Home → Learn → Concrete Mix Design IS 10262

IS 10262:2019 · Concrete Technology

Concrete Mix Design as per IS 10262 — Complete Guide with 3 Worked Examples

⏱ 20 min read📅 June 2026✅ IS 10262:2019🎓 GATE relevant

Concrete mix design is the process of selecting the right proportions of cement, water, fine aggregate (sand), and coarse aggregate (gravel/crushed stone) to achieve a specified compressive strength, workability, and durability at minimum cost. IS 10262:2019 provides the Indian standard procedure — a systematic, step-by-step method that starts from the required characteristic strength and ends with a complete batch recipe in kg/m³. This guide walks through every step with three worked examples and 10 GATE MCQs.

1. Introduction

In Indian construction, nominal mixes (1:2:4 for M15, 1:1.5:3 for M20) were the norm for decades. But for any grade above M20, IS 456 mandates design mix — a scientifically proportioned mix that accounts for the actual properties of your cement, aggregates, and water. IS 10262:2019 (replacing the 2009 edition) is the current standard for this process.

The goal is simple: achieve the required strength reliably (not just on average, but with a statistical guarantee) while maintaining adequate workability for placement and compaction, and sufficient durability for the exposure environment. A well-designed mix also minimises cement content — saving cost and reducing heat of hydration.

2. Concept and Theory

Why target strength is higher than characteristic strength

When you order M25 concrete, the characteristic strength fck = 25 MPa means that no more than 5% of test results should fall below 25 MPa. Since concrete strength varies from batch to batch (due to variations in materials, mixing, curing), the mix must be designed for a target mean strength that is higher than fck — high enough that even with normal variability, 95% of results stay above fck. The margin depends on the quality control: better control (lower standard deviation) means a smaller margin is needed.

The role of water-cement ratio

Water-cement (w/c) ratio is the single most important factor controlling concrete strength. Abrams' law states that strength is inversely related to w/c ratio — lower w/c gives higher strength. But too little water makes the concrete unworkable (hard to place and compact). Mix design balances these two competing requirements: low enough w/c for strength and durability, with enough water for the required slump.

What determines workability?

Workability (measured by slump) depends on water content, aggregate shape and grading, use of admixtures, and cement content. IS 10262 provides water content estimates for different maximum aggregate sizes and slump ranges. Superplasticizers can reduce water by 15-30% while maintaining the same slump — this is how high-strength concrete (M40+) achieves low w/c without becoming unworkable.

3. IS Code Background

Code	Subject	What it covers
IS 10262:2019	Concrete mix proportioning	Step-by-step method: target strength, w/c selection, water content, cement content, aggregate proportions. Covers M10 to M100.
IS 456:2000	Structural concrete	Table 5: max w/c and min cement for durability. Table 2: exposure conditions. Cl 8: concrete grades.
IS 383:2016	Aggregates	Grading requirements for fine and coarse aggregates. Zones I–IV for sand grading.
IS 9103	Admixtures	Chemical admixtures — superplasticizers, retarders, accelerators.

4. Key Formulas

Target Mean Strength (IS 10262 Cl 4.2)

f'ck = fck + 1.65 × s

f'ck = target mean compressive strength at 28 days (MPa)
fck = characteristic compressive strength (grade of concrete)
s = standard deviation of test results (MPa)
1.65 = statistical factor for 5% failure probability (one-tailed, 95% confidence)
If no prior data: s = 4.0 (M10-M15), 5.0 (M20-M25), 5.0+ (higher grades per Table 1)

Water-Cement Ratio

Selected from graphs/tables in IS 10262 based on f'ck and cement type
Must not exceed maximum w/c from IS 456 Table 5 for durability:
Mild exposure: 0.55 | Moderate: 0.50 | Severe: 0.45 | Very severe: 0.45 | Extreme: 0.40

Cement Content

Cement = Water content / (w/c ratio)
Check against minimum cement from IS 456 Table 5:
Mild: 300 kg/m³ | Moderate: 300 | Severe: 320 | Very severe: 340 | Extreme: 360
Maximum cement: 450 kg/m³ (to limit shrinkage and heat)

Aggregate Volumes

V_total = 1 m³ = V_cement + V_water + V_CA + V_FA + V_air
V_cement = mass of cement / (specific gravity × 1000)
V_CA from IS 10262 Table 3 (based on max aggregate size and Zone of FA)
V_FA = 1 − V_cement − V_water − V_CA − V_air

5. Important Tables

Standard Deviation for Initial Mix Design (IS 10262 Table 1)

Concrete Grade	Standard Deviation s (MPa)
M10, M15	3.5
M20, M25	4.0
M30, M35, M40, M45, M50	5.0

Water Content for 25–50mm Slump (IS 10262 Table 2, extract)

Max Aggregate Size	Water (kg/m³)
10mm	208
20mm	186
40mm	165

For higher slump, add 3% water per 25mm increase in slump above 50mm.

