Code of practice for design and construction of floors and roofs using precast reinforced/prestressed concrete ribbed or cored slab unit

IS 10297: Scope - Key Formulas, Tables & Specifications

1. Scope & Sampling (Clause 1.2 & 10.1)

• Sampling for dimensional checks is based on lot size.
• Refer to Table 2 for sample sizes and rejection criteria:

• Sampling procedure follows Appendix A.

2. Dimensional Tolerances (Clause 5.1 & 9.1)

Summary

• Sampling size & rejection depend on lot size (Table 2).
• Dimensional tolerances ensure quality control.
• Follow Appendix A for detailed sampling procedure.

flowchart LR
    A[Lot Size] --> B{Sample Size & Rejection}
    B --> C[First Sample Size & Rejection No.]
    B --> D[Second Sample Size & Rejection No.]
    E[Dimensional Check] --> F[Apply Tolerances]
    G[Sampling] --> H[Appendix A Procedure]

This ensures systematic quality control for precast concrete units under IS 10297.

IS 10297: Key Formulas, Tables & Specifications for Dimensions and Design

1. Cross-Sectional Dimensions Tolerance

• Clause 9.1.2:
  Tolerance = +3 mm or ±0.1% of dimension, whichever is greater

2. Tolerance Limits for Moulds (Clause 5.1 & 9.2)

3. Sampling & Rejection Criteria (Clause 1.2, Table A-1 & Table 2)

Summary

• Dimensions must be controlled within specified tolerances to ensure quality.
• Sampling plans guide quality control for lot acceptance.
• Use the larger tolerance between +3 mm and ±0.1% for cross-sections.

flowchart TD
    A[Start: Lot of Units] --> B{Lot Size?}
    B -->|Up to 100| C[Sample 5 units]
    B -->|101-300| D[Sample 8 units]
    B -->|301-500| E[Sample 13 units]
    B -->|501+| F[Sample 20 units]
    C --> G{Reject units > 2?}
    D --> G
    E --> G
    F --> H{Reject units > 3 (1st) or 4 (2nd

IS 10297 - Materials: Key Specifications & Tables

1. Material Standards (Clause 3.1)

• Materials must conform to:
  • IS 456-1978 (Plain and Reinforced Concrete)
  • IS 1343-1980 (Prestressed Concrete)

2. Sampling for Dimensional Requirements (Clause 1.2, Table 2)

• Sampling ensures quality control on dimensional accuracy.

3. Tolerances of Moulds (Clause 5.1, Table 1)

• These tolerances ensure mould accuracy for precast units.

Summary Diagram: Material Conformance Flow

flowchart TD
    A[Material Selection] --> B{Conform to IS Codes?}
    B -->|Yes| C[IS 456-1978 & IS 1343-1980]
    B -->|No| D[Reject Material]
    C --> E[Sampling per Lot Size (Table 2)]
    E --> F[Check Dimensions & Tolerances (Table 1)]
    F --> G[Accept/Reject Units]

Use these tables and clauses to ensure material quality and dimensional accuracy in precast concrete construction per IS 10297.

IS 10297: Key Design Considerations

• Materials
  Must conform to:

  • IS 456: 1978 (Plain & Reinforced Concrete)
  • IS 1343: 1980 (Prestressed Concrete)

• Fixtures Provision (Clause 13.1)
  Designers must specify locations for:

  • Fan hooks
  • Inserts
  • Electric conduits
    Incorporated within precast units or in-situ joints/screed.

• Load Factors at Demoulding/Handling (Clause 4.3)
  Use a load factor ≥ 1.5 on collapse load to ensure safety during early stages.
  Actual cross-section strength must be verified by calculation or testing.

• Prestressed Ribbed Slabs (Clause 4.4.2)

  • Entire flange considered effective (no T-beam formula).
  • Avoid underestimating prestressing force by assuming partial flange effectiveness.

Summary Table for Load Factor

flowchart TD
    A[Design Considerations] --> B[Materials per IS 456 & IS 1343]
    A --> C[Provision for Fixtures]
    A --> D[Load Factor ≥ 1.5 at Demoulding]
    A --> E[Full Flange Effective in Ribbed Slabs]

This ensures safety and durability in prestressed concrete precast elements.

