Recommended Practice for Recycling of Bituminous Pavements

IRC 120 - Introduction: Key Specifications and Tables

Overview

IRC 120 focuses on recycling of pavements using foamed bitumen and other methods. The introduction covers:

• Types of recycling: Cold In-Place (CIR), Cold In-Plant (CIP), Hot In-Place (HIR), Hot In-Plant (HIP), Full Depth Reclamation (FDR)
• Variability management in reclaimed materials
• Mix design considerations for recycled pavements
• Quality assurance and testing protocols

Important Tables & Specifications

Sample Quantities (A1.3.3.3)

Key Formula for Bulk Density (Typical)

[ \text{Bulk Density} = \frac{\text{Mass of compacted sample}}{\text{Volume of sample}} ]

Summary Diagram: Recycling Process Flow

flowchart TD
    A[Pavement Condition Assessment] --> B[Selection of Recycling Method]
    B --> C{Cold or Hot Recycling?}
    C -->|Cold| D[Cold In-Place / In-Plant Recycling]
    C -->|Hot| E[Hot In-Place / In-Plant Recycling]
    D --> F[Mix Design using Foamed Bitumen]
    E --> F
   

IRC 120 - Scope: Key Specifications & Tables

Scope Overview:

• Covers mix design, construction, and quality control for foamed bitumen stabilized layers used in cold recycling of pavements.
• Includes procedures for sampling, testing, and quality assurance of materials and layers.

Key Tables & Specifications:

Important Notes:

• Batch: Used for quality control sampling.
• ITS (Indirect Tensile Strength): Key strength test for foamed bitumen mixes.
• Moisture/Density Relationship: Essential for compaction control.

flowchart TD
    A[Scope: Foamed Bitumen Stabilisation] --> B[Sampling & Preparation]
    B --> C[Sample Quantities]
    B --> D[Mix Design & Testing]
    D --> E[Quality Assurance Testing]
    E --> F[Material Properties Control]
    F --> G[Compaction, Thickness, Strength]

This summarizes the scope and key parameters for foamed bitumen stabilization per IRC 120.

IRC 120: Investigations for Recycling - Key Points

1. Criteria for Investigation

• Pavement Condition: Assess surface defects, cracking, rutting.
• Pavement Composition & History: Identify layers, materials, previous repairs.
• Structural Evaluation: Determine load-bearing capacity.
• Material Properties: Test reclaimed aggregate grading, binder content.

2. Key Considerations (Table 1 Highlights)

3. Recycling Methods

• Reclamation: Milling, pavement demolition, full depth reclamation (FDR).
• Cold Recycling: Cold in-place (CIR), cold in-plant (CIP).
• Hot Recycling: Hot in-plant (HIP), hot in-place (HIR).

4. Mix Design Procedure for Foamed Bitumen

• Calibration of bitumen flow rate.
• Adjustment of foam expansion and half-life.
• Target binder content and gradation per reclaimed material.

5. Important Parameters for Success

• Proper evaluation of reclaimed material variability.
• Correct mix design and binder modification.
• Quality control during construction.
• Depth and proportion limits of recycled materials.

Example: Mix Design Formula (Foamed Bitumen Stabilisation)

[ \text{Optimum Bitumen Content} = \text{Bitumen content that achieves target stability and durability} ]

flowchart TD
    A[Pavement Investigation] --> B{Condition Assessment}
    B -->|Good| C[Recycling Not Required]
    B -->|Surface Defects| D[Cold Recycling]
    B -->|Structural Damage| E[Full Depth Reclamation]
    D --> F[Mix Design & Binder Improvement]
    E --> F
    F --> G[Construction & Quality Control]
    G --> H[Performance Monitoring]

For detailed procedures and annexures, refer to IRC 120 Annex 1 and Appendix I.

IRC 120: Assessment of Pavement Condition and Defects

IRC 120 does not provide explicit formulas but outlines key criteria and methods for assessing pavement condition:

Key Parameters for Pavement Condition (Clause 3.1)

• Cracking: Type, extent, and severity (e.g., longitudinal, transverse, alligator cracks)
• Rutting: Depth and length of depressions in wheel paths
• Potholes: Number, size, and severity
• Surface Roughness: Measured by International Roughness Index (IRI) or Roughness Index (RI)
• Skid Resistance: Friction values to assess safety

Typical Assessment Methods

• Visual surveys and distress mapping
• Roughness measurement using profilometers
• Deflection testing (FWD) for structural evaluation

Common Formulas

• Serviceability Index (PSI) (adapted from AASHTO, similar principles apply):

[ PSI = 5.03 - 1.91 \log(1 + RD) - 0.01 \times (N_{alligator}) - 0.01 \times (N_{patch}) ]

