by M60 concrete is a high-strength design-mix concrete with a specified characteristic compressive strength of 60 MPa at 28 days. When GGBS is used with OPC cement, the mix must be designed using the water-to-binder ratio rather than treating GGBS as ordinary cement.
This article presents an illustrative M60 concrete mix design using OPC 53-grade cement, GGBS, crushed stone sand, 20 mm and 12.5 mm coarse aggregates and a superplasticizer.
The adopted binder system contains:
- OPC 53-grade cement = 390 kg/m³
- GGBS = 150 kg/m³
- Total cementitious binder = 540 kg/m³
- GGBS replacement level = 27.8% by mass of total binder
The design is based on the absolute-volume method described in IS 10262:2019. The final mix must be confirmed through laboratory trials, workability testing, cube testing and project approval.
Page Contents
1. Design Stipulations
| Property | Adopted value |
|---|---|
| Grade of concrete | M60 |
| Characteristic compressive strength at 28 days | 60 MPa |
| Cement | OPC 53 grade |
| Supplementary cementitious material | GGBS |
| Maximum nominal aggregate size | 20 mm |
| Fine aggregate | Crushed stone sand, assumed Zone II |
| Exposure condition | Moderate exposure for RCC |
| Target slump | 150 mm |
| Method of placement | Pumping or bucket placement |
| Degree of supervision | Good |
| Type of coarse aggregate | Crushed angular aggregate |
| Chemical admixture | Superplasticizer conforming to IS 9103 |
| Entrapped air | 1% |
| Basis of calculation | Saturated surface dry aggregate condition |
The target slump of 150 mm is used for this worked example. The actual slump requirement must be finalized according to reinforcement congestion, placing method, pumping distance, temperature and project specifications.
2. Applicable Standards
The following standards should be referred to along with the latest applicable amendments:
- IS 10262:2019 — Concrete Mix Proportioning — Guidelines
- IS 456:2000 — Plain and Reinforced Concrete — Code of Practice
- IS 383:2016 — Coarse and Fine Aggregate for Concrete
- IS 269 — Ordinary Portland Cement
- IS 9103 — Concrete Admixtures
- IS 1199 — Methods of Sampling and Analysis of Concrete
- IS 516 — Methods of Tests for Strength of Concrete
- Applicable standard or approved specification for GGBS
Always verify the latest revisions, amendments, project specifications and local requirements before final approval.
3. Material Properties
The following material properties are assumed for this preliminary calculation.
| Material | Specific gravity | Water absorption |
|---|---|---|
| OPC 53-grade cement | 3.15 | Not applicable |
| GGBS | 2.91 | Not applicable |
| Superplasticizer | 1.096 | Not applicable |
| 20 mm coarse aggregate | 2.66 | 0.29% |
| 12.5 mm coarse aggregate | 2.64 | 0.36% |
| Crushed stone sand | 2.59 | 2.88% |
| Water | 1.00 | Not applicable |
Coarse aggregate blend
The coarse aggregate blend is assumed as follows:
- 20 mm aggregate = 10%
- 12.5 mm aggregate = 90%
Weighted specific gravity of coarse aggregate:
Weighted specific gravity:
= (0.10 × 2.66) + (0.90 × 2.64)
= 2.642
The weighted absorption of the coarse aggregate blend is approximately 0.35%.
The actual specific gravity, absorption, moisture content and grading must be determined from laboratory tests before finalizing the mix.
4. Target Mean Strength
The characteristic strength of M60 concrete is:
fck = 60 MPa
For good quality control, the assumed standard deviation is:
s = 5 MPa
Target mean strength using the standard-deviation method:
Target mean strength = fck + 1.65s
= 60 + (1.65 × 5)
= 68.25 MPa
The second requirement is:
Target mean strength = fck + X
For M30 to M60 grades:
X = 6.5 MPa
Therefore:
Target mean strength = 60 + 6.5
= 66.5 MPa
The higher value is adopted:
Target mean strength = 68.25 MPa
A value of 73 MPa should not be used as a general target mean strength for M60 concrete unless it is specifically required by an approved project design basis.
5. Selection of Binder System
The total cementitious binder is adopted as:
Total binder = 540 kg/m³
The binder is divided as follows:
| Binder material | Quantity | Percentage of total binder |
|---|---|---|
| OPC 53-grade cement | 390 kg/m³ | 72.2% |
| GGBS | 150 kg/m³ | 27.8% |
| Total binder | 540 kg/m³ | 100% |
GGBS replacement percentage:
= 150 ÷ 540 × 100
= 27.8%
The selected GGBS percentage is a preliminary trial value. It is not a universal requirement for M60 concrete.
