Asphalt paver
An asphalt or road paver is a machine that can be used to produce unbound and bound layers such as sand , gravel , asphalt and concrete . In addition to the conventional machines, special shapes have also been developed that are tailored to a specific installation method (such as the compact asphalt paver). A basic distinction is made between tracked and wheeled pavers. In common parlance, the designation black pavers or pavers for short has established itself for this type of machine . The term tar machine is commonly used incorrectly .
An important step in the development of asphalt pavers was the introduction of hydraulic extending screeds in the 1970s. For the first time, total paving widths of up to 12 meters could be achieved. The emergence of the high-compaction screed was also significant in the 1980s. These two components were continuously developed in the following decades and are part of all modern asphalt pavers.
work environment
Pavers are used by the construction industry in all areas and can be found in road and path construction , embankment and landfill construction and occasionally also in gardening and landscaping , in sports field construction or track construction. In addition to the main task of paving rolled asphalt , the machine can also be used to pave sand, crushed stone, hydraulically bound base courses and concrete according to the profile. The mechanical installation of mastic asphalt is only possible with a mastic asphalt plank .
In the classic installation method, horizontal installation, the material to be installed is fed by a truck tipper without an engaged gear , which is pushed off the machine in a special bracket (push-off bar) attached to the front. When installing on inclines, as can occur in landfill and hydraulic engineering, conventional variants or conversions in the form of a slope paver are available for use. Other application profiles are installation in an inclined position or the manufacture of track tracks and profile construction in track and landscaping.
As a rule, the pre- compacted material behind the machine is further compacted and smoothed by rollers . The use of a feeder may be necessary depending on the construction tender and the procedure . The machine originally developed for the compact asphalt paver is used as a contactless connection element to the mix transport vehicles and uses a conveyor belt to transfer the material.
construction
The components of a paver consist of the travel drive, the material container (receiving container), the scraper belts, distribution auger, screed, heating and automatic leveling system. The material transport and distribution in the machine is automated and can be overridden by hand if necessary. The basic structure of the machines is always the same, but depending on the manufacturer, details such as usability and design of the various components can vary.
The paving quality of the paver always depends on the condition of the subgrade or the subsoil, the material to be paved, the paving thickness, the paving width, the paving speed, the degree of wear on the screed and, when paving asphalt, the temperature of the mix as well as the weather conditions and the material in front of the screed.
traction drive
The drive of the machine consists either of chains or wheels; in the majority, however, chain-driven pavers (paving speed 0–29 m / min) can be seen (also recommended from 6.50 m working width). The tracked pavers have better traction and are therefore ideally suited for large pave widths (up to 16 m). Wheeled pavers, on the other hand, are more mobile and allow a higher paving speed (0–40 m / min); In addition, the wheel drive makes them easier to move from one construction site to the next (self-propelled - no low-loader necessary).
Most pavers in the USA are equipped with vibratory screeds. Chain pavers therefore have high-speed chain drives (high-speed runners); Like the wheeled paver, they differ fundamentally from European models. They achieve paving speeds that can be up to 76 m / min.
Diesel engines from different manufacturers with a power range of approx. 33 kW to 259 kW are used as the engine.
Material container, scraper belts and distribution auger
The material container of the paver is located at the front and is used to hold the material to be paved. Depending on the size of the machine, the capacity is between 5 t and 14 t, which can be increased to an average of 20 t by using material container inserts. The side walls can be folded in hydraulically and allow complete emptying.
The further transport is taken over by up to two forward and backward moving conveyor belts, which can also be controlled independently. With them the material is transported through the machine into the screw space.
The even distribution of the material in front of the screed is achieved by two rotating screw conveyors . The independent augers can be extended with appropriate parts depending on the installation width. The bearing block is adjustable in height and can be adapted to the various paving thicknesses. Like the scraper belt, the screws can be reversed.
Screed
The pavers differ from other construction machines, such as caterpillars or graders , by their floating screed, with which small bumps in the substructure can be reduced or compensated for without interfering with the control. Its job is to compact the mix evenly over the entire paving width and to create a closed, even structure. A basic distinction is made between rigid and extending screeds. All screeds have a mechanical or hydraulic roof profile adjustment in the middle . The installation dimension without extending or add-on parts is called the basic width or basic screed.
