Mix Design Of Concrete Calculation For M20, M25 & M30 [Pdf]

Mix design concrete is a crucial process in the concrete making that involves determining the proportions and ingredients of concrete to achieve the desired strength, workability, durability, and other properties. It is essential to design a concrete mix that meets the specific requirements of a construction project.

The mix design of concrete takes into account various factors such as the compressive strength required, the type and size of aggregates, the water-cement ratio, the shape of coarse aggregates, the workability needed, the exposure conditions, and the type of cement used. These factors play a crucial role in determining the performance and longevity of the concrete structure.

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Mix Design of Concrete

The calculate mix design for concrete following step to be followed.

Data Required Mix Design

i. Design Data

(a) Characteristic compressive strength of concrete required at end of 28 days = M 25

(b) Nominal maximum size of aggregate used = 20 mm

(d) Required workability at site = 50-75 mm (slump Value)

(e) Quality control is done as per IS: 456 – 2000

(f) Type of exposure Condition of concrete (as defined in IS: 456) = Mild

(g) Type of cement used = PSC conforming IS: 456 – 2000

(h) Method of placing Concrete on Site = pumpable concrete

(ii) Material testing data (determined in the laboratory)

(a) Specific gravity of cement = 3.15

(b) Specific gravity of FA = 2.64

(d) Aggregates are assumed to be having surface dry conditions.

(e) Fine aggregates are confirmed to Zone II of IS – 383

Mix Design of Concrete Procedure

The following steps are to be followed for concrete mix design calculation,

Step-1 Determining the Target Strength of Concrete

Himsworth constant for 5% risk factor is 1.65 & standard deviation is taken from IS: 456 2000 for M – 25 Grade of concrete is 4.0.

Standard Deviation for Mix Design of Concrete — **Standard Deviation**

f_target = f_ck + 1.65 x S

= 25 + 1.65 x 4.0 = 31.6 N/mm²

Where,

S = Standard Deviation (N/mm²) = 4 (Refer: IS 10262- 2009 table -1)

Step-2 Determining Water-Cement ratio

Refer: IS 456, (page no 20) Table 5

Maximum water-cement ratio taken for Mild exposure condition = 0.55

Assume the water-cement ratio as 0.50 for the experiment base

0.5 < 0.55, hence it is OK.

Step-3 Selection of Water Content for Mix

Refer: IS 10262- 2009 Table 2

Maximum water content is taken = 186 Kg (maximum size of aggregate = 20 mm)Correction in water content is

Estimated water content for mix = 186+ (3/100) x 186 = 191.6 kg /m³

Step-4 Selection of Cement Content for Mix

Water-cement ratio = 0.50
Corrected water content for mix = 191.6 kg /m³
Refer to IS 456 – 2000, Table 5
Minimum cement Content required for mild exposure condition = 300 kg/m3
383.2 kg/m3 > 300 kg/m3, hence, OK.
This value is required to be checked for durability requirements from IS: 456 – 2000
In this example for mild exposure and for reinforced concrete, the minimum cement content is 300 kg/m3 which is less than 383.2 kg/m³. Hence cement content adopted = 383.2 kg/m³.
IS: 456: 2000, clause 8.2.4.2
Maximum cement content for mix = 450 kg/m³.

Step-5 Estimation of Coarse Aggregate Proportion for Mix

Refer to IS 10262- 2009, Table 3

For Nominal max. size of aggregate for mix = 20 mm,
Zone of fine aggregate = Zone II
And For w/c = 0.5
The volume of coarse aggregate per unit volume of Concrete = 0.62

Table for Correction in Estimation of Coarse Aggregate Proportion

(Note 1: For every ±0.05 increase or decrease change in w/c, the coarse aggregate proportion is to be changed by 0.01. If the w/c is less than 0.5.)

The volume of coarse aggregate is required to be increased to reduce the fine aggregate content in the mix. If the water-cement ratio is more than 0.5, the volume of coarse aggregate is to be reduced to increase the fine aggregate content.

If the coarse aggregate is not of an angular shape, the volume of coarse aggregate is required to be increased suitably, based on experience-based.)

(Note 2: For pumpable concrete or congested reinforcement in structure the coarse aggregate proportion may be reduced up to 10%)

Hence, the Volume of coarse aggregate per unit volume of total Volume of concrete = 0.62 x 90% = 0.558

Volume of fine aggregate in mix = 1 – 0.558 = 0.442

Step-6 Estimation of the Mix Materials

The volume of concrete is taken = 1 m³

Volume of cement = (Weight of cement / Specific gravity of cement) x (1/100) = (383.2/3.15) x (1/1000) = 0.122 m³

The volume of water = (Weight of water / Specific gravity of water) x (1/1000)

