Two-layer surface treatment is performed on unbound (gravel or crushed stone) surfaces with the aim of removing dust and creating more comfortable driving conditions. The two-layer surface treatment is performed with gravel and crushed stone roads that see low traffic: local roads, village streets, house driveways.
- removal of dust from the road;
- more comfortable driving;
- reduction in all maintenance costs (the road does not need to be graded);
- longer service life of the road.
Technologically, the two-layer surface treatment is similar to the single-layer surface treatment. The difference is that the pouring of the bitumen emulsion and the spreading of the fine crushed stone is performed in two layers. Coarser gravel is used in the lower layer, and finer gravel, in the upper layer.
Before the two-layer treatment, one must check the load-bearing capacity and the technical condition of the existing gravel road and, if necessary, strengthen the road surface and maintain the water drainage system (cleaning the culverts, cutting the brush, removing roadside vegetation, and repairing settlements and potholes in the road surface).
The surface of the road becomes similar to asphalt; however, this surface cannot be compared to the durability and load capacity of asphalt. It is not intended for heavy traffic, and the durability of this road surface depends on the traffic load. Every 5–7 years, these roads need to be renovated with a single-layer treatment, which ensures the waterproofing of the road surface, extends its life, and improves traffic safety.