Project on Concrete Mix Design for various grades of Concrete
Aim:
To prepare the Mix-Design of the concrete for the grade M35 with fly ash and M50 without fly ash as per Indian Standards.
Introduction:
Mix design of concrete is the proportioning of concrete ingredients which are used to provide strength and durability for the structures using the following standards,
a) IS Method: Concrete mix proportioning guidelines (IS 10262-2019) and Recommended guidelines for concrete mix design IS 10262 -1982.
Step by Step Procedure:
a) The concrete mix design for M35 grade concrete:
Stipulations:
Grade designation: M 35
Type of cement: OPC 53 grade confirming to IS 8112
Maximum nominal size of aggregate: 20 mm
Minimum cement content: 320 kg/m3
Maximum water-cement ratio: 0.45
Workability: 50-75 mm (slump)
Exposure condition: Severe (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.
II) Test Data for Materials:
The specific gravity of cement: 3.15
The specific gravity of Coarse aggregate: 2.74
Specific Gravity of Fine aggregate: 2.67
Water absorption, Coarse aggregate: 0.5%
Water absorption, fine aggregate: 1%
Chemical admixture: Superplasticizer conforming to IS 9103.
III) Target Mean Strength:
ft = fck + 1.65 x S
ft = target average compressive strength at 28 days,
fck = characteristic compressive strength at 28 days, and
S = standard deviation
The Standard deviation, S is taken as 5.0 N/mm2 (Table I of IS 10262:2009)
Therefore, target strength = 35+ 1.65 x 5.0 = 43.25 N/mm2.
Selection of Water-Cement Ratio:
From Table 5 of IS 456:2000,
The maximum permissible water-cement ratio is 0.45.
Selection of Water Content:
From Table 2 of IS 456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.
Estimated water content for 75 mm slump =186+0.03 x 186 =191.58 litres.
Based on trials with Super plasticizer water content reduction of 20% has been achieved. Hence, the arrived water content =153 L
Calculation of Cement Content and Fly ash:
Water-cement ratio =0.45
Cement content = 153/0.45 = 340.58 kg/m3
From Table 5 of IS 456, the minimum cement content for ‘Severe’ exposure condition is 320 kg/m3.
It is 340.58 kg/m3 which is greater than 320 kg/m3, hence OK.
To proportion the mix containing fly ash the following steps are suggested.
The % of fly ash needs to be decided based on the project requirement and quality of materials.
In some cases increase the cementitious material can be warned. An increase in cementitious material content and its percentage is based on experience and trials.
In this increase of 10%, cementitious material content is considered.
Cementitious Material Content=340.58*1.1=375 kg/m3
Water content=153 L
W/C ratio=153/375=0.408
Flyash 30% of total cementitious material content=375*30=112.5kg/m3
Cement = 375-112.5=262.5kg/m3
Flyash can be utilized =112.5kg/m3
The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content:
From Table 3 of IS 10262:2000, the 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.
The corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.45 = 0.63.
For pumpable concrete, these values should be reduced by 10 percent. Therefore, volume of coarse aggregate = 0.63 x 0.9 = 0.567.
Volume of fine aggregate content =1 – 0.567 =0.433
IV) Mix Calculations:
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)
= (262.5/3.15) X (1/1000)
= 0.083 m3
Volume of flyash= 112.5/2.2*0.001 =0.0051m3
c) Volume of water = (Mass of water/specific gravity of water) X (1/1000)
= (153/1) X (1/1000)
= 0.153 m
d) Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)
= (6.81/1.145) X (1/1000)
= 0.00594 m3
d) Volume of all aggregate = (a – (b + c + d))
= 1 – (0.112 + 0.083+0.153 + 0.00594)
= 0.65 m3
e) Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000
= 0.65 x 0.567 x 2.74 x 1000
= 1010 kg
f) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000
= 0.65 x 0.433 x 2.67 x 1000
= 746.26 kg
V) Concrete Mix Proportions
Cement = 262.5 kg/m3
Fly ash= 112.5kg/m3
Water = 153 kg/m3
Super plasticizer = 6.81 kg/m3
Fine aggregates = 746 kg/m3
Coarse aggregate = 1010 kg/m3
W/C = 0.40
Result:
Mix Proportion arrived: 1: 2.18: 3
b) The concrete mix design for M50 grade concrete:
Stipulations:
Grade designation: M 50
Type of cement: OPC 53 grade confirming to IS 8112
Maximum nominal size of aggregate: 20 mm
Minimum cement content: 320 kg/m3
Maximum water-cement ratio: 0.45
Workability: 50-75 mm (slump)
Exposure condition: Severe (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.
II) Test Data for Materials:
The specific gravity of cement: 3.15
The specific gravity of Coarse aggregate: 2.74
Specific Gravity of Fine aggregate: 2.67
Water absorption, Coarse aggregate: 0.5%
Water absorption, fine aggregate: 1%
Chemical admixture: Superplasticizer conforming to IS 9103.
III) Target Mean Strength:
ft = fck + 1.65 x S
ft = target average compressive strength at 28 days,
fck = characteristic compressive strength at 28 days, and
S = standard deviation
The Standard deviation, S is taken as 5.0 N/mm2 (Table I of IS 10262:2009)
Therefore, target strength = 50+ 1.65 x 5.0 = 58.25 N/mm2.
Selection of Water-Cement Ratio:
Assume water-cement ratio is 0.35.
Selection of Water Content:
From Table 2 of IS 456:2000, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.
Estimated water content for 75 mm slump =186+0.03 x 186 =191.58 litres.
Based on trials with Super plasticizer water content reduction of 20% has been achieved. Hence, the arrived water content =153 L
Calculation of Cement Content and Fly ash:
Water-cement ratio =0.35
Cement content = 153/0.35 = 437 kg/m3
From Table 5 of IS 456, the minimum cement content for ‘Severe’ exposure condition is 320 kg/m3.
It is 437 kg/m3 which is greater than 320 kg/m3, hence OK.
The Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content:
From Table 3 of IS 10262:2000, the 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.
The corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.
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 – 0.567 =0.415
IV) Mix Calculations:
a) Volume of concrete = 1m3
b) Volume of cement = (Mass of cement/specific gravity of Cement) X (1/1000)
= (437/3.15) X (1/1000)
= 0.139 m3
c) Volume of water = (Mass of water/specific gravity of water) X (1/1000)
= (153/1) X (1/1000)
= 0.153 m
d) Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)
= (6.81/1.145) X (1/1000)
= 0.00594 m3
d) Volume of all aggregate = (a – (b + c + d))
= 1 – (0.139 +0.153 + 0.00594)
= 0.70 m3
e) Mass of coarse aggregate = Volume of all Aggregate X Volume of Coarse Aggregate X Specific Gravity of Coarse Aggregate X 1000
= 0.70 x 0.567 x 2.74 x 1000
= 1087 kg
f) Mass of fine aggregate = Volume of all Aggregate X Volume of Fine Aggregate X Specific Gravity of Fine Aggregate X 1000
= 0.70 x 0.433 x 2.67 x 1000
= 810 kg
V) Concrete Mix Proportions
Cement = 437 kg/m3
Water = 153 kg/m3
Super plasticizer = 6.81 kg/m3
Fine aggregates = 810 kg/m3
Coarse aggregate = 1087 kg/m3
W/C = 0.35
Result:
Mix Proportion arrived: 1: 1.8: 2.5