= (191.6/1) x (1/1000) = 0.1916 m³

Volume of aggregates = a – (b + c ) = 1 – (0.122 + 0.1916) = 0.6864 m³

Weight of coarse aggregates = 0.6864 x 0.558 x 2.84 x 1000 = 1087.75 kg/m³

Weight of fine aggregates = 0.6864 x 0.442 x 2.64 x 1000 = 800.94 kg/m³

Concrete Mix Proportions for Concrete 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
W/c = 0.5
For trial -1 of concrete in the lab & to check its properties.
It will satisfy durability & economy.
For making trial -1, the mass of ingredients required will be calculated for 4 no’s cubes assuming 25% wastage.
Volume of concrete required for Making 4 cubes = 4 x (0.15³x1.25) = 0.016878 m³
Wt. of Cement = (383.2 x 0.016878) kg/m³ = 6.47 kg
Wt. of Water = (191.6 x 0.016878) kg/m³ =3.23 kg
Wt. of Coarse aggregate = (1087.75 x 0.016878) kg/m³ =18.36 kg
Wt. of Fine aggregates = (800.94 x 0.016878) kg/m^{3 =} 13.52 kg

Downloads: Excel Sheet for Concrete Mix Design as per is 10262-2009

Step-7 Correction for Absorption / Moisture of Aggregate

As we assumed the aggregate is a saturated surface dry condition, therefore no correction is required.

Step-8 Concrete Trail Mixes

Concrete Trial Mix 1

The mix proportion is determined in Step 6 Make trial mix -1 & with this proportion, concrete is manufactured and tested for fresh concrete properties requirements like workability, bleeding, and finishing qualities.
In this Trial Mix,
Slump value = 25 mm
Compaction Factor = 0.844
From the Mix Slum test, the concrete is workable and had a true slump of about 25 mm and it is free from segregation and bleeding.
Required slump = 50-75 mm
So modifications and changes are needed in trial mix 1 to get the desired workability.

Concrete Trial Mix 2

To increase the workability of concrete mix from 25 mm to 50-75 mm an increase in water content by +3% is to be made.
The corrected water content for mix = 191.6 x 1.03 = 197.4 kg.
As mentioned earlier to adjust fresh concrete properties the water-cement ratio should not be changed. Hence
Cement Content = (197.4/0.5) = 394.8 kg/m³
Which also need to satisfy durability requirement.
Volume of aggregate in Concrete = 1 – [{394.8/(3.15×1000)} + {197.4/(1 x 1000)}] = 0.6773 m³
Weight of coarse aggregate = 0.6773 x 0.558 x 2.84 x 1000 = 1073.33 kg/m³
Weight of fine aggregate = 0.6773 x 0.442 x 2.64 x 1000 = 790.3 kg/m³

Concrete Mix Proportions for Trial Mix 2

Weight of Cement = 384.8 kg/m³
Weight of Water = 197.4 kg/m³
Weight of Fine aggregate =790.3 kg/m³
Weight of Coarse aggregate = 1073.33 kg/m³
For making trial -2, the Weight of material required will be calculated for 4 no’s cubes assuming 25% wastage.
Volume of concrete required for 4 cubecasting = 4 x (0.153 x1.25) = 0.016878 m3
Weight of Cement = (384.8 x 0.016878) kg/m3 = 6.66 kg
Weight of Water = (197.4 x 0.016878) kg/m3 =3.33 kg
Weight of Coarse aggregate = (1073.33 x 0.016878) kg/m3 =18.11 kg
Weight of Fine aggregates = (790.3 x 0.016878) kg/m3 = 13.34 kg
In this trial Mix,
Slump value for mix = 60 mm
Compaction Factor for mix = 0.852
So, from the results of the slump of Mix, the concrete is workable and had a true slump of about 60 mm.
Required slump = 50-75 mm
So, it satisfied the desired workability by satisfying the requirement of a 50-75 mm slump value.
Now, we have to go for trial mix-3

Concrete Trial Mix 3

In this trial mix water/cement ratio is to be decreased by 10% keeping the water content constant.
Water cement ratio = 0.45
With the reduction of 0.05 in w/c, we have to increase of coarse aggregate fraction by 0.01.
Coarse aggregate fraction in mix = 0.558 +0.01 =0.568
W/c = 0.45 and water content for mix = 197.4 kg/m³
Cement content for mix = (197.4/0.45) = 438.7 kg/m³
Volume aggregate in total volume of concrete = 1 – [{438.7/(3.15 x 1000)} + (197.4/1000)] = 0.664 m³
Weight of coarse aggregate = 0.664 x 0.568 x 2.84 x 1000 = 1071.11 kg/m³
Weight of fine aggregate = 0.664 x 0.432 x 2.64 x 1000 = 757.28 kg/m³

M 25 Mix Design

For the Compressive Strength of concrete vs. C/W graph for a target strength of 31.6 MPa, we found

Water cement ratio = 0.44
Weight of water content = 197.4 kg/m³
Weight of Cement content = (197.4/0.44) = 448.6 kg/m³
The volume of aggregate in a total volume of concrete = 1 – [{448.6/(3.15 x 1000)} + (197.4/1000)] = 0.660 m³With a reduction of 0.05 in w/c, we have to increase of coarse aggregate fraction by 0.01.
Coarse aggregate volume = 0.558 +0.01 = 0.568 m³
Volume of fine aggregate in mix = 1 – 0.568 = 0.432 m³
Weight of coarse aggregate = 0.660 x 0.568 x 2.84 x 1000 = 1064.65 kg/m³
Weight of fine aggregate = 0.660 x 0.432 x 2.64 x 1000 = 752.71 kg/m³

Mix Design of Concrete Calculation For M20, M25 & M30 [Pdf]