A Rubble Master impact crusher, with an operating weight of only 23 tonnes, has demonstrated what can be achieved in road-building applications in a single operation (screening only once).
The track-mobile Rubble Master RM80, coupled with on-site recycling, has made it possible to counteract the cost pressure of transporting an old concrete surface to an intermediate storage site for processing and screening in a stationary plant and subsequent return to the job site.
In just four weeks, the 1.2km stretch of the northbound carriageway on the A3 autobahn near Passau, near the German-Austrian border, was refurbished cost-effectively in a single operation with the Rubble Master RM80. The mobility of the crusher was supported by the Rubble Master oversize grain separator. Half the carriageway was removed in the process and the entire material was fed into the crusher by the excavator.
The Rubble Master power system mastered the logistical challenge on-site, without any intermediate storage, by discharging and levelling the finished graded material – a defined grain size of 0-45mm – onto the substructure. Between 50 and 60 metres of autobahn were completed daily, by crushing, screening and immediately reusing around 4600m3 of concrete in total.
DEFINING AGGREGATE IN A SINGLE PASS
The Rubble Master OS80 oversize grain separator, combined with the high throughput impact crusher RM80, was used to produce defined aggregate in a single pass. The OS80 was fitted to the crusher?s discharge belt using quick release levers, maintaining unrestricted movement of the crusher around the site. A defined grain size of 0-22mm to 0-63mm was achieved in a single operation from asphalt, concrete or natural rock. Three comb-cascades ensured that oversize material was separated in full from the end product. Power was supplied from the crusher generator. Only one low-bed trailer was required to transport the entire system.
This method was also employed in Estonia. In spring 2005, a motorway project was launched for a new 90km stretch from Tallinn to St. Petersburg. The carriageway was broken up along a 5km stretch of the entire width of the first carriageway while the second carriageway was used for the traffic flow. Here too, the excavator fed the broken material to the Rubble Master, using its crawler gear to reverse slowly and form a pile of crushed material that was later spread across the carriageway and flattened. This way it was possible on-site to crush the asphalt down to 0-40mm for cost-effective reuse at the same place. All in all, 110,000 tonnes of asphalt was processed in 100 days – 120tph on average.
RECYCLING OF BITUMEN ROADS
Rubble Master?s impact crushers have also been instrumental in the mobile recycling of bituminous material, notably a RM100 used by
Thoma Bau-u Recycling GmbH & Co KG based in Lower Bavaria in 2007.
?Because tar has to be fully recycled,? explained Robert Thoma, ?we process the broken up roads that contain tar with a mobile crusher operating directly on the customer?s job site. The excavated material is then crushed in the RM100 down to the required aggregate size, mixed and a binder and water are added in accordance with the acceptability test, resulting in an environmentally safe, stable top layer in road building. Over 200tph of ready to use 0-32mm graded material were produced from broken asphalt material at a road-building operation near Giessen – with only one operator required for the RM100, combined with the OS100.?
Rubble Master machines were also used in 2007 in a road-building project in the Bavarian Forest. The old road was excavated and stored on a nearby site. Around 2500 tonnes of bituminous blocks containing hard rock gravel were recycled on-site to make a 0-32mm aggregate that was then reused as a 15cm thick foundation layer. The entire material was processed in two and a half days, including set up and removal.
STANDARDISED GRAIN IN A CLOSED CIRCUIT
The Rubble Master power system is available as an add-on for the RM100 that, in tandem with the OS100, delivers high value, standardised aggregate in a single pass. Using a closed loop system with integrated oversize grain refeeding, it is possible to produce more of the desired grain fraction and increase performance, thanks to continuous feeding with coarse blocks and oversize grain. The OS100 screens reliably, thanks to four comb-cascades. The advantage – and also the starting point in the product development – is that the crusher can be operated at maximum throughput, with a large crushing gap and low wear impact. The OS100 can be ready for operation in 10 minutes. This way, Rubble Master users can fulfil the tasks and requirements on all job sites and in any surroundings cost-effectively, and use the outstanding quality to earn a reputation as recycling specialists.
Source: Global Crushing and Screening