The dead weight and the compaction units of the screed should produce the greatest possible pre-compaction, so that different paving thicknesses have little influence on the rolling dimension during final compaction. During paving, the screed is only connected to the machine via two pulling points. It is only supported by the built-in material. Changes in altitude are achieved by changing the angle of attack. The cylinder for raising and lowering has no function, but can be specifically controlled by some manufacturers in order to relieve the screed with non-load-bearing material and thus to achieve a higher paving thickness. A screed blocking, on the other hand, is standard and, after stopping in the floating position, allows the screed to move without the screed changing its height.
If asphalt is paved, the temperature and composition of the material also have an influence on the behavior of the screed. For example, a high temperature causes the screed to rise, while colder material causes the screed to sink. The different types of asphalt and the addition of recycled material also influence the load-bearing capacity and thus the paving thickness. To prevent the asphalt from sticking, the screed can be heated electrically or with gas, depending on the manufacturer.
If the screed is widened with add-on parts, pre-scrapers and duct guide plates are available. These are necessary in order to achieve a uniform mix of material even with large paving widths and to prevent the material from segregating.
Depending on the type of screed, different units are available for compaction:
- Rammer with vibration
- The tamper is set in vertical motion by an eccentric shaft. It compresses (stuffs) the respective material into the existing cavities, the vibration ensures a closed surface structure.
- Double tamper (only ABG ( Volvo-ABG) = world patent)
- Patented high-compaction screed with double tamper and vibration for optimal paving of any material (asphalt, rolled and lean concrete).
- Tamper
- The tamper is set in vertical motion by an eccentric shaft. It compresses (stuffs) the respective material into the existing cavities.
- vibration
- The vibration is generated by an imbalance shaft on the screed plate across the direction of travel.
- Pressure profile (exclusively VÖGELE)
- In addition to rammers and vibrations, the pavers from the company Vögele can be equipped with a maximum of two pressure bars. These are hydraulically operated with a frequency of ~ 68 Hz and a pressure of max. 130 bar pressed onto the mix (no real compaction - duplication of the basic compaction). The pressure bars are arranged after the screed plate.
Automatic leveling
Basically, pavers can pave material in certain layer thicknesses without assistance. Driving according to “strength” is mostly used when the ground allows even paving. Various methods are available to compensate for larger unevenness or to follow a previously defined profile. The designation and technology used varies depending on the manufacturer.
Normally, the specified height is taken from a wire on the left and right and converted in height and cross slope by controlling the leveling cylinder. With one-sided scanning, the automatic system has an inclination sensor on the screed that can be used to set transverse inclinations. In addition, the height sensors can also be used to remove from curbs, gutters or directly from the floor. While mechanical height sensors were still in use in the 1990s, manufacturers in the 21st century are offering ultrasonic scanners that use an internal filter to compensate for unevenness in the floor.
Processes with rotating lasers, laser scanning of the subsurface, 3D control and a combination of several ultrasonic sensors (Big-MultiPlex-Ski, Vögele or Big Sonic-Ski from MOBA) have further increased the accuracy.
Special forms
In the course of time, several special forms of the asphalt paver were developed, which were specifically built for new paving methods.
Compact asphalt paver
The construction company Kirchner and the construction machinery manufacturer Vögele developed the compact asphalt paver in the 1990s to pave the surface and binder course in one operation with one device "hot on hot". Kirchner built two modules that were coupled with a commercial paver from the Super 2500 series. However, problems with increasing the working width ultimately led to cooperation with Dynapac. Module 1 was a self-supporting material container for asphalt binders enlarged to 45 t . The second module comprised the technical part of the surface course paver and the energy supply. The scraper belts were replaced by screw conveyors. Another material container for the top layer was installed behind the first container. The two screeds for pre-compaction run offset one behind the other. The final compaction of both layers is carried out by roller in one operation. The mix feed is carried out alternately by one or two feeders with conveyor belts at the same time. Compared to conventional paving, in which the binder course is 8 cm and the surface course 4 cm thick, the thicknesses of compact asphalt are 10 cm and 2 cm. In the series production taken over by Dynapac, the type was further developed and improved. The first series machine was based on the F300, which was supplemented by the AM300 add-on module and used by the Bunte company in 2004 .
