Guidelines for Gap Graded Wearing Course with Rubberised Bitumen-(Bitumen Rubber)

IRC SP 107 - Scope: Key Points

• Scope (Clause 2, Page 3): Covers specifications for the use of Rubberized Bitumen (RB) in Hot Mix Asphalt (HMA) for highways.
• Includes materials, blending, pumping, mix design, laying, quality assurance, and weather limitations.
• Applies to the preparation and application of bitumen-rubber binders and mixes.

Important Tables & Specifications

Crumb Rubber Gradation (% Passing)

Summary

• The scope defines the entire process from materials to quality control for RB mixes.
• Ensures uniformity in crumb rubber gradation and controlled dosing via mass meters.
• Critical for durability and performance of rubberized bituminous pavements.

flowchart LR
    A[Materials] --> B[Blending Bitumen Rubber]
    B --> C[Pumping RB Binder]
    C --> D[Mix Design Criteria]
    D --> E[Mixing & Laying]
    E --> F[Quality Assurance]
    F --> G[Final Pavement

Personnel of the Highways Specifications and Standards Committee (HSSC) - IRC SP 107

• Convenor: Das, S.N. - Director General (Road Development), MoRTH, New Delhi
• Co-Convenor: Additional Director General, MoRTH, New Delhi
• Member-Secretary: Prasad, Vishnu Shankar - Chief Engineer (R), MoRTH, New Delhi

Key Members include:

• Basu, S.B. (Chief Engineer Retd., MoRTH)
• Bongirwar, P.L. (Advisor, L&T Mumbai)
• Bose, Dr. Sunil (Head, FPC Divn. CRRI Retd.)
• Duhsaka, Vanlal (Chief Engineer, PWD Mizoram)
• Gangopadhyay, Dr. S. (Director, CRRI)
• Jain, Dr. S.S. (Prof., IIT Roorkee)
• Kumar, Ashok (Chief Engineer Retd., MoRTH)
• Lal, Chaman (Director, NRRDA)
• Pateriya, Dr. I.K. (Director Tech., NRRDA)
  ...and others from MoRTH, CRRI, IIT, NRRDA, and industry.

Ex-Officio Members:

• President, Indian Roads Congress (Bhowmik, Sunil)
• Honorary Treasurer, IRC (Das, S.N.)
• Secretary General, IRC (Nahar, Sajjan Singh)

Summary Table (Excerpt)

IRC SP 107 - Materials Key Points

1. Aggregates Specifications (Clause 3.3.1)

Gradation of Gap Graded Aggregates (Table 2):

2. Crumb Rubber Gradation (Clause 10.1.3)

IRC SP 107 - Mix Design Criteria for Gap Graded Bitumen-Rubber Mix

Key Specifications (Table 5)

Aggregate Requirements (Tables 2 & 3)

• Gradation (Gap graded aggregates):

• Physical Properties:

Bitumen-Rubber Binder Properties (Table 4)

• Base bitumen: VG 30 (traffic > 30 msa & max temp ≥ 30°C), VG 10 otherwise
• Viscosity at 177°C: 1500 - 4000 cP
• Softening point: ≥ 60°C
• Elastic recovery: ≥

Key Specifications & Formulas for Production of Crumb Rubber (IRC SP 107)

1. Crumb Rubber Quality (Clause 3.1 & Table 1)

• Wire content: < 0.01%
• Fabric content: < 0.95%
• Gradation for blending with bitumen:

2. Quantity of Crumb Rubber

• Minimum 15% by weight in bitumen blend.
• Can be 20% or higher depending on particle fineness.
• Finer particles → lower quantity needed to achieve required viscosity.

3. Production Process (Clause 13.2)

• Steps: shredding → tearing → shearing → grinding → granulation.
• Separation: magnetic (steel) & cyclonic (fibres).
• Controls: hydraulic/mechanical/electrical/electronic for feed, conveyance, size control.
• Packaging & storage facilities.

4. Natural Rubber Content (Clause 6)

• Some scrap tyres (esp. car tyres) may lack sufficient natural rubber.
• CALTARN Guidelines recommend:
  • CRM with 40-48% natural rubber content.
  • Blend: 25±2% high natural rubber CRM + 75±2% scrap tyre CRM.
• Natural rubber improves performance characteristics.

