Road Construction:
Pavement Engineering & Cost Guide

Pavement Types

Flexible Pavements (Asphalt / Bituminous)

The dominant pavement type worldwide for roads with low-to-medium traffic. A flexible pavement distributes load through the granular base and sub-base layers — the asphalt surface provides a smooth riding surface and water resistance but contributes only modestly to structural capacity. Designed using the AASHTO Guide for Design of Pavement Structures or the UK's HD 26/06 (Design Manual for Roads and Bridges).

A typical flexible pavement cross-section for a medium-traffic road includes: 200–300mm compacted sub-base (crushed stone or gravel), 150–200mm base course (crushed stone), 50–75mm binder course (bituminous macadam), and 30–40mm wearing course (dense bitumen macadam or stone mastic asphalt).

Rigid Pavements (Portland Cement Concrete)

Concrete pavements are stiffer than asphalt, distribute loads over a wider area, and are more durable in heavy traffic conditions (airports, motorways, ports). Higher initial cost but lower lifetime maintenance cost under high-load traffic. Jointed Plain Concrete Pavement (JPCP) with contraction joints at 4–6m intervals is the most common type. Governed by FHWA Concrete Pavement Design Guide and IRC:58 in India/Pakistan context.

Composite Pavements

Asphalt overlay on a concrete base — combining the structural rigidity of concrete with the smooth riding quality and ease of maintenance of asphalt. Common in airport runways and heavily loaded industrial yards.

Pavement Layer Design

Subgrade

The natural soil or engineered fill upon which the pavement is built. Subgrade strength is characterised by the California Bearing Ratio (CBR) test (ASTM D1883 / IS:2720 Part 16). A CBR of 2–3% represents weak clay subgrade; 10%+ is strong granular material. Pavement thickness is inversely related to subgrade strength — weak subgrades require significantly thicker pavement structures.

Sub-Base

A granular layer (crushed stone, gravel, or stabilised material) between subgrade and base. Provides drainage, frost protection, and additional load distribution. Minimum thickness typically 150mm; up to 450mm on weak subgrades.

Base Course

The main structural layer in flexible pavements. Must be well-graded, crushed stone with controlled gradation per ASTM D2940 or equivalent. Provides the primary load distribution from traffic to sub-base and subgrade.

Bituminous Layers

Binder and wearing courses. Asphalt mix design follows Asphalt Institute MS-2 (Marshall Mix Design) or the increasingly adopted Superpave methodology. Mix temperature, bitumen grade (Pen 60/70 in hot climates, Pen 40/50 in cold), and aggregate gradation are the key controlled variables.

Regional Cost Benchmarks 2025

Two-lane road, 7m carriageway width, standard terrain (moderate earthworks), flexible asphalt pavement:

Engineering Standards

FAQ