ALL YOU WANT TO KNOW ABOUT MIX DESIGN -lceted LCETED INSTITUTE FOR CIVIL ENGINEERS

## Mar 2, 2020

ALL YOU WANT TO KNOW ABOUT MIX DESIGN

Definition:
Mix design can be defined as the process of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible.

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As per IS456:2000, Different grades of concrete are classified into  M5, M7.5, M10, M15 etc., whereas M stands for Mix and the number behind M stands for Characteristic Compressive strength (fck) of the concrete in N/mm2 @28 days when checked with 15cm×15cm×15cm cube

LCETED TRIVIA

What is the value of 1 Newton in KG?

1 Newton: 1 Newton in Earth gravity is the equivalent weight of 1/9.80665 kg on Earth. This is derived using Newton's second law f=ma and assuming Earth the gravity of 9.80665 m/s2. 1 N (Earth) = 0.101971621297793 kg.

kilogram-force [kgf]
 kilogram-force [kgf] Newton [N] 0.01 kgf 0.0980665 N 0.1 kgf 0.980665 N 1 kgf 9.80665 N 2 kgf 19.6133 N 3 kgf 29.41995 N 5 kgf 49.03325 N 10 kgf 98.0665 N 20 kgf 196.133 N 50 kgf 490.3325 N 100 kgf 980.665 N 1000 kgf 9806.65 N

Concrete Mixes are generally divided into two different types:

1. Nominal Mix
Nominal Mix is generally adopted for small scale constructions.

2. Design Mix
Quantity of various ingredients of concrete can be calculated by mix design method.

There are several mix design procedures. BIS recommended mix design procedure is given IS 10262-2009.

Nominal mixes may be used for grades lower than M20. But for M20 also it is not advisable to use nominal mixes always. Properties of ingredients of concrete such as cement, sand and coarse aggregate change from place to place. Thus design mix proportion is to be prepared based on the properties of locally available materials.

Mix design procedure as per IS:10262-2009

1. Target mean strength is to be calculated from design strength and standard deviation.

2. Selection of water-cement ratio depending on exposure condition and experience of the designer.

3. Calculation of water content corresponding to the maximum nominal size of aggregate and given slump range of 25-50mm. This
calculated water content is to be adjusted for slump, aggregate angularity and superplasticizer if used.

4. Calculation of cement content from W/c ratio and water context

5. The volume of coarse aggregate per unit volume of total aggregate is to be obtained from table given in IS 10262. Adjustments are to be applied for the W/c ratio.

6. Lastly, quantities of all sand and coarse aggregate per unit volume of concrete are to be calculated from their respective specific gravities.

hope you get an idea what is a mix design

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