Nominal mix and design mix are two different methods of proportioning the ingredients of concrete. Nominal mix is a simpler and less scientific method, while design mix is a more complex and accurate method.
Nominal mix
- The proportions of the ingredients are based on experience and tradition.
- The water-cement ratio is not calculated, but is assumed to be a fixed value.
- The mix is suitable for simple concrete works, such as footings and slabs.
Design mix
- The proportions of the ingredients are calculated based on the desired strength, workability, and durability of the concrete.
- The water-cement ratio is calculated to ensure that the concrete has the desired strength.
- The mix is suitable for more complex concrete works, such as columns, beams, and foundations.
Comparison of Nominal Mix and Design Mix
| Characteristic | Nominal Mix | Design Mix |
|---|---|---|
| Complexity | Simple | Complex |
| Accuracy | Less accurate | More accurate |
| Suitability | Simple concrete works | Complex concrete works |
| Cost | Less expensive | More expensive |
Advantages of Nominal Mix
- Simple and easy to use
- Less expensive
Disadvantages of Nominal Mix
- Less accurate
- Not suitable for complex concrete works
Advantages of Design Mix
- More accurate
- Suitable for complex concrete works
- Can be customized to meet specific requirements
Disadvantages of Design Mix
- More complex and time-consuming to use
- More expensive
Which method to use?
The choice of whether to use nominal mix or design mix depends on the specific project. For simple concrete works, nominal mix may be sufficient. However, for more complex concrete works, design mix is the preferred method.
In general, design mix is the preferred method for concrete works where the following are important:
- Strength
- Durability
- Workability
- Accuracy
If you are unsure which method to use, it is always best to consult with a civil engineer.