Concrete Mix Design is the procedure of selecting suitable proportions of cement, sand, and aggregates for concrete to achieve the desired strength in structures.
In the Concrete Mix Design process each and every ingredient of concrete is tested in the laboratory. The Mix Design process is normally implemented for the structure that needs higher grades of concrete like M25, M30, etc, and where consumption of Concrete is high.
Concrete Mix Design for M20, M25, M30, and higher grades of concrete can be calculated from the example given below.
Table of Contents
Concrete Mix Design Procedure
Data Required for Concrete Mix Design
(i) Concrete Mix Design Provision
⦁ Characteristic Compressive Strength needed in the field at 28 days grade designation = M 25
⦁ Maximum size of aggregate = 20 mm
⦁ Workability = 55-75 mm ( slump value )
⦁ Degree of quality control = Good ( as per IS 456 )
⦁ Exposure type = mild
⦁ Cement type = Portland Slag Cement ( IS 455 )
⦁ Concrete placing method = By using a pump
⦁ The shape of Coarse Aggregate = Angular
(ii) Laboratory test data of material
⦁ The specific gravity of cement = 3.15
⦁ The specific gravity of Coarse aggregate = 2.84
⦁ The specific gravity of fine aggregate = 2.64
⦁ Aggregates are assumed as saturated surface dry
⦁ Zone 2 Fine Aggregate – IS 383
Procedure for Concrete Mix Design of M25 Concrete
Step 1 – Determine Target Strength
Hinsworth constant = 1.65 ( for 5% risk factor )
Standard Deviattion ( S ) = 4 ( for M25 as per IS 10262-2009 )
Formula for tragert strength is
FTarget = Fck + 1.65*S
FTarget = 25+1.65*4
Step 2 — Determine water / cement ratio:-
As per Table 5 of IS 456
Maximum water/cement ratio for Mild exposure condition = 0.55
Depending on experience, select the water-cement ratio as 0.5.
0.5<0.55, ( OK )
Step 3 — Determine Water Content
As per IS 10262-2009
Maximum water content = 186 Kg/m3 (Nominal maximum size of aggregate – 20 mm)
Correction in Water content
| Parameters | Values as per Standard reference condition | Values as per Present Problem | Departure | Correction in Water Content |
| Slump | 25-50 mm | 50-75 | 25 | (+3/25) x 25 = +3 |
| Shape of Aggregate | Angular | Angular | Nil | – |
| Total | +3 |
Estimated water content = 186+ (3/100) x 186 = 191.6 kg /m3
Step 4 — Determine of Cement Content
As we know
Water/cement ratio = 0.5
Estimated water content = 191.6 kg /m3
As per IS 456 Table No 5
Minimum cement Content = 300 kg/m3 ( mild exposure condition )
383.2 kg/m3 > 300 kg/m3, (OK)
Now check for durability requiremnt from IS 456
In the present scenario against mild exposure and for the case of reinforced concrete the minimum cement content is 300 kg/m3 which is less than 383.2 kg/m3.
So,Cement content adopted = 383.2 kg/m3.
According to IS: 456 clause 8.2.4.2
Maximum cement content = 450 kg/m3.
Step 5: Determination of Coarse Aggregate proportion:-
As per Table 3 of IS 10262- 2009,
Nominal maximum size of aggregate = 20 mm,
Fine Aggregate = Zone II
Water/cement = 0.5
The volume of coarse aggregate per unit volume of total aggregate = 0.62
Table for correction in the estimation of the coarse aggregate proportion
| Parameter | Values as per Standard reference condition | Values as per the present problem | Departure | Correction in Coarse Aggregate proportion | Remarks |
| W/c | 0.5 | 0.5 | Nil | See Note 1 | |
| Workability | pump able concrete | -10% | See Note 2 | ||
| Total | -10% |
Note 1: For every ±0.05 change in the water/cement ratio, the coarse aggregate proportion is to be changed by 0.01. If the water/cement ratio is less than 0.5 (standard value), the volume of coarse aggregate is needed to be increased to decrease the fine aggregate content. If the water/cement ratio is more than 0.5, the volume of coarse aggregate is to be reduced to enhance the fine aggregate content. If the coarse aggregate is not angular, the volume of coarse aggregate may be required to be increased suitably, based on experience.
Note 2: For pump-able concrete or congested reinforcement the coarse aggregate proportion may be decreased up to 10%.