Where:

• (RD) = rut depth (mm)
• (N_{alligator}) = number of alligator cracks per unit area
• (N_{patch}) = number of patches per unit area

Typical Defect Severity Classification (Qualitative)

flowchart TD
    A[Pavement Condition Assessment] --> B[Visual Survey]
    A --> C[Roughness Measurement]
    A --> D[Deflection Testing]
    B --> E[Identify Cracks, Potholes]
    C --> F[Measure IRI or RI]
    D --> G[Evaluate Structural Capacity]

Summary: Use visual distress surveys, roughness indices, and deflection tests to assess pavement condition. Severity of defects guides maintenance priorities. For detailed structural evaluation

IRC 120: Reclaiming and Reprocessing of Pavement Materials

Key Specifications & Concepts

• Design & Technology Integration: Successful recycling depends on:

  • Designing with reclaimed material properties
  • Appropriate reclamation and reprocessing methods
  • Ensuring strength, durability, and serviceability

• Recycling Types:

  • In-place Recycling: Reclaim and reuse on site
  • In-plant Recycling: Reclaim and process off site

• Recycling Methods:

  • Cold Recycling:
    • Foam Bitumen
    • Emulsion
    • Stabilization
  • Hot Recycling:
    • Hot In-Place
    • Hot In-Plant

Important Tables & Clauses

Mix Design Formula (Foam Bitumen Stabilization)

• Optimum Bitumen Content (OBC) is determined by trial mixes, balancing:
  • Stability
  • Flow
  • Air voids
  • Moisture susceptibility

Overview Diagram (Reclamation & Recycling Types)

graph TD
    A[Reclamation & Recycling] --> B[In-place Recycling]
    A --> C[In-plant Recycling]
    B --> B1[Cold Recycling]
    B --> B2[Hot Recycling]
    C --> C1[Cold Recycling]
    C --> C2[Hot Recycling]
    B1 --> B1a[Foam Bitumen]
    B1 --> B1b[Em

Management of Reclaimed Material Stockpile (IRC 120)

• Reference: Appendix III to Annex 1 (IRC 120) details stockpiling and management of reclaimed materials (RBM).

Key Specifications from IRC 120:

• Moisture Control (Clause 3.14):
  • Cover stockpiles with shelters/buildings to prevent precipitation.
  • Use conical stockpiles to shed water naturally.
  • Place stockpiles on paved, sloped surfaces for drainage.
  • Avoid ponding by shaping piles continuously during construction.
  • Minimize heavy equipment on top of piles to prevent compaction.
  • Limit stockpile height to 3 m to reduce self-consolidation.

Best Practices Summary:

flowchart TD
    A[Reclaimed Material] --> B[Stockpile on Paved, Sloped Surface]
    B --> C{Shape Stockpile}
    C -->|Conical Shape| D[Water Shedding]
    C -->|Irregular Shape| E[Correct Shape During Build]
    B --> F[Limit Height ≤ 3m]
    B --> G[Minimize Heavy Equipment on Top]
    B --> H[Cover Stockpile to Prevent Moisture]

This approach ensures quality RBM with minimized moisture and compaction, optimizing bituminous plant efficiency.

Cold Recycling Methods (IRC 120 Key Points)

Cold recycling reuses existing pavement materials without heat, using agents like emulsions, foam bitumen, rejuvenators, or cementitious additives.

Types of Cold Recycling:

• Cold In-Place Recycling (CIR): Recycling done on-site. Control of mixing time and foam bitumen injection is critical.
• Cold In-Plant Recycling (CIP): Recycling done in a plant with precise control on mixing and foaming.
• Full Depth Reclamation (FDR): Pulverization of full pavement depth (100-300 mm), mixing with additives (foam bitumen, cement, lime), compaction, and overlay.

Key Specifications:

• Bitumen for foaming: Penetration grade 60-150 (IS:73), no anti-foaming agents.
• Foaming characteristics:
  • Expansion ratio: 8-10 times
  • Half-life: ~6 seconds
  • Temperature: 160°C - 190°C
• Pulverization gradation: Max 40 mm, conforming to IRC 37.
• Sand Equivalent (SE): ≥ 30%
• Indirect tensile strength (100 mm specimen):
  • Dry: > 225 kPa
  • Wet: > 100 kPa
• Voids: 6-8%
• Resilient modulus: As per IRC 37.

Process Flow (CIR & CIP):

flowchart LR
  A[Reclaimed Material] --> B[Mixing with Foam Bitumen]
  B --> C[Mixing Time Control]
  C --> D[Paving & Compaction]
  D --> E[Finished Pavement]

Important Considerations:

• Design sensitive to RBM properties.
• Proper logistics to ensure continuous production, paving, and compaction.
• Separate mix designs for each material combination.

