Top 9 Proven Steps for Bituminous Concrete (BC) Construction
Bituminous Concrete (BC) is the final wearing course of flexible pavement laid in 30–50 mm thickness over DBM or bituminous base. Construction shall strictly follow MoRTH Clause 507, including approved mix design, controlled laying temperature, proper compaction and quality control tests.
1. Scope
This work covers preparation of surface, tack coat application, production of BC mix, transportation, laying, compaction, joint treatment and quality control testing in accordance with MoRTH Clause 507.
2. Reference Standards
- MoRTH Specifications – Clause 507 (5th Revision)
- IRC: SP: 84 – Manual of Specifications
- IS: 73, IS: 15462 – Bitumen
- IS: 2386 (All Parts) – Aggregates
3. Equipment Required
- Hot Mix Plant with automatic controls
- Sensor paver with electronic screed
- Tandem vibratory rollers and PTR
- Bitumen pressure distributor
- Mechanical broom and air compressor
- Core cutting machine
4. Materials
4.1 Bitumen
VG-30 / VG-40 paving bitumen or modified bitumen conforming to IS:73 / IS:15462, as specified in contract.
4.2 Aggregates
Aggregates shall satisfy physical requirements of MoRTH Table 500-16 including impact value, flakiness, elongation and stripping resistance.
4.3 Mineral Filler
Cement, hydrated lime or stone dust conforming to MoRTH Table 500-9.
5. Aggregate Grading & Binder Content (Table 500-17)
| IS Sieve (mm) | BC Mix-1 (19 mm) | BC Mix-2 (13.2 mm) |
|---|---|---|
| 19 | 90–100 | 100 |
| 13.2 | 59–79 | 90–100 |
| 4.75 | 35–55 | 53–71 |
| 0.075 | 2–8 | 4–10 |
| Min Bitumen (%) | 5.2 | 5.4 |
6. Mix Design
- Marshall Mix Design (MS-2)
- Job Mix Formula approved by Engineer
- Plant trial mandatory before bulk production
7. Construction Operations
7.1 Surface Preparation
Existing surface shall be clean, dry and uniformly tack coated as per MoRTH Clause 503.
7.2 Laying & Compaction
- Minimum laying temperature: 130°C
- Rolling sequence: Breakdown → Intermediate → Finish
- Compaction completed before temperature drops below limit
7.3 Joints
Longitudinal and transverse joints shall be cut vertically, painted with hot bitumen and properly compacted.
8. Quality Control Tests (MoRTH Section 900)
| Test | Frequency |
|---|---|
| Aggregate Grading | 1 per 400 t (min 2/day) |
| Binder Content | 1 per 400 t |
| Marshall Stability | 3 per 400 t |
| Density (Core) | 1 per 700 m² |
Acceptance Criteria
- Minimum field density ≥ 92% of Gmm
- Surface regularity within specified tolerance
- No segregation, bleeding or cracking
9. Opening to Traffic
Traffic shall be permitted only after cooling of BC surface and written approval from Engineer-in-Charge.
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