1. Nagarjuna college of engineering and technology
Devanahalli, bangalore
Presentation on
Mix design of concrete
By:
Ms. Preethi a v,
Asst professor
Dept. of civil engg.
Ncet, bangalore
8/24/2019

2. Methods of Concrete Mix Design are as follows:
:introduction:
Mix Design is the science of determining the relative proportions of the ingredients of concrete to achieve the desired properties in the most economical way.
Methods of Concrete Mix Design are as follows:
Indian standard recommended method IS:
American Concrete Institute Method of Mix Design
BS Method
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3. :principles of mix design:
The environment exposure condition for the structure
The grade of concrete, their characteristic strength and standard deviations
Type of Cement
Type and sizes of aggregates and their sources of supply
Nominal maximum sizes of aggregates
maximum and minimum cement content
water cement ratio
Degree of workability of concrete on placing conditions
Air content inclusive of entrained air
Maximum/minimum density of concrete
Maximum/minimum temperature of fresh concrete
Type of water available for mixing and curing
Source of water and the impurities present in it
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7. Indian standard recommended method IS:10262-2009
Design Mix for M20 Grade of Concrete
Design stipulations
Characteristic compressive strength at 28days = 20N/mm2
Maximum size of aggregates = 20mm
Type of aggregates = Crushed Rock
Workability = 25mm to 50mm
Degree of quality control = Good
Type of exposure = Severe
Type of cement = OPC 53 Grade
Minimum cement content = 250 kg/m3
Maximum cement content = 450 kg/m3
Maximum water cement ratio = 0.50
Method of concrete placing = Manual
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8. Data obtained from tests on ingredients in the laboratory
Cement = Ordinary Portland Cement (53 grade)
Specific gravity of cement = 3.09
Aggregates
Specific gravity of :
Coarse aggregates = 2.676
Fine aggregates = 2.57
Water absorption
Coarse aggregates = NIL
Fine aggregates = NIL
Free moisture
Fine aggregates = NIL
Sieve analysis (as per IS: )
  Fine aggregates = Zone III
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9. Target Strength for mix Proportioning F'ck= fck + 1.65S =20 + 1.65*4
=26.60N/mm2
Where F'ck = Target average compressive strength at 28 days.
fck = Characteristic compressive strength at 28 days
S = Standard deviation (Table-1 of IS: )
Selection of w/c
From table 5 of IS: , maximum water content = 0.50
Based on trial and error W/c = 0.50
Selection of water content
From table 2 of IS: , maximum water content for 20mm aggregate =186litres
Estimated water content f or 25-50mm slump=1861itres
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10. Calculation of cement content W/c = 0.50 Cement content = 186/0.50
` =372 kg/m3
From Table 5 of IS 456, minimum cement = 250kg/m3
Therefore 372kg/m3 > 250kg/m3, Hence O.K.
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 III) for water-cement ratio of = 0.64.
Volume of coarse aggregate = 0.64m3
Volume of fine aggregate =1-0.64
= 0.36 m3
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13. :american concrete institute method of mix design:
Data to be collected:
i) Fineness modulus of selected Fine Aggregates
ii) Unit weight of dry rodded coarse aggregate
iii) Specific gravity of Coarse and Fine aggregates
iv) Absorption characteristics of both Coarse and Fine aggregates
v) Specific gravity of Cement
From the minimum strength specified, estimate the average deisgn strength by using standard deviation.
Find the water/cement ratio from the strength and durability points of view. Adopt the lower value.
Maximum size of the aggregate to be decided.
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14. Workability in terms of slump need to be decided.
The total water in kg/m3 of concrete is determined, corresponding to the selected slump and selected maximum size of aggregate.
Cement content if computed by dividing the total water content by the water/cement ratio.
Select the bulk volume of dry rodded coarse aggregate per unit volume of concrete, for the particular maximum size of coarse aggregate and fineness modulus of fine aggregates.
Weight of C.A per cubic meter of concrete is calculated by multiplying the bulk volume with bulk density.
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15. Solid volume of C.A in one cubic meter of concrete is calculated by knowing the specific gravity of C.A.
Similarly the solid volume of cement, water and volume of air is calculated in one cubic meter of concrete.
The solid volume of F.A is computed by subtracting from the total volume of concrete the solid volume of cement, CA, water and entrapped air.
Weight of FA is calculated by multiplying the solid volume of FA by specific gravity of FA
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16. :american concrete institute method - design example:
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27. Thank you
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