Recommended Practice for Bituminous Penetration Macadam (Full Grout)
1966 Edition

This section introduces IRC 20, providing essential specifications and tables related to constructing bituminous penetration macadam pavements:

• Coarse Aggregate Spreading Quantities (Table 2): | Thickness (Compacted) | Volume (m³/10 m²) | |----------------------|------------------| | 50 mm | 0.60 | | 75 mm | 0.90 |

• Grading of Key Aggregate (Table 3): Percent passing varies for different sieves based on compacted layer thickness.

• Key Aggregate Spreading Quantities (Table 4): | Thickness (Compacted) | Volume (m³/10 m²) | |----------------------|------------------| | 50 mm | 0.15 | | 75 mm | 0.18 |

• Seal Coat Material Requirements (Table 5): | Material | Size Description | Quantity per 10 m² | |----------|------------------|-------------------| | Chippings | Passing 9 mm, retained on 6 mm sieve | 0.09 to 0.11 m³ | | Binder | - | 9.8 to 12 kg |

• Bituminous Binder Application Rates (Table 6): | Thickness (Compacted) | Binder Type | Quantity (kg/10 m²) | |----------------------|----------------------|---------------------| | 50 mm | Straight-run bitumen | 50 | | | Road tar RT-4/RT-5 | 60-65 | | 75 mm | Straight-run bitumen | 68 | | | Road tar RT-4/RT-5 | 82-88 |

• Construction Guidelines:

  • No operations below 16°C or during damp, foggy, or rainy weather.
  • Proper base and aggregate preparation with adequate compaction.
  • Rolling procedures and surface deviations limited to 12 mm.
  • Traffic to be allowed after 24 hours or earlier with speed limits.

Details derived from IRC 20 clauses 1, 2.36, 3.2.3–3.2.6, 4.1–4.6, and 5.

This part covers the baseline requirements for aggregates and seal coat materials as per IRC 20:

• Coarse Aggregate Quantities (Table 2): | Compact Thickness | Volume (m³/10 m²) | |-------------------|------------------| | 50 mm | 0.60 | | 75 mm | 0.90 |

• Key Aggregate Gradation (Table 3): | Sieve Size | % Passing for 50 mm | % Passing for 75 mm | |------------|--------------------|--------------------| | 38 mm | - | - | | 25 mm | - | 100 | | 19 mm | 100 | 35-70 | | 12 mm | 35-70 | - | | 9 mm | - | 0-15 | | 4.75 mm | 0-15 | - | | 2.36 mm | 0-5 | 0-5 |

• Key Aggregate Quantities (Table 4): | Compact Thickness | Volume (m³/10 m²) | |-------------------|------------------| | 50 mm | 0.15 | | 75 mm | 0.18 |

• Seal Coat Material Details (Table 5): | Material | Size Description | Amount per 10 m² | |----------|------------------|-----------------| | Chippings | Passing 9 mm, retained on 6 mm sieve | 0.09 to 0.11 m³ | | Binder | Straight-run bitumen or road tar | 9.8 to 12 kg |

These parameters ensure correct layering and material quality for road pavement layers as defined within IRC 20 clauses 3.2.1 to 3.2.6.

This section details the material requirements for bituminous penetration macadam following IRC 20:

• Coarse Aggregate Volumes (Table 2):

  • 50 mm compacted layer requires 0.60 m³ per 10 m²
  • 75 mm compacted layer requires 0.90 m³ per 10 m²

• Key Aggregate Gradation (Table 3): Percent passing varies by sieve size and compacted thickness. For instance, 50 mm thickness requires 100% passing 19 mm sieve and 35-70% passing 12 mm sieve.

• Key Aggregate Volumes (Table 4):

  • 50 mm thickness: 0.15 m³ per 10 m²
  • 75 mm thickness: 0.18 m³ per 10 m²

• Seal Coat Materials (Table 5):

  • Chipping: passing 9 mm, retained on 6 mm sieve, quantity 0.09 to 0.11 m³ per 10 m²
  • Binder: straight-run bitumen or road tar, 9.8 to 12 kg per 10 m²

These guidelines guarantee proper gradation and quantities for long-lasting bituminous layers.

