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 as per Indian Standards
Introduction:
- Concrete mix-design is a systematic process of choosing the proportions of various materials uesd for concrete
- A good mix design should posses the quality of material which imparts strength , durability and workability of concrete
- There are three types of mix-design they are,
- nominal mix , standard mix and design mix
- Nominal and standard mix are used for M5 to M25 grade of concrete
- In this design the M35 grade of concrete is designed by using Design mix
IS standards used:
As per indian standard 10262:2019 and IS 456-2000 and recommended guideliness for concrete mix design IS 10262:2009
Step by step procedure
a) The concrete mix design for M35 grade concrete
1) Stipulations:
Grade of concrete : M35
Type of cement : opc 43 grade confirming to IS 8112
Nominal size of aggregate : 20 mm
Minimum cement content : 360 kg/m3 (from table 5 of IS 456 2000 for "extreme" exposure condition
Workability : 75mm slump value
Exposure condition : extreme exposure
Degree of supervision : Good
Type of aggregate : angular
Method of concrete placement : Pumping
Maximum cement content : 450 kg/m3
Chemical admixture : superplasticizer confirming to IS 9103
2) Test data for materials
Specific gravity of cement : 3.15
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Specific gravity of fly ash : 2.2
Specific gravity of chemical admixture : 1.145
Water absorption of fine aggregate : 1%
Water absorption of coarse aggregate : 0.5%
Sieve test : for coarse aggregate : confirming to table 2 of IS 383
For fine aggregate : confirming to grading zone of Zone 2 of table 4 of IS 383
3) calculation of target mean strength:
f(t) = fck + 1.65S
f(t) = average compressive strength after 28 days,
fck = characteristics compressive strength after 28 days
S = standard deviations
As per IS 10262 - 2019 of table 2
The standard deviation s, is taken as 5 N/mm2
Therefore, target mean strength = 35+1.65*5 = 43.25 N/mm2
4) Selection of water-cement ratio:
From table 5 of IS 456 2000,
The maximum water-cement ratio for "extreme" exposure condition = 0.40
According to IS 10262:2019 graph,
The water-cement ratio for target strength of 43.25 N/mm2 = 0.38
Therefore, final water-cement ratio = 0.38
5) calculation of water content:
From table 4 of IS 10262:2019, maximum water content for 20 mm aggregate = 186 liters (for slump of 25 to 50mm)
Estimated water content for slump of 75 mm = 186 + 3/100*186 = 191.58 liters
Based on experience the superplasticizer reduce water upto 25% hence,
The arrived water content = 191.58*0.75 = 144 liters
6) calculation of cement and fly ash content:
Water-cement = 0.38
Cementitious content = Watercontent/water-cement ratio = 144/0.38 = 379 kg/m3
From table 5 of IS 456 2000, the minimum cement content for "extreme" exposure condition = 360 kg/m3
we have obtained 379 kg/m3 (379 > 360) hence okay,
Based on experience and trial increasing the cementitious content = 10%
Cementitious content (cement + flyash) = 379*1.10 = 417 kg/m3
Water content = 144 liters
so, water-cement ratio = 0.34
Amount of fly ash added = 30% of cementitious content = 417*0.3 = 125 kg/m3
Cement content = 417-125 = 292 kg/m3
Saving of cement = 125 kg/m3
New cement content = 292 kg/m3
7) Proportions of volume of coarse and fine aggregates:
From table 3 of IS 10262:2009 , volume of coarse aggregate corresponding to 20 mm size of aggregate and fine aggregate Zone 2 for water-cement ratio of 0.5 = 0.62
But the water-cement ratio we have obtained = 0.38
For at rate of -/+ 0.01 for every +/- 0.05 change in water-cement ratio = [(0.5-0.38)0.01/0.05] = 0.024
Therefore, corrected volume of coarse aggregate for water-cement ratio of 0.38 = 0.62+0.024 = 0.644
For pumpable concrete these values are reduced to 10%
Volume of coarse aggrgate = 0.644 * 0.9 = 0.58
Volume of fine aggregate = 1-0.58 = 0.42
8) Mix calculaction:
a) Volume of concrete = 1m3
b) Volume of cement = mass of cement /specific gravity of cement *1/1000 = 292/3.15*1/1000 = 0.092 m3
c) Volume of fly ash = mass of fly ash/specific gravity of fly ash *1/1000 = 125/2.2 *1/1000 = 0.056 m3
d) Volume of water = mass of water /specific gravity of water *1/1000 = 144/1*1/1000 = 0.144 m3
e) Volume of chemical admixture = mass of chemical admixture /specific gravity *1/1000 = 8.34/1.145 *1/1000 = 0.0072 m3
f) Volume of total addregate = [a-(b+c+d+e)] = [1-(0.092+0.056+0.144+0.0072)] = 0.70 m3
g) Volume of coarse aggregate = volume of total aggregate * volume of coarse aggregate *specific gravity of coarse agggate *1000 = 0.70*0.58*2.74*1000 = 1112 kg/m3
h) volume of fine aggregate = volume of total aggregate *volume of fine aggregate *specific gravity of fine aggregate
*1000 = 0.70 *0.42*2.74*1000 = 805 kg/m3
9) Mix proportions:
Cement = 292 kg/m3
Fly ash = 125 kg/m3
Cementitious content = 379 kg/m3
