precast reinforced concrete planks and joists for roofing and flooring

IS 13990: Scope and Key Specifications

• Scope: IS 13990 covers specifications for precast concrete L-panel units used in roofing.

• Dimensions & Tolerances (Clause 6.2.1.1):

• Rounding Off (Clause 4.1.2 & IS 2:1960):
  Final test or analysis values must be rounded off following IS 2:1960 rules, retaining the same number of significant figures as specified.

Summary:

• Use ±4 mm for length tolerance.
• Use ±2 mm for width and depth tolerance.
• Follow IS 2:1960 for rounding numerical results.

flowchart LR
    A[Precast L-Panel Units] --> B[Dimension Checks]
    B --> C{Dimension Type}
    C -->|Length| D[± 4 mm]
    C -->|Width| E[± 2 mm]
    C -->|Depth| F[± 2 mm]
    B --> G[Rounding Off]
    G --> H[IS 2:1960 Rules]

This ensures compliance with IS 13990 for precast roofing panels.

IS 13990: Reinforcement Key Points

• Main Reinforcement (Clause 5.2.1):

  • Use 3 equally spaced bars along plank length.
  • Diameter as per design requirements.
  • Must satisfy maximum spacing limits per IS 456:1978.

• Distribution Reinforcement:

  • Should be ≥ minimum slab reinforcement specified in IS 456:1978.

• Steel Grade:

  • Use steel as per IS 456:1978 recommendations.
  • Mild steel bars of 6 mm dia, Grade I (IS 432 Part 1:1982) for transverse reinforcement at 200 mm c/c if detailed design is absent.

Relevant IS 456:1978 Reinforcement Limits (Summary)

Typical Reinforcement Layout (Mermaid.js)

graph LR
A[Main Bars: 3 bars] -->|Equally spaced| B[Along plank length]
C[Distribution Bars] -->|≥ IS 456 min| D[Perpendicular to main bars]
E[Transverse Bars] -->|6 mm dia @ 200 mm c/c| F[Joist spacing < 1.5 m]

Summary: Use 3 equally spaced main bars along planks, distribution bars per IS 456 minimum, and mild steel 6 mm dia transverse bars at 200 mm spacing if no detailed design is available.

IS 13990: Shapes, Dimensions and Tolerances Summary

1. Tolerances on Mould Dimensions (Clause 6.2.1.1)

2. Casting Tolerances on Plank Dimensions (Clause 4.3)

3. Reinforcement

• As per IS 456:1978 specifications.
• Minimum 15 mm clear cover for reinforcement in RCC planks.

Notes:

• These tolerances ensure dimensional accuracy and structural integrity.
• Bow and twist control is critical for proper fit and load transfer.

graph TD
A[Plank Dimensions] --> B[Length ±5 mm]
A --> C[Width ±3 mm]
A --> D[Thickness ±2 mm]
A --> E[Bow ±2 mm]
A --> F[Twist 1 mm]

Use these tolerances during quality control for precast RCC elements.

IS 13990: Reinforcement Details Summary

Key Points from IS 13990 with IS 456 Reference

• Steel for Reinforcement: As per IS 456: 1978 (typically Fe415 or Fe500 grade).

• Main Reinforcement in Planks (Clause 5.2.1):

  • Use 3 equally spaced bars of required diameter along plank length.
  • Distribution reinforcement ≥ minimum recommended for slabs in IS 456.
  • Bar spacing must satisfy maximum spacing limits from IS 456 (usually ≤ 3 times slab thickness or 300 mm).

• Reinforcement for RCC Joists (Clause 5.2.3):

  • Follow design per IS 13994: 1994.
  • In absence of detailed design, use:
    • Main reinforcement: As per IS 13990 Clause 1.5.
    • Transverse reinforcement: 6 mm dia mild steel bars (IS 432 Part 1) @ 200 mm c/c.

Typical Reinforcement Spacing Limits (from IS 456)

Example: Main Reinforcement Area Calculation

[ A_s = \frac{M}{0.87 f_y d} ]

• (M) = design moment
• (f_y) = yield strength of steel (e.g., 415 MPa)
• (d) = effective depth

flowchart LR
    A[Design Moment & Load] --> B[Calculate Required \(A_s\)]
    B --> C[Select Bar Diameter & Number]
    C --> D[Check Spacing per IS 456 & IS 13990]
    D --> E[Provide 3 Equally Spaced Bars in Planks]
    D --> F[Provide Transverse Bars @ 200mm c/c in Joists]

Summary: Use 3 main bars equally spaced in planks, distribution bars as per IS 456 minimum, and transverse bars (

IS 13990: Key Specifications for Casting and Curing of Precast Elements

1. Mould Preparation

• Apply bond release agent on inner sides of mould.
• Place mould on smooth concrete platform coated with bond release agent or wrinkle-free old newspaper.