IS 10297: Manufacturing and Moulds - Key Specifications & Tolerances

1. Mould Types (Clause 5.1)

• Bottom mould: timber, masonry, concrete, steel, FRP, plastic, or approved materials.
• Side moulds: timber, steel, FRP, plastic.
• Masonry/concrete moulds must have a smooth, accurately finished top surface.

2. Reinforcement for Masonry Moulds

• Use chicken mesh or fibre reinforcement on the top surface to enhance durability.

3. Tolerances of Moulds (Table 1, Clauses 5.1 & 9.2)

4. Design Load Factor (Clause 4.3)

• Apply a load factor of 1.5 for limit state of collapse at demoulding and handling stages.
• Verify cross-section strength by calculation or tests.

flowchart TD
    A[Mould Manufacturing] --> B[Bottom Mould]
    A --> C[Side Moulds]
    B --> D[Materials: Timber, Masonry, Concrete, Steel, FRP, Plastic]
    C --> E[Materials: Timber, Steel, FRP, Plastic]
    D --> F[Surface Finish: Smooth, Accurate]
    F --> G[Reinforcement: Chicken Mesh/Fibre (for Masonry)]
    H[Tolerances] --> I[Length: -10 mm]
    H --> J[Width: -3 mm]
    H --> K[Height: +3 mm]
    H --> L[Diagonal: ±5 mm]
    H --> M[Warp/Bow: ±3 mm]

This summary ensures moulds meet IS 10297 standards for durability and dimensional accuracy.

Key Concrete Mix & Aggregate Specifications from IS 10297:

• Minimum Concrete Grade:

  • M-15 minimum as per IS 456-1978 for general use.
  • Preferably M-20 or above for reinforced concrete (IS 456:2000).
  • Higher grades required for prestressed concrete per IS 1343-1980.

• Maximum Aggregate Size:

  • Restricted to 12 mm for ribbed and cored slabs with flange thickness < 50 mm.

• Flange Thickness & Reinforcement:

  • Minimum flange thickness: 35 mm with proper compaction.
  • Aggregate max size: 12 mm.
  • Reinforcement mesh spacing in flange ≤ spacing for slabs per IS 456.
  • Max unreinforced concrete area ≤ 15t² (t = flange thickness).
  • For 35 mm flange, max mesh spacing: 150 mm both ways.

Summary Table:

This ensures adequate strength, durability, and compaction for prestressed and reinforced concrete units.

Casting and Curing of Units as per IS 10297

• Concrete Grade:
  • Minimum M-15 (IS 456:1978)
  • Preferably M-20 or above for reinforced concrete units
  • For prestressed units, follow IS 1343:1980
• Aggregate Size:
  • Max 12 mm for ribbed/cored slabs with flange thickness < 50 mm (Clause 7.1)
• Reinforcement Handling:
  • Avoid distortion during storage, handling, and casting (Clause 6.2)
  • Use welded reinforcement ladders/meshes for mass production
• Surface Preparation:
  • Provide castellations/roughening on unit sides for better keying with in-situ concrete (Clause 5.3)
• Curing:
  • Follow IS 456:1978 curing methods (water curing, moist curing)
  • Low-pressure steam curing allowed for early strength gain (Clause 8.2)

Typical Curing Duration (IS 456:1978)

Summary Diagram of Process

flowchart TD
    A[Prepare Reinforcement] --> B[Place in Mould]
    B --> C[Cast Concrete Mix (M20+)]
    C --> D[Surface Roughening (Castellations)]
    D --> E[Curing (Water/Steam)]
    E --> F[Stripping & Storage]

This ensures durable, strong precast units with good bond at joints.

IS 10297: Handling, Transportation, and Erection of Precast Concrete Units

Key Specifications & Guidelines

• Transportation Orientation:
  • Units must be transported with main reinforcement at the bottom (Clause 11.3).
• Lifting Points:
  • Rope slings tied at 1/5th length from each end for lifting (Clause 11.3).
• Overhang Limits:
  • When using trolleys, overhang ≤ 1/5th of unit length (Clause 11.3).
• Lifting Methods:
  • Manual, chain pulley blocks, hoists, or cranes are permitted (Clause 11.3).

Strength & Stability Requirements

• Units must have adequate strength during:
  • Handling, stacking, transporting, placing (Clause 4.1b)
  • Under design loads + dead load of in-situ concrete (Clause 4.1c)
• Follow IS 456 (Plain & Reinforced Concrete) and IS 1343 (Prestressed Concrete) for design and strength checks.
• Consider delayed early strength if Portland Pozzolana Cement is used (Note under Clause 4.1).

