Asphaltrecycling of Benninghoven

The use of Asphalt Recycling is not only subject to economic constraints but also to the statutory provisions for waste management in order to save our valuable resources. These targets are focused in many publications and reports, and primarily manifested in the technical delivery conditions directives for granulated asphalt (TLAG).

There is no mention of any grinding criteria or method that significantly influences the quantity or quality of the granulate which then has a direct impact of the additions for reclaimed asphalt into the Asphalt Plant.

Partly proposed in the directives were measures to avoid the degradation of granulate sizes. In the second part it is stated that the grinding process in unavoidable. However, according to previous experience, it can be assumed that the grinding process still occurs when utilizing machines such as impactors.

The challenge
These well known crushers are primarily developed for material such as hard rock and concrete demolition. Therefore a high energy input is inevitable for the crushing process.
This type of process leads to fragmentation of the aggregates within the reclaimed asphalt and a huge amount of fines is unavoidable. This alters the grading curve compared to the original material.

To obtain the required aggregate size of the end product large quantities of virgin rock must be added. From a mathematical standpoint this limits the addition of asphalt granulate.
Fine grained material in the crushed asphalt absorbs large quantities of water when it is stored in the uncovered stockpiles. This additional water needs to be evaporated in another process.
High fines can also cause problems within Asphalt mixing plants (recycling drum in particular). Requiring regular cleaning which is costly and labour intensive. This is another very important aspect that should be taken into consideration.

The solution
The first concept impact crusher for reclaimed asphalt was launched more than twenty years ago to fulfill the criteria mentioned above. Unfortunately this machine had some disadvantages by the design, especially being sensitive to the iron components that are frequently found in feed material.

Benninghoven has constantly continued the research and development for this improved technology. In developing the machine, the main criteria for the Benninghoven R&D team was to design a highly efficient granulator capable of breaking reclaimed asphalt blocks and planings down to a perfect recyclable size without reducing the original stone content. Another most important issues was to develop a machine which can handle trapped steel without damaging the machine.