Thus,
Volume of Coarse Aggregate ( CA ) per unit volume of total aggregate = 0.62 x 90% = 0.558
Volume of Fine Aggregate ( FA ) = 1 – 0.558 = 0.442
Step 6: Determine mix ingredients
a) Volume of concrete = 1 m3
b) Volume of cement = (Mass of cement / Specific gravity of cement) x (1/100)
= (383.2/3.15) x (1/1000) = 0.122 m3
c) Volume of water = (Mass of water / Specific gravity of water) x (1/1000)
= (191.6/1) x (1/1000) = 0.1916 m3
d) Volume of total Aggregates = a – (b + c ) = 1 – (0.122 + 0.1916) = 0.6864 m3
e) Mass of Coarse Aggregates = 0.6864 x 0.558 x 2.84 x 1000 = 1087.75 kg/m3
f) Mass of Fine Aggregates = 0.6864 x 0.442 x 2.64 x 1000 = 800.94 kg/m3
Concrete Mix proportions for Trial Mix 1
Cement = 383.2 kg/m3
Water = 191.6 kg/m3
Fine Aggregates = 800.94 kg/m3
Coarse Aggregate = 1087.75 kg/m3
Water/cement ratio = 0.5
In trial -1 casting of concrete in the lab, to check its properties.
It will satisfy both durability & economy.
For casting trial -1, the mass of ingredients needed will be calculated for 4 no’s cube assuming 25% wastage.
Vol of Concrete needed for 4 cubes = 4 x (0.153 x1.25) = 0.016878 m3
Cement = (383.2 x 0.016878) kg/m3 = 6.47 kg
Water = (191.6 x 0.016878) kg/m3 =3.23 kg
Coarse Aggregate = (1087.75 x 0.016878) kg/m3 =18.36 kg
Fine Aggregates = (800.94 x 0.016878) kg/m3 = 13.52 kg
Step 7: Correction due to moist aggregate:-
As we know the aggregate is saturated surface dry condition so no correction is needed.
Step 8: Concrete Trial Mixes:-
Concrete Trial Mix 1:
The mix proportion as calculated in Step 6 works as trial mix1. With this proportion, concrete is manufactured and tested for fresh concrete properties requirements which are workability, bleeding, and finishing qualities.
In this scenario,
Value Of Slump= 25 mm
Compaction Factor = 0.844
From the slump test, we can say that
Concrete Mix is cohesive, workable, and had a true slump of approx 25 mm and it is free from segregation and bleeding.
Desired slump value = 50-75 mm
So modifications are required in trial mix 1 to achieve the desired workability.
Concrete Trial Mix 2:
To enhance the workability from 25 mm to 50-75 mm an increase in water content by +3% is to be made.
Corrected water content = 191.6 x 1.03 = 197.4 kg.
As mentioned earlier to adjust fresh concrete properties the water-cement ratio will not be altered.
Thus
Cement Content = (197.4/0.5) = 394.8 kg/m3
Which also satisfies required durability .
Volume of all in aggregate= 1 – [{394.8/(3.15×1000)} + {197.4/(1 x 1000)}] = 0.6773 m3
Mass of coarse aggregate ( CA ) = 0.6773 x 0.558 x 2.84 x 1000 = 1073.33 kg/m3
Mass of fine aggregate ( FA ) = 0.6773 x 0.442 x 2.64 x 1000 = 790.3 kg/m3
Concrete Mix Proportions for Trial Mix 2
Cement = 384.8 kg/m3
Water = 197.4 kg/m3
Fine aggregate =790.3 kg/m3
Coarse aggregate = 1073.33 kg/m3
For casting trial -2, the mass of ingredients required will be calculated for 4 no’s cube assuming 25 % wastage.
Vol of concrete nedeed for 4 cubes = 4 x (0.153 x1.25) = 0.016878 m3
Cement = (384.8 x 0.016878) kg/m3 = 6.66 kg
Water = (197.4 x 0.016878) kg/m3 =3.33 kg
Coarse aggregate = (1073.33 x 0.016878) kg/m3 =18.11 kg
Fine aggregates = (790.3 x 0.016878) kg/m3 = 13.34 kg
In this scenario,
Slump value = 60 mm
Compaction Factor = 0.852
So, from slump test we can say,
The mix is very cohesive, workable, and had a true slump of about 60 mm.
It virtually flowed during vibration but did not exhibit any segregation and bleeding.
Desired slump value = 50-75 mm
Thus, it has achieved the desired workability by satisfying the requirement of a 50-75 mm slump value.
Now, Let’s go for trial mix-3.
Concrete Trial Mix 3:
In this case, the water-cement ratio is varied by +10% keeping water content constant. In the present case, the water-cement ratio is raised to 0.55 from 0.5.
An increase of 0.05 in the water/cement ratio will entail a reduction in the coarse aggregate fraction by 0.01.