Summary Diagram of Crumb Rubber Production

flowchart LR
    A[Discarded Tyres] --> B[Shredding]
    B --> C[Tearing & Shearing]
    C --> D[Grinding & Granulation]
    D --> E[Separation]
    E --> F[Magnetic (Steel Removal)]
    E --> G[Cyclonic (Fibre Removal)]
    F & G --> H[Size Fraction Control]
    H --> I[Packaging & Storage]

This concise summary aligns with IRC SP 107:2015 provisions for crumb rubber production and usage in bituminous mixes.

Bitumen-Rubber Binder Preparation (IRC SP 107)

1. Blending Process (Clause 4)

• Temperature for mixing: Bitumen heated to 190℃ before adding crumb rubber.
• Mixing: Two stages — mixing and reaction in separate chambers.
• Reaction: Maintain at 190℃ with agitation for 60 minutes.
• Post-reaction storage: Keep at 180-190℃; do not hold above 160℃ for more than 10 hours. For longer storage, cool to 130-140℃ and reheat before use.
• Additives: Calcium carbonate powder may be added to crumb rubber for free flow.

2. Proportions & Mixing

• Accurate proportioning of crumb rubber and base bitumen.
• Avoid rubber agglomeration or floating.
• Rubber must be dry and free-flowing.

3. Properties of Bitumen-Rubber Binder (Table 4)

4. Aggregate Gradation (Table 2) & Physical Requirements (Table 3)

• Gradation example for gap graded aggregates:

• Physical properties include cleanliness, particle shape, strength, polishing, durability, and water absorption as per IS:2386.

5. Mix Design Criteria (Table 5)

| Property

IRC SP 107 - Mixing and Laying of Rubberized Bituminous (RB) Mix

Key Specifications:

• Mixing Temperature: 160℃ to 170℃
• Compaction Temperature: 140℃ to 150℃
• Use of Warm Mix Additives: Allowed to reduce mixing/compaction temperatures.
• Laying Restrictions:
  • Do not lay RB mix over cracked pavements with cracks ≥12.5 mm wide.
  • Use SAMI with CRMB/PMB as per MORTH specs over cracked pavements.
• Weather Limitations:
  • Air temperature > 15℃
  • Wind speed < 40 km/h at 2 m height
  • Avoid rainy conditions
• Spreading: Must be done by self-propelled paving machine.

Summary Table:

Notes:

• Follow IRC-MORTH guidelines for quality assurance.
• Proper temperature control ensures workability and compaction.
• Use SAMI treatment when laying over cracked pavements for durability.

flowchart LR
    A[Mixing] -->|160-170℃| B[Spreading]
    B --> C[Compaction]
    C -->|140-150℃| D[Finished Pavement]
    E[Weather Check] -->|Temp > 15℃ & Wind < 40 km/h| B
    F[Crack Check] -->|No cracks ≥12.5 mm| B
    F -->|Cracks ≥12.5 mm| G[SAMI Treatment]
    G --> B

This concise guide aligns with IRC SP 107 Clause 7.1 and weather limitations for effective RB mix laying.

IRC SP 107: Weather Limitations for Rubberized Bitumen (RB) Mix Laying

• Air Temperature: Must be above 15°C to ensure proper compaction; below this, compaction issues arise.
• Wind Speed: Should not exceed 40 km/h at 2 m height to avoid rapid cooling and poor bonding.
• Rain: Laying must be avoided during rainy conditions to prevent moisture-related defects.
• Mixing Temperature: Between 160°C and 170°C (IRC-MORTH guidelines).
• Compaction Temperature: Between 140°C and 150°C; warm mix additives may reduce these temperatures.
• Pavement Condition: Do not lay RB mix over pavements with cracks wider than 12.5 mm; use SAMI with CRMB/PMB for cracked pavements.

flowchart TD
    A[Start Laying RB Mix] --> B{Check Weather}
    B -->|Air Temp > 15°C| C{Wind Speed ≤ 40 km/h?}
    B -->|Air Temp ≤ 15°C| D[Delay Laying]
    C -->|Yes| E{Is it Rainy?}
    C -->|No| D
    E -->|No| F[Proceed with Laying]
    E -->|Yes| D

This ensures quality compaction and durability of the rubberized bitumen pavement.

