Any ground surface that you can step on which carries a considerable amount of weight or load is called a pavement. Pavements are primarily constructed for use by vehicles and pedestrians, transferring the load from the upper surface to the natural soil. The earliest record of the first constructed pavements is from the 4000 BC. They consist of stone paved streets or timber roads, with roads of the earlier times dependent on stone, gravel and sand for construction. Road and pavement construction has evolved.
There are two broad categories that pavements can fall into: flexible pavement and rigid pavement. How is the one different from the other?
Source: About Civil
Flexible pavements are those consisting of a mixture of asphaltic or bituminous material and aggregates placed on a bed of compacted granular material of appropriate quality in layers over the subgrade. Its design is based on the principle that a load of any magnitude diminishes as the load is transmitted downwards from the surface. The load spreads over an increasingly larger area, which carries it deep enough into the ground through successive layers of granular material. This is why materials with high degree of strength are used at or near the surface without the need for steel reinforcement.
Source: Flexible Pavements
On the other hand, rigid pavements are associated with rigidity or flexural strength or slab action so the load is distributed over a wide area of subgrade soil. They are usually laid in slabs with steel reinforcement, with design based on providing a structural cement concrete slab of sufficient strength to resist the loads from traffic. Rigid pavements require high modulus of elasticity.
Rigid pavement. Source: RRJ
The main difference between the flexible and rigid pavements is based on the manner in which the loads are distributed to the subgrade. The pavement design is also one major factor, with flexible pavements reliant on subgrade strength and rigid pavement dependent on the flexural strength of concrete.
Moreover, temperature variations are sensitive in rigid pavements inducing heavy stresses; whereas such do not produce stress in flexible pavements. Deformations pose permanent settlements in rigid pavements; while in flexible pavements, they have self-healing properties that can recover from heavier wheel loads.