Wheel loads are transferred by grain-to-grain contact through granular structure. Stresses decrease with depth, hence multi-layered with high quality materials at top. Typical layers: seal coat, surface course, binder course, base course, sub-base, compacted subgrade [citation:4].
Load distributed by slab action (flexural strength) – pavement behaves like elastic plate resting on subgrade. Types: JPCP, JRCP, CRCP, prestressed. Usually placed directly on subgrade or single granular/stabilized layer [citation:4][citation:10].
| Layer | Material | Thickness (mm) – Highway | Thickness (mm) – Industrial |
|---|---|---|---|
| Seal coat | Thin asphalt treatment | 6–10 | 6–10 |
| Surface course | Dense graded asphalt concrete | 40–50 | 50–75 |
| Binder course | Asphalt binder (coarse mix) | 50–100 | 75–125 |
| Base course | Crushed stone / WMM / stabilized | 150–250 | 200–300 |
| Sub-base course | Granular sub-base (GSB) | 150–200 | 150–250 |
| Compacted subgrade | Natural soil (≥95% proctor) | 500 (min) | 500 (min) |
Industrial pavements often have thicker base/sub-base due to heavy loads [citation:5].
| Layer | Material | Thickness (mm) – Highway | Thickness (mm) – Industrial |
|---|---|---|---|
| Concrete slab (PCC) | M40–M50, reinforced or plain | 250–350 | 350–500 |
| Base / sub-base | Lean concrete / GSB / CTB | 100–150 | 150–300 |
| Compacted subgrade | Natural soil (CBR ≥5%) | 500 (min) | 500 (min) |
For heavy industrial, base may be cement-treated (CTB) or lean concrete [citation:4][citation:10].
Thin surface treatment (chip seal) to waterproof surface, provide skid resistance, and seal micro-cracks [citation:4].
Highest quality layer – dense graded asphalt concrete. Provides friction, smoothness, drainage, and resistance to wear [citation:4].
Main structural layer – distributes load to base course. Coarser mix with less asphalt [citation:4].
Prime coat: low-viscosity bitumen on granular base to penetrate and bond. Tack coat: light asphalt emulsion between bituminous layers [citation:4].
Crushed stone, WMM (wet mix macadam), or stabilized (cement/bitumen). Provides structural support and drainage [citation:4][citation:9].
Granular sub-base (GSB) – reduces stress on subgrade, improves drainage, prevents fines intrusion. Often omitted if subgrade is strong [citation:4].
Industrial roadways (Illinois specification example): Base course 10" No. 9 gravel in 2 lifts, primed with MC-O liquid asphalt (⅓ gal/yd²). Surface: 2" binder + 1" surface course (hot plant mix I-11) [citation:5].
Plain concrete with closely spaced contraction joints (5–10m). Dowel bars for load transfer. Most common for highways [citation:4].
Reinforcement mesh allows longer joint spacing (10–30m). Dowels required [citation:4].
No contraction joints – reinforcement controls cracking. Used for heavy traffic [citation:4][citation:10].
Steel fibres enhance flexural strength and crack control. Used in industrial pavements [citation:10].
| Layer | Material | Compaction | Typical CBR / Modulus |
|---|---|---|---|
| Subgrade | Natural soil (clay/sand) | 95–98% MDD | CBR ≥5% (highway), ≥8% (industrial) |
| Sub-base (GSB) | Granular material (0–75mm) | 98% MDD | Modulus 100–200 MPa |
| Base (WMM/CTB) | Crushed stone / cement-treated | 98–100% MDD | Modulus 250–600 MPa |
Resilient modulus of unbound granular base sensitive to moisture and stress [citation:9].
| Parameter | Highway (typical) | Industrial (heavy duty) |
|---|---|---|
| Design life | 20–30 years | 25–40 years |
| Traffic loading | ESAL (standard axles) | Very high, channelized (forklifts, containers) |
| Concrete slab thickness | 250–350 mm | 350–500 mm |
| Base course thickness | 150–250 mm | 250–400 mm (often treated) |
| Surface finish | Skid-resistant tining / texture | Heavy broom / hardener |
| Joint spacing | 4–5 m (JPCP) | 3–4 m (to reduce curling) |
| Activity | Output | Team / Equipment |
|---|---|---|
| Subgrade preparation (grading + compaction) | 500–800 m² | Grader, roller, 4 labour |
| GSB / WMM laying | 300–500 m² | Paver / motor grader + roller |
| Bituminous binder course (paver) | 100–150 tonnes (≈500–700 m²) | Paver, 2 rollers, 6 labour |
| Bituminous surface course | 80–120 tonnes | Paver, 2 rollers, finishing crew |
| Concrete paving (slipform paver) | 100–200 m³ (≈300–600 m² for 250mm slab) | Paver, 8–12 labour |
| Joints cutting (concrete) | 400–600 linear metres | Saw crew (2 labour) |
Asphalt-treated or cement-treated permeable base for drainage – used in urban roads to manage stormwater [citation:9].
RAP (reclaimed asphalt pavement) or RCA (recycled concrete aggregate) increasingly used in base/subbase for sustainability [citation:9].
Used between subgrade and sub-base to improve load distribution and reduce rutting [citation:9].
Er. Kuljit Singh · Arshavtar.in