- 2081 Baisakh · 8 marks
Bituminous pavement types and quality control
Short answer
Types include surface dressing, premix carpet, bituminous macadam, DBM and bituminous concrete. Field quality control: test aggregates and bitumen, design mix by Marshall method, check temperatures, compaction density not less than 98% of lab density, thickness, surface regularity, and binder content by extraction.
Explain the types of bituminous pavements. How the quality of bituminous pavement can be controlled in the field?
Types of bituminous pavements
Bituminous pavements are classified by the layer, method of mixing and surface treatment.
| Type | Description | Typical use |
|---|---|---|
| Surface dressing (single/double) | Bitumen sprayed on base and covered with stone chips, rolled | Low-cost wearing course; renewal coat |
| Seal coat / fog seal | Thin film of bitumen and chips/sand over an existing surface | Sealing cracks, restoring skid resistance |
| Penetration macadam (grouting) | Coarse stone layer rolled and then bitumen grouted into it | Medium traffic base/wearing course |
| Premix carpet / open-graded premix | Hot pre-coated 13.2 mm and 11.2 mm chips laid 20 mm thick and sealed with a seal coat | Rural and district roads |
| Bituminous macadam (BM) | Open-graded mix of coarse aggregate and bitumen, 50-100 mm | Binder/base course |
| Dense bituminous macadam (DBM) | Dense-graded mix, 50-100 mm, Marshall design | Binder and base course on highways |
| Asphalt (bituminous) concrete (BC) | Dense-graded hot mix with filler, 30-50 mm | Wearing course of highways |
| Mastic asphalt, SMA, gap graded, cold mix | Special mixes for bridge decks, heavy traffic or small repairs | Specialised |
Field quality control
Quality of bituminous construction is controlled in three stages.
- Materials - test aggregate (LAA, AIV, flakiness, water absorption, stripping value, soundness) and bitumen (penetration, softening point, ductility, viscosity, flash point) before use and at a fixed frequency (e.g. every 100 m3 of aggregate and every consignment of bitumen).
- Mix design and plant control - Marshall mix design (stability, flow, air voids, VMA) and job-mix formula; temperature of aggregate and bitumen; accuracy of proportioning; check of grading from hot bins; mix temperature at plant.
- Field control - temperature of mix at delivery and rolling (not less than 120-130 C at the start, 70 C at the end), rate of spread of binder (tray test), thickness (level survey/cores), compaction (core density not less than 98 percent of laboratory density), surface regularity (3 m straight edge, bump integrator), camber and joints; extraction test for binder content and gradation on random samples; no laying in rain or at air temperatures below 10 C.
Records are kept lot-wise; defective lots are rejected or reworked as per the contract.
✓ Answer checked by Claude Opus 5.5 (high effort)
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