The most important use of asphalt today is in road construction (Zakar 148). When it has been properly mixed with the correct aggregate material it becomes highly suitable for all kinds of pavement applications. It is also widely used to prepare the base of roads.
Asphalt road construction is multi-layered in form. The subgrade layer is itself covered by a base cover upon which is laid a final coating. Early classical base courses consisted of a handmade, packed layer which was then graveled. Later this technique of construction was replaced, on a global basis, by a flexible asphalt layer in which asphalt gravel or sand asphalt had been mixed (Ibid. 149).
Asphalt as a road construction and/or road repair solution offers design, cost and durability advantages over concrete. The following will serve to put these issues into perspective.
Asphalt products are used to produce low cost, "flexible" pavements for primarily highway and airport applications. The term "flexible" is used to distinguish this type of pavement structure from those made utilizing portland cement. The latter are termed "rigid" pavement structures. Rigid pavements are used when the application requires a high beam strength (Larson 177).
This "flexible pavement" classification may be further divided into highly flexible and marginally flexible sub-units. Assignment to one of these sub-units usually depends on whether solid or liquid asphalt material is utilized in the construction process. Low or marginally flexible pavements are made with emulsion products and are widely used. In low flexibility applications, the aggregate material and the asphalt product are separately applied to the roadbed and there mixed to form the pavement. Highly flexible applications utilize more asphalt and are used in those instances where there are high wheel loads and high traffic volumes (Ibid. 178).
Asphalt pavements represent a combination of mineral, agg...