GGBS generally affects early-age strength development, heat of hydration, setting time, slump retention and curing requirements. The final replacement percentage must be established through trials using the actual cement and GGBS proposed for the project.
6. Selection of Water-to-Binder Ratio
Since both OPC and GGBS are used, the relevant ratio is the water-to-binder ratio:
Water-to-binder ratio = Free water ÷ Total cementitious binder
For this preliminary design, the adopted water-to-binder ratio is approximately:
W/B = 0.328
The selected value is below the assumed maximum ratio for the chosen exposure condition. The final ratio must satisfy both strength and durability requirements and must be confirmed by trial testing.
The terms water-to-binder ratio and water-cement ratio should not be used interchangeably in a GGBS mix.
7. Estimation of Water Content
For 20 mm nominal maximum size aggregate and 50 mm slump, the starting water content is taken as:
Water content at 50 mm slump = 186 kg/m³
Required target slump = 150 mm
Increase in slump:
150 − 50 = 100 mm
Number of 25 mm increments:
100 ÷ 25 = 4 increments
Assuming a 3% increase in water for every 25 mm increase in slump:
Water content at 150 mm slump:
= 186 × [1 + (4 × 0.03)]
= 186 × 1.12
= 208.32 kg/m³
For this illustrative GGBS trial, a 15% water reduction is assumed through the use of a superplasticizer.
Water after admixture reduction:
= 208.32 × (1 − 0.15)
= 177.07 kg/m³
Adopted free water:
Free water = 177.1 kg/m³
The 15% reduction is only a trial assumption. Actual water reduction depends on cement-GGBS-admixture compatibility, aggregate grading, temperature, mixing time and dosage.
8. Superplasticizer Quantity
The superplasticizer dosage is assumed as 0.67% by mass of total binder.
Superplasticizer quantity:
= 0.67% × 540
= 3.62 kg/m³
Adopted superplasticizer quantity:
Superplasticizer = 3.62 kg/m³
The actual dosage must be finalized through compatibility and trial-mix testing. Excessive dosage may cause segregation, excessive slump, delayed setting or other concrete-performance problems.
9. Absolute Volume Calculation
The calculation is based on 1 m³ of concrete and saturated surface dry aggregate condition.
Volume of OPC cement
Volume of OPC:
= 390 ÷ (3.15 × 1000)
= 0.1238 m³
Volume of GGBS
Volume of GGBS:
= 150 ÷ (2.91 × 1000)
= 0.0515 m³
Volume of water
Volume of water:
= 177.07 ÷ (1.00 × 1000)
= 0.1771 m³
Volume of superplasticizer
Volume of superplasticizer:
= 3.62 ÷ (1.096 × 1000)
= 0.0033 m³
Volume of entrapped air
For 20 mm aggregate in non-air-entrained concrete:
Entrapped air = 1%
Volume of air:
= 1 ÷ 100
= 0.0100 m³
Volume of aggregate
Volume of aggregate:
= 1 − (Volume of OPC + Volume of GGBS + Volume of water + Volume of admixture + Volume of air)
= 1 − (0.1238 + 0.0515 + 0.1771 + 0.0033 + 0.0100)
= 0.6343 m³
Therefore:
Total aggregate volume = 0.6343 m³
The entrapped-air volume must be included in the absolute-volume calculation. Omitting it overestimates the available aggregate volume.
10. Proportion of Coarse and Fine Aggregate
For 20 mm aggregate and Zone II sand, the volume of coarse aggregate per unit volume of total aggregate at a water-to-binder ratio of 0.50 is taken as:
Coarse aggregate fraction at W/B 0.50 = 0.62
The adopted water-to-binder ratio is approximately 0.328.
Reduction from 0.50:
0.50 − 0.328 = 0.172
Increase in coarse aggregate fraction:
= (0.172 ÷ 0.05) × 0.01
= 0.034
Corrected coarse aggregate fraction:
= 0.62 + 0.034
= 0.654
For this preliminary pumping trial, the coarse aggregate fraction is adopted as:
Coarse aggregate fraction = 0.55
The selected value is lower than the calculated value to provide additional paste and fine aggregate for pumpability. It is a preliminary trial value and is not a fixed code requirement.
Fine aggregate fraction:
= 1 − 0.55
= 0.45
Fine aggregate fraction = 0.45
The final aggregate fractions must be confirmed through slump, segregation, pumpability, density and strength trials.
