Specification for Semi-Dense Bituminous Concrete

IRC 95 - Introduction: Key Points & Tables

• Scope: IRC 95 covers design, materials, and construction of bituminous mixes for road surfacing.
• Design Criteria: Emphasizes durable, economical, and weather-resistant pavements.
• Materials: Classified by grading numbers with specific sieve size passing percentages.

Key Table: Grading of Aggregates (by % passing weight)

Notes:

• Grading 1 is coarser; Grading 3 is finer.
• Proper grading ensures workability and strength of bituminous mixes.

For detailed mix design and construction, refer to clauses 3 to 7 in IRC 95.

IRC: 95 - Scope Summary

The Scope section (Clause 2) of IRC 95 defines the application limits and coverage of the code, primarily for designing and constructing bituminous macadam and bituminous concrete pavements for roads.

Key Points:

• Applies to flexible pavements using bituminous materials.
• Covers materials, design, construction, and quality control.
• Intended for highways and roads subjected to various traffic loads.
• Specifies grading requirements for aggregates used in bituminous mixes.

Important Table: Aggregate Grading (Table 4 - Materials)

Design Criteria (Brief)

• Mix design follows job mix formula (Clause 5).
• Construction and quality control ensure durability and performance.

This scope ensures standardized pavement design for durability and safety on Indian roads.

flowchart TD
    A[Scope: Flexible Pavements] --> B[Materials]
    A --> C[Design Criteria]
    A --> D[Construction]
    A --> E[Quality Control

IRC 95 - Design Criteria (Clause 3)

Key specifications for bituminous mix design using the Marshall method:

Notes:

• Marshall Stability ensures adequate strength.
• Flow values indicate flexibility.
• Vv controls air voids for durability.
• VMA ensures sufficient binder film around aggregates.
• Binder content is optimized via Marshall design to meet above criteria.

This table guides mix design to achieve durability and performance in bituminous pavements.

flowchart TD
    A[Start: Aggregate Selection] --> B[Determine Binder Content]
    B --> C[Prepare Marshall Specimens]
    C --> D[Apply 50 Compaction Blows Each End]
    D --> E[Measure Stability & Flow]
    E --> F{Check Criteria}
    F -->|Meets| G[Finalize Mix Design]
    F -->|Fails| B

Key Specifications & Tables for Materials (IRC 95)

1. Aggregate Grading (TABLE 4)

2. Coarse Aggregate Requirements (TABLE 3)

• Note: Water absorption up to 2% allowed in exceptional cases.

3. **Fine

Job Mix Formula (IRC 95) - Key Points

The Job Mix Formula (JMF) defines the proportions of coarse aggregate, fine aggregate, filler, and bitumen to achieve the desired mix properties for semi-dense bituminous concrete.

1. Design Criteria (Marshall Method)

2. Aggregate Specifications

• Coarse Aggregate: Crushed, angular, clean, tough, free from deleterious matter.
• Fine Aggregate: Passing 2.8 mm sieve, retained on 90 µm sieve.
• Filler: Inert, passes 710 µm sieve, with specified gradation.

3. Physical Requirements of Coarse Aggregate

4. Job Mix Formula Calculation

• Blend aggregates by weight or volume to meet the target gradation.
• Use laboratory-determined optimum bitumen content.
• Ensure the mix meets Marshall criteria.
• Use representative samples from actual materials.

5. Summary Formula

[ \text{JMF} = \text{Coarse Aggregate} + \text{Fine Aggregate} + \text{Filler} + \text{Bitumen (Optimum

IRC 95 - Key Construction Specifications & Formulas

1. Base Preparation (Clause 6.1)

• Base must be clean, dust-free, and firm.
• Fill potholes/ruts with premixed materials and compact well.

2. Materials (Clause 4)

• Coarse Aggregate: Crushed, angular, clean; retained on 2.8 mm sieve.

  • Max limits:
    • Aggregate Impact Value: 30%
    • Los Angeles Abrasion: 40%
    • Flakiness Index: 30%
    • Stripping Value: 25%
    • Water Absorption: 1% (up to 2% in exceptional cases)
    • Soundness (Sodium sulphate loss): 12% max
    • Soundness (Magnesium sulphate loss): 18% max

• Fine Aggregate: Passing 2.8 mm and retained on 90 µm sieve; clean, hard, durable.

• Filler: Inert, passing 710 µm sieve; 90% passing 180 µm, 70% passing 90 µm; e.g., stone dust, cement.

3. Job Mix Formula (Clause 5)

• Blend aggregates by weight or volume to achieve desired gradation.
• Use laboratory-determined optimum bitumen content.
• Ensure materials used in construction match lab samples.

4. Aggregate Gradation (Typical)

IRC 95 - Controls (Clause 7) Summary

Key Quality Control Measures:

• Aggregate Gradation:

  • Periodic sieve analysis at cold feeder to maintain original job mix gradation.
  • Physical properties tested every 50-100 m³ or as directed.

• Binder Checks:

  • Penetration & softening point per IS:1203 & IS:1205.
  • Bitumen temperature: 150–177°C, viscosity 150–300 cSt.
  • Temperature difference between aggregate & bitumen ≤ 14°C.

• Aggregate Temperature:

  • Should not exceed 163°C (±10°C tolerance lower side).

• Mix Sampling:

  • One sample per 100 tonnes or daily per plant.
  • Tests: Marshall stability, flow, voids, density, bitumen content, and aggregate gradation after extraction.

Permissible Variations from Job Mix Formula (Table 4)

Additional Notes:

• Use a field laboratory for quality control at all stages.
• Maintain uniform compaction to achieve ≥98% lab density.
• Rolling sequence: edges → center; super-elevated sections from lower to upper edge.
• Avoid excessive water or oil on rollers; keep wheels moist only.

flowchart TD
    A[Aggregate Sampling] --> B[Gradation Check]
    B --> C{Within Limits?}
    C -- Yes --> D[Proceed]
    C -- No --> E[Adjust Mix]
    D --> F[Bitumen Sampling]
    F --> G[Penetration & Softening Point Tests]
    G --> H{Within Limits?}
    H -- Yes --> I[Mix Production]
    H -- No --> J[Adjust Binder]

IRC 95: Weather and Seasonal Limitations - Key Points

• Mix Temperature at Laying:
  • Maximum: 160°C
  • Minimum: 120°C
• Rolling Operations:
  • Should be done when mix temperature is between 80°C and 160°C to avoid shoving or hair cracks.
  • Rolling must be completed before temperature falls below 80°C.
• Thickness Check:
  • Use penetration depth of hot steel scale correlated with surface area and plant output.
• Field Density Test:
  • Conduct one test per 500 m² or less.
  • Density should be at least 98% of laboratory density.

Aggregate Physical Requirements (Table 3)

Summary Diagram: Temperature & Rolling Window

gantt
    title Mix Temperature & Rolling Operations
    dateFormat  HH:mm
    axisFormat  HH:mm
    section Temperature (°C)
    Mix laid (120-160°C) :active, a1, 12:00, 4h
    Rolling window (80-160°C) :a2, after a1, 3h
    Rolling complete before <80°C :milestone, a3, after a2, 0h

Note: Proper weather conditions (dry, moderate temperature) are essential to maintain these limits and ensure quality compaction and durability.