Paving thin asphalt overlay hot on spray seal

Spain | Tarragona

Offering cost-efficiency and speed, Sorigué consequently won the contract for rehabilitating the surface course of the 3km-long dam promenade in the Catalonian port city of Tarragona. Sorigué’s idea was to overlay the existing surfacing with a thin layer applied to a spray seal of polymer-modified bitumen. The spray seal prevents water penetrating inside the structure – a major advantage for a dam promenade which is regularly flooded with sea water due to strong winds and heavy seas.

The points in favour of the process: it’s cost-effective, time-saving and durable. Cost-effective because the thinner layer significantly reduces milling and material costs. Besides which, there is no need for costly adjustments and the installation of new curbs. Time-saving because spraying the high-quality polymer-modified bitumen and paving the surface course can take place in a single pass. Last but not least, the pavements rehabilitated by paving thin overlays are exceedingly durable. The sprayed binder forms a continuous film on the lower layer, effectively sealing the road structure against water and significantly extending the service life of the new pavement.

In order to produce a particularly high-quality bond between layers when overlaying the surface course, Sorigué used an emulsion called ELASTAM which was developed by the company itself and contains 65% of polymer-modified bitumen and 35% of water. The polymer-modified emulsion guarantees very rapid “breaking” so that the film of emulsion can be overlaid with hot asphalt immediately after spraying. The SprayJet module ensures that the emulsion is always sprayed in exactly the right quantity. Unlike the case when using conventional methods, job site vehicles and paver do not drive over the film of emulsion so that it remains intact over the full width.

The set rate of spread was relatively high, at 1.1kg/m². Alfredo Bobis, product developer for Sorigué explains why this was so: “Using a high rate of spread produces a reliable tack coat on all bases and ensures a strong bond between the layers. In addition, it also allows more bitumen to be mixed into the asphalt retroactively. All in all, this extends the service life of the new surfacing in line with demands for sustainable road construction.”

Sorigué have devoted more than three years to paving thin overlays on spray seal. Having focussed on VÖGELE SprayJet technology from the outset, the company is now fully familiar with this technique. The brand-new generation of VÖGELE spray pavers was used in Tarragona – the SUPER 1800-3i SprayJet. The paving team responsible for paving the 3km-long and 10m-wide surface course in less than two days was naturally very keyed up.

Even for experienced paving pros, the SUPER 1800-3i SprayJet sets new standards in terms of handling. Operation of the SprayJet module has been consistently integrated into the ErgoPlus 3 operating concept. The central element is the colour touch screen. It’s positioning on the emulsion tank ensures that it can easily be seen and reached by the paver operator at all times. All preparatory, spraying and cleaning functions can be selected and started in a few swift moves via various menus. Settings for the work flows are mainly performed automatically. This assures the machine’s availability and long-term value and prevents potential operator errors.

“The nozzles can be calibrated and individually activated or deactivated just as easily. Another function that we liked was the all-automatic cleaning of emulsion lines and valves. Only a few settings are needed to start the cleaning program. Up to three cleaning cycles can be set, depending on the degree of fouling. It is also possible to clean only a few selected circuits. A preservative can also be added to prevent emulsion sticking to the lines. It is a real innovation that saves a lot of time!” raves José Antonio Rodríguez.

The ErgoPlus 3 user interface for the SprayJet module is consistently based on the ErgoPlus 3 operating concept of the paver operator’s console. Together, these two make the paver and SprayJet module a single organizational unit. All SprayJet functions, such as topping up with emulsion, setting the nozzles, circulating and spraying emulsion, as well as subsequent emptying and automatic cleaning of the nozzles, can be conveniently selected and monitored via the touch screen mounted on the module.

All the required information is displayed in the Spray menu: current emulsion temperature, filling level of the emulsion tank, rate of spread and spray pressure, as well as the actuated nozzles.

Rehabilitation of the surface course along a promenade in the port of Tarragona in northern Spain