Water content = 144 liters
Fine aggregate = 805 kg/m3
Coarse aggregate = 1112 kg/m3
Chemical admixtures = 8.34 kg/m3
water-cement ratio = 0.34
10) Result:
The arrived mix proportion for M35 grade is,
1 : 2.12 : 2.93
b) The concrete mix design for M50 grade concrete
Aim:
- To prepare the Mix-Design of the concrete for the grade M50 as per Indian Standards
Introduction:
- Concrete mix-design is a systematic process of choosing the proportions of various materials uesd for concrete
- A good mix design should posses the quality of material which imparts strength , durability and workability of concrete
- There are three types of mix-design they are,
- nominal mix , standard mix and design mix
- Nominal and standard mix are used for M5 to M25 grade of concrete
- In this design the M50 grade of concrete is designed by using Design mix
IS standards used:
As per indian standard 10262:2019 and IS 456-2000 and recommended guideliness for concrete mix design IS 10262:2009
Step by step procedure
The concrete mix design for M50 grade concrete
1) Stipulations:
Grade of concrete : M50
Type of cement : opc 53 grade confirming to IS 8112
Nominal size of aggregate : 20 mm
Minimum cement content : 320 kg/m3 (from table 5 of IS 456 2000 for "severe" exposure condition
Workability : 100 mm slump value
Exposure condition : severe exposure
Degree of supervision : Good
Type of aggregate : angular
Method of concrete placement : Pumping
Maximum cement content : 450 kg/m3
Chemical admixture : superplasticizer confirming to IS 9103
2) Test data for materials
Specific gravity of cement : 3.15
Specific gravity of coarse aggregate : 2.74
Specific gravity of fine aggregate : 2.74
Specific gravity of chemical admixture : 1.145
Water absorption of fine aggregate : 1%
Water absorption of coarse aggregate : 0.5%
Sieve test : for coarse aggregate : confirming to table 2 of IS 383
For fine aggregate : confirming to grading zone of Zone 2 of table 4 of IS 383
3) calculation of target mean strength:
f(t) = fck + 1.65S
f(t) = average compressive strength after 28 days,
fck = characteristics compressive strength after 28 days
S = standard deviations
As per IS 10262 - 2019 of table 2
The standard deviation s, is taken as 5 N/mm2 for M50 grade
Therefore, target mean strength = 50+1.65*5 = 58.25 N/mm2
4) Selection of water-cement ratio:
From table 5 of IS 456 2000,
The maximum water-cement ratio for "severe" exposure condition = 0.45
Bon the experience, assumed water-cement ratio = 0.40
According to IS 10262:2019 graph,
The water-cement ratio for target strength of 58.25 N/mm2 = 0.33
Therefore, final water-cement ratio = 0.33
5) calculation of water content:
From table 4 of IS 10262:2019, maximum water content for 20 mm aggregate = 186 liters (for slump of 25 to 50mm)
Estimated water content for slump of 100 mm = 186 + 6/100*186 = 197 liters
Based on experience the superplasticizer reduce water upto 30% hence,
The arrived water content = 197 * 0.7 = 138 liters
6) calculation of cement content:
Water-cement = 0.33
Cement content = Water content/water-cement ratio = 138/0.33 = 418 kg/m3
From table 5 of IS 456 2000, the minimum cement content for "severe" exposure condition = 320 kg/m3
we have obtained 418 kg/m3 (418 > 320) hence okay,
7) Proportions of volume of coarse and fine aggregates:
From table 3 of IS 10262:2009 , volume of coarse aggregate corresponding to 20 mm size of aggregate and fine aggregate Zone 2 for water-cement ratio of 0.5 = 0.62
But the water-cement ratio we have obtained = 0.33
For at rate of -/+ 0.01 for every +/- 0.05 change in water-cement ratio = [(0.5-0.33)0.01/0.05] = 0.034
Therefore, corrected volume of coarse aggregate for water-cement ratio of 0.33 = 0.62+0.034 = 0.654
For pumpable concrete these values are reduced to 10%
Volume of coarse aggrgate = 0.654 * 0.9 = 0.59
Volume of fine aggregate = 1-0.59 = 0.41
8) Mix calculaction:
a) Volume of concrete = 1m3
b) Volume of cement = mass of cement /specific gravity of cement *1/1000 = 418/3.15*1/1000 = 0.132 m3
c) Volume of water = mass of water /specific gravity of water *1/1000 = 138/1*1/1000 = 0.138 m3
d) Volume of chemical admixture = mass of chemical admixture /specific gravity *1/1000 = 8.36/1.145 *1/1000 = 0.0073 m3
e) Volume of total addregate = [a-(b+c+d)] = [1-(0.092+0.056+0.144)] = 0.72 m3
f) Volume of coarse aggregate = volume of total aggregate * volume of coarse aggregate *specific gravity of coarse agggate *1000 = 0.72*0.59*2.74*1000 = 1168 kg/m3
g) volume of fine aggregate = volume of total aggregate *volume of fine aggregate *specific gravity of fine aggregate
*1000 = 0.72 *0.41*2.74*1000 = 810 kg/m3
9) Mix proportions:
Cement = 418 kg/m3
Water content = 138 liters
Fine aggregate = 810 kg/m3
Coarse aggregate = 1168 kg/m3
Chemical admixtures = 8.36 kg/m3
water-cement ratio = 0.33
10) Result:
The arrived mix proportion for M50 grade is,
1 : 1.93 : 2.8 for 0.33 w/c