**1. Introduction**

The concept of circular economy is expected to bring many benefits to both economic development and the environment. The potential environmental factors are those such as decreasing the use of natural resources, limitation of emissions, recycling, fewer material losses through recycling, etc. [1,2]. The circular economy can also be seen as the next possible step in the evolution of waste management systems, including the development of sustainable materials that will allow closed loops. It could be possible through the introduction of manufacturing processes by being able to reuse materials at the end of their useful life [2,3]. This issue is important in the context of a realistic introduction of the circular economy into existing systems [4,5]. Materials corresponding to the needs of this model are, among others, geopolymers.

Geopolymers are a class of synthetic inorganic aluminosilicate materials, usually formed as a result of the reaction of aluminosilicates (e.g., fly ash or metakaolin) with a solution of silicates under usually strongly alkaline or sometimes acidic conditions [5,6]. Their synthesis has been estimated to emit about five–six times less carbon dioxide than the production of Portland cement and needs significantly less energy for the manufacturing

**Citation:** Korniejenko, K.; Figiela, B.; Pławecka, K.; Bulut, A.; ¸Sahin, B.; Aziza ˘gao ˘glu, G.; Łach, M. Characterization of a Coal Shale from Marcel Mining as Raw Material for Geopolymer Manufacturing. *Mater. Proc.* **2023**, *13*, 21. https://doi.org/ 10.3390/materproc2023013021

Academic Editors: Katarzyna Mróz, Tomasz Tracz, Tomasz Zdeb and Izabela Hager

Published: 14 February 2023

**Copyright:** © 2023 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/).

process [7,8], but it is not only the advantages of geopolymer materials that take into account the circular economy approach. One of the most important benefits is the possibility of using waste for production [5,7]. One of the most promising opportunities is mine tailings [7,9]. These types of wastes are reachable in aluminosilicate, which is a main component of the geopolymerization process [9,10].

In recent years, there has been a visible increase in interest in the use of mine tailings for the production of geopolymer materials in the literature [9,11,12]. Previous investigations were related to different kinds of waste, including coal shales [10], gold mining [13], tungsten mining waste mud [14], copper tailing [15], zinc mining [16], garnet tailings from molybdenum mines [17], and others [7,18]. From the point of view of Poland and neighboring countries, the promising materials are coal shales. Coal mine tailings represent a significant waste stream that is used for geopolymer manufacturing. The current work shows the possibility of using a coal shale from Marcel mining for this purpose. This mine tailing has not been previously analyzed as a raw material for geopolymerization. The main aim of the presented research is to characterize the raw material, design geopolymers based on mining waste from Marcel mining, and determine potential applications for them.