Key provisions for bituminous binders from IRC 20 include:

• Acceptable binders include straight-run bitumen grades 80/100, 60/70, 30/40; road tar grades RT-4 and RT-5; and suitable cutbacks depending on climate.

• Coarse aggregate spreading volumes: | Compacted Thickness | Volume (m³/10 m²) | |---------------------|------------------| | 50 mm | 0.60 | | 75 mm | 0.90 |

• Key aggregate gradation and amounts: | Sieve Size | % Passing (50 mm) | % Passing (75 mm) | |------------|------------------|------------------| | 38 mm | - | - | | 25 mm | - | 100 | | 19 mm | 100 | 35-70 | | 12 mm | 35-70 | - | | 9 mm | - | 0-15 | | 4.75 mm | 0-15 | - | | 2.36 mm | 0-5 | 0-5 |

• Key aggregate quantities: | Compacted Thickness | Volume (m³/10 m²) | |---------------------|------------------| | 50 mm | 0.15 | | 75 mm | 0.18 |

• Seal coat materials and quantities: | Material | Size Description | Amount per 10 m² | |----------|------------------|-----------------| | Chipping | Passing 9 mm, retained on 6 mm sieve | 0.09 to 0.11 m³ | | Binder | Suitable grade bitumen or road tar | 9.8 to 12 kg |

• Bituminous binder application rates: | Compacted Thickness | Straight-run Bitumen (kg/10 m²) | Road Tar RT-4/RT-5 (kg/10 m²) | |---------------------|---------------------------------|------------------------------| | 50 mm | 50 | 60-65 | | 75 mm | 68 | 82-88 |

• Construction instructions:

  • No work below 16°C or in wet, foggy, or rainy weather.
  • Aggregates must be dry before binder application.
  • Rolling sequence and surface tolerances as specified.
  • Traffic allowed after minimum 24 hours with speed restrictions if opened earlier.

Aggregate specifications per IRC 20 include:

• Coarse Aggregate Volumes (Table 2): | Compact Thickness | Volume (m³/10 m²) | |-------------------|------------------| | 50 mm | 0.60 | | 75 mm | 0.90 |

• Key Aggregate Gradation (Table 3): | Sieve Size | 50 mm (%) | 75 mm (%) | |------------|-----------|-----------| | 38 mm | - | - | | 25 mm | - | 100 | | 19 mm | 100 | 35-70 | | 12 mm | 35-70 | - | | 9 mm | - | 0-15 | | 4.75 mm | 0-15 | - | | 2.36 mm | 0-5 | 0-5 |

• Key Aggregate Volumes (Table 4): | Compact Thickness | Volume (m³/10 m²) | |-------------------|------------------| | 50 mm | 0.15 | | 75 mm | 0.18 |

• Seal Coat Materials (Table 5): | Material | Size Description | Amount per 10 m² | |----------|------------------|-----------------| | Chipping | Passing 9 mm, retained on 6 mm sieve | 0.09 to 0.11 m³ | | Binder | Straight-run bitumen or road tar | 9.8 to 12 kg |

• Aggregates must be clean, durable, strong, roughly cubical, and free from harmful substances.

These tables and guidelines regulate selection, grading, and quantities for aggregates used in bituminous penetration macadam layers.

Essential construction steps for Bituminous Penetration Macadam (BPM) according to IRC 20 include:

• Weather Restrictions: No BPM laying below 16°C or when pavement is wet, foggy, rainy, or dusty.

• Base Preparation: Leveling and shaping base to uniform section; filling potholes and compacting; priming as needed.

• Coarse Aggregate Spreading and Compaction: Uniform spreading with edge protection; compaction using 10-ton roller starting at shoulders overlapping by 30 cm; surface tolerances within ±12 mm verified by templates; rolling halts before void closure to permit binder penetration.

• Bituminous Binder Application: Applied at prescribed rates and temperatures; aggregate surface must be dry; use pressure distributor or nozzles; pouring pots allowed only if authorized.

