- 1. RMC overview
- 2. Manufacturing process flow
- 3. Key IS codes
- 4. Mix design components
- 5. Mix design workflow (IS 10262:2019)
- 6. Typical mixes (illustrative)
- 7. QC at RMC plants
- 8. Troubleshooting
- 9. QA responsibilities
- 10. Digital integration
- 11. Consultant checklist
- 12. Reference standards
- Disclaimer
Purpose: consultant-ready guide to RMC production, IS codes, mix design workflow, QA, and troubleshooting. Use the TOC to jump to sections.
1. RMC overview
Ready-mix concrete is batched in a controlled plant and delivered in a plastic state. It improves quality, speed, and traceability compared to site-mixed concrete.
2. Manufacturing process flow
- Material selection and testing → cement, SCMs, aggregates, water, admixtures per IS 383, IS 9103.
- Batching by weight → automated system, ±1% precision.
- Mixing → central mixer or transit mixer for uniformity.
- Delivery → controlled slump retention via admixtures.
- Placing and compaction → target delivery within 90 minutes of batching.
- Curing and strength testing → cubes at 7 and 28 days per IS 516.
3. Key IS codes
Code | Description |
IS 4926:2021 | Ready-mixed concrete — specification |
IS 456:2000 | Design and durability provisions |
IS 10262:2019 | Concrete mix design procedure |
IS 383:2016 | Aggregates for concrete |
IS 9103:2021 | Chemical admixtures |
IS 516:2021 | Strength testing methods |
IS 16415:2015 | Self-compacting concrete |
IS 1199:2018 | Workability tests |
ASTM C94 / EN 206 | International references |
4. Mix design components
Component | Function | Key control |
Cement / SCMs | Binder | Grade, consistency, setting |
Fine aggregate | Filler | Zone I–IV, silt content |
Coarse aggregate | Skeleton | Size, shape, impact value |
Water | Hydration | Potability, w/c control |
Admixtures | Rheology/strength | Dosage, compatibility |
Fibres (optional) | Toughness | 0.3–1.0% by volume |
5. Mix design workflow (IS 10262:2019)
Step | Description | Reference |
1 | Define grade (fck) | e.g., M25, M40 |
2 | Target mean strength | fck + 1.65 × SD |
3 | Select w/c | Per IS 456 Table 5 |
4 | Water content | IS 10262 Table 2 |
5 | Cementitious content | w/c and SCM replacement |
6 | FA:CA ratio | By size and sand zone |
7 | 1 m³ volume balance | Account for air |
8 | Aggregate mass | Specific gravity |
9 | Moisture/absorption | SSD correction |
10 | Admixture dosage | % of cementitious |
11 | Verify slump and strength | Lab/site trials |
6. Typical mixes (illustrative)
Grade | w/c | Cement (kg/m³) | SCM | FA:CA | Slump | 28-day strength |
M20 | 0.55 | 320 | 20% fly ash | 60:40 | 75–100 mm | 26 MPa |
M30 | 0.45 | 360 | 30% slag | 55:45 | 100–125 mm | 40 MPa |
M40 (HPC) | 0.38 | 420 | 8% silica fume | 55:45 | 125–150 mm | 52 MPa |
M50 (PQC) | 0.32 | 440 | 25% GGBS | 60:40 | 25–50 mm | 62 MPa |
M60 (SCC) | 0.30 | 450 | 30% GGBS | 55:45 | 650 mm flow | 70 MPa |
7. QC at RMC plants
Stage | Test | Standard | Frequency |
Incoming material | Sieve analysis, SG, moisture | IS 2386 | Daily / batch |
Batching | Calibration | IS 4926 | Weekly |
Fresh concrete | Slump/flow/temperature | IS 1199 | Every truck |
Cube sampling | Compressive test | IS 516 | 6 cubes / 100 m³ |
Hardened concrete | UPV / rebound | IS 13311 | Periodic |
Water quality | pH, solids | IS 3025 | Monthly |
8. Troubleshooting
Quick fixes for common RMC issues
Problem | Cause | Action |
Slump loss | Long transit, poor admixture | Use slump-retaining PC, manage transit time/temperature. |
Segregation | High w/c, over-vibration | Increase fines, reduce water, optimize vibration. |
Low cube strength | High w/c, poor batching | Calibrate plant, verify w/c at site, redesign mix. |
High concrete temperature | Hot weather | Chilled water, shade aggregates, adjust timing. |
Rejected loads | Site delays | Placement plan, standby pumps. |
9. QA responsibilities
Level | Responsibility | Focus |
Design | Consultant / QA lab | Proportions, trials |
Production | RMC plant | Calibration, batching, records |
Site | Site engineer / QC | Testing, curing, reports |
10. Digital integration
- IoT batching with auto slump tracking and MTC
- Moisture sensors for live corrections
- Data logs per pour for traceability
11. Consultant checklist
- Obtain approved mix design from plant.
- Verify calibration certificates for weighing systems.
- Keep transit time ≤ 90 minutes; monitor for initial set.
- Oversee cube casting and curing as per IS 516.
- For HPC, confirm SCM + admixture compatibility.
- Maintain digital batching and test logs per pour.
12. Reference standards
Standard | Description |
IS 456:2000 | Plain and reinforced concrete |
IS 10262:2019 | Mix design |
IS 4926:2021 | RMC specification |
IS 9103:2021 | Admixtures |
IS 383:2016 | Aggregates |
IS 516:2021 | Compressive/flexural tests |
ASTM C94, EN 206 | International standards |
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.