Concrete Mix design using DOE-British method

Concrete Mix Design

Definition

“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”

Concrete mix design is the process of finding the right proportions of cement, sand, and aggregates for concrete to achieve target strength in structures.

Methods of Concrete Mix Design

1. Department Of Environment (DOE - British) method

2. ACI Method of Mixed Proportioning

3. Road note No. 4 (Grading Curve) method

4. Trial and Adjustment Method

5. Maximum density method

6. Indian Road Congress, IRC 44method

7.Fineness modulus method

Department Of Environment (DOE - British) method

• The DOE method is used to design a concrete mix in accordance with the British DoE mix design method.

• This method of concrete design was first introduced in 1950, under the name “Road Note No 4”, which was later replaced by “Design of Normal Concrete Mixes” in 1975 by the British Department of Environment (DoE).

• The DOE method was first published in 1975 and then revised in 1988.

• Often referred to as the British Standard concrete mix design.

• The DOE method is applicable to concrete mixes for most purposes.

• DOE method help to calculate the exact amount of materials required to produce 1 m3 of concrete.

DOE method contains different stages in the concrete mix design process:

Step 1: Determine the target mean strength

Step 2: Determine the water/cement ratio

Step 3: Determine the water content

Step 4: Determine the cement content

Step 5: Determine the total aggre­gate content

Step 6: Determine the fine aggregate content

Step 7: Determine the mix proportion of the concrete mix for a given volume

Example of Concrete Mix design

• Characteristic compressive strength 30 N/mm2 at 28 days

• Defective rate 2.5 %

• Cement: OPC class 42.5

• Slump required, 10 - 30 mm

• Maximum free-water/Cement ratio 0.55

• Minimum Cement content 290 kg/m3

• Coarse aggregate: Uncrushed single-sized 20 mm

• Fine aggregate: Uncrushed with 70% passing 600 μm sieve

• Relative density of aggregate: 2.6 (assumed)

• The volume of the trial mix: 0.05 m3

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Step 1: Determine the target mean strength

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Step 2: Determine the water/cement ratio

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Step 3: Determine the water content

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Step 4: Determine the cement content

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Step 5: Determine the total aggre­gate content

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Step 6: Determine the fine aggregate content

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Step 7: Determine the mix proportion of the concrete mix for a given volume