Project on Concrete Mix Design for various grades of Concrete
Concrete Mix Design For M35 grade concrete with fly ash
Concrete Mix Design: Concrete is complex material & has the right mix of constituent concrete which if not done properly will have adverse affect on properties of concrete hence right propertion of all the constituents is important, it is process of selecting suiatable ingredient durability & workability as economical as possible is known as concrete mix design.
Aim & Objective of Concrete Mix Design: Concrete mix design is to acheive predetermined minimum strength & durability is most economical manner & cost of concrete mainly depend upon the cost of material & cost of labor since cost of concrete is many times more than the other constituents.
Procedure Step by Step:
I) Stipulation for proportioning: The section has specifications of the materials & requirements of the concrete to be made
a) Grade Designation: M35
b) Type of cement: OPC 43 Grade
c) Type of mineral admixture: Fly ash
d) Maximum nominal size of aggregate: 20mm
e) Minimum cement content: 320kg/m^3
f) Maximum water cement ratio: 0.45
g) Workability: 100mm(Slump value for pumpable concrete)
h) Exposure condition: Severe (for reinforced concrete)
i) Degree of Supervision: Good
j) Type of aggregate: Crushed angular aggregate
k) Maximum cement content: 450Kg/m^3
l) Chemical admixture type: Superplaster
II) Test Data for material: Various laboratory tests on materials are required to use in this actiob & standard values are assumed below
a) Cement used: OPC 43 grade
b) Specific Gravity of cement: 3.15
c) Admixture: Fly ash
d) Specific gravity of fly ash: 2.2
e) Chemical admixture: Superplasticizer
f) Specific gravity of coarse aggregate :2.74 & Fine aggregate: 2.74
g) Water absorption: Coarse aggregate: 0.5% & Fine aggregate: 1.0%
h) Fine surface moisture
Coarse aggregate: Nil & Fine aggregate: Nil
i) Sieve Analysic
For coarse & fine aggregate use IS383
III) Target strength for mix proportioning: The strength of the concrete may deviate based on the quality of material, method of mixing and construction practices. hence target strength should be higher than required strength of concrete. The value of standard deviation for different grades of concrete is given IS456
f'ck= fck+1.65S
S=5 N/mm^2
ft= 35+1.65*5 =43.25 N/mm^2
IV) Selection of Water Cement Ratio: Maximum water cement ratio for different grades of concrete is given in table 5-IS456. we can reduce the water cement ratio based on your requirements & it directly affects the strength of concrete.
From Table5- IS456:2000 for severe exposure, maximum water cement ratio=0.45
Water cement ratio=0.38
0.38 < 0.45 Hence ok
V) Selection of Water Cement: Above water content is for 25 to 50 mm slump, but we need 100mm slump , so we need to increase the water content to get required slump. Clause 4.2 IS1026 suggest to increases 3% of water-Content to get an extra 25mm slumphence we increase water cement by 6% to get additional 50mm Slump for concrete.
Estimated water content for 100mm slump= 186+6/100*186= 197ltr
As superplasticizer is used the water content can be reduced up to 30%
Based on trials water content= 197*0.71= 140ltr
VI) Calculation of Cement content: Adopted water cement ratio: 0.40
Total Cementitious(Cement+fLy ash) Required =Water content/Water Cement Ratio
=140/0.40 =350 Kg/m^3
From Table5-IS456 minimum content for severe exposure condition =320kg/m^3
Since fly ash is used the amount of cementitious content(cement+fly ash) shall increased to get good workability and strength, increased the cementitious content by 10%.
