How is the target mean strength calculated?

Using the formula f'ck = fck + 1.65 S, where f'ck is the target strength, fck is the characteristic strength, and S is the standard deviation from Table 1.

Where can I find the initial water content for my mix?

Table 2 gives the starting water content for a 25-50mm slump based on the nominal maximum size of aggregate. This value is then adjusted for the actual target slump.

What if my calculated cement content is lower than specified in IS 456?

The minimum cement content specified in IS 456 (Table 5) for the relevant exposure condition must be adopted, even if your calculation yields a lower value.

How do I determine the proportions of coarse and fine aggregates?

First, find the volume of coarse aggregate as a percentage of total aggregate volume from Table 3. The remaining volume is assigned to the fine aggregate.

IS 10262

: 2009

Concrete Mix Proportioning - Guidelines

SupersededEssentialGuidelinesBIMMaterials Science · Admixtures and Chemical Products for Concrete

Superseded by IS 10262:2019

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This standard provides guidelines for designing concrete mixes to achieve specific target strengths, workability, and durability. It details a step-by-step calculation method to determine the optimal proportions of cement, water, aggregates, and admixtures, based on the properties of the constituent materials.

Provided guidelines for the proportioning of concrete mixes, including considerations for using admixtures.

Quick Reference Values

Target Strength Factor1.65 (for f'ck = fck + 1.65 S)

Assumed Standard Deviation for M25 grade4.0 N/mm²

Assumed Standard Deviation for M30-M50 grades5.0 N/mm²

Estimated entrapped air in 20mm nominal max size aggregate concrete2.0 percent

Initial water content for 20mm aggregate (50mm slump)186 kg/m³

Typical water reduction with superplasticizer20 to 30 percent

Key Formulas

f'ck = fck + 1.65 S — Target mean compressive strength

Volume = (Mass of material / Its Specific Gravity) x (1 / 1000) — Absolute volume calculation for each ingredient

Practical Notes

The mix design obtained from this code is a starting point. Trial mixes are mandatory to verify and adjust proportions using actual site materials.

Durability requirements from IS 456 (Table 5) regarding maximum water-cement ratio and minimum cement content must be checked and must supersede the calculated values if they are more stringent.

Accurate determination of material properties like aggregate specific gravity, water absorption, and gradation is critical for a successful mix design.