Quality Assurance in IRC SP 107 (Clause 13)

• Calibration:
  All equipment and components must be calibrated and recalibrated regularly to maintain uniform quality over time and across locations.

• Trial Runs:
  Equipment settings should be finalized only after successful trial runs and properly documented.

• Supervision:
  Plant operations must be supervised by experienced personnel.

• Checks:
  Quality checks are mandatory at every step before proceeding to the next operation.

Summary Table for Quality Assurance Requirements

Additional Notes:

• Ensure mix design and material properties comply with IRC SP 107 Annexure 1.
• Maintain traceability of calibration and quality records for audits.

flowchart TD
    A[Start Operation] --> B[Calibrate Equipment]
    B --> C[Conduct Trial Runs]
    C --> D{Trial Successful?}
    D -- Yes --> E[Document Settings]
    D -- No --> B
    E --> F[Supervise Operation]
    F --> G[Perform Step-wise Quality Checks]
    G --> H{All Checks Passed?}
    H -- Yes --> I[Proceed to Next Step]
    H -- No --> F
    I --> J[End Operation]

This ensures consistent quality in bitumen-rubber mix production and laying as per IRC SP 107.

Performance Characteristics - IRC:SP:107 (Key Formulas, Tables & Specs)

1. Bitumen-Rubber Binder Properties (Table 4)

2. Mix Design Criteria (Table 5) for Gap Graded Bitumen-Rubber Mix (40-50 mm thickness)

3. Aggregates Gradation (Table 2)

4. Physical Requirements of Aggregates (Table 3)

• Cleanliness: < 2% passing 0.075 mm sieve (IS:2386 P-1)
• Flakiness & Elongation Index: < 30%
• LA Abrasion: < 25%
• Aggregate Impact Value: <

Advantages of Bitumen Rubber Technology (IRC SP 107 - Clauses 15 & related)

• Increased Viscosity & Film Thickness:
  Rubberized bitumen binder achieves very high viscosity (1500-4000 cP), enabling thicker binder film (~18 microns vs. 9 microns in normal bitumen), improving aggregate coating and durability.

• Reduced Temperature Susceptibility:
  Rubber imparts elasticity, reducing brittleness at low temperatures and softening at high temperatures.

• Improved Rutting Resistance:
  High viscosity and stone-to-stone contact in gap-graded aggregates enhance rutting resistance.

• Enhanced Durability:
  Better resistance to cracking, ageing, and reflection cracking; suitable as overlay on cracked pavements and concrete.

• Noise Reduction:
  Rubber layer dampens vehicle-tyre interaction noise.

• Environmental Benefit:
  Utilizes waste rubber (tyres), promoting recycling.

• Cost Effectiveness:
  Requires thinner layers for equal or better performance, reducing life-cycle costs.

Thickness Equivalency Table (Against Dense Graded BC)

Key Properties for Design (Clause 12)

Summary Diagram: Bitumen Rubber Benefits

graph LR
A[Crumb Rubber in Bitumen] --> B[Swelling & High Viscosity]
B --> C[Thicker Binder Film]
C --> D[Improved Aggregate Coating]
D --> E[Enhanced Rutting & Crack Resistance]
E --> F[Durability & Noise Reduction]
F --> G[Environmental & Cost Benefits]

References: IRC SP 107 Clauses 11.3, 12, 13, 15; CALTARN Guidelines; Indian lab studies (IIT Kharagpur).

Indian Studies and Field Trials - IRC SP 107 Highlights

Key Points from Indian Context:

• Indian research validates R-B (Rubberized Bitumen) mixes for viscosity and fatigue life.
• Experimental stretches (12-24 months) show promising performance.
• Benefits include waste utilization, GHG reduction, minor capital investment, and improved pavement performance.

Specifications & Field Trial Guidelines

Fatigue Life & Mix Design

• Gap graded B-R mixes show significantly higher fatigue life than dense graded bituminous concrete.
• Laboratory tests (IIT Kharagpur) and CALTRANS studies confirm better performance of gap graded mixes for overlays.

