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← Back to Blog PILLAR · CONCRETE MATERIALS · 24 JUL 2026
Pillar · Concrete Materials

Concrete Materials
Field Handbook —
Cement, SCMs, Aggregates, Water.

A pillar on the four materials that decide every cube result before the admixture drop touches the mix. Indian cement grades, supplementary cementitious materials, aggregates and water — what each contributes, what each must not bring, and how the four interact under Indian conditions.

24 Jul 2026 | 22 min read | Last reviewed: 24 Jul 2026
MATERIALS TABLEAU IS 269 · IS 3812 · IS 383 · IS 456 CEMENTIS 269 FLY ASHIS 3812 AGGREGATE · IS 383 SAND · ZONE II WATERIS 456 Cl 5.4 FOUR INPUTS · ONE CONCRETE SYSTEM
Materials composition map — five constituents into one Concrete node Five labelled circles sit around a central Concrete circle. Each peripheral node is connected to the centre by a line. The cement node is filled in brand orange; the other four nodes (SCM, aggregate, water, admixture) are filled in design-system grays. Indian standards labels sit below each node name. MATERIALS COMPOSITION MAP five constituents combine to form concrete — cement highlighted in brand orange CONCRETE combined system CEMENT IS 269 / 8112 / 12269 SCM IS 3812 / 16714 / 15388 AGGREGATE IS 383 WATER IS 456 Cl 5.4 ADMIXTURE IS 9103 / 2645 Source: IS 269 · IS 3812 · IS 16714 · IS 15388 · IS 16354 · IS 383 · IS 456 Cl 5.4 · IS 9103 · IS 2645.
Concrete is a combined system of cement, SCM, aggregate, water and admixture — the cement node alone is brand orange to mark its weight in the reaction.

Think of a perfect cup of chai. The same kettle, the same fire, the same boil — but if the tea is stale, the milk is sour, the sugar is wet or the water is hard, the cup tastes different every time. Concrete works the same way. Cement sets the heat, water sets the recipe, sand and stone set the bulk, and the SCMs set the flavour. Change any one of the four and the cube result changes too. Four materials, one system.

1. Cement — the three Indian grades

Ordinary Portland Cement (OPC) is the binder. IS 269:2015 sets the three grades that dominate Indian practice — OPC 33 (plaster, masonry, low-rise), OPC 43 (general RCC, houses, low-rise commercial), and OPC 53 (high-rise, bridges, precast, HPC; higher early strength). The numbers are the minimum 28-day compressive strength in N/mm² (MPa) on a 1:3 cement-sand mortar, not a quality ranking. Apart from OPC, blended cements dominate part of the market — PPC (IS 1489 Part 1 with fly ash, IS 1489 Part 2 with calcined clay), PSC (IS 455 with GGBS), and composite cements. A higher-grade cement does not compensate for a poor mix design. Lower w/c and tighter curing earn higher strength; the grade only sets the upper-bound reactivity.

Two pressure cookers on the same stove: one small and heavy, the other large and light. The small one builds pressure in eight minutes; the large one needs twenty. Cement grade is the cooker size — it tells you how fast the cement reaches peak heat, not whether the concrete inside is better. A 53-grade cement on a slab mass-poured will release more heat in the first 24 hours than a 43-grade; mass-pour engineers often choose the lower grade for the slower, more even heat curve. Grade does not equal quality.

2. Supplementary cementitious materials — fly ash, GGBS, silica fume, metakaolin

SCMs are finely divided materials that react with the calcium hydroxide (CH) released by OPC hydration. The pozzolanic reaction adds C-S-H gel — the same strength-giving phase that OPC produces — but slower, contributing to long-term strength and a tighter pore structure.

Replacement ranges are not interchangeable across SCMs — IS 456 Cl 8.2.4.2 caps total mineral admixture content, not each SCM individually, so a blend that stacks fly ash and GGBS still has to clear the same combined ceiling as a single-SCM mix.