Quick Reference Table: Sling & Overhang Positions

Diagram: Sling Positions for Lifting Precast Unit

graph LR
A[End of Unit] -- 1/5 L --> B(Sling Point 1)
C[Other End] -- 1/5 L --> D(Sling Point 2)
B -- Rope Sling --> E(Lift)
D -- Rope Sling --> E(Lift)

Summary: Always transport precast units with reinforcement at the bottom, sling at 1/5th length from ends, limit trolley overhang to 1/5th length, and ensure strength per IS 456/1343 during all stages.

IS 10297: Tolerances Summary

1. Unit Tolerances (Clause 9.1)

• Cross-sectional dimensions:
  +3 mm or ±0.1%, whichever is greater.

2. Mould Tolerances (Clause 9.2 & Table 1)

Notes:

• Negative tolerance means the actual dimension can be smaller by that amount.
• Positive tolerance means the actual dimension can be larger.
• Warp/Bow tolerance controls the flatness or straightness deviation.

flowchart TD
    A[Mould Dimensions] -->|Length| B[ -10 mm ]
    A -->|Width| C[ -3 mm ]
    A -->|Height| D[ +3 mm ]
    A -->|Diagonal| E[ ±5 mm ]
    A -->|Warp/Bow| F[ ±3 mm ]

This ensures preciseness in precast concrete unit manufacturing as per IS 10297.

IS 10297: Sampling and Testing Key Points

Sampling (Clause 10.1 & Appendix A)

• Sampling must follow Appendix A procedures.
• Units are randomly selected from the lot (see IS 4905-1968 for random sampling method).

Sample Size and Rejection Criteria (Table 2, Clause 1.2)

• Procedure:
  • Take the first sample; if rejected (exceeding rejection number), take a second sample.
  • If second sample also fails, reject the entire lot.

Testing Criteria (Clause A-2)

• Number of tests depends on sample size.
• Units must conform to dimensional and quality requirements.

flowchart TD
    A[Start: Select Lot] --> B[Random Sampling per IS 4905]
    B --> C{Sample Size per Lot Size}
    C -->|Acceptable| D[First Sample Test]
    D --> E{Rejection Number Exceeded?}
    E -->|No| F[Lot Accepted]
    E -->|Yes| G[Second Sample Test]
    G --> H{Rejection Number Exceeded?}
    H -->|No| F
    H -->|Yes| I[Lot Rejected]

Summary: Follow Table 2 for sample sizes and rejection numbers; random sampling per IS 4905; test samples for dimensional conformity; reject lot if criteria exceed limits.

IS 10297: Key Points on Lifting Hooks and Stacking of Precast Units

Lifting Hooks (Clause 11.1)

• Location: Hooks/holes at 1/5th length from ends for structural advantage.
• Material: Made from mild steel reinforcing bars with adequate capacity to carry self-weight during demoulding, handling, and erection.
• Post-erection: Hooks can be cut or bent inside screed/joint concrete.

Transportation (Clause 11.3)

• Orientation: Main reinforcement always at the bottom during transport.
• Lifting points: Rope slings tied near ends at 1/5th length from either end.
• Overhang limit: Max overhang from trolleys = 1/5th length.
• Methods: Manual, chain pulley blocks, hoist, or crane.

Stacking of Units (Clause 11.2)

• Support placement: Supports at about 1/6th span from ends; no support at center.
• Reinforcement position: Main reinforcement always at the bottom of stacked units.

Summary Table:

graph LR
A[Precast Unit] --> B[Lifting Hooks at 1/5 length]
A --> C[Supports at 1/6 span from ends]
A --> D[Main Reinforcement at Bottom]
B --> E[Hook made of mild steel bars]
C --> F[No support at center]
D --> G[Ensures stability during transport & stacking]

This ensures safe handling, transport, and stacking without damaging the units or reinforcement.

IS 10297: Joint Construction and Curing Key Points

Joint Construction

• Ribbed slab units without end diaphragm over masonry walls require concrete bed blocks beneath ribs (Clause 11.5.1).
• Use concrete mix of minimum M-15 grade (IS 456:1978), preferably M-20 or above for reinforced/prestressed units (Clause 7.1).
• Max aggregate size: 12 mm for ribbed/cored slabs with flange thickness < 50 mm.

