Diffeece between nominal mix and design mix?

Answer 1

a nominal mix is that mix in which we adopt the various ingredients such as1:2:3,1:2.5:4etc here the strength will not be the desired strength and generally here we take the ingredients per unit vol

a design mix is that mix in we find the ratio of the different ingredients as per the desired strength and the ingredients would be in per unit weight

Answer 2

Nominal mix and design mix are two different approaches used in concrete mix design, which determine the proportions of various ingredients to achieve the desired concrete properties. Here's a comparison between nominal mix and design mix:

Nominal Mix:

1. Definition: Nominal mix refers to a mix design approach where the proportions of ingredients in concrete are prescribed based on approximate or nominal ratios. These ratios are typically based on past experience or general guidelines rather than specific testing or engineering calculations.

2. Proportions: The proportions of cement, sand, and coarse aggregates are expressed in volume or weight ratios. For example, a common nominal mix for ordinary concrete is 1:2:4, indicating one part cement, two parts sand, and four parts coarse aggregates by volume.

3. Simplicity: Nominal mix designs are relatively simple and easy to use, making them suitable for small-scale construction projects or situations where specific concrete performance requirements are not critical.

4. Lack of Precision: Since nominal mixes rely on approximate ratios, the actual properties of the resulting concrete may vary, making it less precise and consistent compared to design mix.

5. Limited Flexibility: Nominal mixes offer limited flexibility to adjust concrete properties according to specific project requirements, as the proportions are fixed and not tailored to the desired performance characteristics.

Design Mix:

1. Definition: Design mix involves a systematic and scientific approach to determine the concrete mix proportions based on comprehensive laboratory testing, engineering calculations, and desired performance requirements.

2. Proportions: Design mix determines the precise proportions of cement, aggregates, water, and often admixtures based on the desired concrete strength, workability, durability, and other specific requirements.

3. Customization: Design mix allows for customization and optimization of concrete properties to meet project specifications and performance criteria. It considers factors such as aggregate properties, cement type, water-cement ratio, and admixture use to achieve the desired results.

4. Precision and Consistency: Design mix is based on rigorous testing and calculations, leading to more precise and consistent concrete performance. It ensures that the concrete meets the desired strength, durability, and workability requirements.

5. Complexity: Design mix is a more complex and involved process that requires laboratory testing, technical expertise, and consideration of various factors. It is typically employed for large-scale construction projects or situations where specific performance requirements are critical.

In summary, nominal mix relies on approximate ratios and past experience, offering simplicity but limited precision and flexibility. Design mix, on the other hand, employs a scientific approach, laboratory testing, and engineering calculations to achieve precise and tailored concrete properties according to project requirements.