Fly ash (IS 3812) is the most-used SCM in India. Class F (low-calcium) is the default; Class C (high-calcium) is less common and more variable. GGBS (IS 16714) is a latent hydraulic, slower than OPC but stronger at 90 days. Silica fume (IS 15388) is very fine, very reactive, used in HPC and bridge applications. Metakaolin (IS 16354) is a calcined clay; reactive in the first 7 days, expensive. The detailed IS-clause reading and the blend-cap logic live in the companion article Supplementary Cementitious Materials in India; this pillar summarises the selection logic.

3. Aggregates — coarse, fine, and the grading that decides the water demand

Aggregate forms ~70–80% of the volume of normal-weight concrete. IS 383 sets the limits for graded coarse and fine aggregates from natural sources. The single most important test for sand is the grading envelope; for coarse aggregate, the single most important test is the combined grading of the design mix.

Indicative aggregate grading curves Three lines for 20 mm coarse, 10 mm coarse, and fine aggregate against IS 383 grading envelopes. Fine aggregate lying above the upper envelope raises water demand; below the lower envelope raises paste demand. Sieve size (mm, log scale, indicative) Cumulative passing (%) 0.15 0.30 0.60 1.18 2.36 4.75 10 20 Coarse 20 mm IS 383 envelope Fine aggregate (river sand) INDICATIVE — IS 383 ENVELOPES

Source: ConcreteInfo schematic; verify against IS 383 table limits for the applicable grading zone. Grading outside the envelope raises paste demand, water demand, or both; the cube cost is hidden in the fine-aggregate zone.

Coarse aggregate is normally 20 mm nominal, sometimes 10 mm or 12.5 mm for thin sections. Fine aggregate is graded into four IS 383 zones (I to IV); Zone II is the most common in Indian concrete. The fines modulus (sum of cumulative percentages retained on 150 µm to 4.75 mm sieves divided by 100) is a single number that summarises the gradation; a higher fines modulus means a coarser sand. A sand that crosses the fine-to-coarse boundary between pours can change the water demand by 5–10 L/m³ — enough to shift the mix from a 0.45 w/c to a 0.50 w/c without anybody touching the water bucket.

4. Water — IS 456 Cl 5.4, mixing and curing

Water serves two purposes in concrete: it triggers cement hydration at mixing, and it continues the hydration at the surface during curing. IS 456 Cl 5.4 sets the limits for both roles. The clumsiest failure is not unknown water — it is the silent creep of silt, chlorides or sulphates from a reused water tank.

Source: ConcreteInfo schematic; limits reproduced from IS 456 Cl 5.4 (verify against the current revision). Chloride and sulphate limits are stricter for RCC than for plain cement concrete; testing is yearly minimum, more often if the source is variable.

IS 456 Cl 5.4 lists the quantitative limits: pH not less than 6; chlorides ≤ 500 mg/L for RCC (≤ 2000 mg/L for plain cement concrete); sulphates ≤ 400 mg/L; suspended matter ≤ 2000 mg/L; organic ≤ 200 mg/L; initial setting time within ± 30 minutes of the control. Drinking water is normally acceptable without testing; well water, borehole water, tank water, and recycled process water must be tested at least once at source and thereafter in line with project specification. Curing water has the same chemistry limits as mixing water — curing with salty water leaves salt on the surface, accelerates carbonation and may compromise cover durability.

5. Admixtures — the fifth ingredient, drawn on top of the four

Admixtures are chemicals added in small quantities to modify the fresh or hardened behaviour of concrete. IS 9103 covers performance and uniformity for most chemical admixtures; IS 2645 covers integral waterproofing; IS 6932 covers accelerators. Plasticizers / superplasticizers (PCE) reduce water 5–30% at equal workability — the most common admixture in Indian concrete. Retarders / set-modifiers delay initial set for hot weather, long transit, or SCC. Accelerators reduce setting time for early strength, repair, or cold-weather work; calcium-chloride accelerators are restricted in RCC because they accelerate steel corrosion. Viscosity modifiers, air-entrainers, shrinkage reducers are used in SCC, freeze-thaw exposure, and large pour shrinkage control. The four materials are the substrate; the admixture is the last 1–2% of the mix that decides whether the substrate performs as designed.