• Key Aggregate Placement: Applied immediately following binder penetration; rolled and broomed until fully locked; maintaining grade and cross-section.

• Seal Coat Application: Applied prior to traffic opening; heated binder spread followed by chippings and rolling.

• Traffic Opening: Preferably after 24 hours; if earlier, vehicle speed limited to 15 km/h.

Material quantities and sizes are detailed in tables for coarse aggregate, key aggregate, and binders ensuring quality and durability.

According to IRC 20 Clause 4.1, bituminous penetration macadam should not be constructed when ambient temperature is under 16°C or when conditions are damp, foggy, rainy, or dusty. This ensures effective binder application and compaction. For cold climates, Grade 175/225 bitumen is recommended, while Grade 80/100 suits warm regions. Road tar grades RT-2 and RT-3 are suitable for hilly and plains respectively. Equipment must be ready and aggregates dry before binder application at specified rates. Final surface uniformity and compaction should be verified before allowing traffic, ideally after 24 hours, with speed restrictions if opened sooner.

IRC 20 Clause 4.3 specifies that the underlying base must be prepared to a uniform grade and cross-section, with all potholes and depressions filled and compacted before BPM layers are applied. Priming may be used following IRC tentative guidelines. Key tables inform aggregate quantities and gradations to ensure proper layering. Spreading and compaction should achieve consistent depth and profile, with surface irregularities limited to 12 mm. Binder must be applied at correct temperatures and rates, followed by immediate key aggregate spreading and rolling. Seal coats are applied before traffic opening. Weather restrictions apply to guarantee quality.

For effective compaction of coarse aggregate in BPM per IRC 20:

• Spreading quantities (Table 2): 0.60 m³/10 m² for 50 mm thickness, 0.90 m³/10 m² for 75 mm thickness.

• Key aggregate gradation varies with thickness (Table 3). For example, 50 mm thickness requires 100% passing 19 mm sieve.

• Key aggregate spreading amounts (Table 4): 0.15 m³/10 m² for 50 mm, 0.18 m³/10 m² for 75 mm.

• Seal coat materials (Table 5): chippings and binder quantities specified.

These measures ensure correct layer thickness, grading, and compaction for long-lasting pavements.

The procedure for applying bituminous materials as defined in IRC 20 includes:

• Coarse aggregate volumes per specified compacted thickness.

• Key aggregate gradation and quantities according to layer thickness.

• Seal coat material types and amounts.

• Binder application rates: straight-run bitumen ranges from 50 to 68 kg/10 m² depending on thickness; road tar RT-4/RT-5 varies from 60-88 kg/10 m².

• Binder must be applied at the correct temperature with dry aggregate using pressure distributors for uniform coverage.

• Key aggregate is spread immediately after binder penetration, rolled, and broomed until fully locked.

• Seal coat is applied before traffic is allowed.

• Construction must avoid conditions below 16°C or wet weather to ensure proper bonding.

For applying key aggregates in BPM as per IRC 20:

• Aggregate size depends on compacted thickness (50 mm or 75 mm) as per Tables 1 and 3.

• Coarse aggregate quantities: 0.60 m³/10 m² for 50 mm and 0.90 m³/10 m² for 75 mm thickness.

• Key aggregate gradation varies by sieve size and thickness.

• Key aggregate quantities: 0.15 m³/10 m² for 50 mm and 0.18 m³/10 m² for 75 mm thickness.

• Aggregates must be placed using approved methods ensuring proper interlock and stability.

These guidelines ensure the bituminous layer's strength and durability.

Per IRC 20 Clause 5, traffic should ideally be permitted on the bituminous penetration macadam surface 24 hours after completion of rolling. If traffic must be allowed sooner, vehicle speeds must be restricted to 15 km/h. Prior to opening, seal coats must be applied with heated binder and chippings, followed by rolling for uniformity. Surface tolerances include maximum longitudinal undulation of 12 mm and cross-profile variation not exceeding 8 mm. These practices ensure a stable, uniform surface resistant to early damage.