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Design New Products with Natural Stone Waste
Major events in the history of human civilization are often labelled with terms such as Stone Age, Iron Age, Bronze Age, Industrial Revolution, or Information Age. Today, the new era of Re-use, Reduce and Recycling has already started. Those events, so remarkable for the human being, have a common characteristic: the discovery, extraction, processing and use of natural materials from the Earth, many of them giving name to its era. The extractive industry plays a crucial role in the current development of our society, providing key raw materials for the industry. However, the negative impact associated with this activity is evident. The growing demand for nonrenewable resources, because of the continuous growth of the world's population, makes it urgent to look for other alternatives, to guarantee the sustainability of the planet. Knowing that the mining industry and particularly in natural stone quarries, the percentage of unused stone material (waste) can reach 70% of the total volume of extracted stone, laying down that new uses for the waste materials is a priority which promotes the new paradigm of circular economy and sustainable development. This work explores the possibility of reuse waste generated by the stone extraction industry, through the production of composite materials formulated with stone particles of different grain size joined together by an epoxy resin. The stones used in this study were obtained from the residues from two quarries of natural stone, a marble quarry located in the south of Portugal and a schist quarry in the north of Portugal. The physical-mechanical properties of the stones used were already known and are published in the Catalogue of Portuguese Ornamental Stones. Subsequently, the physical-mechanical properties of the original rocks were compared with those determined in the produced samples. The manufacture of samples made it possible to evaluate the behaviour of the components of the mixture from the aesthetical point of view, but also in terms of their main features, through testing; the physical and mechanical properties were determined. The results led us to conclude that the composite with the most promising properties does not present enough mechanical resistance for structural applications, like some ornamental rocks do; however, it represents a great opportunity to design decorative artefacts for different industrial sectors. Considering the results obtained, a lamp and a decorative panel were designed and manufactured using shale and marble, taking advantage of the observed contrast between dark and opaque shale grains with translucent and light grains of marble.