ASPHALT RECYCLING

A special field of application

Proven crushing technology

WITH EXCELLENT RESULTS

How to get a high amount of usable granulate from clods and milling material

Crush + Size Technology has developed special core competencies in the development of efficient crushing processes based on rotating rollers.

The process, which is advantageous in many applications, also shows its advantages especially in asphalt recycling. Because here it is of particular importance for the quality of the recycling material if the supporting grain – i.e. the aggregate for the primary asphalt production – is separated from the bond with the bitumen binder in such a way that it can be used again in the next asphalt mixing process with virtually no loss of quality.

In order to achieve such a result, a primary crusher crushes the asphalt to be extracted to a size of < 100 mm in a primary crushing step. In order to be able to even cope with bulky chunk sizes and large edge lengths the crushing tool was manufactured in a way that direct draw-in of the feed material by means of large digging teeth is ensured. At low circumferential speed the teeth grab into the material so that it is already pre-crushed in a gentle and low-wear way. Clods and plates with edge lengths of up to 1.8 m and thickness of up to 400 mm are processed.

Particles below the defined target granulation are being discharged over a sieving grate before they reach the crushing unit. By means of this concept it is possible to reach capacities an amount of 150 t/ h while the amount of large clods in the feed material can be up to 50%.

The secondary crushing step takes up the complete material from the primary crusher and crushes only those grain sizes which are larger than the target granulation. The double roll system is characterized by an innovative tooth technology which is causal for a high crushing ratio.

This process is convincing because naturally existing predetermined breaking points in the old asphalt are utilized. This means that pressure leads to a precise separation exactly between stone grain and binder filling. In this way, reliable granulations of < 11 to < 22 mm can be produced. Due to limited crushing space geometry the amount of oversized grain is less than 1%.

THE RESULT COUNTS

Sieving analyses from extracted samples have revealed that granulations 0/22 from asphalt clod material only contained sand portions of 12% and less than 2% dust. The grain form of the stone fraction regained from this procedure is cubical. The largely separated bitumen binder concentrates in the form of adhesions on single stones. These results are proving a very gentle processing of the old asphalt. Especially the low amount of sand shows that the original stone matrix in its structure is almost complete and without undesired additional sand and dust particles in the target grain due to an overload of stress are found. Even for bitumen there is an ideal separation so that it can be used again as an important valuable substance.

Safe operation

WITH HIGH PERFORMANCES

Both crushers have a hydraulic overload protection in order to automatically remove disturbing material from the crushing space without damage of the machine. In order to immediately react upon changing material characteristics in the feed material, also the crushing gap in both crushing steps can individually be adjusted by means of the control panel during the crushing process. The application of a subsequent sieving unit is possible for example in order to lead back oversized grain to the secondary crusher.

Depending on the needs of the operator, the roll crushing unit can be either a track mobile or a wheeled mobile crushing unit. The crushers can also serve as individual modules in stationary asphalt processing or recycling plants.

Depending on the machine size the crushers achieve performances of up to 300 t/h. In order to ensure an efficient operation of the unit, the control system takes over the optimum feed. In the knowledge around the user demands regarding the availability, all Crush & Sizes machines can be equipped with a quick-change system with which the rolls can be exchanged in no time.