• Method of concrete placing: pumping
• Degree of supervision: Good
• Type of aggregate: crushed angular aggregate
• Maximum cement content:360kg/cum
• Chemical admixture type: super plasticizer

DATA OBTAINED:

• Cement used: OPC43grade(IS 12269)

SPECIFIC GRAVITY OF CEMENT:3.15

• Fly ash - specific gravity:2.2
• Coarse aggregate - specific gravity:2.74
• Fine aggregate - specific gravity:2.74
• Water absorption of coarse aggregate:0.5%
• Coarse aggregate - sieve analysis as per Table 2 of IS 383
• Fine aggregate - sieve analysis as per grading zone 1 of Table 4 of IS 383

PROCEDURE:

• Target strength for mix proportion is obtained from

fck = fck+1.65(Table 1 : IS 10262-2009)

Considering s = 5N/sq-mm

Thus FCK = 35+1.65(5) = 43.25 N/sq-mm

• WATER - CEMENT RATIO:

Considering maximum water - cement ratio = 0.4(Table 5: IS 456 2000)

• WATER CONTENT

Maximum water content for 20mm aggregate = 186 liters(Table 2: IS 10262:2009)

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

However, it super plasticizer is used, the water content can be reduced up to 20% to 30%

Thus the water content obtained is 197-(30% of 197) = 132 liters

Adopt 140 liters

• CEMENT CONTENT

Adopted w/c ratio = 0.4

Cement content = 140/0.4 = 350 kg/cum

Minimum cement content for moderate exposure = 320 kg/cum.(Table 5 : IS 456 2000)

350 kg/cum > 320 kg/cum

Hence ok

• FLY ASH CONTENT

Considering 10% increase in cementitious material

Thus, cementious content = 350x1.1 = 385 kg/cum

Fly ash = 30% of total cementious cement = 385 x 0.3 = 115 kg/cum

• PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINAL AGGREGATE:

Volume of coarse aggregate and final aggregate for w/c ratio o.5 = 0.6 (Table 3: IS 10262:2009)

In this case w/c ratio is 0.4.Therefore volume of coarse aggregate is required to be increased to decreased the fine aggregate content. As the w/c ratio is reduced by 0.1,the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+0.01 for every ±0.05 change in w/c ratio).

Thus ,the corrected proportion of volume of coarse aggregate for w/c ratio of 0.4 = 0.62

For pumpable concrete , it can be reduced up to 10%. Hence, volume of coarse aggregate = 0.62 x 0.9 = 0.56

volume of fine aggregate = 1-0.56 = 0.44

MIX CALCULATIONS

The following mix calculations are carried out:

• Volume of concrete = 1 cum
• Volume of cement = Mass of cement / (specific gravity x 1000) = 270/(3.15x1000) = 0.86 cum
• Volume of fly ash = Mass of fly ash/(specific gravity x 1000) = 115/(2.2x1000) = 0.52 cum
• Volume of water = mass of water/(specific gravity x 1000) = 140/(1x1000) = 0.14 cum
• Volume of chemical admixture = Mass of chemical admixture/(specific gravity x 1000) = 7.6/(1.145x1000) = 0.006 cum
• Volume of all in aggregate = (1-(0.086+0.052+0.14+0.006)) = 0.716 cum
• Mass of coarse aggregate = volume of all aggregate x volume of coarse aggregate x specific gravity of coarse aggregates x 1000 = 0.716x0.56x2.74x1000 = 1098 kg/cum
• Mass of fine aggregates = volume of all aggregate x volume of fine aggregate x specific gravity of fine aggregate x 1000 = 0.716x0.44x2.74x1000 = 863 kg/cum

RESULT

Mix proportion obtained:

Cement = 270 kg/cum

Fly ash = 115 kg/cum

Water = 140 liters

Fine aggregate = 863 kg/cum

Coarse aggregate = 1098 kg/cum

Chemical admixtures = 7 kg/cum

W/C ratio = 0.4

Mix proportion by weight = 1:2.24:2.85

CONCLUSION

The slump should be measured and the water content and admixture can be adjusted to obtain the required slump.

The mix proportion can be adjusted and reworked as per requirement.

2.Concrete mix design for M50 without fly ash

Data required:

Grade designation: M50

Type of cement: OPC 43 grade conforming to IS 8112

Maximum nominal size of aggregate: 20mm

Exposure type: Extreme (reinforced)

Minimum cement content: 360 kg/m^3

Workability: 100mm slump

Method of concrete placing: Pumping

Type of aggregate: Crushed angular

Maximum cement content: 450 kg/m^3

Chemical admixture : Super plasticizer

Specific gravity of cement: 3.15

Specific gravity of fine aggregate: 2.61

Specific gravity of coarse aggregate: 2.73

Coarse and fine aggregate: Grade 1

Target strength:

f'ck = fck + 1.65s

s = 5 (From table 1 of IS 10262 2009)

f'ck = 50 + (1.65 x 5) = 58.25 N/mm^2

Selection of water cement ratio:

From table 5 IS 456:2000, For severe exposure condition maximum w/c = 0.40

Adopt w/c = 0.33

Selection of water content:

Maximum water content = 186lit (From Table 2, 10262: 2009)

For 100mm slump, water content = 186 + ((6/100)x186) ≈≈197

Super plasticizer reduces 29% of water content.

Hence new water content = (71/100)x197 = 139.87

Calculating cement content:

Water/cement = 0.33

cementitious content = 139.87/0.33 = 424 > 360 kg/m^3

Therefore cementitious content = 424 kg/m^3

2.5% of super plasticizer of cementitious content = (2.5/100)x424 = 10.6 kg/m^3

Proportioning of volume of coarse and fine aggregate:

From table 3 IS 10262:2009, for 0.5 w/c, volume of coarse aggregate = 0.6

As per A7 IS 10262:2009, for w/c = 0.33 the volume of coarse aggregate = 0.636

Since the concrete is pumpable reduce the volume of coarse aggregate by 10%

Volume of coarse aggregate = 0.636x.91 = 0.578

Volume of fine aggregate = 1-0.578 = 0.421

Mix calculations:

1. Volume of concrete = 1m^3
2. Volume of cement = (Mass of cement/specific gravity of cement)x(1/1000)

= (424/3.15)x(1/1000) = 0.134 m^3

1. Volume of water = (Mass of water/specific gravity of water)x(1/1000)

= (139.87/1)x(1/1000) = 0.139 m^3

1. Super plasticizer is upto 2% of mass of total cementitious content

= (10.6/1.15)x(1/1000) = 0.0092 m^3

1. Volume of aggregate = a - (b+c+d+) = 1- (0.134+0.139+0.0092) = 0.717 m^3
2. Mass of coarse aggregate = f x volume of coarse aggregate x specific gravity of coarse aggregate

= 0.717x0.578x2.73x1000 = 1131 kg

1. Mass of fine aggregate = f x volume of fine aggregate x specific gravity of fine aggregate

= 0.717 x 0.421 x 2.61x1000

= 787 kg

Mix Proportioning:

Cement = 424 kg/m^3

Fine aggregate = 787 kg/m^3

Coarse aggregate = 11131 kg/m^3

W/C = 0.33

Admixture = 10.6 kg/m^3