2. Reinforcement Cover

• Maintain 15 mm cover for RC planks.
• Maintain 25 mm cover for joists (bottom cover).

3. Concrete Specifications

• Use well-graded aggregate:
  • Max size 10 mm for planks.
  • Max size 20 mm for joists.
• Pour concrete in layers; compact each using a plate vibrator.
• Finish top surface with rough trowel marks for planks.

4. Casting Sequence (Planks)

• Pour 30 mm depth concrete first, compact.
• Place longitudinal and tapering members.
• Pour remaining concrete, compact.
• After ~0.5 hr, remove tapering members.
• Strip mould after ~2 hours (weather dependent).
• After 24-30 hours, slide and tilt unit for vertical curing.

5. Casting Sequence (Joists)

• Place reinforcement cage with stirrups projecting out.
• Fix top spacers.
• Pour concrete, compact with plate/needle vibrator.
• Strip mould after 3-4 hours.
• After 48-72 hours, slide and transport for curing.

Summary Table:

flowchart TD
    A[Prepare Mould with Bond Release Agent] --> B[Place Reinforcement Cage]
    B --> C[Pour Concrete Layer 1 (Planks: 30mm)]
    C --> D[Compact with Plate Vibrator]
    D --> E[Place Longitudinal

IS 13990: Sampling and Marking - Key Points

Sampling (Clause 7.2)

• For lots ≤ 300 units: Select 5 units at random.
• For lots > 300 units: Select 5 units for every additional 300 units or part thereof.
• Random selection procedure as per IS 4905:1968.

Marking (Clause 7.3)

• Samples must be suitably marked for future identification of the lot they represent.

Testing (Annex A)

• Precast planks: Tested at 28 days after in-situ concrete placement.
• Precast joists: Tested at 28 to 33 days after casting.

Rounding Off (Clause None)

• Follow IS 2:1960 for rounding test results.
• Retain the same number of significant figures as specified values.

Sampling Table Summary

Marking Requirements

• Mark samples clearly with lot identification.
• Ensure traceability throughout testing and record keeping.

flowchart TD
    A[Lot of Units] --> B{Lot Size ≤ 300?}
    B -- Yes --> C[Select 5 Samples]
    B -- No --> D[Select 5 + 5 per extra 300 units]
    C & D --> E[Mark Samples with Lot ID]
    E --> F[Conduct Tests at Specified Age]

This ensures representative sampling and traceability as per IS 13990.

IS 13990: Testing Procedures for Precast Reinforced Concrete Planks and Joists

Key Testing Specifications

• Age of Testing (Annex A-1):

  • Planks: 28 days after in-situ concrete casting in haunch.
  • Joists: 28 to 33 days after casting.

• Dimensional Test & Deflection Recovery Test (Clause 8.1):

  • Routine tests to verify dimensions and deflection behavior.
  • Failure load test is a type test for new designs or size changes.

• Load Application for Deflection Test (Annex A-3.2):

  • Apply uniformly distributed load = 1.25 × imposed design load.
  • Load applied via concrete/steel blocks or hydraulic jacks with self-reacting frame.
  • Load held for 24 hours; deflection recorded.
  • Load removed; residual deflection recorded after another 24 hours (deflection recovery).

Rounding Off Results (Clause None)

• Use IS 2:1960 rules.
• Retain significant figures equal to those specified in the standard.

Summary Table for Deflection Test

flowchart LR
    A[Start Testing] --> B{Component Type}
    B -->|Plank| C[Wait 28 days after haunch concrete]
    B -->|Joist| D[Wait 28-33 days after casting]
    C --> E[Apply 1.25 × design load uniformly for 24 hrs]
    D --> E
    E --> F[Record deflection]
    F --> G[Remove load]
    G --> H[Record residual deflection after 24 hrs]
    H --> I[Compare with acceptance criteria]

This procedure ensures conformity to IS 13990 for structural performance and durability of precast elements.