Admixtures are the tools, not the recipe. A 0.45 w/c mix with no admixture is a 0.45 w/c mix; a 0.45 w/c mix with a 20% water-reducer is a 0.38 w/c mix with the same workability — and that moves the strength class.

6. How the four materials interact before the admixture drop

A mix design is not four independent inputs. Each input changes the answer the other three give. The interactions below are the ones that decide whether a mix design lands or fails.

The reading order on a batch ticket is: cement + SCM + water + admixture first (binder envelope), then aggregate (volume envelope), then the cubes are the receipt. A change in one input without re-running the trial mix is the most common reason a tested design mix fails in production. The interactions above are the trial-mix inclusion checklist; every change after the trial mix must be re-validated against the same checklist.

Field-checklist blocks

A site-side questionnaire, an inspector's checklist, and three worked examples that show how a material change moves through the design mix, the trial mix, the production batch, and the cube result.

Questionnaire — five questions to ask before the materials decision

  1. What is the approved cement grade and IS code, and is the supplier's test certificate current? Does the project permit a substitute grade, and is the substitution procedure documented?
  2. What is the SCM blend envelope (fly ash / GGBS / silica fume / metakaolin) per IS 456 Cl 8.2.4.2, and does the project's exposure class require stricter limits? Is the SCM source approved and the test certificate on file?
  3. Is the aggregate grading within IS 383 for the chosen zone, and is the fines modulus tracked pour-by-pour? Are the stockpile discipline and source-stability checks documented?
  4. Does the water source pass IS 456 Cl 5.4 for mixing AND curing, and is the test certificate within the validity window? Are chlorides, sulphates, silt and pH measured at the frequency the project specification requires?
  5. Which admixture IS code applies (IS 9103, IS 2645, IS 6932), and is the supplier's test certificate current? Has the cement source + admixture combination been validated in a trial mix within the last 6 months?

Inspector's checklist — five records or actions to verify

  1. Cement delivery log: each cement lot is logged with delivery date, supplier, IS code, grade, test certificate reference, and the silo or store it was loaded into; the FIFO rotation is followed; the supplier's test certificate is on file and current.
  2. SCM delivery log: each SCM lot is logged with the same metadata plus the IS code (IS 3812, IS 16714, IS 15388, IS 16354); the test certificate's LOI, residue, specific surface and activity index are checked against the approved specification.
  3. Aggregate grading log: grading tests are run at the frequency the project specification requires (typically each 100 m³ or each source change); the results are plotted against IS 383 envelope; out-of-envelope lots are quarantined and re-tested.
  4. Water test certificate: the source is logged; the IS 456 Cl 5.4 limits are checked; the test certificate is on file; the test is re-run at the frequency the project specification requires (typical: every 3 months, or every source change).
  5. Admixture delivery log: each admixture lot is logged with the supplier's test certificate; the concentration/activity is checked against the approved specification; the shelf-life is verified; the storage temperature is in the supplier's window.

What happens if… two worked examples

Example 1 — store substitutes OPC 53 for OPC 43 mid-pour without a re-trial

What happens. A site engineer specifying M30 for a coastal structure runs short of the approved OPC 43 lot. The store swaps in an OPC 53 bag to keep the pour moving, without telling the QA team or re-running a trial mix. The batch is placed against the original OPC 43 design mix.
Likely outcome. OPC 53 reaches peak heat faster and can shift water demand and workability at the same w/c, so the design mix's water content and admixture dose are no longer validated for the cement actually in the batch. The cube result may still pass, but the acceptance is against the wrong basis — the trial mix was never re-run for the grade that was actually used.
Preventive correction. Lock cement-grade substitution behind a documented sign-off; any grade change triggers a fresh trial mix before the next pour, not after the cube result comes back.

Example 2 — borehole curing water used without a current test certificate

What happens. The plant's tanker supply runs short mid-pour and the crew tops up curing water from an on-site borehole that was tested once, well before the project started, and never retested against IS 456 Cl 5.4.
Likely outcome. Untested borehole water can carry chlorides, sulphates or dissolved salts above the mixing-water limits; using it for curing leaves salts on the surface, can accelerate carbonation, and puts cover durability at risk on a structure where durability was the reason for specifying that grade in the first place.
Preventive correction. Treat every water-source change — mixing or curing — as a material substitution: log it, test it against IS 456 Cl 5.4 before use, and keep the certificate on file alongside the cement and SCM records.

