Base course
Base layers ( also called outdated ceiling substructure ) are in the streets and roads the subdivisions of the superstructure of the road body. You wear layer ( pavement ) and with heavily loaded roads a binder layer.
Establishing a base layer requires that the ground is suitable, mainly means that he is steadfast, strong, true to profile and level. Down the structural layers are limited by the subgrade.
It is divided into unbound and bound base layers.
Unbound layers
Among the unbound layers include the frost protection layer, gravel and crushed stone layer and the soil improvement.
Gravel and crushed stone layers differ only slightly from the frost protection layers. Main difference are the Sieblinienbänder that allow only small variations in the grain size distribution.
The soil conditioner is used in soils that are too wet, fine-grained and unstable. It aims to improve the workability and trafficability of the soil. To achieve this is to either increase the proportion of coarse particle, which is referred to as a mechanical ground improvement. Or it may be blended small amounts of fine lime (CaO) or hydrated lime (Ca ( OH) 2) or hydraulic binder.
Bonded layers
The bonded layers include soil stabilization, bitumen bound base layers, base layers with hydraulic binders, as well as the pavement surface.
By ground stabilization of the resistance against mechanical and climatic stresses to be permanently increased. The floor should be permanently stable and resistant to frost. This is achieved by mixing cement or high- hydraulic lime, which are referred to as a binder. The choice of binder depends on the grain size distribution of the soil. Previously also tar and bitumen were used.
Bitumen bound base layers are referred to as asphalt base courses. They consist of the minerals grit, gravel or sand, and bitumen 70/100 or 50/70, partly as 30 / 45th Increasingly, asphalt granulate is used, which is removed from the old streets and is installed after the treatment again.
At the base layers with hydraulic binders include hydraulically bound base ( HGT) and concrete layers.
Hydraulically bound base (HGT ) consist of a graded granular structure 0/ 32 or 0/ 45, which consists of natural or synthetic minerals, such as grit, gravel or sand. The binder is cement, road binders or highly hydraulic lime. Be installed the layers with pavers. After installation, they must be kept moist for at least three days. In some cases, grooves are placed in transverse and longitudinal direction. This " predetermined breaking point " uncontrolled crack formation is avoided.
Concrete layers are made of concrete, an artificial rock made of cement, concrete aggregate or aggregate (sand and gravel or crushed stone ) and water. It can also be used as concrete additives and concrete admixtures, such as Condenser or retarders. The concrete for the base layers is measured according to DIN 1045, and has the strength classes C12/15 C20/25 or correspond. Be installed concrete layers by pavers, with stationary or towed formwork. The concrete must be kept moist after installation. Through joints and dummy joints uncontrolled cracking is to be avoided.
The road surfaces are the top layer of the road body and belong to the category of the bound layers. A distinction is made between asphalt pavement, concrete floors and plaster ceilings. See the main article on road surfaces.
Standardize
As a basis for the structural layers used in Germany ZTV SoB -StB 04