IS 10262:2009 vs 2019 — What Changed
IS 10262:2019 is the current revision and supersedes the 2009 edition. The good news for anyone who learned the 2009 method: the overall procedure is unchanged, and for the most common case (20 mm angular aggregate) the two editions give practically the same answer. The calculator defaults to 2019 and keeps 2009 as a legacy option.
What stayed the same
The backbone of the method did not change. Both editions use the same target-mean-strength formula (f′ck = fck + 1.65s), the same "adopt the lower of the strength-based and IS 456 durability-based water-cement ratio" rule, and the same absolute-volume approach to split the mix into cement, water, admixture and aggregate. The assumed standard-deviation values are identical (3.5 for M10–M15, 4.0 for M20–M25, 5.0 for M30 upward), and the base water content is the same in both: 208, 186 and 165 kg/m³ for 10, 20 and 40 mm aggregate.
What actually changed
1. Coarse aggregate proportion table
The table giving the volume of coarse aggregate per unit volume of total aggregate (Table 3 in 2009, Table 5 in 2019) changed for the smaller size. For 20 mm aggregate the values are identical in both editions. For 10 mm aggregate the 2019 values are higher by 0.04 across all sand zones; for 40 mm the top two zones dropped slightly.
| Nominal size / Zone | 2009 | 2019 |
|---|---|---|
| 10 mm, Zone I | 0.44 | 0.48 |
| 10 mm, Zone II | 0.46 | 0.50 |
| 20 mm, Zone I | 0.60 | 0.60 |
| 20 mm, Zone II | 0.62 | 0.62 |
| 40 mm, Zone IV | 0.75 | 0.73 |
The adjustment rule is unchanged: the value is for w/c 0.50 and moves by 0.01 for every 0.05 change in w/c.
2. Aggregate shape water adjustment
The reduction in water for less-angular aggregate was revised. Angular and sub-angular are unchanged; gravel and rounded gravel need slightly less reduction in 2019.
| Aggregate shape | 2009 | 2019 |
|---|---|---|
| Angular (crushed) | 0 | 0 |
| Sub-angular | −10 kg | −10 kg |
| Gravel with some crushed particles | −20 kg | −15 kg |
| Rounded gravel | −25 kg | −20 kg |
3. Entrapped air
The 2019 edition explicitly subtracts entrapped air (about 1.5%, 1.0% and 0.8% of concrete volume for 10, 20 and 40 mm aggregate) when working out the aggregate volume. Our 2009 legacy mode leaves this out, matching how the 2009 worked example is usually presented. In practice this trims the aggregate by roughly 1%.
4. Reference slump wording
The base water content is quoted for a 50 mm reference slump in 2019 (a "25–50 mm" range in 2009). The ±3% per 25 mm slump adjustment is the same in both.
Does it change my mix?
For the most common design — 20 mm angular aggregate — the coarse aggregate table and the shape adjustment are identical, so the two editions agree closely; 2019 gives about 1% less aggregate because it accounts for entrapped air. The differences become visible mainly when you use 10 mm aggregate, or gravel/rounded aggregate. You can switch the "Standard" field in the calculator between 2019 and 2009 and watch the numbers move for yourself.
Frequently asked questions
Which edition should I use?
Use IS 10262:2019 — it is the current standard. The 2009 mode is provided for reference, for comparing against older mix designs, or where a project specifically calls for it.
Is the 2009 method wrong now?
Not conceptually — the procedure is the same. 2019 simply refined a few table values and made the entrapped-air step explicit. Either way, IS 10262 requires trial batches before use.