Guidelines for Design and Construction of Continuously Reinforced Concrete Pavement (CRCP)

IRC 118: Introduction - Key Points

• Scope: IRC 118 covers Continuous Reinforced Concrete Pavements (CRCP) design, construction, and maintenance.
• Purpose: To provide guidelines for CRCP with or without elastic joints.
• Pavement Composition: Typically includes a reinforced concrete slab, sub-base, and subgrade layers.
• Design Focus: Thickness design, reinforcement detailing, joints, shoulders, and distress management.
• Personnel: The Highways Specifications and Standards Committee (H-3) oversees the code.

Typical Pavement Composition (from IRC 118)

Key Design Aspects:

• Thickness Design: Based on expected traffic, subgrade strength, and durability.
• Reinforcement: Longitudinal steel designed to control cracking and provide load transfer.
• Joints: Types and spacing to control cracking patterns.

Summary Table (Excerpt)

For detailed formulas and design examples, refer to clauses 6 (Thickness Design) and 7 (Design of Reinforcement).

flowchart TD
    A[Pavement Composition] --> B[Concrete Slab]
    A --> C[Sub-base]
    A --> D[Subgrade]
    B --> E[Reinforcement Design]
    B --> F[Thickness Design]
    E --> G[Joints and Lapping]

Note: For exact formulas and reinforcement tables, consult clauses 6, 7, and 12 of IRC 118.

Difference Between CRCP with Elastic Joints and Without Joints (IRC 118)

Key Specification for Elastic Joints (IRC 118 Clause 9)

• Joint filler: Elastic material (bituminous or polymer-based)
• Dowel bars: Typically 25-30 mm diameter, length ~500 mm, spaced at 300 mm
• Joint width: 10-20 mm to allow expansion/contraction

Summary Diagram

flowchart LR
    A[CRCP without Joints] --> B(Cracks develop naturally)
    B --> C(Load transfer via steel)
    A --> D(Lower maintenance)
    
    E[CRCP with Elastic Joints] --> F(Elastic joints at intervals)
    F --> G(Load transfer via dowel bars)
    F --> H(Joint filler accommodates movement)
    E --> I(Requires joint maintenance)

This distinction guides design and maintenance strategies for CRCP pavements per IRC 118.

Advantages and Disadvantages of CRCP (IRC 118)

Advantages of CRCP:

• Eliminates transverse joints, reducing maintenance and joint-related distresses.
• Provides longer pavement life due to better load transfer.
• Reduces noise from wheel impacts.
• Suitable for heavy traffic and highways.
• Minimizes water infiltration and subgrade erosion.

Disadvantages of CRCP (Clause 3.2):

• Not recommended in marine climates due to corrosion risk unless epoxy-coated or galvanized steel is used.
• Difficult to repair utility lines beneath pavement because CRCP is continuous.
• Not economical for light traffic roads (village roads, urban streets) or short lengths.
• Manual construction is slow, costly, and leads to many transverse joints; mechanized construction preferred.

Summary Table:

flowchart LR
    A[CRCP Advantages] --> B[No transverse joints]
    A --> C[Longer pavement life]
    A --> D[Suitable for heavy traffic]
    A --> E[Reduces noise]
    F[CRCP Disadvantages] --> G[Corrosion risk in marine climates]
    F --> H[Repair difficulty for utilities]
    F --> I[Not for light traffic roads]
    F --> J[Manual construction costly]

This summary aids decision-making for CRCP application per IRC 118 guidelines.

Types of Distresses in CRCP (IRC 118)

Key Distresses:

• Longitudinal Cracks: Caused by shrinkage and temperature stresses.
• Transverse Cracks: Controlled by continuous reinforcement; spacing and reinforcement reduce their width.
• Punchouts: Localized failures near transverse cracks due to loss of support or high stresses.
• Edge Breaks: Occur near pavement edges, mitigated by proper shoulder design.
• Joint Failures: At unavoidable construction, longitudinal, terminal, and transition joints.