Volume of Coarse Aggregate per m³ (IS 10262 Table 3, extract)

Max Agg Size	Zone I (coarsest sand)	Zone II	Zone III	Zone IV (finest sand)
10mm	0.50	0.48	0.46	0.44
20mm	0.66	0.64	0.62	0.60
40mm	0.75	0.73	0.71	0.69

6. Step-by-Step Design Procedure

Stipulations: Grade (fck), exposure condition, max nominal aggregate size, workability (slump), type of cement, admixture use.
Target strength: f'ck = fck + 1.65s.
Water-cement ratio: From IS 10262 graph for f'ck. Check ≤ max w/c from IS 456 Table 5.
Water content: From IS 10262 Table 2 for max aggregate size and required slump. Adjust for slump, admixture.
Cement content: Water ÷ (w/c). Check ≥ minimum from IS 456. Check ≤ 450 kg/m³.
Coarse aggregate volume: From Table 3 based on aggregate size and sand zone. Adjust ±10% for pump/non-pump.
Fine aggregate volume: Remaining after deducting cement, water, CA, and entrapped air from 1 m³.
Convert volumes to masses using specific gravities of materials.
Trial batch: Make trial mixes, test slump and cube strength at 7 and 28 days.
Adjust: Modify water, w/c, or proportions based on trial results.

7. Worked Examples

Example 1 — M25 Mix Design (Beginner)

Design M25 concrete. Moderate exposure. OPC 43 grade. 20mm aggregate. Zone II sand. Slump 75mm. Sp. gravity: cement 3.15, FA 2.65, CA 2.68.

Step 1 — Target Strength

f'ck = 25 + 1.65 × 4.0 = 25 + 6.6 = 31.6 MPa

Step 2 — W/C Ratio

From IS 10262 graph for OPC 43, f'ck = 31.6 → w/c ≈ 0.50
IS 456 max for moderate exposure = 0.50 → ✅ Use 0.50

Step 3 — Water Content

For 20mm aggregate, 25–50mm slump: 186 kg/m³
For 75mm slump: +3% per 25mm above 50mm = +3% → 186 × 1.03 = 191.6 ≈ 192 kg/m³

Step 4 — Cement Content

C = 192 / 0.50 = 384 kg/m³
Min for moderate exposure = 300 → 384 > 300 ✅
Max = 450 → 384 < 450 ✅

Step 5 — Aggregate Volumes

V_cement = 384/(3.15×1000) = 0.122 m³
V_water = 192/1000 = 0.192 m³
V_air = 0.02 (2% entrapped for 20mm)
V_CA = 0.64 (Table 3, 20mm, Zone II) → absolute vol = 0.64 × (1−0.122−0.192−0.02) = 0.64 × 0.666 = 0.426 m³
V_FA = 1 − 0.122 − 0.192 − 0.02 − 0.426 = 0.240 m³

Step 6 — Masses per m³

Cement = 384 kg
Water = 192 kg
FA = 0.240 × 2.65 × 1000 = 636 kg
CA = 0.426 × 2.68 × 1000 = 1142 kg
Total = 384 + 192 + 636 + 1142 = 2354 kg/m³

Example 2 — M30 with Superplasticizer (Intermediate)

Design M30. Severe exposure. OPC 53 grade. 20mm aggregate. Zone II sand. Slump 100mm. Superplasticizer reduces water by 20%.

Step 1 — Target

f'ck = 30 + 1.65 × 5.0 = 38.25 MPa

Step 2 — W/C

For f'ck = 38.25 with OPC 53: w/c ≈ 0.42
IS 456 max for severe = 0.45 → 0.42 < 0.45 ✅

Step 3 — Water

Base = 186 kg (20mm, 25-50mm slump)
Slump adjustment for 100mm: +6% → 197 kg
Superplasticizer −20%: 197 × 0.80 = 158 kg/m³

Step 4 — Cement

C = 158/0.42 = 376 kg/m³ > 320 (min for severe) ✅

Example 3 — M20 Nominal Check (Conceptual)

Compare the IS 10262 designed M20 mix with the traditional nominal mix 1:1.5:3 (by weight).

Nominal Mix 1:1.5:3

Assuming cement = 380 kg → FA = 570 kg → CA = 1140 kg
Water ≈ 190 kg → w/c = 190/380 = 0.50
Total = 2280 kg/m³

IS 10262 Design Mix for M20

f'ck = 20 + 1.65×4.0 = 26.6 MPa
w/c ≈ 0.55 (mild exposure max)
Water = 186 kg, Cement = 186/0.55 = 338 kg
This saves about 42 kg cement per m³ compared to nominal — a significant cost saving over a full building.

