General Guidelines About the Equipment for Bituminous Surface Dressing

IRC SP 34 - Introduction: Key Points

IRC SP 34 is a Special Publication by the Indian Roads Congress focused on surface dressing equipment and procedures.

Key Highlights from the Introduction:

• Purpose: To provide guidelines on types, specifications, and use of equipment for surface dressing of roads.
• Scope: Covers mechanical brooms, binder distributors, aggregate chip spreaders, combined bitumen & aggregate spreaders, and rollers.
• Objective: Enhance road surface quality, durability, and skid resistance through standardized equipment use.
• Structure: The document is divided into sections detailing equipment types, specifications, operational guidelines, and safety precautions.

Important Tables and Sections in IRC SP 34:

Summary Diagram of Equipment Flow:

flowchart LR
    A[Mechanical Brooms] --> B[Binder Distributors]
    B --> C[Aggregate Chip Spreader]
    C --> D[Combined Bitumen & Aggregate Spreader]
    D --> E[Rollers]
    E --> F[Finished Surface]

For detailed formulas or specific equipment specs, refer to respective sections (4-8) in IRC SP 34. The Introduction primarily sets the framework and scope.

IRC SP 34 – Scope Summary

The Scope section (Clause 2, Page 2) of IRC SP 34 defines the range of equipment and procedures covered for surface dressing on roads. It includes specifications for:

• Mechanical brooms
• Binder distributors
• Aggregate chip spreaders
• Combined bitumen and aggregate spreaders
• Rollers
• Use of equipment and precautions

Key Points:

• The publication provides detailed specifications and operational guidelines for equipment used in surface dressing.
• It ensures uniformity and quality in application of bituminous surface treatments.
• Related documents include IS:2093 (Distributors), IS:2094 (Heaters), IRC:23, IRC:48, and IRC:96 dealing with surface dressing methods and equipment.

Useful Table Reference:

Note: For detailed formulas or operational parameters, refer to respective clauses. For example, binder distributor application rates and spreader calibration formulas are in Clause 5 and 6.

flowchart TD
    A[Scope of IRC SP 34] --> B[Mechanical Brooms]
    A --> C[Binder Distributors]
    A --> D[Aggregate Chip Spreaders]
    A --> E[Combined Bitumen & Aggregate Spreaders]
    A --> F[Rollers]
    A --> G[Use of Equipment & Precautions]

This structure ensures comprehensive coverage of surface dressing equipment and practices under IRC SP 34.

IRC SP 34: Types of Equipment - Key Points

IRC SP 34 classifies equipment used in surface dressing mainly into:

• Mechanical Brooms: For cleaning the road surface before dressing.
• Binder Distributors: To spray bitumen uniformly.
• Aggregate Chip Spreaders: For spreading aggregates evenly.
• Combined Bitumen and Aggregate Spreaders: Integrated equipment for spraying bitumen and spreading aggregates simultaneously.
• Rollers: For compacting the surface dressing.

Key Specifications & Notes:

• Mechanical Brooms: Should have adjustable brushes and dust control.
• Binder Distributors: Must ensure uniform bitumen application; spray bar pressure and speed are critical.
• Aggregate Spreaders: Require calibrated hopper and conveyor systems for uniform aggregate distribution.
• Rollers: Typically pneumatic or steel-wheeled; weight and speed affect compaction quality.

Typical Parameters (from IRC practice):

For detailed operational guidelines and calibration, refer to respective clauses (4 to 8) in IRC SP 34.

flowchart LR
    A[Mechanical Broom] --> B[Binder Distributor]
    B --> C[Aggregate Chip Spreader]
    C --> D[Roller]
    D --> E[Finished Surface Dressing]

This sequence ensures proper cleaning, bitumen application, aggregate spreading, and compaction for durable surface dressing.

Mechanical Brooms (IRC SP 34, Clause 4)

• Purpose: Clean road pavement surface free from dust before binder application to ensure proper adhesion.
• Types: Towed or powered; commonly pulled type or tractor-mounted.
• Bristle Materials: Fibre, steel, or nylon.
• Operation: More efficient than hand brooms; used before spreading binder.

Key Specifications & Notes:

• Mechanical brooms must thoroughly clean the surface.
• Use light broom pressure when removing excess aggregates after traffic has passed and bond has developed (Clause 9.6).
• No detailed formulas or tables are provided in IRC SP 34 for mechanical brooms.
• Refer to Fig. 1 in IRC SP 34 for typical mechanical broom illustration.