For detailed mix design, construction, and quality control, refer Annex 1 and Appendix I of IRC 120.

This summary captures the essential formulas, tables, and specifications for cold recycling from IRC 120.

Hot Recycling Methods (IRC 120) - Key Points

Types:

• Hot In-Plant Recycling (HIP)

  • Uses up to 30% Reclaimed Bituminous Material (RBM).
  • Requires rejuvenators to soften oxidized binder.
  • RBM is not heated directly to avoid fumes.
  • Plant modifications needed (feed system, process changes).
  • Can be continuous or batch type.

• Hot In-Place Recycling (HIR)

  • Heats existing pavement surface with infrared radiation.
  • Scarifies bituminous surface.
  • Adds virgin/corrective mix and rejuvenators.
  • Mixes scarified and new materials.
  • Features: scarifier, collecting hopper, conveyors, mixing unit, spreading auger, compaction unit.

Selection Criteria (from Clause 4.4 Table):

*HIR: Hot In-Place Recycling, HIP: Hot In-Plant Recycling, CIR: Cold In-Place Recycling, CIP: Cold In-Plant Recycling

Important Specifications:

• Bitumen for foaming (for cold recycling): Penetration grade 60-150, expansion ratio 8-10, half-life ~6 seconds, temp. 160-190°C.
• Mix design: Must consider RBM variability, rejuvenator type, aggregate grading.
• Logistics: Coordinated production, paving, and compaction critical for success.

Simplified HIR Plant Process Flow:

flowchart LR
  A[Infrared Heating] --> B[Scarifier]
  B --> C[Collecting Hopper]
  C --> D[Add Binder/Rejuvenator]
  D --> E[Conveyor to Proportioning Hopper]

IRC 120: Mix Design & Testing Procedures for Foamed Bitumen Stabilisation

Key Steps & Specifications:

1. Sample Preparation (Clause A1.3.3)

   • Conduct standard soil tests (grain size, Atterberg limits).
   • Ensure representative proportioning of soil and filler.
   • Use adequate sample quantities for repeatability.
   • Measure hygroscopic moisture content to adjust mix water.
   • Include active filler as per soil characteristics.

2. Mixing (Clause A1.4)

   • Mix prepared soil samples with foamed bitumen at controlled temperatures.
   • Maintain foaming characteristics (expansion ratio, half-life).

3. Specimen Manufacture (Clause A1.5)

   • Prepare 100 mm diameter briquette specimens for testing.

4. Curing (Clause A1.6)

   • Cure specimens under specified conditions (temperature, humidity, time).

5. Testing

   • Bulk Density (Clause A1.7)
   • Indirect Tensile Strength (ITS) (Clause A1.8.1)
     • ITS is critical to assess strength development.

6. Quality Assurance (Appendix II)

   • Monitor foaming characteristics, compaction, layer thickness.
   • Maintain daily production records.
   • Use moisture-density relationship to control compaction.

Important Formulas:

• Indirect Tensile Strength (ITS):

[ ITS = \frac{2P}{\pi t d} ]

Where:

• (P) = maximum load (N)
• (t) = specimen thickness (mm)
• (d) = specimen diameter (mm)

Summary Table: Sample Quantities for Mix Design

flowchart TD
    A[Sample Collection] --> B[Standard Soil Tests]
    B --> C[Representative Proportioning]
    C --> D[Mixing with Foamed Bitumen]
    D --> E[Specimen Manufacture

IRC 120: Quality Control & Assurance for Foamed Bitumen Stabilised Layers

Key Quality Requirements & Tests

Indirect Tensile Strength (ITS) Calculation (Equation A1.9)

[ ITS = \frac{2P}{\pi \times h \times d} ]

• P = Maximum load (kN)
• h = Specimen height (cm)
• d = Specimen diameter (cm)

ITS Test Procedure Summary

1. Load briquette at 50.8 mm/min diametrically.
2. Record max load (P).
3. Calculate ITS.
4. For soaked ITS, soak specimens 24h @ 25°C, surface dry, then test.

Minimum ITS Strength Requirements

Sample Quantities for Tests

IRC 120: Equipment and Technology for Recycling - Key Points

1. Overview of Recycling Technologies (Clause 1.5)

• Two main types:
  • In-place recycling
  • In-plant recycling
• Each with two variants:
  • Cold recycling:
    • Foam bitumen
    • Emulsion
    • Stabilization
  • Hot recycling:
    • Hot process
    • Cold process

2. Important Processes

• Reclamation: Milling, ripping, breaking of pavement materials.
• Handling: In-place or off-site management of reclaimed materials.
• Processing: Achieve design gradation by adding fresh aggregates and binders.
• Construction: Laying and compaction of the recycled mix.

