P U B L I C I D A D E

ABRIR
FECHAR

P U B L I C I D A D E

ABRIR
FECHAR
Voltar

High-tech effects

In addition to allow the increase in paving width, concept advances improve the degree of compaction and the leveling  of asphalt material layers

A not always remembered fact, asphalt vibrating pavers have this name as a reference to the system used by the older machines: vibration of the compacting table through which the mixture was placed. In the two last decades, however, significant improvements occurred in relation to these basic functions. The innovations that made easy the operation include leveling system, wider paving extensions and table-installed compacting devices.

According to the experts, the first significant advancement occurred in the compaction of asphalt material by the table. In addition to vibration, a device known as tamper was created. This device was located in the front of the table moving up and downwards in high speed. This helps the pre-compaction of the material even before it passes through the vibrating plates located in the rear of the table.

There are several suppliers and manufacturers of this type of equipment in Brazil, such as Ciber, that offers a national model, the AF 5000 Plus, equipped with compacting table with vibration and tamper. And Vögele—a company that is also part of the Wirtgen Group—developed special tables equipped with pressure bars to be used in applications with thick or granular-based layer compaction.

According to the company, these bars are located in the edge of the vibrating plates and are hydraulically powered to carry out a high load on the pre-compacted material. The degree of compaction depends on several factors, but may reach 95 percent using these tables that are available for the larger pavers of the brand, starting from the model Super 1800-3.

According to Ciber, the development of asphalt pavers also allowed to increase paving width. In these situations, the compacting table has hydraulically-controlled openings. In addition, it is possible to install bolted mechanic extension on both sides, increasing the maximum paving width. Each model has its own measures, whose capacity depends on its engine power and hydraulic system features. Model Super 1800-3, for example, has 6 m of maximum hydraulic opening of the table and may reach a paving width of 9 m using mechanical extensions.

PRINCIPLES

According to the application and training engineer from Ciber, Juliano Gewehr, the compacting table has to be heated during the paving to prevent the adherence of the hot asphalt material to the cold metallic structure. “The conventional way of heating the table is the use of a cooking-gas cylinder that feeds four burners that transmit heat to the wiper plates”, says him.

According to him, instead of using gas and fire, it is currently possible to use tables with electric heating. “These tables have electric resistances positioned on its entire length, powered by a generator located in the frame of the paver”, explains him. “And Ciber is the sole manufacturer of equipment with hydraulic heating in Brazil, offering the models Super 1300-3 and Super 1303-3.”

Although the compacting table works in the floating mode, what ensures self-leveling during paving works, the use of electronic systems of leveling is recommended, as pointed by Gewehr. “During the floating mode, the table remains stable and the asphalt material passes under it. This keeps constant the thickness and corrects small irregularities, comments him. “Tables are side-fixed in the frame, what allows independent movements up and downwards.”

However, the engineer remembers that when the base is too irregular, the principle of floating is not enough to correct irregularities. “In this case, the use of electronic leveling systems allows to eliminate larger variations of the layer in the place where the machine is moving”, says him.

The principle of the electronic system is simple. It includes a sensor connected to an accessory that reads an external reference that may be a sidewalk, a curb or a road lane. The movement of the table will follow the reading of this reference, even with high irregularities in the surface. “In a project that demands high quality and accuracy, such as airport runways, a sensor connected to a guide installed by a topography team is used”, says Gewehr. “This way, paving is carried out with maximum accuracy in relation to longitudinal regularity and to the angle of trim for rainwater flow”