Important Formulas & Tables

Transverse Reinforcement Steel Percentage (Pt):

[ P_t = \frac{Y_c \times W \times F}{2 \times f_s} \times 100 ]

Where:

• (P_t) = % of transverse steel
• (Y_c) = Unit weight of concrete (kN/m³)
• (W) = Pavement width (m)
• (F) = Friction factor of base
• (f_s) = Allowable working stress in steel (75% of yield strength)

Friction Factors for Base Materials

Specifications

• Max spacing of transverse bars: 610 mm
• Minimum distance from transverse construction joints: 500 mm
• Shoulders: Full-depth concrete or tied jointed concrete shoulders recommended to reduce edge stresses and punchouts.

flowchart LR
    A[Concrete Shrinkage & Temperature] --> B(Longitudinal Cracks)
    B --> C(Transverse Reinforcement Controls Crack Width)
    C --> D(Punchouts near Transverse Cracks)
    E[Edge Stress] --> F(Edge Breaks)
    G[Joints] --> H(Construction, Longitudinal, Terminal & Transition)
    H --> I(J

Typical Pavement Composition (IRC 118)

• Subgrade:

  • Minimum thickness: 500 mm
  • Compaction: ≥ 97% Maximum Dry Density (MDD) (IS 2720-Part 8)
  • Soaked CBR: ≥ 10% at 97% MDD
  • Uniform moisture and compaction essential for uniform support.

• Base Course:

  • Layer below concrete pavement (also called upper subbase)
  • Materials:
    • Dry Lean Concrete (DLC) or
    • Dense Bituminous Layer (preferred to prevent erosion)
    • Granular or cement-treated layers possible but need quality control
  • Bituminous layer on top of granular or cement-treated layers recommended to control erosion.
  • Use of 5 mm non-woven geotextile on bituminous base improves performance.

• Concrete Pavement Thickness:

  • Generally 250 mm to 300 mm, depending on traffic volume
  • Extra 10-15 mm thickness for wear and texture depth
  • Design per IRC:58 with no reduction for CRCP thickness.

graph TD
    Subgrade --> BaseCourse
    BaseCourse --> ConcretePavement
    BaseCourse -->|Bituminous Layer| ErosionControl
    ErosionControl --> ConcretePavement

This layered system ensures structural integrity and durability of pavement.

IRC 118: Thickness Design for Cement Concrete Pavement

• Reference Standard: Use IRC:58 for pavement thickness design in India.
• Thickness Range: Typically 250 mm to 300 mm depending on traffic volume.
• Additional Allowance: Add 10-15 mm extra thickness for wear, tear, and surface texture depth.
• Design Notes:
  • Thickness for Continuously Reinforced Concrete Pavement (CRCP) is not reduced from jointed pavement thickness due to performance issues.
  • Base course should be well designed (preferably Dry Lean Concrete or dense bituminous) to prevent erosion.
  • Use of a 5 mm non-woven geotextile on bituminous base can improve pavement performance.

Summary Table

This approach ensures durable pavement thickness aligned with IRC guidelines and practical experience.

flowchart TD
    A[Traffic Volume] --> B{Pavement Thickness}
    B -->|Low to Medium| C[250 mm]
    B -->|High| D[300 mm]
    C & D --> E[Add 10-15 mm for wear]
    E --> F[Final Pavement Thickness]
    F --> G[Base Course: DLC or Bituminous]
    G --> H[Optional: 5 mm Geotextile Layer]

This diagram shows the decision flow for thickness design and base course layering.

Design of Reinforcement in IRC 118 (Clause 7.1.3 & 7.0)

• Pavement Thickness (h): 300 mm (M-40 grade concrete)
• Pavement Width (b): 7.0 m with a longitudinal joint
• Longitudinal Steel Percentage (ρ): 0.7%
• Steel Grade: Fe 500

Key Formula for Longitudinal Steel Area (As):

[ A_s = \rho \times b \times h ]

Where:

• ( A_s ) = Area of longitudinal reinforcement (mm²)
• ( \rho ) = Steel percentage (in decimal, 0.007 for 0.7%)
• ( b ) = Width of pavement (mm)
• ( h ) = Thickness of pavement (mm)

Calculation Example:

[ A_s = 0.007 \times 7000 \times 300 = 14700 \text{ mm}^2 ]

Specifications:

• Use Fe 500 grade steel for reinforcement.
• Reinforcement bars should be placed longitudinally along the pavement.
• Follow IRC:58 for detailed thickness design and joint specifications.
• Lapping length and cover as per IRC 118 clauses.