3. Key Equipment Requirements (Annex 1, A1.1)

• Calibration of bitumen flow rate for foamed bitumen stabilization.
• Milling machines, mixing plants, and spreading equipment for both cold and hot recycling.

4. Mix Design Considerations (Table 1 Highlights)

Simplified Process Flow Diagram (Fig. 1 Overview):

flowchart LR
    A[Reclamation] --> B[Handling of Reclaimed Material]
    B --> C[Processing]
    C --> D[Construction]
    subgraph Recycling Types
        E1[In-place Recycling]
        E2[In-plant Recycling]
    end
    subgraph Variants
        F1[Cold Recycling]
        F2[Hot Recycling]
    end
    A --> E1 & E2
    E1 & E2 --> F1 & F2
    F1 -->|Foam Bitumen, Emulsion, Stabilization| C
    F2 -->|Hot Process, Cold Process| C

Summary: IRC 120 emphasizes a holistic approach covering reclamation, processing, and construction with specific equipment and mix design protocols, especially for foam bitumen cold recycling. Calibration and proper handling ensure quality and compatibility of recycled pavements.

IRC 120: Environmental and Economic Considerations in Recycling

Key Points on Recycling Options (Clause 4.4)

*Note: Full Depth Recycling applies for granular base defects.

Environmental & Economic Considerations Summary

• In-place recycling (HIR, CIR) maximizes reclaimed material use, ideal for shallow defects.
• In-plant recycling (HIP, CIP) suits deeper recycling but uses ~30% reclaimed materials.
• Choice between hot/cold methods depends on:
  • Economic feasibility
  • Environmental impact (energy use, emissions)
  • Capability to meet mix design requirements

Mix Design & Improvement

• Manage variability in reclaimed materials (aggregate grading, binder content).
• Improve binder properties (e.g., foamed bitumen).
• Follow mix design procedures (see Annex 1 for foam bitumen stabilization).

flowchart LR
    A[Defect Severity & Depth] --> B{Type of Recycling}
    B -->|Shallow defects| C[In-place Recycling (HIR, CIR)]
    B -->|Deep defects| D[In-plant Recycling (HIP, CIP)]
    C --> E[Maximize Reclaimed Material Use]
    D --> F[Use ~30% Reclaimed Material]
    E & F --> G[Consider Economics & Environment]

For detailed mix design and quality control, refer to Annex 1 and Appendix I of IRC 120.

IRC 120: Documentation & Reporting Key Points

1. Quality Assurance & Daily Records

• Maintain daily production records for in-situ and in-plant treatments.
• Compile as-built data with daily production and QA test results (Clause A2.2.3).

2. Testing Frequency & Methods (Clause A2.3)

3. Indirect Tensile Strength (ITS) Test (Clause A1.8.1)

[ ITS = \frac{2P}{\pi \times h \times d} ]

• (P) = maximum load (N)
• (h) = specimen height (cm)
• (d) = specimen diameter (cm)
• Test at 50.8 mm/min deformation rate.
• Test both dry and soaked specimens (24 hr soak at 25°C).

4. Minimum Strength Requirements (Clause A1.9)

5. Sample Quantities for Tests (Clause A1.3.3.3)

IRC 120 Appendices Key Points:

The appendices primarily focus on Foamed Bitumen Stabilisation for cold recycling of pavements, covering:

Appendix I to Annex 1 – Mix Design Procedure for Foamed Bitumen Stabilisation

• A1.1 Equipment Requirements: Calibration of bitumen and water flow rates.
• A1.2 Foaming Characteristics: Determination of bitumen foaming properties.
• A1.3 Sampling & Preparation:
  • Field and in-plant sampling.
  • Sample blending and preparation for mix design.
  • Standard soil tests, moisture content, active filler requirements.
• A1.4 Mixing: Prepared samples with foamed bitumen.
• A1.5–A1.7: Manufacture and curing of 100 mm briquette specimens; bulk density determination.
• A1.8 Strength Tests: Indirect Tensile Strength (ITS) test procedures.
• A1.9: Interpretation of test results.

Appendix II to Annex 1 – Quality Assurance Testing

• Daily production records for in-situ and in-plant treatments.
• Quality requirements for foaming characteristics, layer thickness, compaction.
• Strength characteristics from field samples and briquette specimens.
• Moisture-density relationship tests.

Important Tables & Specifications (Summary):

Typical Formula for Bulk Density (ρ):

[ \rho = \frac{\text{Mass of specimen (g)}}{\text{Volume of specimen (cm}^3)} ]

For 100 mm diameter briquette (height h):

[ V = \pi \times