Asphalt and concrete are two commonly used materials for road pavements. The term “flexible” paving asphalt and “stiff” to concrete pavement concerns the rigidity of the material and shape of each material transmits vehicle loads to the underlying road base.
Flexible pavements are composed of a layer of asphalt placed over compacted soil, or if necessary, a layer of crushed rock or gravel. A designer determines the required pavement thickness of asphalt pavement by assessing soil conditions and traffic volume and mix of vehicles, cars, trucks, buses and more – that will take to the road.
Concrete is composed of sand and crushed rock, hydraulic cement, water and additives which adjust its engineering properties. Concrete is also placed on a ground or crushed rock base. Both asphalt and concrete pavement designs, add lime or cement to the underlying soil can improve stability.
The selection of a rigid or flexible pavement for a particular application depends on several factors. Often, an analyst conducted an analysis to evaluate alternative pavement based on initial cost and the costs of rehabilitation and maintenance required over the life of the pavement life cycle cost. The Department of Transportation notes that other considerations include ease selection of floor construction, security, such as skid resistance, noise and traffic problems of climate or weather, among others.