Challenge

Project on Concrete Mix Design for various grades of Concrete

HHarshith Reddy V14 Sept 2023

DESIGN

MIX DESIGN : M35

AIM : To develop a mix design for M35 grade of concrete containing 20% of fly ash and 80% of cement

Step-1 STIPULATIONS FOR PROPORTIONING

Grade designations : M35
Type of cement : OPC 43 grade
Type of mineral admixture : Fly Ash
Maximum nominal size of aggregate : 20 mm
Minimum cement content : 320kg/m^3
Maximum water-cement ratio : 0.45
Workability : 100mm
Exposure condition : severe
Method of concrete placing : pumping
Degree ofsupervision : good
Type of aggregate : crushed angular aggregate
Maximum cement (OPC) content : 450 kg/m^3
Chemical admixture type : superplasticizer

Step -2 TEST DATA FOR MATERIALS

Cement used : OPC 43 grade conforming to IS 8112
Specific gravity of cement. : 3.15
Fly ash : Conforming to IS 3812 (Part I)
Specific gravity of fly ash : 2.2
Chemical admixture : Superplasticizer conforming to IS 9103
Specific gravity of:
Coarse aggregate : 2.74
Fine aggregate : 2.74
Water absorption:
Coarse aggregate : 0.5%
Fine aggregate : 1%
Free (surface) moisture:
Coarse aggregate : nil
Fine aggregate : nil
Sieve analysis:
Coarse aggregate : Conforming to IS 383 table 2
Fine aggregate : grading zone 1 Conforming to IS 383 table 4

Step -3 TARGET STRENGTH FOR MIX PROPORTIONING

fck' = fck + 1.65 s

where,

fck'= target mean compressive strength at 28 days,
fck = characteristics compressive strength at 28 days
s = standard deviation.
Standard Deviation, s = 5 N/mm2. (From table 1 of IS 10262)
Therefore, target mean strength = 35 + 1.65 x 5 = 43.25 N/mm^2

Step-4 SELECTION OF WATER·CEMENT RATIO

Maximum water-cement ratio = 0.45. ( From table 5 of IS 456)
Based on experience. adopt water-cement ratio as 0.40.
0.40 < 0>

Step -5 SELECTION OF WATER CONTENT

Maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range, from table 2 of IS 10262)
Increase water content by 3% for 25mm increase in slump
Estimated water content for 100 mm slump= 186+ (6/100)×186= 197.16 litre
Reduce water content by 25% as superplasticizer is used
Water = 0.75×197.16 =147.87litre

Step -6 CALCULATION OF CEMENT AND FLY ASH CONTENT

W/C = 0.40
Cement content = W/0.4 = 147.87/0.4 =370kg
Consider 20% of fly ash as part replacement of cement
As fly ash is being used increase the cementitious content by 10%
C= 370×1.1 = 407kg
Fly ash = 0.2 × 407 = 81.4kg
Cement = 407 -81.4 = 325.6kg

Step -7 PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water-cement ratio of 0.50 =0.60.
Increase the volume of coarse aggregates by 0.02 for decrease in water cement ratio of 0.1
Volume of coarse aggregate = 0.6+0.02 =0.62
For pumpable concrete decrease the Coarse aggregate content by 10%
Therefore Coarse aggregate volume = 0.62 ×0.9 =0.558
Volume of Fine aggregate = 1-0.558 =0.442

Step -8 MIX CALCULATIONS

Volume of concrete = 1m^3
Volume of cement = ( mass of cement/ Specific gravity of cernent) × (1/1000)

= (325.6/3.15) ×(1/1000) = 0.103m^3

Volume of fly ash= ( mass of fly ash/ Specific gravity of fly ash) × (1/1000)

= (81.4/2.2)×(1/1000)= 0.037m^3

Volume of water= ( mass of water/ Specific gravity of water) × (1/1000)
= (147.87/1)×(1/1000)= 0.148m^3

Volume of chemical admixture (2% of cementitious material) = ( mass of admixture/ Specific gravity of admixture) × (1/1000)

= (8.14/1.145)×(1/1000)= 0.007m^3

Volume of all in aggregate = (1-(0.103+0.037+0.148+0.007) = 0.705m^3
Mass of coarse aggregate = Volume of all in aggregate x volume of coarse aggregate x Specific gravity of coarse aggregate × 1000

=0.705 × 0.558 ×2.74 × 1000 = 1077.8kg

Mass of Fine aggregate = Volume of all in aggregate x volume of fine aggregate x Specific gravity of fine aggregate × 1000

= 0.705 × .442 × 2.74 × 1000 = 853.8kg

Step -9 MIX PROPORTION

Cement = 325.6kg
Fly ash = 81.4kg
Fine aggregate = 853.8kg
Coarse aggregate = 1077.8kg
Water = 147.87kg
Admixture = 8.14kg
Proportion = 1: 2.09 : 2.64

MIX DESIGN: M50

AIM : To develop a mix design for M50 grade of concrete.

