Project on Concrete Mix Design for various grades of Concrete
Answer
M35 grade concrete with fly ash
1) Stipulation for proportioning
a) Type of cement:- M35
b) Type of cement:- OPC 43 grade conforming to IS 8112.
c) Type of mineral admixture:- Fly ash conforming to IS 3812(part1)
d) Maximum nominal size of aggregate:- 20mm
e) Minimum cement content:- 320 kg/m3 ( from Table 5 of IS 456:2000 - exposure condition)
f) Maximum water-cement ratio:- 0.45 (From Table 5 of IS 455:2000 - Exposer Condition)
g) Workability:- 100mm (slump value for pumpable concrete)
h) Method of concrete placing:- Pumping
i) Exposure condition:- Severe (for reinforced concrete)
j) Degree of supervision:- Good
k) Maximum cement content:- 450 kg/m3
l) Type of aggregate:- Crushed angular aggregate
m) Chemical admixture type:- Superplasticzer
2) Test data for material
a) Cement used:- OPC 43 grade conforming IS 8112
b) Specific Gravity of cement:- 3.15
c) Fly ash:- Conforming to IS 3812 (Part 1)
d) Specific gravity of fly ash:- 2.2
e) Chemical admixture:- Superplasticizer conforming to IS 9103
f) Specific gravity of:
- Coarse aggregate:- 2.74
- Fine aggregate:- 2.74
g) Water absorption:
- Coarse aggregate:- 0.5%
- Fine aggregate:- 1.0%
h) Free surface moisture:
Coarse aggregate:- Nill
Fine aggregate:- Nill
3) Target strength for mix proportioning
f'ck= fck + 1.65 S
From Table1 of IS 10262:2009, Standard Deviation, S= 5 N/mm2
Therefor, Target strength = 35 + 1.65 x 5
= 43.25 N/mm2
4) Selection of Water-Cement ratio:
From Table 5 of IS 456:2000 for severe exposure, maximum water-cement ratio=0.45
Based on experience, adopt water-cement ratio as 0.40
0.40<0.45, Hence O.K
5) Selection of water content
From Table2 of IS 10262:2009, Maximum water content for 20mm aggregate= 186 liter (for 25mm to 50mm slump range)
Extimate water content for 100mm slump = 186 + 6/100 x 186 = 197 liters
As superplasticizer is used, the water content can be reduced up to 30%
Based on trails water content reduction of 29% is achieved with plasticizer.
Hence the arrived water content = 197x0.71 = 140 litre
6) Calculation of cement content:
Water-cement ratio = 0.40
Cementitious material(cement+fly ash) content = 140/0.40 = 350kg/m3
From Table5 of IS 456 Minimum cement content for 'severe' exposure condition = 320kg/m3
350 kg/m3 > 320 kg/m3, Hence OK
Cementitionus material content:- 350x 1.10= 385 Kg/m3
Water content :- 140 kg/m3
Water cement ratio:- 140/385 = 0.364
Fly ash @ 30% total cementitions material content:- 385x30% = 115kg/m3
Cement (OPC):- 385-115 = 270 kg/m3
Saving of cement while using fly ash:- 350-270= 80 kg/m3
Fly ash being utilized:- 115 kg/m3
7) Proportion of volume of coarse aggregate and fine aggregate:
From Table3 of IS 10262:2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (zone1) for water-cement ratio of 0.5=0.6
Therefore, correctioj bolume of coarse aggregate for the water-cement ratio of 0.4=0.62
For plumbable concrete these values are reduce by 10%
Therefore, Volume of coarse aggregate=0.62x0.9 = 0.56
Volume of fine aggregate = 1-0.56=0.44
8) Mix calculation:
a) Volume of concrete:- 1m3
b) Volume of cement:- Mass of cement/specific gravity of cement x 1/1000 = 270/3.15 x 1/1000 = 0.086m3
c) Volume of fly ash:- Mass of fly ash/Specific gravity of fly ash x 1/1000 = 115/2.2 x 1/1000 = 0.052m3
d) Volume of water:- Mass of water/Specific gravity of water x 1/1000 = 140/1 x 1/1000 = 0.140m3
e) Volume of Chemical Admixture:- Mass of chemical admixture/Specific gravity of chemical admixture x 1/1000 = 7.6/1.145 x 1/1000 = 0.006m3
f) Volume of aggregate:- (a- (b+c+d+e)) = (1-(0.86+0.052+0.140+0.006)) = 0.716m3
g) Mass of coarse aggregate:- f x volume of coarse aggregate x specific gravity of coarse aggregate x 1000 = 0.716 x 0.56 x 2.74 x 1000 = 1089 kg/m3
h) Mass of fine aggregate:- f x volume of fine aggregate x specific gravity of fine aggregate x 1000 = 0.716 x 0.44 x 2.74 x 1000 = 863 kg/m3
9) Mix proportions:
Cement:- 270 kg/m3
Fly ash:- 115 kg/m3
water:- 140 kg/m3
Fine aggregate:- 863 kg/m3
Coarse aggregate:- 1098 kg/m3
Chemical admixture:- 7 kg/m3
Water-cement ratio:- 0.364
Mix ratio: 1:2.24:2.85
# M50 grade concrete without Fly ash
Grade Designation = M-50
Type of cement = O.P.C-43
Admixture = Sika [Sikament 170 ( H ) ]
Fine Aggregate = Zone-II
Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66
Minimum Cement (As per contract) =400 kg / m3
Maximum water cement ratio (As per contract) = 0.45
Mix Calculation: –
1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa
2. Selection of water cement ratio:-
Assume water cement ratio = 0.35
3. Calculation of water: –
Approximate water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table No. 5 , IS : 10262 ). As plasticizer is proposed we can reduce water content by 20%.
Now water content = 180 X 0.8 = 144 kg /m3
4. Calculation of cement content:-
Water cement ratio = 0.35
Water content per cum of concrete = 144 kg
Cement content = 144/0.35 = 411.4 kg / m3
Say cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3)
Hence O.K.
5. Calculation for C.A. & F.A.: [ Formula’s can be seen in earlier posts]-
Volume of concrete = 1 m3
Volume of cement = 412 / ( 3.15 X 1000 ) = 0.1308 m3
Volume of water = 144 / ( 1 X 1000 ) = 0.1440 m3
Volume of Admixture = 4.994 / (1.145 X 1000 ) = 0.0043 m3
Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 +0.0043 = 0.2791 m3
Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m3
Volume of F.A. = 0.7209 X 0.33 = 0.2379 m3(Assuming 33% by volume of total aggregate )
Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m3
Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919 kg/ m3
Say weight of F.A. = 621 kg/ m3
Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365 kg/ m3
Say weight of C.A. = 1284 kg/ m3
Considering 20 mm: 10mm = 0.55: 0.45
20mm = 706 kg .
10mm = 578 kg .
Hence Mix details per m3
Increasing cement, water, admixture by 2.5% for this trial
Cement = 412 X 1.025 = 422 kg
Water = 144 X 1.025 = 147.6 kg
Fine aggregate = 621 kg
Coarse aggregate 20 mm = 706 kg
Coarse aggregate 10 mm = 578 kg
Admixture = 1.2 % by weight of cement = 5.064 kg.
Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043