8. GATE MCQs

Q1. The target mean strength for M25 concrete with standard deviation 4 MPa is:

(a) 25 MPa
(b) 29 MPa
(c) 31.6 MPa
(d) 33 MPa

Answer: (c)
f'ck = 25 + 1.65 × 4 = 25 + 6.6 = 31.6 MPa.

Q2. The constant 1.65 in the target strength formula corresponds to:

(a) 10% probability of failure
(b) 5% probability of failure
(c) 1% probability of failure
(d) 50% probability of failure

Answer: (b)
1.65 is the z-value for 5% failure probability (one-tailed normal distribution, 95% confidence level).

Q3. Maximum w/c ratio for severe exposure as per IS 456 Table 5 is:

(a) 0.55
(b) 0.50
(c) 0.45
(d) 0.40

Answer: (c)
Severe = 0.45. Moderate = 0.50. Mild = 0.55. Very severe = 0.45. Extreme = 0.40.

Q4. As w/c ratio decreases, concrete strength:

(a) Decreases
(b) Increases
(c) Remains same
(d) First increases then decreases

Answer: (b)
Abrams' law: strength is inversely related to w/c ratio. Less water per unit cement → denser cement paste → higher strength.

Q5. Maximum cement content per m³ recommended by IS 456 to limit shrinkage is:

(a) 350 kg
(b) 400 kg
(c) 450 kg
(d) 500 kg

Answer: (c)
IS 456 Cl 8.2.4.2 limits maximum cement to 450 kg/m³ to avoid excessive shrinkage and heat of hydration.

Q6. Entrapped air content assumed for 20mm max aggregate size is approximately:

(a) 0.5%
(b) 1.0%
(c) 2.0%
(d) 3.0%

Answer: (c)
IS 10262 assumes entrapped air of about 2% for 20mm aggregate, 1.5% for 40mm, and 3% for 10mm.

Q7. A superplasticizer reduces water content by approximately:

(a) 5–10%
(b) 15–30%
(c) 40–50%
(d) 1–3%

Answer: (b)
Superplasticizers (high-range water reducers) typically reduce water by 15–30% while maintaining the same workability.

Q8. Zone I sand compared to Zone IV sand is:

(a) Finer
(b) Coarser
(c) Same grading
(d) Has more silt

Answer: (b)
Zone I = coarsest sand, Zone IV = finest. Coarser sand requires more coarse aggregate volume (from Table 3).

Q9. The minimum cement content for moderate exposure is:

(a) 220 kg/m³
(b) 300 kg/m³
(c) 340 kg/m³
(d) 360 kg/m³

Answer: (b)
IS 456 Table 5: Mild = 300, Moderate = 300, Severe = 320, Very severe = 340, Extreme = 360 kg/m³.

Q10. If the calculated cement content is less than the minimum from IS 456, you should:

(a) Use the calculated value anyway
(b) Increase cement to the minimum
(c) Increase w/c ratio
(d) Reduce aggregate

Answer: (b)
Always use at least the minimum cement for the exposure condition. The minimum exists for durability, not strength — reducing it would compromise long-term performance.

9. Common Mistakes

Mistake 1: Confusing characteristic strength (fck) with target strength (f'ck). The mix is designed for f'ck = fck + 1.65s, not fck. Using fck directly means 50% of cubes will fail.

Mistake 2: Not checking w/c against IS 456 durability limits. Even if the strength requirement allows w/c = 0.55, severe exposure limits it to 0.45. Durability governs over strength.

Mistake 3: Ignoring water content adjustment for slump. The base water content from Table 2 is for 25–50mm slump. Higher slumps need more water — but it's better to use admixtures than extra water.

Mistake 4: Not accounting for aggregate moisture. Field aggregates have surface moisture (add extra weight) or absorbed moisture (subtract water from mix). Ignoring this changes the actual w/c ratio significantly.

10. Quick Revision Summary

Memorise:

f'ck = fck + 1.65s (1.65 = 5% failure probability)
s values: 3.5 (M10-15), 4.0 (M20-25), 5.0 (M30-50)
Max w/c (IS 456): Mild 0.55, Moderate 0.50, Severe 0.45, Extreme 0.40
Min cement (IS 456): 300 (Mild/Moderate), 320 (Severe), 340 (VS), 360 (Extreme)
Max cement = 450 kg/m³
Cement = Water / (w/c ratio)
Entrapped air: ~1.5% (40mm), ~2% (20mm), ~3% (10mm)
Sand zones: I = coarsest, IV = finest
Superplasticizer: reduces water by 15–30%

Design concrete mixes automatically

StructLearn Pro generates IS 10262 compliant mix designs for any grade — from M20 to M60 — with automatic durability checks per IS 456.

Start Free →