Summary Table (Conceptual):

flowchart LR
    A[Road Surface] --> B[Mechanical Broom Cleaning]
    B --> C[Clean Surface]
    C --> D[Binder Application]
    D --> E[Aggregate Spreading]
    E --> F[Traffic Passage]
    F --> G[Excess Aggregate Removal (Light Broom Pressure)]

For detailed mechanical broom selection and operation, consult IRC SP 34 Clause 4 and related equipment manuals.

Key Specifications and Types of Binder Distributors (IRC SP 34 - Clause 5)

Binder distributors are crucial for uniform application of binder in surface dressing. The main requirements are:

• Uniform spreading at a prescribed rate and temperature
• Matching chip spreader output in a working day
• Mechanical bulk distributors only (hand-held methods not acceptable)

Types of Binder Distributors:

Principal Components:

• Spray bar for binder distribution
• Heated insulated storage tank
• Gear-type positive displacement pump, often with separate engine
• Air compressor for tank pressure and burner operation
• Burners for heating binder

Important Relationships:

[ \text{Rate of Spread} \propto \frac{1}{\text{Travel Speed}} ]

(for pressurised tank, constant volume, and constant pressure types)

Diagram: Binder Distributor Components

graph LR
A[Heated Binder Tank] --> B[Gear Pump]
B --> C[Spray Bar with Nozzles]
B --> D[Air Compressor & Burners]
E[Engine] --> B
E --> D

Summary:
For most surface dressing, constant volume or constant pressure distributors are preferred. Constant pressure types offer easier calibration and flexible nozzle control, while constant volume types are better for heavy binder applications.

Aggregate Chip Spreader - IRC SP 34 Key Points

Types of Aggregate Chip Spreaders (Clause 6.1)

• Tail gate spreader: Mounted on tipper tailgate; simplest and cheapest.
• Truck attached (towed) spreader: Hopper on wheels, propelled by tipper truck.
• Self-propelled spreader: Most effective; hopper, conveyors, and metering roll for uniform spreading.

Tail Gate Chip Spreader (Clause 6.2)

• Rate of spread depends on gravity and truck speed.
• Metering devices (feed roller driven by truck wheels/fifth wheel) help maintain uniform discharge despite speed variations.

Truck Attached Spreaders (Clause 6.3)

• Hopper with augers distributes aggregate evenly.
• Propelled by tipper truck.

Self-propelled Spreader (Clause 6.4)

• Hopper receives chippings from tipper.
• Conveyor belts move chippings to transverse hopper.
• Metering roll controls discharge rate.

Calibration & Rate of Spread (from Clause 5.3.4 for binders, applicable conceptually)

• Application rate (liters/sqm) = Output (liters/min) ÷ [Speed (m/min) × Spray width (m)]
• For aggregate spreaders, calibration involves weighing aggregate spread over known area at constant speed.

Specifications Summary (Clause 6 & 5.3.5)

• Adjustable spread width.
• Metering device or feed roller for uniform discharge.
• Hopper capacity suitable for job size.
• Self-propelled or trailer type preferred for uniformity.
• Calibration charts or tests to ensure correct application rate.

flowchart LR
    TipperTruck -->|Loads| Hopper
    Hopper -->|Conveyor Belts| TransverseHopper
    TransverseHopper -->|Metering Roll| PavementSurface
    PavementSurface -->|Aggregate Spread| UniformLayer

This diagram illustrates the self-propelled spreader operation flow.

For detailed machine selection and calibration, refer to IRC SP 34 clauses 6 and 5.3.4-5.3.5.

Combined Bitumen and Aggregate Spreader (IRC SP 34)

Key Points:

• Type: Tail gate type spreader that simultaneously sprays bitumen and spreads aggregate.
• Function: Ensures uniform application of bitumen binder and aggregate chips in one pass, improving efficiency.

Specifications & Requirements (from clauses 5.3 & 6):

• Bitumen Distributor:

  • Tank capacity: 5,000 to 16,000 liters, insulated steel with internal baffles.
  • Heating: Flue tubes with burners (kerosene/diesel) and binder circulation pump to prevent coking.
  • Spray bar: Adjustable width and height; each nozzle with cut-off valve and adjustable spray angle.
  • Speed control: Fifth wheel or electronic speedometer; calibration charts for application rate.
  • Instruments: Thermometer, contents gauge, tachometer, pressure gauge (constant pressure type), pump tachometer (constant volume type).

• Aggregate Spreader:

  • Types: Tail gate, truck attached, self-propelled.
  • Tail gate spreader can have metering devices (feed rollers driven by truck wheels) for uniform discharge.
  • Self-propelled spreaders use conveyor belts and metering rolls for precise aggregate distribution.