Summary Table for Longitudinal Steel:

flowchart LR
    A[Pavement Width (b)] --> C[Calculate Steel Area]
    B[Pavement Thickness (h)] --> C
    C --> D[Steel Percentage (ρ)]
    D --> E[Area of Steel (As) = ρ × b × h]
    E --> F[Select Fe 500 Steel Bars]

This concise approach ensures proper longitudinal reinforcement design for CRCP per IRC 118.

IRC 118 - Shoulders (Clause 8 Highlights)

Paved shoulders are crucial for CRCP edge slab safety and to reduce punchouts. Key points:

• Types of Shoulders:

  • Full-depth concrete shoulder: Continuation of CRCP pavement, common in the USA.
  • Tied jointed plain/reinforced concrete shoulders: Use short transverse joint spacing to reduce joint movement and cracking; tie rods connect shoulder slabs to main pavement.

• Purpose:

  • Reduce edge stress on CRCP.
  • Prevent large punchouts.
  • Provide structural support and safety at pavement edges.

• Construction Tips:

  • Full-depth shoulders are most effective in reducing edge stress.
  • Joint spacing in shoulders should be shorter than mainline to minimize cracking.
  • Tie rods must be provided to connect shoulders to the main CRCP.

Summary Table: Shoulder Types

For detailed reinforcement and jointing requirements, refer to Clause 7 (Reinforcement) and Clause 9 (Joints) of IRC 118.

flowchart LR
    A[CRCP Pavement] --> B[Full-depth Concrete Shoulder]
    A --> C[Tied Jointed Concrete Shoulder]
    C --> D[Short Transverse Joints]
    C --> E[Tie Rods Connection]
    B --> F[Edge Stress Reduced]
    C --> F

Note: Proper shoulder design enhances pavement durability and reduces maintenance.

Key IRC 118 Specifications for Joints in CRCP

1. Longitudinal Joint (Clause 9.2)

• Continuous longitudinal reinforcement bars run throughout the pavement width.
• Additional 2 m long longitudinal bars placed at transverse construction joints for continuity.
• Longitudinal bars tied to transverse bars fixed on chair assemblies.

2. Expansion Joint (Clause 9.4.1.1)

• Provided to accommodate thermal expansion.
• Usually placed at terminal and transition joints.
• Filled with compressible filler and sealed with suitable joint sealant.

3. Transverse Construction Joint (Clause 9.1)

• Required when paving stops >30 minutes.
• Stop-end used to prepare joint.
• Groove filled with joint sealant.
• Additional 2 m long longitudinal bars placed between main bars.
• Transverse bars placed across the joint.

4. Transverse Reinforcement (Clause 7.2 & Table 7.2)

[ P_t = \frac{Y_c \times W_s \times F}{2 f_s} \times 100 ]

Where:

• (P_t) = % transverse steel
• (Y_c) = Unit weight of concrete (kN/m³)
• (W_s) = Pavement width (m)
• (F) = Friction factor (see table below)
• (f_s) = Allowable steel stress (75% of yield strength)

Max spacing: 610 mm
Distance from joint: ≥ 500 mm

5. Friction Coefficients for Base Materials

6. Shoulders

• Full-depth concrete or tied jointed plain/reinforced concrete.
• Connected with tie rods to main slab.
• Helps reduce

Lapping of Longitudinal Reinforcement (IRC 118)

• Lap Length (L_lap):
  [ L_{lap} = 35 \times d ]
  where d = diameter of the bar.

• Key Specifications:

  • Bars are usually up to 12 m long; laps are necessary for continuity.
  • Laps must be staggered; no more than 1/3 of laps in one location.
  • Minimum spacing between laps: 1.2 m to avoid weak planes.
  • Welding of TMT bars is not preferred; rely on lap splicing.

• Reasoning:
  Based on USA studies, 33 times bar diameter ensures adequate bond strength; IRC 118 adopts 35 times for safety.

Summary Table

flowchart LR
    A[Start: Bar Length < 12m] --> B[Provide Lap Splice]
    B --> C[Lap Length = 35 × d]
    C --> D[Stagger laps]
    D --> E[Max 1/3 laps at one location]
    E --> F[Maintain 1.2 m spacing between laps]
    F --> G[No welding for TMT bars]

This ensures structural integrity and bond strength in longitudinal reinforcement for CRCP pavements.

