Recycling of secondary raw materials from end-of-life car tires

The huge quantity of end-of-life tires discarded annually in developed countries is posing major environmental problems due to restrictions against disposal in landfills and to difficulties in obtaining suitable products to be sold in the market as secondary raw materials. Actually, mechanical processing of the tires in shredding, granulation and pulverization plants is not a fully satisfactory solution because of operational drawbacks (high energy consumption, considerable wear, low technical efficiency), in addition to the poor quality of the components. A new technology has been developed at the University of Cagliari based on the use of high velocity jets of water enabling to achieve a thorough disintegration of the rubber, leaving a very clean steel product. The rubber granules so obtained can be used either for municipal water filtration or for the manufacture of paving and building elements or as a component of surface layer in roadways, thus contributing to the improvement of living conditions in urban areas

Waterjet rough finishing of stone surface

The paper deals with the assessment of the potential application of plain waterjet for surface treatment of stone materials as an alternative to technologies traditionally employed for this task, like bush-hammering, sand-blasting and flaming.Waterjetting has been already proposed in the market for rough finishing of surfaces making use of a fast rotating head provided with multiple nozzles. At the University of Cagliari considerable research has already been carried out using either abrasive or plain waterjet, stationary or pulsed, generated through a fan-type nozzle aiming at obtaining an evenly treated surface.Aparticular goal of the tests described in the paper is that of developing a technique enabling to make engravings on the stone in order to achieve special aesthetic effects. The experimental results obtained on a broad set of rocks show that the technology is viable on both technical and economic grounds, allowing to obtain excellent results at a relatively low processing cost by resorting to multiple line nozzles

Improvement of Disc Cutter Performance by Water Jet Assistance

Abstract This article deals with the problem of assisting disc cutters by means of high-velocity jets of water, with the aim of increasing the excavation rate while improving the working conditions, with particular reference to wear. The results of an experimental research undertaken at the Waterjet Laboratory of the University of Cagliari on a medium–hard abrasive rock clearly show that a higher removal rate is achieved owing to the weakening action of a jet directed on one side of the disc, causing deeper penetration. This outcome is interpreted on the basis of the scale formation model, which explains why smaller scales are obtained on the water jet’s side of the groove. Accordingly, it is suggested that the results can be further improved if the jet is directed ahead of the tool along the same path, since, in this way, larger scales can be produced on both sides