Calibration Formulae for Bitumen Application:

[ \text{Litres per sqm} = \frac{\text{Output of spray bar (litres/min)}}{\text{Speed (m/min)} \times \text{Spray width (m)}} ]

[ \text{Speed (m/min)} = \frac{\text{Output of spray bar (litres/min)}}{\text{Application rate (litres/sqm)} \times \text{Spray width (m)}} ]

Summary Table:

IRC SP 34 - Rollers (Clause 8 Summary & Key Points)

While the provided context lacks detailed formulas or tables specifically for rollers, key specifications and considerations from IRC SP 34 and general practice include:

Roller Types & Functions:

• Steel Wheel Rollers: Traditional, but may crush weak aggregates or crack poorly shaped chippings.
• Rubber Tyred Rollers: Provide kneading action, better for compaction without aggregate damage.
• Pneumatic Tyred Rollers: Effective for sealing and embedding aggregates.

Key Specifications:

• Rollers must ensure uniform compaction without damaging aggregates.
• Rolling should be done immediately after spreading aggregates to embed them properly.
• Avoid excessive pressure which can crush aggregates or cause bridging over surface depressions.

General Guidelines:

• Use multiple passes with decreasing pressure to achieve optimum compaction.
• Rolling speed should be slow enough to allow proper embedding but fast enough to maintain productivity.
• For surface dressing, rolling is critical to ensure aggregate retention and proper binder-aggregate bonding.

Related Notes from IRC SP 34:

• Loose aggregates should be removed by power broom after rolling and traffic passage (Clause 9.6).
• Combined bitumen and aggregate spreaders (Clause 7) help improve uniformity before rolling.

Summary Table: Roller Selection Criteria

flowchart LR
    A[Aggregate Spreading] --> B[Rolling]
    B --> C{Roller Type}
    C --> D[Steel Wheel Roller]
    C --> E[Pneumatic Tyred Roller]
    C --> F[Rubber Tyred Roller]
    D --> G[High Pressure, risk of crushing]
    E --> H[Kneading action, uniform compaction]
    F --> I[Gentle compaction, finishing]
    B --> J[Embed aggregates & ensure bonding]

For detailed design and operational

IRC SP 34: Use of Equipment and Precautions (Clause 9)

This clause emphasizes safe and efficient operation of surface dressing equipment to ensure quality and worker safety.

Key Points:

• Pre-operation Checks: Inspect all equipment (rollers, spreaders, binders) for wear, leaks, and calibration.
• Calibration: Ensure bitumen and aggregate spreaders are calibrated for uniform application rates.
• Speed Control: Maintain recommended speeds for each equipment type to avoid uneven dressing.
• Safety Measures: Use protective gear, ensure clear communication, and maintain safe distances.
• Environmental Precautions: Avoid operations in wet or windy conditions to prevent material loss.
• Maintenance: Regular cleaning and servicing to prevent clogging and mechanical failures.

Typical Equipment Parameters (from related clauses):

flowchart LR
    A[Pre-operation Checks] --> B[Calibration]
    B --> C[Operation at Recommended Speed]
    C --> D[Safety Measures]
    D --> E[Environmental Precautions]
    E --> F[Regular Maintenance]

For detailed formulas and calibration tables, refer to Clauses 4-8 of IRC SP 34.

Key Documents for Surface Dressing (IRC SP 34 - Appendix 1):

• Ministry of Surface Transport (Roads Wing), Specifications for Road & Bridge Works (1988, 2nd Rev.)
• IS:2093-1962 – Specifications for Distributors for Tar and Bitumen
• IS:2094-1962 – Specifications for Heaters for Tar and Bitumen
• IRC:23-1966 – Tentative Specifications for Two Coat Bituminous Surface Dressing
• IRC:48-1972 – Tentative Specifications for Bituminous Surface Dressing using Precoated Aggregates
• IRC:96-1987 – Tentative Specification for Two Coat Surface Dressing using Cationic Bitumen Emulsion
• IRC HRB Special Report No. 7 – State of Art: Surface Dressing

Important Specification Notes:

• Removing Excess Aggregates (Clause 9.6):
  Use a power broom with light pressure after traffic has passed and bitumen-aggregate bond is established.

• Equipment Types Covered:
  Mechanical brooms, binder distributors, aggregate chip spreaders, combined spreaders, rollers.

Typical Surface Dressing Process (Simplified):

flowchart LR
    A[Surface Preparation] --> B[Binder Application]
    B --> C[Aggregate Spreading]
    C --> D[Rolling]
    D --> E[Excess Aggregate Removal]
    E --> F[Traffic Opening]

For detailed design specs, quality controls, and equipment use, refer to the above documents and IRC SP 34 Appendix 1.