Step-1 STIPULATIONS FOR PROPORTIONING

Grade designations. : M50

Type of cement. : OPC 43 grade

Maximum nominal size of aggregate. : 20 mm

Minimum cement content. : 320kg/m^3

Maximum water-cement ratio. : 0.45

Workability. : 100mm

Exposure condition. : severe

Method of concrete placing. : pumping

Degree ofsupervision. : good

Type of aggregate. : crushed angular aggregate

Maximum cement (OPC) content. : 450 kg/m^3

Chemical admixture type. : superplasticizer

Step -2 TEST DATA FOR MATERIALS

Cement used. : OPC 43 grade conforming to IS 8112

Specific gravity of cement. : 3.15

Chemical admixture. : Superplasticizer conforming to IS 9103

Specific gravity of:

Coarse aggregate. : 2.74

Fine aggregate. : 2.74

Water absorption:

Coarse aggregate. : 0.5%

Fine aggregate. : 1%

Free (surface) moisture:

Coarse aggregate. : nil

Fine aggregate. : nil

Sieve analysis:

Coarse aggregate. : Conforming to IS 383 table 2

Fine aggregate. : grading zone 1 Conforming to IS 383 table 4

Step -3 TARGET STRENGTH FOR MIX PROPORTIONING

fck' = fck + 1.65 s

where,

fck'= target mean compressive strength at 28 days,

fck = characteristics compressive strength at 28 days

s = standard deviation.

Standard Deviation, s = 5 N/mm2. (From table 1 of IS 10262)

Therefore, target mean strength = 50 + 1.65 x 5 = 58.25 N/mm^2

Step-4 SELECTION OF WATER·CEMENT RATIO

Maximum water-cement ratio = 0.45. ( From table 5 of IS 456)

Based on experience. adopt water-cement ratio as 0.35

0.35< 0> 0.45

Step -5 SELECTION OF WATER CONTENT

Maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range, from table 2 of IS 10262)

Increase water content by 3% for 25mm increase in slump

Estimated water content for 100 mm slump= 186+ (6/100)×186= 197.16 litre

Reduce water content by 25% as superplasticizer is used

Water = 0.75×197.16 =147.87litre

Step -6 CALCULATION OF CEMENT CONTENT

W/C =0.35

Cement content = W/0.35 = 147.87/0.35 =422.28kg

Step -7 PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT

From Table 3. volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone I) for water-cement ratio of 0.50 =0.60.

Increase the volume of coarse aggregates by 0.02 for decrease in water cement ratio of 0.1 , and for decrease in water cement ratio by 0.15, increase it by 0.03

Volume of coarse aggregate = 0.6+0.03 =0.63

For pumpable concrete decrease the Coarse aggregate content by 10%

Therefore Coarse aggregate volume = 0.63 ×0.9 =0.567

Volume of Fine aggregate = 1-0.567 =0.433

Step -8 MIX CALCULATIONS

Volume of concrete = 1m^3

Volume of cement = ( mass of cement/ Specific gravity of cernent) × (1/1000)

= (422.28/3.15) ×(1/1000) = 0.134m^3

Volume of water= ( mass of water/ Specific gravity of water) × (1/1000)

= (147.87/1)×(1/1000)= 0.148m^3

Volume of chemical admixture (2% of cementitious material) = ( mass of admixture/ Specific gravity of admixture) × (1/1000)

= (8.14/1.145)×(1/1000)= 0.007m^3

Volume of all in aggregate = (1-(0.134+0.148+0.007) = 0.711m^3

Mass of coarse aggregate = Volume of all in aggregate x volume of coarse aggregate x Specific gravity of coarse aggregate × 1000

=0.711 × 0.567 ×2.74 × 1000 = 1104.6kg

Mass of Fine aggregate = Volume of all in aggregate x volume of fine aggregate x Specific gravity of fine aggregate × 1000

= 0.711× .433 × 2.74 × 1000 = 843.5kg

Step -9 MIX PROPORTION

Cement = 422.28kg

Fine aggregate = 843.5kg

Coarse aggregate = 1104.6kg

Water = 147.87kg

Admixture = 8.14kg

Proportion = 1: 2.0: 2.61

Project on Concrete Mix Design for various grades of Concrete

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in your own course.