How is target mean strength calculated?

It's the characteristic strength plus a margin: f'ck = fck + 1.65 × S, where S is the assumed standard deviation from Table 2 (Clause 5.3).

What is the starting point for determining water content?

Table 4 gives an approximate water content for a given nominal maximum aggregate size to achieve a slump of 50-75 mm. This is adjusted for different slumps or admixtures.

How is the volume of coarse and fine aggregate determined?

First, the volume of coarse aggregate per unit volume of total aggregate is estimated from Table 5. Then, using absolute volume calculations, the remaining volume is filled by the fine aggregate.

Does this standard replace IS 456 for mix design?

No, it provides the detailed 'how-to' procedure for mix design, which must satisfy the 'what-to-do' requirements (like min. cement, max. w/c ratio) laid out in IS 456.

IS 10262

: 2019

Concrete Mix Proportioning - Guidelines

CurrentEssentialGuidelinesBIMMaterials Science · Concrete

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This standard provides guidelines for proportioning concrete mixes to achieve specified requirements for workability, strength, and durability. It details a systematic, step-by-step process for concrete mix design using the properties of the constituent materials, supplemented with illustrative examples.

Provides guidelines for the proportioning of concrete mixes.

Quick Reference Values

Target Strength Formulaf'ck = fck + 1.65 S

Assumed Std. Deviation for M25 concrete4.0 N/mm² (for good quality control)

Max Water Content for 20mm aggregate186 kg/m³ (for 50-75 mm slump)

Volume of Coarse Aggregate (20mm, Zone II Sand)0.62 per unit volume of total aggregate

Minimum Cement Content for Moderate Exposure (PCC)240 kg/m³ (as per IS 456)

Max W/C Ratio for Severe Exposure (RCC)0.45 (as per IS 456)

Key Formulas

f'ck = fck + 1.65 × S — Target Mean Compressive Strength

V = [W + (C/Sc) + (fa/Sfa) + (ca/Sca)] / 1000 — Absolute volume of fresh concrete

Practical Notes

The mix design process is iterative. Always conduct trial mixes to verify and adjust proportions to achieve the required fresh and hardened concrete properties.

The values in tables (e.g., water content, aggregate volume) are initial estimates for specific conditions. They must be adjusted based on the actual material properties, desired workability (slump), and use of admixtures.

Ensure the final mix design not only meets strength targets but also complies with the durability requirements (min. cement, max. w/c ratio) specified in IS 456 for the intended exposure condition.