Pavement material is any material that is used in laying surfaces such as roads and walkways that are meant to support human and vehicular movement. Pavement materials are in general, composite materials, that is, they are usually mixed aggregates of different materials. Generally, there has been an evolvement in the types of materials used for pavement from gravel, cobblestone and granite setts to concrete or asphalt laid on a base that is compacted. As would be expected, the types of pavement material used depends to a large extent on the degree and intensity of human and vehicular weights to which it is expected to be subjected to over a determined period of time. In other words, the type of pavement material used as well as its thickness and width depends on its intended use.
Types of Traffic and Classes of Pavement Materials
Traffic is classified into five types and each of these is usually assigned a commensurate type of pavement material and required thickness and width. The first class of traffic has to do with parking lots, driveways and roads in rural areas. Pavement thickness for this class of traffic road is about three inches. The class two is for roads in residential areas, class three is for collector roads, and class four is for arterial roads while the fifth class pertains to highways, express roads or interstate roads. The thickness for the fifth class of roads is about ten inches. The thickness of the pavement material depends on environmental factors, the traffic class, the qualities of the material used as a base and the type of pavement material used.
Some Types of Pavement Materials
Asphalt is one of the most commonly used pavement materials in modern times. It is sometimes called bituminous cement and it is made of aggregates held together by asphalt cement. Usually, it is prepared by heating the aggregate mixed with asphalt cement to a high temperature, usually about 1500 C. The heated mixture is then transported to the site where the road is to be constructed. In some cases and for special purposes, the mixture may be prepared at somewhat lower temperatures.
Concrete is made up of cement which is a type of material that is used for binding. It is an aggregate of lime, alumina, silica and gypsum that has been mixed with sand and water. When cured, concrete is hard and impervious, very much like stone. It can be reinforced with steel rods or fibred glass to increase its strength. Concrete can as well be formed in different shapes.