Deflection Recovery Test (IS 13990: Clause 9.2 & Annex A)

• Test Setup (Clause A-3.1 & A-3.2):

  • Unit simply supported with 50 mm bearing over smooth brick wall finished with 1:4 cement mortar.
  • Haunches filled with M15 concrete, cured for 14 days.
  • Uniform load = 1.25 × imposed design load applied via loading blocks or hydraulic jacks.
  • Dial gauge at mid-span, least count ≤ 0.02 mm, zeroed under self-weight + applied load.

• Loading & Measurements:

  • Load applied and maintained for 24 hours.
  • Deflection under load recorded at 24 h: ( \delta_{24h} ).
  • Load removed, residual deflection recorded after 24 h: ( \delta_{res} ).

• Acceptance Criteria (Clause 9.2):

  • If ( \delta_{res} \geq 0.75 \times \delta_{24h} ), unit passes.
  • If ( \delta_{res} < 0.75 \times \delta_{24h} ), unit fails.
  • If maximum deflection under load ( < 40 \times \frac{l}{D} ) (where ( l ) = effective span in mm, ( D ) = overall depth in mm), deflection recovery test not required.

Key Formula:

[ \text{Deflection Recovery} = \frac{\delta_{res}}{\delta_{24h}} \times 100% \quad \geq 75% ]

[ \text{Skip recovery test if } \delta_{max} < 40 \times \frac{l}{D} ]

Diagram of Test Setup (simplified):

  graph LR
    A[Brick Wall] -->|50 mm bearing| B[Precast Unit]
    B -->|Load applied uniformly| C[Loading Blocks/Hydraulic Jacks]
    B -->|Dial gauge at mid-span| D[Deflection Measurement]

Summary:
The test ensures the unit recovers at least 75% of its deflection after load removal, confirming elastic behavior and durability. If deflection is

IS 13990: Certification and Marking Key Points

Certification Marking (Clause 10.2 & 10.2.1)

• Components may be marked with the BIS Standard Mark.
• Use of the Standard Mark is regulated by the Bureau of Indian Standards Act, 1986.
• Licensing conditions for using the Standard Mark are provided by BIS.

Marking Specifications (Clause 10.1)

Each precast component must be legibly and indelibly marked with:

• Manufacturer identification (source of manufacture)
• Month and year of manufacture

Testing Specifications (Annex A)

• Age of Testing:
  • Planks: Tested at 28 days after in-situ concrete placement.
  • Joists: Tested at 28 to 33 days after casting.
• Dimensional conformity: Follow IS 2:1960 for rounding off numerical test results.

Summary Table: Marking & Testing

flowchart LR
    A[Manufacture] --> B[Marking: ID, Month & Year]
    B --> C{Use BIS Mark?}
    C -- Yes --> D[Apply BIS Standard Mark]
    C -- No --> E[No BIS Mark]
    B --> F[Test at specified age]
    F --> G[Planks: 28 days after in-situ concrete]
    F --> H[Joists: 28-33 days after casting]

This ensures traceability, quality assurance, and compliance with IS 13990.

IS 13990: Test Methods for Precast Planks and Joists

Key Specifications & Testing Requirements

• Scope: Covers precast reinforced concrete planks and joists up to 1.5 m length for roofing and flooring.
• Age of Testing:
  • Planks: Tested at 28 days after in-situ concrete in haunch.
  • Joists: Tested between 28 to 33 days after casting.
• Dimensional Conformity: Ensures planks and joists meet specified dimensions (Clause A-2).

Relevant Standards Referenced

• IS 432 (Part 1): Mild steel and medium tensile steel bars for reinforcement.
• IS 456: Code of practice for plain and reinforced concrete.
• IS 1199: Methods of sampling concrete.
• IS 15916: Design and construction of floors and roofs with precast planks and joists.

Typical Test Methods Include:

• Load Testing: To verify strength and deflection under service and ultimate loads.
• Dimensional Checks: Length, width, thickness, and reinforcement placement.
• Visual Inspection: For cracks, honeycombing, and surface finish.

Summary Table: Age of Testing

flowchart TD
    A[Casting of Precast Joists/Planks] --> B{Planks or Joists?}
    B -->|Planks| C[In-situ Haunch Concrete Laid]
    C --> D[Wait until 28 days]
    B -->|Joists| E[Wait 28 to 33 days]
    D --> F[Perform Load & Dimensional Tests]
    E --> F

For detailed test procedures, refer to Annex A of IS 13990 and related IS codes above.