So,Coarse aggregate as percentage of total aggregate = 0.558 – 0.01 = 0.548
W/c = 0.55
Water content will be kept constant.
Cement content = (197.4/0.55) = 358.9 kg/m3
So, volume of all in aggregate
= 1 – [{(358.9/(3.15 x 1000)} + (197.4/1000)] =0.688 m3
Mass of coarse aggregate = 0.688 x 0.548 x 2.84 x 1000 = 1070.75 kg/m3
Mass of fine aggregate = 0.688 x 0.452 x 2.64 x 1000 = 821 kg/m3
Concrete Mix Proportions of Trial Mix 3
Cement = 358.9 kg/m3
Water = 197.4 kg/m3
FA = 821 kg/m3
CA = 1070.75 kg/m3
For casting trial -3, the mass of ingredients required will be calculated for 4 no’s cube assuming 25% wastage.
Vol of concrete nedded for 4 cubes = 4 x (0.153 x1.25) = 0.016878 m3
Cement = (358.9 x 0.016878) kg/m3 = 6.06 kg
Water = (197.4 x 0.016878) kg/m3 =3.33 kg
Coarse aggregate = (1070.75 x 0.016878) kg/m3 =18.07 kg
Fine aggregates = (821 x 0.016878) kg/m3 = 13.85 kg
In this scenario,
Slump value = 75 mm
Compaction Factor = 0.89
So, from slump test we can say,
Mix is stable, cohesive, and workable and had a true slump of about 75 mm.
Desired slump = 50-75 mm
So, it has achieved desired workability by satisfying the requirement of 50-75 mm slump value.
Now, let us go for trial mix-4.
Concrete Trial Mix 4:
In this case, the water/cement ratio is reduced by 10% keeping water content constant.
W/c = 0.45
A reduction of 0.05 in w/c will entail and increase of coarse aggregate fraction by 0.01.
Coarse aggregate fraction = 0.558 +.01 =.568
W/c = 0.45 and water content = 197.4 kg/m3
Cement content = (197.4/0.45) = 438.7 kg/m3
Volume of all in aggregate
= 1 – [{438.7/(3.15 x 1000)} + (197.4/1000)] = 0.664 m3
Mass of coarse aggregate = 0.664 x 0.568 x 2.84 x 1000 = 1071.11 kg/m3
Mass of fine aggregate = 0.664 x 0.432 x 2.64 x 1000 = 757.28 kg/m3
Concrete Mix Proportions of Trial Mix 4
Cement = 438.7 kg/m3
Water = 197.4 kg/m3
FA = 757.28 kg/m3
CA = 1071.11 kg/m3
For casting trial -4, the mass of ingredients needed will be calculated for 4 no’s cube assuming 25% wastage.
Volume of concrete needed for 4 cubes = 4 x (0.153 x1.25) = 0.016878 m3
Cement = (438.7 x 0.016878) kg/m3 = 7.4 kg
Water = (197.4 x 0.016878) kg/m3 =3.33 kg
Coarse aggregate = (1071.11 x 0.016878) kg/m3 =18.07 kg
Fine aggregates = (757.28 x 0.016878) kg/m3 = 12.78 kg
A local correction due to moisture condition of aggregate is again applied on this proportions. With corrected proportions three concrete cubes are cast and tested for 28 days compressive strength.
Recommended mix proportion of ingredients for grade of concrete M25:
From Compressive Strength vs. c/w graph for target strength 31.6 MPa we get,
W/c = 0.44
water content = 197.4 kg/m3
Cement content = (197.4/0.44) = 448.6 kg/m3
Volume of all in aggregate
= 1 – [{448.6/(3.15 x 1000)} + (197.4/1000)] = 0.660 m3
A reduction of 0.05 in w/c will entail and increase of coarse aggregate fraction by 0.01.
Coarse aggregate fraction = 0.558 +.01 =.568
Volume of fine aggregate = 1 – 0.568 = 0.432
Mass of coarse aggregate = 0.660 x 0.568 x 2.84 x 1000 = 1064.65 kg/m3
Mass of fine aggregate = 0.660 x 0.432 x 2.64 x 1000 = 752.71 kg/m3
Frequently Asked Questions
Nominal Mix specifies the proportion of the Cement, Sand, and Aggregates without making an organized effort to know their individual properties. It has a volumetric batching.
This is an old technique for mixing concrete in a manner like 1 cement: 2 sand : 3 aggregates by their volume. Mix the dry ingredients ( cement, sand, and aggregates ) and slowly add water until concrete becomes workable. This concrete mixture may need to be changed based on the aggregate used to provide workable concrete.