References & further reading

  1. IS 269:2015 (Sixth Revision) — Ordinary Portland Cement — Specification. Bureau of Indian Standards. The single current OPC standard, covering all grades — 33 (plaster, masonry, low-rise), 43 (general-purpose structural, the most common grade in Indian RCC for low-rise and housing), and 53 (high-strength, for high-rise, bridge and precast). The Sixth Revision consolidated the formerly separate IS 8112 (43 grade) and IS 12269 (53 grade) standards, both now withdrawn, into this single document.
  2. IS 3812 (Part 1 & 2):2013 — Pulverized Fuel Ash — Specification. Bureau of Indian Standards. The Class F / Class C fly ash specification; Pt 1 pozzolana, Pt 2 admixture in cement, mortar and concrete.
  3. IS 16714:2018 (Amend. 1:2019) — Ground Granulated Blast Furnace Slag — Specification. Bureau of Indian Standards. The current Indian GGBS standard, supersedes IS 12089:1987; grade 80/100/120 by Slag Activity Index.
  4. IS 15388:2003 — Silica Fume — Specification. Bureau of Indian Standards. Microsilica for cementitious systems; min SiO₂, max LOI, specific surface.
  5. IS 16354:2015 (Reaff. 2020) — Metakaolin for Use in Cement, Cement Mortar and Concrete — Specification. Bureau of Indian Standards. Calcined kaolin-grade pozzolanic SCM in Indian practice.
  6. IS 383:2016 — Coarse and Fine Aggregates for Concrete — Specification. Bureau of Indian Standards. The grading-envelope standard for natural and crushed aggregates; the plant-side sieve analysis is read against this standard.
  7. IS 456:2000 (Amend. 6:2024) — Plain and Reinforced Concrete — Code of Practice. Bureau of Indian Standards. Cl 5.4 (water), Cl 8.2.4.2 (mineral admixtures), Cl 9 (cover), Cl 10 (design constants), Cl 15 (mixing, placing, compaction, curing), Cl 16 (acceptance). The Indian general code.
  8. IS 9103:1999 (Reaff. 2018) — Concrete Admixtures — Specification. Bureau of Indian Standards. Performance and uniformity for chemical admixtures; pairs with the supplier's test certificate for the brand-specific dose window.
  9. IS 2645:2003 — Integral Waterproofing Compounds for Cement Mortar and Concrete — Specification. Bureau of Indian Standards. For waterproofing admixtures; verify against the project specification.
  10. ACI 211.1 — Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete. American Concrete Institute. US mix-proportioning counterpart to IS 10262; useful when reading international specifications.
  11. ASTM C150 / C150M — Standard Specification for Portland Cement. ASTM International. US counterpart to IS 269:2015; Type I/II/V map roughly to OPC grades.
  12. ASTM C618 — Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. ASTM International. US counterpart to IS 3812; classifies fly ash as Class F / Class C.
  13. ASTM C494 / C494M — Standard Specification for Chemical Admixtures for Concrete. ASTM International. US counterpart to IS 9103; Type A / D / F map roughly to water-reducer / retarder / superplasticizer.

Year notes: IS 269 was first published in 1958; the current revision is IS 269:2015 (Sixth Revision). IS 8112 (43 grade) and IS 12269 (53 grade) were withdrawn and consolidated into IS 269:2015's Sixth Revision, which now covers all three OPC grades in one document. IS 16714 superseded IS 12089 (1987) in 2018. IS 383 was first published in 1960; the current revision is IS 383:2016. IS 456 is the Fourth Revision (2000) with multiple amendments; the most recent at the time of writing is Amendment No. 6 (April 2024); verify the current BIS catalogue before tendering.

Frequently Asked Questions

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About the author

Amit Haridas

Founder & Proprietor, ConcreteInfo. 25+ years of experience in concrete technology, RMC plant operations, construction quality, consulting and technical training across India. NRMCA CTI certified, ISO Lead Auditor.