Profile Corrective Course (Dense Bituminous Macadam) – Construction Methodology

Profile Corrective Course (PCC) using Dense Bituminous Macadam (DBM) is executed to correct pavement profile irregularities such as depressions, sags, uneven camber and surface undulations before laying the final overlay.

1.0 Scope and Surface Preparation

The Profile Corrective Course is a bituminous layer of variable thickness (typically 50–100 mm) laid over an existing granular or bituminous surface to restore the correct longitudinal and cross profile as per approved drawings.

1.1 Existing Bituminous Surface

• Repairs: Potholes, cracks and distressed areas shall be repaired as per MoRTH Clauses 3004.2 & 3004.3.
• Scarifying: Where specified, existing bituminous layer shall be scarified without disturbing underlying layers.
• Base Preparation: Exposed surface reworked, compacted and primed if required as per Clause 502.
• Tack Coat: Bituminous emulsion applied uniformly before laying PCC DBM.

1.2 Existing Granular Surface

• Surface cleaned of loose material and dust.
• Priming carried out as per MoRTH Clause 502 before bituminous layer.
• Surface to be firm, dry and broom-cleaned.

1.3 Pre-Laying Checks

Existing top levels shall be jointly checked and recorded before and after preparation to confirm thickness and profile correction.

2.0 Plant, Machinery & Equipment

3.0 Materials & Mix Production

3.1 Materials

• Coarse & fine aggregates from approved quarries
• Bitumen: VG-30 / VG-40 (IS:73)
• Tack Coat: Rapid setting bituminous emulsion

3.2 Job Mix Formula (JMF)

JMF shall be prepared in the site laboratory using Marshall Method and approved by IE/PMC. The procedure is identical to DBM/BC mix design as per MoRTH Section 500.

3.3 Hot Mix Plant Operation

• Bitumen storage temperature: 150–165°C
• Aggregate drying temperature: 150–170°C
• Mixing carried out in controlled, dust-free environment
• Maximum mix temperature not exceeding 165°C

4.0 Laying & Compaction

4.1 Transportation of Mix

• Mix transported in covered tipping trucks.
• Truck beds coated with release agent.
• Mix temperature at dispatch: 155–165°C.

4.2 Tack Coat Application

• Rate of application: 0.25–0.30 kg/m²
• Applied by mechanical sprayer
• DBM laid only after tack coat breaks

4.3 Laying & Finishing

• Sensor wire fixed at 10 m interval for profile control
• Minimum laying temperature: 125°C
• Loose thickness allowance: approx. 25%
• Manual laying permitted in confined areas

4.4 Compaction

• Rolling by vibratory roller followed by PTR
• Rolling from lower edge to higher edge
• Compaction continued until specified density achieved
• Joints cut full depth and edges painted with hot bitumen

5.0 Quality Control & Traffic Management

• Core cutting after 24 hours for density verification
• Routine bitumen testing for each consignment
• Surface finish as per MoRTH Clause 902
• Traffic opened minimum 24 hours after completion
• Traffic managed using cones, barricades and flagmen