Most Important Points to Remember in IS 456:2000
1. Types of Concrete
- PCC and RCC are covered.
- Grades: M10 to M80.
- Nominal mix: Up to M20. Design mix: M25 and above.
2. Structural Design Philosophies
- Limit State Method (mandatory).
- Working Stress and Ultimate Load Methods for reference.
3. Loads and Safety Factors
- Dead, Live, Wind loads as per IS 875.
- Safety factors: Load = 1.5, Concrete = 1.5, Steel = 1.15.
4. Cover to Reinforcement
- Slabs: 20 mm, Beams: 25 mm, Columns: 40 mm.
5. Reinforcement Detailing
- Min. reinforcement: Slabs = 0.12%-0.15%, Beams = 0.2%.
- Max. reinforcement in beams = 4%.
6. Concrete Durability
- W/C ratio ≤ 0.45 for severe conditions.
- Curing: 7 days (OPC), 10 days (blended cement).
7. Structural Member Guidelines
- One-way slab if L > 2×B.
- Column min. size = 150 mm, min. 4 bars (rect.), 6 (circular).
8. Deflection Limits
- Cantilever = L/7, Simply supported = L/20, Continuous = L/26.
9. Construction Joints
- Placed away from high shear zones.
- Proper bonding and surface preparation required.
10. Quality Control
- Cube tests at 7 and 28 days.
- Acceptance: Avg. ≥ fck, individual ≥ fck - 4 MPa.
11. Special Notes
- Earthquake design as per IS 13920.
- Formwork removal: Slab – 7–14 days, Beam – 14–21 days.