Since 2007, the Vögele company has relied on normal series machines with its "InLine Pave" concept, which have been slightly modified. The machine train consists of a feeder, the binder course paver with transfer module and the paver. In contrast to the Dynapac paver, the paver runs on the pre-compacted binder course. Sticking is prevented by wider floor plates on the crawler track and a water spray device. Cinder and pavers have an enlarged material container that is inserted into the standard receptacle. The machine train is equipped with a distance control.
With the inclusion of the InLine Pave process in 2012 in the ZTV Asphalt-StB regulations, both processes are officially approved.
Spray paver
Spray pavers were developed to produce thin layers in hot construction on sealing (DSH-V) in the context of road repairs and to apply the required binding agent evenly with 200 g / m² to 1500 g / m². The pavers also have a storage tank with a spray system for bitumen emulsion . The pattern offered by Dynapac has a spray bar on the front and two jet nozzles behind the drive chains in order not to damage the emulsion applied. The capacity of the tank is 2800 l and is thermally insulated. Compared to the original Vogel version, the screed and the spray system can be expanded with an add-on part.
The solution offered by Vögele, upgrading conventional pavers with a SprayJet module, has a standard tank of over 2000 l. This can be expanded by a further 5000 l with a tank insert for the material container. The mixed material is then fed with a feeder through a funnel directly onto the scraper belts. The main and auxiliary tanks are heated. A total of five spray bars are used, which are located behind the push-off bar, to the left and right of the crawler track and in front of the screed. The predecessor Super 1800 SF was equipped with a 4000 l tank. The maximum working width of 5 m has been increased to 6 m in the further development.
The asphalt layer, which is usually 2 cm thick, is only rolled off statically. Conventional installation with pre-spraying is also possible.
Paver with integrated spreader
With the requirement for permanent grip on the road surface and the problems with spreading with rollers, Kirchner designed another type of paver in cooperation with Demag. The idea behind the concept was an even asphalt paving and timely spreading with gravel . The types of spreader attached to the tandem vibratory rollers and their problems of overlapping (increased material consumption), high line load of the drum, undesired pile formation, grit-free strips and the late introduction of the grit should be avoided. The problem of the grit sinking in too much when the material is too hot and the effect it has on the initial grip should be compensated for with bituminized chippings (up to approx. 1% bitumen content).
The prototype was supplemented by a chip spreader, which covered a paving width of 2.50 m to 5 m without any attachments and ran behind the screed. With add-on parts, the working width was expanded to 8 m. The grit was fed with a big bag via a transport device above the material bunker into a storage container with a capacity of 1.5 m³. Despite the advantages of a clean spread pattern and the application of clean chippings, this type could not prevail.
Manufacturer
Photography by Gerhard Dierssen
Well-known manufacturers of asphalt pavers include Ammann , BOMAG and Demag / Dynapac / Marini (part of the Fayat Group ), Vögele (part of the Wirtgen Group ), Volvo CE (formerly ABG / Blaw-Knox ). Companies such as Terex , Gehl Company and Caterpillar (Bitelli was taken over by CAT) are mainly represented in the American market.
See also
literature
- Marc Niggemann: Applied road construction: road pavers in action , Vieweg + Teubner, Wiesbaden, 2012, ISBN = 978-3-8348-2476-9
- Publications of the German Asphalt Association
- Installation guides from construction machinery manufacturers
Web links
Individual evidence
- ↑ Archive link ( Memento of the original from January 27, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ New momentum for compact asphalt. (pdf; 1 MB) bi-baumagazin, December 1, 2012, accessed on April 27, 2013 .
- ↑ Road paver with integrated grit spreader ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , Dr.-Ing. Alfred Ulrich, PDF file, accessed on January 6, 2013.