Summary Diagram of Process Flow

flowchart TD
    A[Indian Field Trials] --> B[Mix Design & Lab Testing]
    B --> C[Experimental Pavement Laying]
    C --> D[Rolling with Steel Wheel Rollers]
    D --> E[Apply Blotter Material (Sand @1 kg/m²)]
    E --> F[Performance Monitoring (12-24 months)]
    F --> G[Validation of Fatigue Life & Crack Resistance]

References:

• Clause 1.4: Indian validation studies
• Clause 5.4: Rolling and compaction specs
• Clause 11: Blotter material application
• Clause 12: Use of gap graded B-R mix

This concise summary aids in understanding Indian field trial practices and key parameters for rubberized bitumen mixes per IRC SP 107.

IRC SP:107-2015 — Thickness Equivalency & Design Considerations for Bitumen-Rubber (B-R) Mix

Key Points:

• Thickness Equivalency:

  • No reduction in design thickness is recommended despite higher fatigue life of gap graded B-R mixes compared to dense graded BC.
  • CALTRANS and IIT Kharagpur lab tests confirm gap graded B-R mixes have significantly higher fatigue resistance and better reflection cracking resistance.
  • Designers adopt a minimum Marshall Stability of 5.4 kN for gap graded B-R mixes.

• Mix Design (Table 5):

• Compaction & Rolling:

  • Rolling should start immediately after laying.
  • Use only steel wheel rollers (3 tandem rollers recommended).
  • Pneumatic tyred rollers are prohibited to avoid mix picking.

• Blotter Material:

  • Apply sand at 1 kg/m² before opening to traffic to prevent mix pickup by pneumatic tires.

Aggregate Gradation for Gap Graded Mix (Table 2):

Summary Diagram:

flowchart TD
    A[Bitumen + Crumb Rubber] --> B[Mixing Chamber at 190°C]
    B --> C[Reaction Chamber (60 min

Environmental and Economic Benefits of Asphalt Rubber (AR) Technology (IRC:SP:107-2015)

Key Environmental Benefits:

• Waste Utilization: Uses scrap tire rubber, aiding safe disposal without greenhouse gas emissions.
• Reduced Noise Pollution: AR pavements reduce vehicle-tyre noise.
• Lower Thickness Requirement: Gap-graded AR mixes require thinner layers, reducing material consumption.
• Durability: Longer fatigue life reduces frequent repairs and associated environmental impacts.

Economic Benefits:

• Thickness Equivalency Table (CALTARN):

• Fatigue Life Improvement:

• Cost Effectiveness: Lower thickness and longer life reduce life cycle costs.

Summary:

• AR technology enhances binder viscosity, elasticity, and durability.
• Suitable for all climates due to rubber elasticity.
• Enables sustainable construction by recycling waste tires.
• Provides high-performance, quieter, and crack-resistant pavements.

flowchart LR
    A[Waste Tires] --> B[Crumb Rubber]
    B --> C[Rubberized Bitumen Binder]
    C --> D[Gap Graded Mix]
    D --> E[Thinner Pavement Layer]
    E --> F[Longer Fatigue Life & Durability]
    F --> G[Environmental & Economic Benefits]

References: Clauses 1.4, 13, 14, 15 of IRC:SP:107-2015.

Challenges & Quality Issues in IRC SP 107 (Clause 16.3 & Quality Assurance):

• Key Concern: Variability in crumb rubber properties causes non-uniform AR binder quality.
• Impact: Difficulty in ensuring consistent quality over project length and across projects.
• Solution:
  • Implement rigorous quality assurance (QA) procedures.
  • Control design parameters based on input material characteristics.

Quality Assurance Highlights (Clause 13 & 16.3)

• Regular testing of crumb rubber and AR binder properties.
• Use of standardized mix design criteria (see Clause 6) to accommodate material variability.
• Monitoring blending, pumping, mixing, and laying processes (Clauses 4, 5, 7).
• Use of gap-graded B-R mix to improve performance and uniformity (Clause 12).
• Continuous supervision and adherence to weather and rolling limitations (Clauses 8, 10).

Typical Mix Design Parameters (Summary from IRC SP 107):

flowchart LR
    A[Crumb Rubber Variability] --> B[Quality Assurance Procedures]
    B --> C[Material Testing]
    B --> D[Controlled Mix Design]
    B --> E[Process Monitoring]
    E --> F[Blending & Pumping]
    E --> G[Mixing & Laying]
    B --> H[Uniform Quality Achieved]

Summary: Uniform AR binder quality is achievable by strict QA, controlling inputs, and following mix design & process guidelines in IRC SP 107.