11. Calculation of Coarse Aggregate
Total coarse aggregate
Total coarse aggregate:
= Volume of aggregate × Coarse aggregate fraction × Specific gravity × 1000
= 0.6343 × 0.55 × 2.642 × 1000
= 921.7 kg/m³
Adopt:
Total coarse aggregate = 922 kg/m³
20 mm aggregate
20 mm aggregate:
= 922 × 0.10
= 92.2 kg/m³
Adopt:
20 mm aggregate = 92 kg/m³
12.5 mm aggregate
12.5 mm aggregate:
= 922 × 0.90
= 829.8 kg/m³
Adopt:
12.5 mm aggregate = 830 kg/m³
12. Calculation of Fine Aggregate
Fine aggregate:
= Volume of aggregate × Fine aggregate fraction × Specific gravity × 1000
= 0.6343 × 0.45 × 2.59 × 1000
= 739.2 kg/m³
Adopt:
Crushed stone sand = 739 kg/m³
13. Preliminary M60 OPC-GGBS Mix Proportion
The following quantities are based on saturated surface dry aggregate condition.
| Ingredient | Quantity per m³ |
|---|---|
| OPC 53-grade cement | 390 kg |
| GGBS | 150 kg |
| Total cementitious binder | 540 kg |
| Free water | 177.1 litres |
| Crushed stone sand | 739 kg |
| 20 mm coarse aggregate | 92 kg |
| 12.5 mm coarse aggregate | 830 kg |
| Total coarse aggregate | 922 kg |
| Superplasticizer | 3.62 kg |
| Water-to-binder ratio | 0.328 |
| Target slump | 150 mm |
| Approximate fresh density | 2382 kg/m³ |
Binder and aggregate relationship
Total binder : Fine aggregate : Coarse aggregate
= 540 : 739 : 922
= 1 : 1.37 : 1.71
This is only a calculated mass relationship. It must not be used for volume batching or as a replacement for an approved design mix.
14. 50-Litre Trial Batch
For a 50-litre trial batch:
50 litres = 0.05 m³
| Ingredient | Quantity for 50 litres |
|---|---|
| OPC 53-grade cement | 19.5 kg |
| GGBS | 7.5 kg |
| Total binder | 27.0 kg |
| Water before moisture correction | 8.85 litres |
| Crushed stone sand | 37.0 kg |
| 20 mm aggregate | 4.6 kg |
| 12.5 mm aggregate | 41.5 kg |
| Total coarse aggregate | 46.1 kg |
| Superplasticizer | 0.18 kg |
The trial batch should be prepared using calibrated weighing equipment. Aggregate moisture corrections must be applied before adding water.
15. Illustrative Moisture Correction
The mix quantities above are based on saturated surface dry aggregate condition.
Assumed field conditions:
- Fine aggregate moisture = 4.0%
- Fine aggregate absorption = 2.88%
- Coarse aggregate moisture = 1.0%
- Coarse aggregate absorption = 0.35%
Fine aggregate correction
SSD fine aggregate:
= 739.2 kg
Approximate oven-dry fine aggregate:
= 739.2 ÷ 1.0288
= 718.6 kg
Wet fine aggregate to be batched:
= 718.6 × 1.04
= 747.3 kg
Free water contributed by fine aggregate:
= 747.3 − 739.2
= 8.0 kg
Coarse aggregate correction
SSD coarse aggregate:
= 921.7 kg
Approximate oven-dry coarse aggregate:
= 921.7 ÷ 1.0035
= 918.4 kg
Wet coarse aggregate to be batched:
= 918.4 × 1.01
= 927.6 kg
Free water contributed by coarse aggregate:
= 927.6 − 921.7
= 5.9 kg
Total free water contributed by aggregates:
= 8.0 + 5.9
= 13.9 kg approximately
Approximate water to be added to the mixer:
= 177.1 − 14.0
= 163.1 litres approximately
This is only an example. Actual moisture content must be measured immediately before batching and recalculated for each production shift.
16. GGBS-Specific Technical Considerations
Early-age strength
GGBS may reduce early-age strength development compared with an OPC-only mix, depending on its fineness, activity, curing temperature and replacement percentage.
Curing
Adequate moist curing is particularly important for GGBS concrete. Poor curing may reduce the expected strength and durability benefits.
Slump retention
GGBS may influence slump retention and setting behaviour. The actual performance must be checked with the selected superplasticizer.
Heat of hydration
GGBS can reduce heat development compared with an equivalent OPC-rich binder system. This benefit must be evaluated together with strength-development requirements.
GGBS replacement level
The adopted 27.8% replacement is a preliminary value. It should not be treated as a universal percentage for all M60 concrete.