Final cementitious content=320*1.10 =352 kg
352 > 320
Fly ash content= 352*0.30= 105.6
=106kg
Cemet Content =Cementitious Content- Fly ash
=352-106 =246
Calculation of super plasticiers 0.6% of mmass of cementitio content =352*(0.6/100)=2.112 kg
VII) Coarse and Fine aggregate:
Coarse aggregate ratio=0.62
Coarse aggregate ratio for water cement ratio 0.38 =0.64 (adding 0.01 for every decrease 0.05 and vice versa
Final fine ratio= 1-0.62=0.38
VIII) Mix calculation of M35 grade concrete
Volume of concrete =1cu.m
Total Volume of Cement= 246/(3.15*1000) =0.078cu.m
Total volume of fly ash= 106/(2.2 *1000)= 0.048 cu.m
Volume of water= 140/1*100 =0.140 cu.m
Volume of super plasticizer= 2.112/(1.12 *1000) =0.0018 cu.m
Total aggregate requirement =A-(B+C+D+E)
=1-(0.078+0.048+0.140+0.0018) = 0.73 cu.m
Coarse aggregate (CA)= F*C.A ratio*S.G*1000
= 0.73*0.62*2.74*1000= 1240.12 Kg
Fine Aggregate (FA)= F*F.A ratio*S.G*1000
=0.73* 0.38*2.74*1000 =760.07 Kg
Cement:246 Kg
Flyash:106 Kg
Fine Agreegate:760.07Kg
Coarse Agreegate:1240.12 Kg
To find the design mix ratio divide the calculated value of all material by the weight of cement, Mix ratio of M35 grade concrete Cement:Flyash:F.A: C.A:Water =1:0.4:3.08:5.04
2.Concrete Mix Design For M50 grade concrete without fly ash
Procedure Step by Step:
I) Stipulation for Proportioning
a) Grade Designation :M50
b) Type of Cement: OPC 43grade
c) Maximum nominal size aggregate 20mm
d) Maximum cement content : 320Kg/M^3
f) Workability: 100mm(slump value for pumpabble concrete)
g) Exposure condition: Severe(for reinforced concrete)
h) Method of concrete placing: Pumping
i) Degree of supervision: Good
j) Type of aggregate: Crushed angular aggregate
k) Maximum cement content: 450Kg/m^3
l) Chemical admixture type: Superplasticizer
II) Test data for material
a) Cement used: OPC 43grade
b) Specific Gravity of cement: 3.15
c) Chemical admixture: Superplasticizer
d)Specific gravity
Coarse aggregate:2.65
Fine aggregate:2.61
e) Water absorption
Coarse aggregate:0.5%
Fine Aggregate: 1.0%
f) Free surface moisture
coarse Aggregate -Nil
Fine Aggregate -Nil
i) Sieve Analysis
Coarse agg & Fine Aggregate are taken from table 2 IS383
III) Target strength for mix proportioning
f'ck= fck+1.65S
=50+1.65*5 =58.25N/mm^2
IV) Selection of water cement ratio
Water cement ratio=0.35
V) Selection of water content
Approximate water content for 20mm maximum size of aggregate =180kg/m^3 (As per table5 IS10262) as plasticizerwe can reduce water content by 20%.
Water Content=180*0.8 =144Kg/m^3
VI) Calculation of cement
Water cement ratio=0.35
Water content/cum of concrete=144 kg
cement content=144/0.35=411.4 Kg/m^3 =412Kg/m^3
VII) Calculation for C.A & F.A
Volume of concrete=1m^3
Volume of cement=412/(3.15x1000) = 0.1308 m^3
Volume of water= 144/1*1000 =0.1440 m^3
Volume of admixture= 4.944/(1.145*1000) =0.0043m^3
Total weight of other materials coarse aggregate= 0.1308+0.1440+0.0043 =0.2791 m^3
Volume of coarse and fine aggregate =1-0.2791= 0.7209m^3
Volume of F.A=0.7209 X 0.33= 0.2379 m^3 (Assuming 33% by volume of total aggregate)
Volume of C.A= 0.7209-0.2379 =0.4830 m^3
Weight of F.A= 0.2379*2.61*1000= 620.91 kg/m^3= 621
Weight of C.A=0.4830*2.655*1000 =1282.36 Kg/m^3=1284kg/m^3
considering 20mm:10mm =0.55:0.45
20mm =706Kg
10mm= 578Kg
Cement= 412*1.025 =422Kg
Water= 144*1.025 =147.6Kg
Fine Aggregate=621Kg
Coarse Aggregate 20mm= 706 Kg
Coarse aggregate 10mm= 578 Kg
Admixture= 1.2% by weight of cement =5.064 kg
Water:Cement:F:A:C.A= 0.35:1:1.47:3.043
Obseravtion:
Mix was cohesive & homgenous
slump 120mm
No. of cube casted =9.no
7days average compressive strength 52.07Mpa
28days average compressive strength =62.52Mpa which is greater than 58.25 Mpa
hence mix accepted