The fortress of Frederiksten in Halden in the south of Norway, overlooking the city and the fjord, makes for a majestic sight. The “Rijksweg” RW 22 highroad runs alongside the coastline up to the border with Sweden. In the summer of 2007, Swedish contractor Skanska carried out resurfacing works on a 5km stretch of this two-lane road, 7m wide. The main challenge of the contract: it was to be carried out without closing the section to traffic and without soiling the carriageway with tack coat. Given these demands, the SUPER 1800-2 with SprayJet Module was the ideal candidate.

Tracks never get in touch with the tack coat

The SUPER 1800-2 placed 4.5cm thick wearing course of asphaltic concrete. In order to obtain a perfect bond with the binder course, Skanska applied thin tack coat in a very small quantity of just 0.2 to 0.3kg per square metre. This thin film of emulsion was not to be damaged by the paver’s tracks – another good reason for using the SUPER 1800-2 with SprayJet Module. The spray bars are positioned so that the paver’s tracks never get in touch with the spray film. Five spray bars with a total of 20 spray nozzles are accommodated on the paver: one large spray bar at the front between the crawler tracks, one on each side between the tracks and the outer edges of the screed and two small spray bars right behind the two crawler tracks.

Variable spray technology

“The SUPER 1800-2 with the new SprayJet Module keeps strictly to the specified rate of spread, irrespective of our pave speed,” says Kurt Heistad, the Operations Manager on site. The reason behind it: the new spray system operates at a low and constant spraying pressure of just 3 bar. Furthermore, spraying does not take place continuously but in pulsed operation. The spray pulses are emitted as a function of the desired rate of spread on the one hand and the pave speed on the other.

Formation of spray mist is avoided

The tack coat applied by Skanska for paving wearing course was an emulsion of very low viscosity with a tendency to form spray mist. The SUPER 1800-2 with SprayJet Module, however, effectively prevents the formation of spray mist due to special nozzles of double-slotted design combined with its low spraying pressure. The prevention of spray mist also enhances substantially the paving team’s working conditions under health aspects, as emulsion fumes are reduced to a minimum.

Heated tank maintains an ideal emulsion temperature

On one day, the beginning of paving was delayed for organizational reasons, but the paver and the rollers had already moved into position. “In situations like this you realize just how important a well heated emulsion tank is. It maintains a constant temperature by a pump circulating the emulsion. The emulsion neither splits nor foams, there is no loss in quality,” says Kurt, the Operations Manager for this job. The tank of the SprayJet Module even maintains an ideal emulsion temperature if the screed is not heated, as for the emulsion tank and the screed separate heating circuits are provided.

Equipped for all situations thanks to its modular design

Skanska took delivery of their new SUPER 1800-2 with SprayJet Module in June 2007. Although, so far, they used the machine exclusively as a spray paver, Skanska also want to operate the SUPER 1800-2 without the SprayJet Module in order to fully exploit the versatility it offers thanks to the modular design. As a screed, Skanska selected the AB 500-2 Extending Screed in TP1 version with tamper and 1 pressure bar. When using the paver as a “normal” SUPER 1800-2 for conventional paving tasks as usual, the screed can be built up with bolt-on extensions to a maximum width of 8.5m, thus covering a broad spectrum of paving jobs.

The SprayJet Module: Even the Smallest Rate of Spread Possible

The VÖGELE SprayJet Module allows to precisely select a rate of spread ranging from a very small quantity of emulsion through to a large quantity. A rate of spread can be selected between 0.2 and 1kg per square metre. Please note that a constant rate of spread is applied irrespective of the pave speed. The possibility of spreading emulsion accurately at a very small rate of just 0.2kg/m2 makes the VÖGELE SprayJet Technology unique in the market. Attention shall be paid to the fact that the spread rates are dependent upon the kind of emulsion used, the emulsion viscosity and the temperature when applied. For the spray bars of the SprayJet Module, 3 different types of slotted spray nozzles are available: nozzles of the sizes 07, 10 or 16. The spray nozzles size 07 have a throughput of 70% compared with the nozzles of size 10 (100%). The nozzles size 16 have a throughput of 160%.