Gravel
When gravel is called grit , which is not bound in the road base, but is on this.
Formation of gravel
Chippings are used in the production of asphalt surfaces and in road maintenance measures . They should ensure sufficient grip on the road surface.
Overdosage of the grit
Depending on the type of asphalt, fresh asphalt surfaces are sprinkled with grit and pressed into the still hot surface. The individual grain of the chippings is bound by the processed bitumen . Due to the insufficient adhesion of the base, not all individual grains stick. This excess grit is called loose chippings .
High-grade gravel is used specifically for road maintenance measures . Depending on the type of measure, the process of stone chippings differs. When producing surface treatments (spraying on binding agent and sprinkling with fine chippings), an excess of chippings is used. There are two development phases. The first phase begins with the application of the excess grit. In the second phase, not completely bound chippings are released from the base due to mechanical stress.
When producing thin layers using cold paving, a mixture of bitumen emulsion and high-grade chippings is applied. On the surface of the completed new road surface, individual grit grains break out due to insufficient contact area. This is gravel .
Special case
The application of gravel can represent a measure for the maintenance of roads : When vehicles with rubber tires are driven on, the surface is tumbled . As a result of this mechanical stress, the coarser aggregate fraction is pressed down and the binder fraction and the fine aggregate fraction migrate to the surface in countercurrent. This creates a smooth surface with less grip. This effect tends to occur only with very soft bitumen or when using coal tar pitches and is rare due to the low level of use. Since the chippings are almost completely pressed into the soft surface, little remains unbound as loose chippings.
Legal
The use of chippings does not pose a threat to road traffic in the legal sense, as warning signs are usually set up and every road user has to adapt their speed to the circumstances.
Furthermore, grit is part of the roadway. Thus, all damage is a general consequence of road use. So if a car in front throws a stone from the road onto its own windshield , the vehicle in front can i. d. Usually not be held liable.
