Concrete Mix Design Calculator (IS 10262:2019)

About the Concrete Mix Design Calculator (IS 10262:2019)

Work out a trial mix for design-mix concrete the way IS 10262:2019 sets it out for ordinary and standard grades (M10 to M60). The calculator takes the target mean strength from the standard deviation or factor X, caps your free water–cement ratio at the IS 456 Table 5 limit, picks the water from Table 4 and adjusts it for aggregate shape, slump and admixture, works out the cement (with optional fly ash or GGBS), sets the coarse-aggregate volume from Table 5 and finishes with the absolute-volume method and a moisture correction.

Every step is shown with its clause, table and numbers, so you can check it against a hand calculation or the standard's worked examples. The defaults are the M40 example of IS 10262 Annex A. The result is a starting point for trial batches — the standard requires trial mixes before a mix is adopted.

The IS 10262 procedure, step by step

• Target strength (cl. 4.2): f′ck = fck + 1.65 S or fck + X, whichever is higher. Without 30 or more test results, S comes from Table 2 (3.5 for M10–M15, 4.0 for M20–M25, 5.0 for M30–M60; add 1 N/mm² for fair site control). X is 5.0, 5.5 and 6.5 for the same groups (Table 1).
• Water–cement ratio (cl. 5.1): read from Fig. 1 for the target strength and the cement's 28-day strength, then checked against IS 456 Table 5; the lower value is adopted.
• Air (cl. 5.2, Table 3): 1.5, 1.0 and 0.8 % for 10, 20 and 40 mm aggregate.
• Water (cl. 5.3, Table 4): 208, 186 and 165 kg/m³ for 10, 20 and 40 mm angular aggregate at 50 mm slump; less about 10 kg for sub-angular aggregate, 15 kg for gravel with some crushed particles and 20 kg for rounded gravel; about 3 % more for every 25 mm of extra slump (or less for lower slump); less the admixture's water reduction (about 5–10 % for water reducers, 20–30 % and more for superplasticisers).
• Cement (cl. 5.4): water ÷ w/c, but at least the IS 456 minimum. With fly ash of 20 % or more the cementitious content may be raised, for example by 10 % for a first trial, and the w/cm recalculated.
• Coarse aggregate (cl. 5.5, Table 5): the volume fraction for w/c 0.50 by aggregate size and sand zone, plus 0.01 for every 0.05 lower w/c (minus for higher), less up to 10 % for pumped or congested work.
• Absolute volumes (cl. 5.7): aggregate volume = 1 − air − (cement ÷ 1000 SGc + water ÷ 1000 + admixture ÷ 1000 SGa + mineral admixture ÷ 1000 SGm). Coarse = aggregate volume × coarse fraction × SG × 1000, and the same for fine aggregate with the rest.

Table 5 coarse-aggregate volumes (w/c 0.50)

• 10 mm: Zone IV 0.54 · Zone III 0.52 · Zone II 0.50 · Zone I 0.48
• 20 mm: Zone IV 0.66 · Zone III 0.64 · Zone II 0.62 · Zone I 0.60
• 40 mm: Zone IV 0.73 · Zone III 0.72 · Zone II 0.71 · Zone I 0.69

The volumes are for crushed (angular) aggregate in saturated surface-dry condition. Crushed or mixed sand usually needs less fine aggregate, so the coarse fraction may be increased. Zone IV sand should not be used in reinforced concrete unless tests show the mix is suitable.

IS 456 durability limits used for the checks

Table 5 (20 mm aggregate) gives the least cement content, the largest free w/c and the lowest grade:

• Reinforced: mild 300 kg/m³, 0.55, M20 · moderate 300, 0.50, M25 · severe 320, 0.45, M30 · very severe 340, 0.45, M35 · extreme 360, 0.40, M40
• Plain: mild 220, 0.60, no minimum grade · moderate 240, 0.60, M15 · severe 250, 0.50, M20 · very severe 260, 0.45, M20 · extreme 280, 0.40, M25

Table 6 adds 40 kg/m³ for 10 mm aggregate and takes off 30 kg/m³ for 40 mm. The cement content in Table 5 includes fly ash and GGBS. Cement — not counting fly ash and GGBS — above 450 kg/m³ needs special consideration of shrinkage, thermal cracking and alkali-silica reaction (cl. 8.2.4.2).

Moisture correction and batching

Table 4 water assumes aggregates in saturated surface-dry (SSD) condition. Free moisture = total moisture − water absorption. Each aggregate's batch mass is its SSD mass × (1 + free moisture), and the water to add is the design water minus the water that wet aggregate brings (or plus what dry aggregate will absorb). In Annex B, sand at 5 % moisture and 1 % absorption carries 4 % free water: 719 kg × 1.04 = 748 kg, bringing 29 kg of water.

The batch table scales the field quantities to your trial-batch volume, and the per-bag column gives the quantities for one 50 kg bag of cement.

Fine aggregate grading zones (IS 383 Table 9)

Percent passing for Zones I / II / III / IV: 10 mm 100 for all · 4.75 mm 90–100, 90–100, 90–100, 95–100 · 2.36 mm 60–95, 75–100, 85–100, 95–100 · 1.18 mm 30–70, 55–90, 75–100, 90–100 · 600 µm 15–34, 35–59, 60–79, 80–100 · 300 µm 5–20, 8–30, 12–40, 15–50 · 150 µm 0–10, 0–10, 0–10, 0–15 (up to 20 for crushed stone sand).

The 600 µm sieve decides the zone. Under cl. 6.3 another sieve may be outside the limits by up to 5 % (10 % in total), but not on the coarse limit of Zone I or the fine limit of Zone IV. The sieve-analysis helper applies these rules after rounding to whole percentages, as the standard's rounding rule requires.

Rounding and the worked examples

Like the examples in Annexes A–C, the calculator rounds the water to the nearest kilogram and the cement content up to the next kilogram (148 ÷ 0.36 = 411.11 → 412 kg), and keeps the selected w/c unless the cementitious content is changed on purpose. It carries the volumes at full precision; Annex A rounds them to three decimals and Annexes B and C round the coarse-aggregate fraction to two, so their aggregate masses can differ from the calculator's by 1 to 6 kg.

Sources

• IS 10262:2019, Concrete Mix Proportioning — Guidelines (second revision): cl. 4.2, 5.1–5.8, Tables 1–5, Fig. 1 and Annexes A–C — archive.org
• IS 456:2000, Plain and Reinforced Concrete — Code of Practice: cl. 8.2.4.2 and Tables 3, 5 and 6 — archive.org
• IS 383:2016, Coarse and Fine Aggregate for Concrete — Specification: cl. 6.3 and Table 9 — archive.org

Limitations

• You read the free w/c from IS 10262 Fig. 1 yourself; the calculator does not redraw the curves. If you know the strength–w/c relationship of your own materials, use that instead.
• M65 and above, self-compacting, air-entrained and mass concrete follow other sections and tables of IS 10262 and are not covered.
• Specific gravities, absorption and admixture effects must come from tests of your materials; the defaults are the values of the IS 10262 examples, not general properties.
• This is an estimate, not a professional design. IS 10262 cl. 5.8 requires trial mixes — check workability, then make mixes at the chosen w/c and about ±10 % before adopting proportions.

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