- 2071 Bhadra
Materials in pavement layers
Short answer
Subgrade uses compacted soil (CBR ≥5%); sub-base, granular material like GSB; base, WBM, WMM or bituminous macadam; binder course, DBM; surface, bituminous concrete or SDBC. Rigid pavements have a concrete slab over DLC. Stronger, costlier materials are placed in upper layers.
Explain the materials used in different layers of the road pavement.
A flexible pavement consists of layers, each made of materials suited to the stress at that level. Materials are specified in NRS 2070 / DoR Standard Specifications and IRC.
| Layer | Function | Materials |
|---|---|---|
| Subgrade (top 500 mm of soil) | Foundation, supports pavement | Natural/compacted soil with CBR at least 5%; improved with lime/cement or granular material |
| Sub-base | Distributes load, drainage, frost protection | Natural gravel, moorum, crushed stone, granular sub-base (GSB), stabilised soil |
| Base course | Main load-bearing and distribution | Water-bound macadam (WBM), wet-mix macadam (WMM), crushed aggregate, bituminous macadam/DBM, cement/lime stabilised |
| Binder course | Links base and surface, gives strength | DBM, bituminous macadam |
| Surface / wearing course | Takes traffic, waterproof, skid-resistant | Bituminous concrete (BC), SDBC, premix carpet, surface dressing, mastic asphalt, cement concrete |
Rigid pavement layers
- Subgrade, granular sub-base, dry lean concrete (DLC) base and pavement quality concrete (PQC) slab of M30-M40 concrete, with dowel and tie bars and joint sealants.
Binders and other materials
- Bitumen (VG-30, 60/70), cutback, emulsion for tack coat and prime coat; cement, lime, fly ash for stabilisation; geotextiles and geogrids; steel in reinforcement.
The materials get stronger and costlier upwards, so cheaper local materials are used in lower layers.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Desirable properties of road aggregates · Transportation Engineering I, chapter 6 · asked 5×
- Types of bitumen and bituminous materials · Transportation Engineering I, chapter 6 · asked 6×
- Why pozzolanic materials are used · Civil Engineering Materials, chapter 4 · asked 2×
- Why composite materials are used · Civil Engineering Materials, chapter 10 · asked 2×
- Pavement layer functions and rigid pavement joints · Transportation Engineering II, chapter 2
- Rolled vs normal concrete; CC pavement construction · Transportation Engineering II, chapter 3