The Asphalt Paving system consists of four main layers: asphalt base coating, base, sub-base and reinforcement of the subgrade. Depending on the intensity and type of traffic, the existing soil and the project life, the coating may consist of a bearing layer and intermediate layers or bonding layers. But in the most common cases, a single layer of asphalt mixture is used as a coating. Getting the right Asphalt Contractor is essential to get the best long lasting results.
Asphalt Paving can be manufactured in a specific plant (machined mixtures), fixed or mobile, or prepared on the runway itself (for surface treatments) by an Asphalt Contractor. In addition to the form of production, the coatings can also be classified according to the type of binder used: hot with the use of asphalt concrete, the so-called Bitumen Concrete or cold with the use of asphalt emulsion.
Bituminous Concrete Hot Machined is the most commonly used in South American countries. It is the product of the mixture of aggregates of various sizes and asphalt cement, both heated at previously chosen temperatures, depending on the viscosity-temperature characteristic of the binder.
More economical, cold-machined asphalt mixtures are suitable for coating streets and low traffic roads, or as an intermediate layer (with superposed asphalt concrete) and in maintenance and asphalt repair operations. In this case, the solutions may be premixed and should receive subsequent surface treatments.
Types of coating
Hot asphalt mixtures can be subdivided by gradation of aggregates and filler (filler). According to the best Asphalt Paving practices the three most common types in hot blends are those listed below. All of them can be used as floor coverings of any volume of traffic, from very low to very high. Click here.
■ Dense graded asphalt concrete: it has a continuous and well-graded grain size curve to provide a composition with few voids. Dense Asphalt Paving concretes are the hot-worked asphalt mixtures most commonly used as asphalt pavement coatings. Its properties, however, are very sensitive to variation in asphalt binder content. In excess or in lack, the binder can generate problems of permanent deformation and loss of resistance, leading to the formation of cracks.
■ Open Graduation Mix: It has a uniform particle size curve with aggregates almost exclusively of the same size. Unlike asphalt concrete, it maintains a large percentage of voids with unfilled air thanks to the small amounts of filler, small aggregate and asphalt binder. This makes this coating drainage, allowing the percolation of water inside the asphalt mixture. This category includes the so-called drainage asphalt mixture, known in Brazil as a porous layer of friction and commonly used as a rolling layer when it is desired to increase the tire-pavement adhesion under rainfall.
■ Discontinuous grading mixture: coatings of this type have larger quantities of large grains than intermediate grains, supplemented by a certain amount of fines. The result is a more resistant material to the permanent deformation with the greater number of contacts between the large aggregates. Stone Matrix Asphalt generally applied in thicknesses ranging from 1 cm, 5 cm and 7 cm, is characterized by the superficially rough macrotexture and the efficient surface drainage. This kind of pavement is usually made by a Paving Company. Click here for more information: http://www.aceblacktop.com/