Cement-content limit
Code checks for this illustrative binder system: OPC cement = 390 kg/m³, which is below the 450 kg/m³ limit applicable to cement content excluding mineral admixtures. GGBS = 150 ÷ 540 × 100 = 27.8% of total cementitious material, which is below the 50% limit when GGBS alone is used as a mineral admixture.
The total binder content of 540 kg/m³ is a preliminary trial value, not a code-prescribed minimum or universal maximum. The final binder content must be confirmed through trial mixes and checked against the latest applicable IS 456 amendments, GGBS requirements and project specifications.
17. Trial Mix and Quality-Control Checks
Before using this mix for structural concrete, conduct trial batches using the actual cement, GGBS, aggregates, water and admixture proposed for the project.
Check the following properties:
- Slump immediately after mixing
- Slump retention during the placing period
- Concrete temperature
- Segregation and bleeding
- Pumpability
- Density and yield
- Admixture compatibility
- Initial and final setting behaviour
- 7-day compressive strength, where required
- 28-day compressive strength
- Cube failure pattern
- Laboratory and batching records
- Curing performance
Do not add uncontrolled water at the site to increase slump. Additional water increases the water-to-binder ratio and may reduce strength and durability.
18. Difference Between OPC-Only and OPC-GGBS M60 Mixes
The OPC-only M60 article uses cement as the only cementitious material.
This article uses:
- OPC 53-grade cement
- GGBS
- Water-to-binder ratio
- GGBS replacement percentage
- GGBS-specific curing and strength considerations
The two designs must not be combined. Their water demand, binder volumes, aggregate quantities, admixture dosage and strength development are different.
Read the separate OPC-only article here:
M60 Concrete Mix Design with OPC Cement as per IS 10262:2019
19. Frequently Asked Questions
What is the target mean strength for M60 concrete?
For the assumptions used in this example, the target mean strength is 68.25 MPa.
What is the GGBS replacement percentage in this mix?
GGBS is 150 kg/m³ out of a total binder content of 540 kg/m³.
GGBS replacement percentage:
= 150 ÷ 540 × 100
= 27.8%
Is the water-cement ratio 0.33 in this mix?
The correct term is water-to-binder ratio because GGBS is included.
The calculated water-to-binder ratio is approximately 0.328.
Is 400 kg/m³ the minimum cement content?
No. The selected OPC quantity is 390 kg/m³ and the total cementitious binder is 540 kg/m³. Minimum cement or binder requirements depend on the exposure condition, applicable standards and project specifications.
Can the same quantities be used with another GGBS source?
No. GGBS fineness, activity, specific gravity, chemical composition and compatibility may vary. A new trial mix is required.
Can this mix be used directly at the construction site?
No. It is a preliminary educational calculation. The final mix requires laboratory and field verification using actual project materials.
Can additional water be added at the site?
Uncontrolled water addition should not be permitted because it increases the water-to-binder ratio. Use an approved admixture adjustment or redesign the mix.
Does GGBS reduce early strength?
It may reduce early-age strength compared with an OPC-only system, depending on the materials, replacement level, temperature and curing. Trial testing is essential.
Conclusion
The preliminary M60 OPC-GGBS concrete mix obtained from this calculation is:
- OPC 53-grade cement = 390 kg/m³
- GGBS = 150 kg/m³
- Total cementitious binder = 540 kg/m³
- Free water = 177.1 litres/m³
- Crushed stone sand = 739 kg/m³
- 20 mm aggregate = 92 kg/m³
- 12.5 mm aggregate = 830 kg/m³
- Superplasticizer = 3.62 kg/m³
- Water-to-binder ratio = 0.328
- Target slump = 150 mm
- GGBS replacement = 27.8%
These quantities are based on assumed material properties and saturated surface dry conditions. The mix must be verified through trial batches, moisture correction, workability testing, curing checks and compressive-strength testing before construction use.
Related Concrete Mix-Design Resources
- Concrete Mix Design
- Concrete Mix Design Calculator as per IS 10262:2019
- Target Mean Strength of Concrete
- Water Content in Concrete Mix Design
- Superplasticizer in Concrete Mix Design
- Moisture Correction in Concrete Mix Design
- Concrete Trial Mix Procedure
- M60 Concrete Mix Design with OPC Cement
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The information on this website is provided for educational purposes only. It does not replace project-specific engineering design, professional advice, approved drawings or construction specifications. Examples, calculations and suggested procedures should not be adopted directly for construction without appropriate verification. Always check the latest applicable standards, amendments, local requirements, project specifications, material-test results and site conditions. Final design, testing, acceptance and construction decisions should be made by qualified professionals and responsible authorities.
