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IS 10262 : 2019

Concrete Mix Proportioning —
Guidelines

The definitive guideline for designing concrete mixes from M20 to M80. This code replaces the 2009 version and introduces updated procedures for high-strength concrete, supplementary cementitious materials (SCMs), and durability-based mix selection.

Published: 2019 (Reaffirmed 2024)
Replaces: IS 10262 : 2009
Committee: CED 2
Pages: 62
🔄
Updated Version: This summary reflects IS 10262:2019. Key changes from 2009 include expanded grade range (M60–M80), revised entrapped air tables, and specific clauses for admixtures.

Scope & Purpose

IS 10262 provides guidelines for establishing the correct proportions of cement, fine aggregate, coarse aggregate, water, and admixtures to produce concrete of specified properties. Cl. 1

It applies to normal weight concrete with compressive strengths ranging from M20 to M80. The code covers both plain and reinforced concrete but does not cover mass concrete or specialized concretes like lightweight or fiber-reinforced unless specifically stated.

💡
Purpose To ensure the produced concrete meets:
  • Strength: Compressive strength requirements at 28 days.
  • Durability: Resistance to environment via W/C ratio and cement content limits.
  • Workability: Slump/compacting factor suitable for placement.
  • Economy: Efficient use of materials without compromising quality.

Design Principles

The mix design process follows the "Limit State Method" philosophy adopted in IS 456. The primary goals are:

🎯
Achieve Target Strength Design for a mean strength higher than the characteristic strength ($f_{ck}$) to account for statistical variability.
💧
Ensure Durability Limit the Water-Cement ratio and ensure minimum cement content based on exposure conditions (IS 456).
⚙️
Maintain Workability Select water content and admixtures to achieve the desired slump without segregation.
⚖️
Maximize Economy Use locally available materials and minimize cement consumption where strength allows.

The standard method used in this code is the Absolute Volume Method, where the sum of volumes of individual ingredients equals the volume of concrete (less air content). Cl. 5.8

Step-by-Step Procedure

IS 10262 outlines a systematic 7-step procedure for mix proportioning. These steps are implemented in our Concrete Mix Calculator. Cl. 5

  1. Determine Target Mean Strength ($f_t$).
  2. Select Water-Cement Ratio ($W/C$).
  3. Select Water Content ($W$).
  4. Calculate Cement Content ($C$).
  5. Determine Aggregate Volumes (Coarse vs Fine).
  6. Calculate Final Masses per $m^3$.
  7. Prepare Trial Mixes and Verify.

Target Mean Strength

Since concrete strength varies statistically, the mix must be designed for a Target Mean Strength ($f_t$) that is higher than the characteristic strength ($f_{ck}$). Cl. 5.2.1

ft = fck + k × s Where k = 1.65 (for 5% failure rate) and s = Standard Deviation

The value of standard deviation ($s$) depends on the grade of concrete and control level:

Grade Standard Deviation (s) N/mm² Control Level
M204.0Good Control
M254.0Good Control
M305.0Good Control
M35 – M405.0Good Control
M45 – M555.0Very Good Control
M60 – M806.0Strict Control
⚠️
No Field Data? If no site history data is available, use the standard values given in Table 2. For high-volume production, conduct initial tests to establish actual $s$.

Selection of Water-Cement Ratio

There are two constraints on the W/C ratio:

🏗️
From Strength Based on the relationship between W/C ratio and compressive strength. Generally, lower W/C yields higher strength. Empirical graphs or formulae (e.g., Abram's Law) are used.
🛡️
From Durability (IS 456) Maximum W/C ratio is strictly limited by exposure conditions (Moderate, Severe, etc.).

The adopted W/C ratio is the lower of the two values calculated above. Cl. 5.4

Exposure Condition Max W/C Ratio Min Cement (kg/m³) Source
Mild0.55300IS 456
Moderate0.50300IS 456
Severe0.45320IS 456
Very Severe0.45340IS 456
Extreme0.40360IS 456

Selection of Water Content

The amount of water depends on the required workability (Slump/Compacting Factor), maximum size of aggregate, and shape of aggregates. Cl. 5.5

Base Values (for 50mm Slump)

Max Size of Aggregate Approx. Water Content (Litres/m³)
20 mm186
40 mm165

Adjustments

  • Slump Adjustment: Increase water by 3% for every 25mm increase in slump above 50mm.
  • Shape Adjustment: Use less water for rounded aggregates (approx. 10-15% reduction compared to angular).
  • Admixtures: Water reducer admixtures can significantly reduce water demand (10–30%).
❌
Do Not Add Water On Site Adding water at the site to increase slump reduces strength and increases permeability. Always re-mix with admixture or reject if segregation occurs.

Calculation of Cement Content

Once Water ($W$) and W/C ratio are fixed, Cement ($C$) is calculated directly: Cl. 5.6

Cement Content (kg/m³) = Water Content / (W/C Ratio)

This calculated value must be checked against the minimum cement content required for durability (from the table in Section "W/C Ratio"). If the calculated value is lower, adopt the minimum.

Proportioning Aggregates

The volume of coarse aggregate (CA) relative to fine aggregate (FA) depends on:

  • W/C Ratio
  • Maximum size of aggregate
  • Fineness modulus of fine aggregate (Sand Zone)

IS 10262 provides Table 3 which gives the Volume of Coarse Aggregate per unit volume of total aggregate for W/C = 0.50. Cl. 5.7

Adjustment Rule: For every 0.05 change in W/C ratio from 0.50, adjust the CA volume by ±0.01.

  • If W/C > 0.50 → Increase CA volume (more paste needed to coat more sand surface? No, actually higher W/C needs less paste, so more agg). Correction: Higher W/C means more water/paste flexibility, usually implies slightly more coarse agg to maintain economy/stability.
  • If W/C < 0.50 → Decrease CA volume (increase FA).

Trial Mixes & Testing

The theoretical design is only a starting point. Physical verification is mandatory. Cl. 7

  1. Prepare 3 Trial Batches: Mix the calculated proportions in the lab or small mixer.
  2. Test Workability: Measure Slump. Adjust water/admixture if necessary (recalculate cement to keep W/C constant).
  3. Cast Cubes: Cast 7 cubes (150mm) for 7-day and 28-day testing.
  4. Analyze Strength: If 28-day strength $\ge$ Target Mean Strength ($f_t$), the mix is approved.
✅
Acceptance Criteria The average strength of the cubes should exceed $f_{ck} + 4$ N/mm² (or specific criteria per IS 456) to ensure safety margins.

Summary of Key Tables

Table No. Description Usage
Table 1Standard Deviation ValuesTo find $s$ for Target Strength calculation.
Table 2Approx. Water ContentFor 50mm slump (20mm/40mm agg).
Table 3Volumes of Coarse AggregateTo split total aggregate into CA and FA.
Table 4Entrapped Air ContentPercentage of air voids based on max agg size.
Table 5Properties of Admixtures(Refer to manufacturer data).

Mix design relies heavily on other standards:

IS 456 : 2000
Plain & Reinforced Concrete — Durability & Limits.
IS 3812
Specifications for Fly Ash (Pozzolana).
IS 4031
Methods of Physical Tests for Hydraulic Cement.
IS 10778
Sampling and Analysis of Concrete.
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