**1. Introduction**

In recent years, the generation of industrial solid waste has increased exponentially around the world. This increase has as main reasons the population increase and the consequent increase in waste production [1]; urbanization processes, generating an increase in the number of inhabitants in large cities and the generation of waste [2]; the industrialization process [3]; and the increase in inappropriate places for the final disposal of waste, through dumps [1,2], which further aggravates this environmental problem.

Given this, the need to find ways to reuse waste is increasingly urgent. An alternative, which will be studied in this work, is the reuse of these wastes in the red ceramic industry, due to the diversity of functions that wastes can play in these types of materials [4]. It is known that the clays used for the production of ceramic artifacts are essentially plastic in nature, which enables, for example, use of waste that introduces non-plastic elements into the clayey mass to control this property [5,6]. As an example, the work of Moreira et al. (2008) [7] evaluated the use of ornamental rock waste in ceramics, proving the technological feasibility and economic advantages obtained with the use of this waste. Similar results were obtained by Amaral et al. (2019) [8]. In this research, the authors evaluated the use of ornamental rock residue in ceramic materials produced by uniaxial pressing. The authors' objective was to evaluate the possibility of applying this waste in paving blocks. The results obtained highlight the feasibility of using waste in the proposed application.

**Citation:** Delaqua, G.; Magalhães, J.; Marvila, M.; Vernilli, F., Jr.; Monteiro, S.; Colorado, H.; Vieira, C. Application of Glass Waste on Red Ceramic to Improve Sintering. *Sustainability* **2022**, *14*, 10454. https://doi.org/10.3390/su141610454

Academic Editor: Cinzia Buratti

Received: 13 July 2022 Accepted: 18 August 2022 Published: 22 August 2022

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Another possibility is the use of waste that helps to reduce the energy expenditure of the material in the calcination stage. This action can be direct through the supply of energy through exothermic reactions, or indirect through the reduction of the melting temperature of the ceramic material. The work by Delaqua et al. (2020) [9] evaluated the use of powdered cigarette waste in red ceramics with satisfactory results in the evaluated properties and proving the energy gain of the ceramic material during burning. Another relevant work with similar characteristics was developed by Delaqua et al. (2020) [10], where the authors evaluated the use of macrophyte biomass in ceramic materials, with positive conclusions.

A waste of great importance from an industrial point of view is glass waste. Only in Brazil, all products made with glass correspond on average to 3% of urban waste, and about 47% of glass packaging is recycled annually in the country, totaling 470 thousand tons per year [11]. Moreover, in general, this waste is 100% recyclable, that is, it can be indefinitely recycled [12]. However, when this waste is wrongly disposed of, it can be harmful, for reasons such that it is not biodegradable, and in most cases, it has a high cutting power [13]. In this article, the use of wastes from the manufacturing process of tempered glass as a melting element in red ceramics was studied, with the waste being removed from the initial manufacturing stage, that is, from the cutting of flat glass.

Other relevant information on glass waste, especially its application in ceramics, is highlighted by Silva et al. (2017) [14]. In this research, the authors developed a literature review on the use of glass waste in ceramic materials, highlighting several advantages obtained with the use of waste. An advantage is that the use of glass waste can reduce the environmental impact of the ceramic industry. Another issue addressed is the diversity of glass waste, which can be obtained from different sources. This information highlights the importance of conducting research with this material.

Another point that deserves to be highlighted is the need to use a typical ternary composition containing clay (30–60% by weight%), feldspar (15–40% by weight%) and quartz (5–30% by weight%) to produce ceramic materials [15,16]. This composition was studied such as in Luo et al. (2021) [17], where the authors evaluated the effect of replacing quartz and clay with fly ash to produce ceramics. In this study, the authors proved the need to use the typical ternary composition to obtain ceramic materials with adequate properties [18]. Thus, it is expected that the use of glass waste will contribute to the ternary composition, adding feldspar to the mix and providing adequate technological properties.

The main innovations of this work are to propose the use of glass waste to replace the sand used as a substitute for clayey masses. Although there are other published works with glass wastes [14,19], the analysis of new methodologies that enable the real application of the waste in ceramic materials is necessary.
