Concrete Mix Design as per IS 10262: A Step-by-Step Method
Overall, concrete mix design is the process of calculating exact proportions of cement, water, sand and coarse aggregate. In turn, the goal is concrete that hits a specified strength, workability and durability. Notably, this follows IS 10262:2019 in India, the current Bureau of Indian Standards code, replacing the 2009 edition. So, get it wrong, and a structure either costs too much, or falls short of its design strength.
Key Takeaways
- In fact, IS 10262:2019 is the Second Revision and the current standard for concrete mix design in India. It replaced IS 10262:2009 and the 1982 code.
- First, target mean strength equals the characteristic strength, fck, plus 1.65 times the assumed standard deviation for that grade.
- Also, design mix is mandatory for M25 and above under IS 456:2000, Clause 9.2, though nominal mix is still permitted for M20 and below.
- The 2019 revision also added proportioning procedures for high strength concrete up to M100, self-compacting concrete and mass concrete.
- Finally, a trial mix must be cast and tested before any design goes to site, because paper calculations are a starting point, not a final answer.
What Is Concrete Mix Design?
In short, concrete mix design is a calculation. Also, it uses tested properties of the cement, sand, aggregate and water on hand. As a result, the output is quantities needed for a target strength, workability and durability. In other words, this replaces the fixed ratios of a nominal mix, such as 1:1.5:3 for M20. However, material properties change by source and season, so a design proven for one quarry’s aggregate does not transfer to another site. Therefore, testing materials at our concrete testing lab before finalising a mix is standard practice.
The IS 10262:2019 Procedure, Step by Step
Overall, IS 10262:2019 sets out six steps:
- Target mean strength. First, add 1.65 times the assumed standard deviation to the characteristic strength, fck, using the standard’s table value for that grade.
- Water-cement ratio. Next, choose the ratio from strength requirements or the durability table in IS 456:2000, whichever is more restrictive.
- Water content. Then, start from the base water content for 20 mm aggregate at 50 mm slump, 186 kg/m³, and adjust for slump, aggregate shape and any admixture.
- Cement content. Divide the water content by the water-cement ratio, then check against the exposure class’s minimum cement content.
- Aggregate proportioning. Next, fix coarse and fine aggregate volumes from the standard’s tables for zone and nominal size, then convert to mass using specific gravities.
- Trial mix and adjustment. Finally, cast a trial batch, check slump and cast cubes. Then adjust water, admixture dosage or aggregate proportion, and repeat until both targets are met.
Standard Deviation: The Number That Decides the Target
The standard deviation used in Step 1 is assumed, not measured, because a new site has no batch of 30 test results yet to calculate from.
Grade of Concrete. | Assumed Standard Deviation. |
M10, M15. | 3.5 N/mm². |
M20, M25. | 4.0 N/mm². |
M30 to M50. | 5.0 N/mm². |
M55 and above. | From site records of 30+ results, or 6.0 N/mm² where none exist. |
For M25 with good site control the deviation is 4 N/mm², so target mean strength works out to 25 plus 1.65 times 4, or 31.6 N/mm². The method is published by the Bureau of Indian Standards as IS 10262:2019.
SCC, PQC and UHPC: What IS 10262 Does and Does Not Cover
IS 10262:2019 covers self-compacting concrete mix design directly, but PQC and UHPC sit outside its scope.
Self-Compacting Concrete (SCC)
Self consolidating concrete mix design, also called SCC mix design, was added in the 2019 revision. Section 4 adjusts powder content, viscosity-modifying admixture dosage and the aggregate skeleton. As a result, concrete flows into place under its own weight rather than by vibration.
Pavement Quality Concrete (PQC)
By contrast, PQC mix design for roads follows IRC:15 and IRC:44 instead, because pavement concrete is accepted on flexural strength, not compressive strength.
Ultra-High-Performance Concrete (UHPC)
Similarly, UHPC mix design sits outside IS 10262:2019, since it typically exceeds 150 N/mm², beyond the standard’s M100 ceiling. Such mixes are usually developed through project-specific procedures instead; the Indian Concrete Institute publishes separate guidance for this strength range.
Common Site Mistakes
Overall, the most common failure is a mismatch: teams apply a mix design without confirming materials match the design’s assumptions.
- Aggregate moisture not adjusted. Free water content shifts with moisture, changing both workability and strength. So, test moisture each batch, and correct the added water against results from an aggregate testing lab.
- Cement or fly ash source changed mid-project. Because a new source shifts fineness and water demand, re-verify the cement before continuing.
- Mixing water not checked. Dissolved salts or organic matter in water weaken concrete, regardless of the design. That is why IS 456:2000 sets limits on mixing water quality.
- Trial mix skipped under time pressure. However, paper numbers assume ideal batching, so only a cast trial cube confirms real strength on site.
Get Your Concrete Mix Design Tested at Jancy Labs
Jancy Labs Private Limited is an accredited civil material testing laboratory (ISO/IEC 17025:2017, Certificate No. TC-12176) in Madurai, Tamil Nadu. We collect samples across Tamil Nadu and accept courier samples from anywhere in India.
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Frequently Asked Questions
What is concrete mix design?
Concrete mix design is the calculation of exact proportions of cement, water, sand and coarse aggregate. It also produces concrete that meets a required strength, workability and durability. Importantly, this is based on tests of the materials, not fixed ratios.
What is the current standard for concrete mix design in India?
IS 10262:2019 is current. Notably, it is the second revision, replacing IS 10262:2009 and the 1982 edition. It now also covers ordinary, standard and high-strength grades up to M100, plus SCC and mass concrete.
How is target mean strength calculated under IS 10262:2019?
Target mean strength equals the characteristic strength, fck, plus 1.65 times the assumed standard deviation for that grade, taken from the standard's table.
Is a design mix mandatory for every grade of concrete?
IS 456:2000 makes a design mix mandatory only for M25 and above. However, a nominal mix with fixed ratios is permitted for M20 and below. So, talk to our concrete testing lab if unsure which route applies.
Does IS 10262 cover mix design for roads or UHPC?
Not directly. Pavement concrete is designed to a flexural strength target under IRC:15 and IRC:44. Meanwhile, UHPC above 150 N/mm2 falls outside IS 10262:2019's M100 ceiling.