Surface treatment (road construction)
The surface treatment (short OB ) is a measure for road repair . A new, very thin layer is applied to the surface of an existing road. This method is also suitable for the intermediate construction of roads .
It is characterized by spraying a substrate with a binding agent and then sprinkling it with an aggregate . This application can take place several times.
Bituminous binders are mostly used for spraying ; and epoxy resins are used.
In Germany, broken natural stone is used for scattering ; this can be pre-bituminized and / or heated.
Procedure
| Step 1 | Pre-cleaning | The base is cleaned to ensure perfect contact between the binder and the base. | |
| 2nd step | Application of the binder | The binding agent is sprayed onto the base from a low height using ramp sprayers. These devices should have a dosed cross-distribution of the binder. | |
| 3rd step | Split off | Fine chippings are applied to the surface . This is done with path- or speed-dependently controlled broad chippings, which have an extremely low height of fall. | |
| 4th step | Rolling | The applied aggregate is usually rolled in by rubber -tyred rollers so that the individual aggregate lies down, presses into the substrate and thus increases the adhesion between the individual aggregate and the binding agent. |
Types of surface treatments
Standard construction methods:
- Surface treatment with simple sprinkling
- The surface treatment with simple sprinkling (alternative: simple surface treatment) is the simplest surface treatment. It consists of a layer of binding agent and aggregate with a closed surface.
- Surface treatment with double sprinkling
- The surface treatment with double sprinkling (alternative: single surface treatment with double sprinkling) consists of one layer of binding agent and two layers of aggregate. The first layer is openly sprinkled with a coarse aggregate, i.e. H. the surface is not closed. The second layer is sprinkled with a finer aggregate. The surface is now closed.
- Double surface treatment
- A double surface treatment consists of two layers of a surface treatment applied one after the other with single sprinkling, whereby the sprinkling has a coarser aggregate than the second.
Special constructions:
- reverse double surface treatment
- It corresponds to a double surface treatment, but the first layer consists of a fine aggregate. It is used on a hard surface, e.g. B. on concrete roads.
- Sandwich surface treatment
- Drinking blanket
- Voltage depleting intermediate layer (Stress Absorbing Membrane Interlayer) [SAMI]
application
With the following road conditions u. a. Surface treatments for application:
Defect of the surface structure
- due to the rough or porous surface
- Grain outbreaks
Abrasion
- Loss of material on the surface
Reduced grip
- due to the accumulation of binding agents or mortar on the surface
- polished grit
Furthermore, it should bridge network cracks, i. H. Accumulations of directionless individual cracks or network-like crack pattern.
In terms of their mode of action, surface treatments show various advantages over other renovation measures. When using highly cohesive binders with pronounced elasticity and good behavior in cold weather, the substrate is adequately sealed.
Due to its coarse structure with micro and macro roughness, the surface treatment of the road gives the road a good grip and at the same time, with sufficient slope, good drainage of surface water without the risk of aquaplaning .
Furthermore, traffic safety is increased by minimizing the glare effect, since the light emitted by oncoming vehicles is reflected back and refracted. The reflected light gives the driver the visual impression of a lighter road.
Also on the Elimination of black spots during winter road surface treatment is appropriate because in it dissolved road salt last longer without being extended. The existing "roughness" also prevents pronounced black ice formation . Freezing rain is excluded from this.
A surface treatment to remedy deficiencies in the load-bearing capacity of the road or as the sole measure for deficiencies in evenness is not suitable .
Dimensioning
When dimensioning surface treatments, the forces acting on site due to rolling traffic must be taken into account.
The grit grains are pressed into the base by vertical forces and standing grains are placed. The grain rearrangement is completed after a short run-in period of the surface treatment, while the indentation becomes noticeable over a longer period of time. The longer the horizontal exposure, the greater the degree of penetration. This only depends on the hardness and temperature of the surface. The degree of penetration is important for the selection of the amount of binder, so that the surface treatment is prevented from sweating through.
The result of this finding is that the amount of binding agent must be dimensioned differently across the cross-section of the road, otherwise the binding agent will leak out on the surface in the lanes. Furthermore, the loosening of the grains is prevented by a predominantly vertical load. The edge areas of the road, however, are generally less heavily loaded by the rolling traffic, so that these areas consequently require a thicker binder film.
In the case of horizontal forces, which predominantly occur in acceleration and braking areas, the aggregates can be released from their embedding if the "adhesive force" is exceeded. The only way to delay this process is to choose a binder with large adhesive and cohesive forces and a coarse-grained chip with a large wettable surface area.
When choosing the binding agent, if possible, one with a medium to high viscosity should be chosen so that the chippings can be easily wetted and thus a durable connection is ensured.
The calculation of the required amount of binding agent is recommended for the standard construction methods in the ZTV BEA-StB. The dimensioning is done empirically due to the lack of clear procedures .
The amount of binder is essentially influenced by the following factors:
- Texture of the surface
- Traffic load and traffic density
- Climatic conditions
In order to achieve the accuracy (± 50 g / m²) of the binding agent application, the machines must be calibrated.
literature
- S. Velske, H. Mentlein: Road construction technology . Werner Verlag, Düsseldorf 2002, ISBN 3-8041-3875-6 , p. 237 ff .