Curing of In-Situ Concrete in Joints

• Cure in-situ concrete for at least 7 days as per IS 456:1978 (Clause 12.1, 8.2).
• After curing, allow concrete to dry for at least 7 days.
• Apply cement slurry coat on joints to fill hairline cracks.
• Optional: Low-pressure steam curing for early strength gain.

Summary Table: Curing Requirements

flowchart TD
    A[Concrete Placement in Joint] --> B[Curing for 7 Days (Water or Steam)]
    B --> C[Drying for 7 Days]
    C --> D[Apply Cement Slurry Coat]
    D --> E[Joint Ready for Service]

References:

• IS 10297: Clause 7.1, 8.2, 11.5.1, 12.1
• IS 456:1978 (Concrete curing and mix design)

IS 10297: Provisions for Fixtures and Inserts in Precast Concrete

Key Provisions (Clauses 13.1 & 13.1.2)

• Designers must specify fixtures (e.g., fan hooks, inserts, electric conduits) to be embedded in precast units or in situ joints.
• Holes/openings for fixtures must be fixed accurately with adequate embedment during precasting.
• No drilling or cutting after precasting unless approved by the engineer.

Reinforcement Cover & Tolerances (Clause 5.1 & Table 9)

Floor Finish Keying (Clause 5.3)

• Provide castellations/depressions/roughening on precast unit sides for better bonding with in situ concrete.
• Use side shutter provisions to enhance keying at joints.

flowchart LR
    A[Design Stage] --> B[Specify Fixtures & Inserts]
    B --> C[Embed Fixtures Accurately]
    C --> D[Precast Unit Fabrication]
    D --> E[No Drilling/Cutting Post Precast]
    E --> F[Engineer Approval if Needed]
    D --> G[Provide Castellations/Roughening]
    G --> H[Better Bonding with In Situ Concrete]

This ensures durability, precise fixture placement, and joint integrity in precast concrete construction.

IS 10297: Quality Control and Inspection Key Points

1. Sampling Plan (Clause 1.2, Table 2)

• Procedure:
  • Select first sample as per lot size.
  • If defectives ≥ first rejection number → Reject lot.
  • If defectives < first rejection number → Take second sample of same size.
  • Combine defectives from both samples; if combined defectives ≥ second rejection number → Reject lot, else accept.

2. Dimensional Tolerances (Clause 5.1, Table 1)

• Units failing any dimensional tolerance are defective.

Summary Flowchart of Inspection Process:

flowchart TD
    A[Select Lot] --> B[Select First Sample]
    B --> C{Defectives ≥ First Rejection Number?}
    C -- Yes --> D[Reject Lot]
    C -- No --> E[Select Second Sample]
    E --> F[Combine Defectives]
    F --> G{Combined Defectives ≥ Second Rejection Number?}
    G -- Yes --> D
    G -- No --> H[Accept Lot]

Use this sampling and tolerance scheme to ensure compliance with IS 10297 quality control requirements.

IS 10297 Appendix Summary: Sampling & Testing of Precast Slab Units

1. Sampling Procedure (Appendix A, Clause 10.1)

• Sampling must follow Appendix A guidelines.
• Random sampling methods are prescribed for quality control.

2. Sample Size & Rejection Criteria (Table 2, Clause 1.2)

• If the first sample fails, a second sample is tested.
• Lot acceptance depends on rejection numbers.

3. Load Test Sampling (Clause 2.2, Appendix A)

• One unit per 300 units (or part thereof) is selected for load testing.
• Lot passes if all tested units meet load requirements.

Key Points:

• Sampling ensures dimensional and load test conformity.
• Lot sizes dictate sample sizes and acceptance criteria.
• Random sampling is mandatory for unbiased quality assurance.

flowchart TD
    A[Start: Lot of Precast Units] --> B{Lot Size?}
    B -->|<=100| C[Sample 5 units]
    B -->|101-300| D[Sample 8 units]
    B -->|301-500| E[Sample 13 units]
    B -->|>500| F[Sample 20 units]
    C --> G[Test samples]
    D --> G
    E --> G
    F --> G
    G --> H{Rejection number exceeded?}
    H -->|No| I[Accept Lot]
    H -->|Yes| J[Sample second lot]
    J --> K{Rejection number exceeded?}
    K -->|No| I
    K -->|Yes| L[Reject Lot]

This concise guide covers the key sampling and testing specifications from IS 10297 Append