- 1. Overview
- 2. Classification
- 3. Properties and tests (IS 2386)
- 4. Fine aggregate grading (IS 383:2016)
- 5. Coarse aggregate grading (typical)
- 6. Moisture and absorption corrections
- 7. Fineness modulus
- 8. Common issues and fixes
- 9. Sustainability notes
- 10. RCA guidance
- 11. Consultant checklist
- 12. Standards and references
- Disclaimer
Purpose: consultant-ready reference on aggregates for concrete. Use the TOC to jump to classification, properties and tests, grading, moisture corrections, QA, and standards.
1. Overview
Aggregates constitute up to 75% of concrete volume and strongly influence workability, strength, shrinkage, and durability. Well-graded, clean aggregates lower permeability and cracking risk.
2. Classification
Type | Description | Examples | Common use |
By size | Fine ≤ 4.75 mm. Coarse > 4.75 mm. | River/M‑sand; 10, 20, 40 mm stone | FA for cohesion/void fill; CA for skeleton |
By source | Natural, manufactured, recycled | River sand, M‑sand, RCA | PCC/mortar, RCC, non‑structural |
By density | Normal, light, heavy | Granite; expanded clay; barite | General; lightweight fills; shielding |
3. Properties and tests (IS 2386)
Property | Significance | IS reference | Typical acceptance |
Specific gravity | Density indicator | IS 2386 (Pt 3) | 2.6–2.9 |
Water absorption | Porosity | IS 2386 (Pt 3) | < 2% (CA), < 3% (FA) |
Aggregate impact value | Shock resistance | IS 2386 (Pt 4) | < 30% (RCC) |
Crushing value | Load-bearing | IS 2386 (Pt 4) | < 30% |
Abrasion (Los Angeles) | Wear resistance | IS 2386 (Pt 4) | < 35% |
Flakiness + elongation | Particle shape | IS 2386 (Pt 1) | < 30% combined |
ASR reactivity | Expansion potential | IS 2386 (Pt 7) | Non‑reactive |
Silt and clay | Impurities | IS 2386 (Pt 2) | < 3% (crushed), < 10% (natural) |
4. Fine aggregate grading (IS 383:2016)
Sieve | Zone I | Zone II | Zone III | Zone IV |
10 mm | 100 | 100 | 100 | 100 |
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 µ | 15–34 | 35–59 | 60–79 | 80–100 |
300 µ | 5–20 | 8–30 | 12–40 | 15–50 |
150 µ | 0–10 | 0–10 | 0–10 | 0–15 |
5. Coarse aggregate grading (typical)
Nominal size | 40 mm | 20 mm | 10 mm |
80 mm | 100 | — | — |
40 mm | 95–100 | — | — |
20 mm | 30–70 | 95–100 | — |
10 mm | 10–35 | 25–55 | 95–100 |
4.75 mm | 0–5 | 0–10 | 0–20 |
6. Moisture and absorption corrections
- Determine SSD condition before batching.
- If dry: add water = absorption% × mass of aggregate.
- If wet: reduce water = moisture% × mass of aggregate.
- A 1% moisture error can change w/c by ≈ 0.02 and reduce strength by up to 8–10%.
7. Fineness modulus
FM = sum of cumulative percentage retained ÷ 100
- Fine aggregate: 2.3–3.1
- Coarse aggregate: 6.5–8.0
8. Common issues and fixes
Issue | Impact | Action |
Excess fines | Shrinkage, cracking | Wash, re‑sieve |
Poor grading | Segregation, bleeding | Blend sizes |
High flakiness | Weak interlock | Limit < 30% |
ASR risk | Expansion | Low‑alkali cement, pozzolans |
Contaminated sand | Poor bonding | Monitor silt/clay |
9. Sustainability notes
- Prefer IS 383 compliant manufactured sand.
- Use recycled aggregates up to 25% for non‑structural works.
- Maintain grading via plant sensors; combine SCMs and low w/c for durability.
10. RCA guidance
Aspect | Typical guidance | Notes |
Replacement level | Up to 25% for non‑structural; case‑by‑case for structural | Trial mixes required; monitor absorption |
Water absorption | Higher than natural aggregates | Apply strict SSD/moisture corrections |
Strength impact | Possible 5–15% reduction | Lower w/c, optimize paste, use SCMs |
Durability | Potentially higher permeability | Target RCPT and water penetration limits |
11. Consultant checklist
- Obtain sieve analysis and FM for each source and batch.
- Approve sources per IS 383 and control moisture daily.
- Favor Zone II sand and a 20 mm + 10 mm blend for dense packing.
- Screen new sources for ASR reactivity.
12. Standards and references
Code | Description |
IS 383:2016 | Specification for coarse and fine aggregates |
IS 2386 (Pt 1–8) | Methods of testing aggregates |
IS 2430 | Sampling of aggregates |
IS 1542 | Sand for plaster |
ASTM C33 | Aggregates specification |
BS 812 | Testing aggregates |
Disclaimer
SpecX is a neutral, brand-agnostic resource based on standards and best practices. Cross-check with project requirements and local codes before finalizing specifications.