Last reviewed 16 Sept 2026 · 7 min read
Sequence of RCC work
- Setting out and levels → 2. Formwork (centering and shuttering) erection → 3. Reinforcement cutting, bending, placing and tying → 4. Inspection (dimensions, cover, laps, embedded items) → 5. Batching and mixing → 6. Transporting and placing → 7. Compaction → 8. Finishing → 9. Curing → 10. Removal of formwork.
Materials on site
- Cement: stored in dry, raised stacks (not more than about 10 bags high), used first-in first-out; lumps indicate deterioration.
- Aggregates: clean, graded, free from clay, silt and organic matter; fine aggregate bulking corrected for moisture.
- Water: potable quality is generally fit for mixing; pH not less than 6.
- Steel: stored off the ground, free from loose rust, oil and mud; grade identified (Fe 415/500/550D marks).
Formwork
Formwork is the temporary mould that holds fresh concrete to shape until it can support itself.
Requirements of good formwork
- Strong enough to carry wet concrete, workers and equipment without failure.
- Rigid — deflections small enough not to distort the member.
- Tight joints to prevent leakage of cement slurry (honeycombing).
- Correct shape, dimensions and levels; smooth surface for finish.
- Easy to erect and strip without damaging concrete; reusable.
- Economical (formwork is commonly a significant share of the cost of the concrete frame).
Materials and types
| Material | Features |
|---|---|
| Timber / plywood | Light, easily cut, limited reuse |
| Steel | Many reuses, good finish, heavy, costly initially |
| Aluminium | Light, reusable |
| Plastic / fibreglass | Complex shapes, domes (waffle slabs) |
Special systems: slip form (continuously moving, for tall silos and cores), jump form, table form, tunnel form.
Removal of formwork
| Member | Minimum period |
|---|---|
| Vertical formwork to columns, walls, beams | 16–24 hours |
| Soffit formwork to slabs (props to be refixed immediately) | 3 days |
| Soffit formwork to beams (props to be refixed immediately) | 7 days |
| Props to slabs spanning up to 4.5 m | 7 days |
| Props to slabs spanning over 4.5 m | 14 days |
| Props to beams and arches spanning up to 6 m | 14 days |
| Props to beams and arches spanning over 6 m | 21 days |
For other cements and lower temperatures, periods are increased. Cantilevers must remain propped until the back-span or anchoring members can resist the moment.
Reinforcement work
- Bars are cut and bent cold to the bar bending schedule; bending is done around a mandrel to specified radii (IS 2502), never by heating.
- Cover is maintained with cement-mortar or concrete cover blocks (same strength as the member concrete) or plastic spacers — not with stone pieces or timber.
- Chairs keep top slab bars in position; bars are tied at intersections with annealed binding wire (commonly 16–18 gauge).
- Laps staggered and placed in low-stress zones; development lengths as designed.
- Before concreting check: bar sizes and numbers, spacing, cover, laps, hooks, stirrup spacing near supports, and embedded conduits.
Bar bending schedule (BBS)
A bar bending schedule lists every bar mark with member, bar shape, diameter, number, cutting length, total length and weight. It is used for cutting and bending, for ordering steel and for billing the quantity of reinforcement.
Unit weight of bars
| Dia (mm) | 6 | 8 | 10 | 12 | 16 | 20 | 25 | 32 |
|---|---|---|---|---|---|---|---|---|
| kg/m | 0.222 | 0.395 | 0.617 | 0.888 | 1.580 | 2.469 | 3.858 | 6.321 |
Standard allowances (common site practice)
| Item | Allowance |
|---|---|
| 45° bend (deduction) | |
| 90° bend (deduction) | |
| 135° bend (deduction) | |
| 180° bend (deduction) | |
| Hook (180°, on plain bars) | add per hook |
| Hook for stirrups (135°) | add about per hook |
| Crank at 45° (bent-up bar), crank height | add per crank |
Allowances differ slightly between offices and standards; the schedule must state the convention used.
Why a crank adds : the inclined length at 45° is against a horizontal length of → extra .