**1. Introduction**

An enormous issue with glass is its one-time use, such as in beverage packaging, squandering a non-biodegradable material that occupies significant space in landfills, reinforcing the reliance on natural resources, and causing damage to the environment [1]. Moreover, dumping glass waste in landfills adds to the disposal issue that is disturbing the biological equilibrium all over the planet [2].

Waste glass, in theory, after sorting and cleaning, could be remelted to manufacture new glass products. However, its variety of colors and contaminations makes recycling laborious, reducing the glass recycling rate. Thereby, waste glass is frequently sent to landfills, contaminating nature, harming the environment, and wasting resources. Around the globe, it is estimated that a whopping amount of glass waste is landfilled each year, approximately 200 million tons, drawing international attention and efforts to develop novel products based on waste glass [3].

**Citation:** Barreto, G.N.S.; Carvalho, E.A.S.; Souza, V.d.S.d.; Gomes, M.L.P.M.; de Azevedo, A.R.G.; Monteiro, S.N.; Vieira, C.M.F. Engineered Stone Produced with Glass Packaging Waste, Quartz Powder, and Epoxy Resin. *Sustainability* **2022**, *14*, 7227. https:// doi.org/10.3390/su14127227

Academic Editor: Mariateresa Lettieri

Received: 31 March 2022 Accepted: 8 June 2022 Published: 13 June 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Compared to other wastes, such as wood and plastic, waste glass presents chemical stability, which makes its reuse in the manufacture of construction materials of great interest due to some advantages over recycling, such as low energy consumption (as it does not need melting) and simplicity in the treatment of waste [4].

Another material that takes a million years to decompose, generating environmental harm when wrongly disposed of, is quartz powder, composed of 99.0% SiO2, 0.8% Al2O3, 0.1% Fe2O3, and 0.1% TiO<sup>2</sup> [5].

Wastes, in general, are nowadays a huge challenge for the industrialized world, since they are usually discarded as useless due to poor technological handling [6]. Improperly disposed of wastes generate a series of disorders, such as destruction of landscape, fauna and flora, air and soil contamination, and populational health risks [7]. For that reason, it is important to propose new sustainable approaches for waste management, representing consistent and effective ways of minimizing these impacts [8].

In that scenario, reusing waste materials in building materials has been attracting research interests, aiming to diminish natural resources wastage, manufacturing costs, and landfilling [9]. With regard to civil construction, waste recycling at any stage would provide sustainable development in this sector, which is considered to be a major waste generator among the macro sectors of the economy, since its consumption of natural resources is approximately 75% [10].

In this sense, the combination of the construction industry with the reuse of waste has become one of the main directions of research [5], with the replacement of raw materials from civil construction with waste products encouraged by the industry, aiming to promote sustainability [11].

Among the civil construction materials, a possible solution to reuse glass and quartz wastes is the development of a novel composite material, called engineered stone (ENS), artificial stones manufactured with a high amount of fine mineral agglomerated polymeric resins [6].

In this way, particulate natural materials of ENS can be substituted by wastes. The wastes are crushed in different granulometries and mixed with resins and additives. This mixture forms a mass that goes through a molding process by means of vibration, compression, and vacuum. The thermosetting resin contained in the paste undergoes a hardening process resulting in the ENS, with dimensions defined by the mold size [12].

Lee and Shin [13] reported on the influence of vacuum, mold temperature, and cooling rate on the production of fiberglass/PET composites. It was observed that specimens preheated without vacuum registered 1.9% porosity, while those made with vacuum registered only 0.3–0.4% porosity. Vacuum-processed samples also achieved better tensile strength values, increasing from 141 Mpa (without vacuum) to 258 Mpa (with vacuum). The authors concluded that the vacuum decreases the porosity, consequently improving the composite's mechanical properties.

Lee et al. [14] studied the effects of compaction pressure, vacuum level, and vibration frequency on the properties of artificial stones produced by vacuum vibrocompression. The authors observed that by increasing the compaction pressure (up to a certain limit), vacuum and vibration diminish porosity and water absorption, enhancing the mechanical properties.

Several studies have proposed the reuse of natural wastes such as marbles, granites, quartzites, and brick waste [14–19] agglomerated by polymeric matrixes, such as epoxy and polyester, to develop engineered stones, producing stones with better mechanical, physical, and chemical properties compared to artificial and natural stones on the market.

This research is focused on producing ENS with quartz powder combined with colorless glass waste from beverage packaging. The decision to use only colorless glass came from the concern with the aesthetic appeal of the final product, since artificial stones with the highest market value are white. The use of glass from beverage packaging had the purpose of finding a sustainable destination for this single-use glass product.

This research's main goal is to confirm the technical feasibility of a novel ENS produced with beverage packaging waste, quartz powder waste, and epoxy resin. The investment in the ENS development could reinsert waste into a manufacturing process along with moving the economy by entering an unexplored and growing industrial area in Brazil [19].
