IRC Code:SP:125-2019 - Guidelines for Cement Grouted Bituminous Mix Surfacing for Urban Roads

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Urban roads require durable, cost-effective, and high-performance surfacing solutions to withstand increasing traffic loads and environmental challenges. The Indian Roads Congress (IRC) Code:SP:125-2019 provides comprehensive guidelines for Cement Grouted Bituminous Mix (CGBM) surfacing, which enhances the strength and longevity of bituminous roads by integrating cementitious grout into high-void bituminous mixes. This technique offers a semi-flexible pavement with superior durability, making it an ideal choice for urban infrastructure development.

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What is Cement Grouted Bituminous Mix (CGBM)?

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CGBM is a specialized pavement construction technique where a high-void bituminous mix is infused with a highly flowable cementitious grout. The grout fills the voids, creating an impervious, water-tight surface with improved structural integrity and load-bearing capacity. This method combines the flexibility of bituminous layers with the rigidity of cement concrete, ensuring long-term durability.

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Benefits of CGBM Technology

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1. Enhanced Durability

• Offers resistance to rutting, fatigue, and moisture damage.
• Reduces susceptibility to bitumen aging and oxidation.

2. Cost-Effectiveness

• Extends pavement life, reducing frequent maintenance costs.
• Requires less material compared to conventional rigid pavement solutions.

3. High Load-Bearing Capacity

• Can support heavy urban traffic without deformation.
• Suitable for roads with a high volume of commercial vehicles.

4. Reduced Water Damage

• The cementitious grout fills voids, making the surface impervious to water.
• Minimizes the risk of potholes and surface deterioration due to rain and flooding.

Key Components of CGBM1. High-Void Bituminous Mix

• Aggregate grading must ensure 25-35% air voids.
• Optimum binder content to prevent excess bleeding.

2. Cementitious Grout

• Composed of cement, water, and mineral additives like fly ash, silica fume, and superplasticizers.
• Designed for high flowability to penetrate all voids efficiently.

Construction Process of CGBMThe application of CGBM surfacing follows a systematic approach to ensure high-performance results:

1. Preparation of the Existing Surface:
   • Clean the surface thoroughly.
   • Apply a tack coat using RS-1 bitumen emulsion.
2. Laying the High-Void Bituminous Mix:
   • A specially graded open-graded bituminous mix is laid using a paver.
   • Compacted with a 10-ton static roller to achieve the required voids.
3. Grout Application:
   • The bituminous layer is cooled to ambient temperature.
   • Cementitious grout is poured and spread to ensure full penetration.
   • Excess grout is removed, and curing is done for 7 days.
4. Final Surface Finish and Quality Checks:
   • Skid resistance test ensures adequate grip.
   • Compressive strength and resilient modulus tests validate structural integrity.

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Performance and Pavement Design Considerations

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The resilient modulus of CGBM is approximately 5000 MPa, making it a strong alternative to conventional bituminous mixes. Structural design considerations include:

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• Layer thickness based on traffic volume:
  • 30 mm for traffic up to 5 MSA.
  • 40-50 mm for traffic exceeding 5 MSA.
• Opening to Traffic: CGBM roads can be opened for light traffic within 24 hours.

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Adoption of CGBM in India

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The Surat Municipal Corporation and several other cities in India have successfully implemented CGBM technology. Research by CRRI (Central Road Research Institute) confirms its effectiveness in urban road applications.

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Conclusion

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‍IRC:SP:125-2019 provides a robust framework for adopting Cement Grouted Bituminous Mix Surfacing for urban roads. With enhanced durability, water resistance, and cost savings, CGBM is a game-changing solution for sustainable road infrastructure in India.

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