IRC 014- 2004: Standard Specifications for Open Graded Premix Carpet (OGPC)

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The construction of durable, long-lasting roads demands adherence to precise standards and guidelines. One such critical specification is for laying Open Graded Premix Carpet (OGPC) as outlined in the IRC:14-2004 code. This blog highlights the significant details and processes involved in the construction of OGPC and seal coats to ensure robust road surfaces suitable for varying climatic, traffic, and terrain conditions.

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Background and Approval Process

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The draft for IRC:14-2004 underwent multiple rounds of discussions and approvals. Initially reviewed by the HSS Committee on December 20, 2003, the draft received final approval with modifications by the Executive Committee and the IRC Council in early 2004. The document was formally approved by the Director General (Road Development) & Special Secretary to the Government of India on May 31, 2004, making it an official standard for construction practices.

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Scope of IRC:14-2004

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The specifications focus on laying 20 mm thick Open Graded Premix Carpet using paving bitumen, modified bitumen, or bitumen emulsion as binders. It includes the types and grades of materials to be used, depending on site-specific conditions. Additionally, the document specifies two types of seal coats:

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1. Type A (Liquid Seal Coat)
2. Type B (Premixed Seal Coat)

These layers serve as wearing courses and ensure road longevity.

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Materials Used

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1. Binder

• Paving Bitumen: Must conform to IS:73 standards.
• Modified Bitumen: Should meet IRC:SP:53 specifications.
• Tack Coat Binder: Use rapid-setting cationic bitumen emulsion (IS:8887).
• Alternate Binder: In snow-bound areas, cutback bitumen (IS:217 or IS:454) can be used with approval.

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2. Coarse Aggregates

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The aggregates should be:

• Clean, hard, and angular.
• Free from flaky, soft, or deleterious material.
• Sourced from crushed rock, gravel, river shingle, or slag.

They must meet the specifications outlined in Table 1 of IRC:14-2004, including a maximum abrasion value of 40% and a maximum flakiness index of 25%.

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3. Fine Aggregates

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For seal coats, fine aggregates should be:

• Crushed stone dust, sand, or grit.
• Clean, durable, and free of organic impurities.
• Tested for a minimum sand equivalent value of 60 (IS:2720 Part 37).

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Quantities of Materials Required

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The tables below summarize the material requirements for OGPC and seal coats:

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Table 2: Aggregates for OGPC (Per 10 m² Road Surface)

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• 13.2 mm Coarse Aggregates: 0.18 m³
• 11.2 mm Coarse Aggregates: 0.09 m³
• Total Aggregates: 0.27 m³

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Table 3: Aggregates for Seal Coat (Per 10 m² Road Surface)

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• Type A: 0.09 m³ (6.7 mm size coarse aggregates).
• Type B: 0.06 m³ (medium coarse sand or fine grit).
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Table 4-6: Binder Requirements

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• Tack Coat: 2.0 to 3.5 kg per 10 m².
• Premix Carpet: 14.6 kg per 10 m².
• Seal Coat Type A: 9.8 kg per 10 m².
• Seal Coat Type B: 6.8 kg per 10 m².

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Construction Procedure

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1. Weather Limitations

Work should not proceed during adverse weather conditions like rain, fog, or dust storms. The minimum air temperature should be 10°C, and wind speeds should not exceed 40 km/h.

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2. Surface Preparation

The road surface should be:

• Free from dust, mud, or debris.
• Repaired for potholes and ruts using appropriate material.
• Primed with a tack coat if granular.

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3. Tack Coat Application

A tack coat ensures bonding between the road surface and OGPC. It should be sprayed uniformly using a pressure sprayer at specified rates and temperatures.

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4. Premix Preparation

• Heating: Bitumen and aggregates are heated separately.
• Mixing: Combine materials in a hot-mix plant to achieve a homogeneous mixture. Ensure the temperature difference between materials does not exceed 15°C.
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5. Spreading and Rolling

• The premix is spread to the desired thickness using a paver.
• Camber boards check the gradient, and irregularities are corrected.
• Rolling is done at specified temperatures to compact the layer.

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Conclusion

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The IRC:14-2004 standard ensures the construction of durable and resilient road surfaces. By following the guidelines for materials, quantities, and procedures, engineers can build roads capable of withstanding diverse climatic and traffic conditions. Proper adherence to these specifications not only enhances road longevity but also ensures safety and sustainability.

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