IRC 118: Construction of Continuously Reinforced Concrete Pavement (CRCP)

Key Construction Specifications (Clause 11.4)

• Steel Reinforcement Restriction: Dumpers or transit mixers cannot move on base course due to steel reinforcement.
• Mix Discharge Methods:
  • Use conveyor belt system or
  • Large transit mixers loading from sides.
• If space permits, side-tipping from dumpers is allowed.
• Paving operation is similar to unreinforced concrete pavement, except for above restrictions.
• Refer to IRC:15 for detailed paving operations.

Important Notes:

• Ensure no direct movement of heavy vehicles on base course to avoid damage.
• Maintain proper alignment and tensioning of steel reinforcement during placement.
• Follow standard curing and compaction procedures as per IRC guidelines.

flowchart LR
    A[Mix Preparation] --> B[Transport to Site]
    B --> C{Sufficient Side Space?}
    C -->|Yes| D[Side-tipping Dumpers]
    C -->|No| E[Conveyor Belt or Large Transit Mixers]
    D & E --> F[Paving Operation (IRC:15)]
    F --> G[Compaction & Curing]

For detailed reinforcement design and thickness, see Clauses 6 & 7 of IRC 118.

IRC 118 — Illustrative Example of Design of Steel (Clause 12)

While IRC 118 does not provide explicit formulas in the example section, the design of longitudinal steel reinforcement in CRCP (Continuously Reinforced Concrete Pavement) follows these key principles from Clauses 7.1.3 and 12.1:

Key Formulas for Longitudinal Steel Design

• Steel Area Required (As):

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

Where:

• ( M ) = Moment (from traffic and temperature stresses)

• ( f_y ) = Yield strength of steel (typically 415 MPa)

• ( z ) = Lever arm (approx. 0.95d, d = effective depth)

• Minimum Steel Percentage:

[ \rho_{min} = 0.0012 \text{ (IRC recommendation)} ]

• Maximum Steel Percentage:

[ \rho_{max} = 0.015 ]

Typical Steel Design Steps (from IRC 118):

1. Calculate bending moments due to traffic and temperature.
2. Determine required steel area ( A_s ) using above formula.
3. Check steel percentage limits.
4. Select bar size and spacing to provide ( A_s ).
5. Ensure proper lapping and anchorage as per Clause 10.

Example Table: Steel Reinforcement

flowchart TD
    A[Calculate Moments] --> B[Determine Required Steel Area \(A_s\)]
    B --> C{Check Steel % Limits}
    C -->|Within Limits| D[Select Bar Size & Spacing]
    C -->|Exceeds Limits| E[Revise Design]
    D --> F[Detail Lapping & Anchorage]

Summary:
IRC 118's example illustrates calculating steel area based on moments, ensuring steel percentage limits, and detailing reinforcement for CRCP durability. Use the above formulas and

IRC 118: Key References, Formulas & Tables Summary

1. Transverse Reinforcement Design (Clause 7.2)

• Formula for % Transverse Steel, ( P_t ):

[ P_t = \frac{Y_c \times W \times F}{2 \times f_s} \times 100 ]

Where:

• ( Y_c ) = Unit weight of concrete (kN/m³)

• ( W ) = Total pavement width (m)

• ( F ) = Friction factor of base layer (from Table below)

• ( f_s ) = Allowable steel stress (75% of yield strength)

• Max spacing of transverse bars: 610 mm

• Min distance from transverse joints: 500 mm

2. Friction Coefficients for Base Materials (Table 1)

3. Shoulder Types for CRCP

• Full-depth concrete shoulder (same as main pavement)
• Tied jointed plain/reinforced concrete shoulders with short transverse joints
• Shoulders must be connected to main pavement with tie rods

4. Types of Joints in CRCP

• Construction Joint
• Longitudinal Joint
• Terminal and Transition Joints

flowchart LR
    A[Base Layer] -->|Friction Factor (F)| B[Transverse Reinforcement Design]
    B --> C[Steel % Calculation]
    C --> D[Spacing & Positioning]
    D --> E[Shoulder Design]
    E --> F[Joints in CRCP]

For detailed design of longitudinal steel and illustrative examples, refer to Clause 12.1 and page 20 of IRC 118.