proceedings Proceedings The Possibility of Using Slag for the Production of Geopolymer Materials and Its Inﬂuence on Mechanical Performances—A Review † Brădut , Alexandru Ionescu *, Adrian-Victor Lăzărescu and Andreea Hegyi NIRD URBAN-INCERC Cluj-Napoca Branch, 117 Calea Flores , ti, 400524 Cluj-Napoca, Romania; adrian.lazarescu@incerc-cluj.ro (A.-V.L.); andreea.hegyi@incerc-cluj.ro (A.H.) * Correspondence: bradut.ionescu@incerc-cluj.ro † Presented at the 14th International Conference INTER-ENG 2020 Interdisciplinarity in Engineering, Mures , , Romania, 8–9 October 2020. Published: 17 December 2020   Abstract: All industries produce wastes or byproducts, and if those are not properly managed, they will cause adverse eﬀects on the environment. As the need for steel increases globally, waste from steel processing will also increase. Hazardous waste from steel processing is produced in the form of a coarse, dense aggregate, called steel slag. The aim of this paper is to present the possibility of using steel slag/blast furnace slag in the production of geopolymer concrete and to present the relevant results regarding the inﬂuence of this industrial byproduct on the mechanical properties of Geopolymer materials. Keywords: geopolymer binders; industrial byproducts; sustainable development 1. Introduction Industrial wastes generated by the various industries are a global problem with multiple social, ﬁnancial and environmental eﬀects. The eﬃcient recycling of wastes and industrial byproducts is more than necessary in order to mitigate their negative eﬀects, to reduce the consumption of other raw materials and to minimize at much as possible greenhouse gas emissions. Construction and demolition waste, ﬂy ash, furnace/steel slag and mining waste can be recycled for reuse and to produce new, innovative materials in thecivil engineering industry. Cement production raises major problems around the world through CO 2 pollution of the atmosphere. Cement production is considered to have a global pollution share of 5–8% by total emissions of CO 2 released into the atmosphere. To reduce the high amount of carbon dioxide emissions released into the atmosphere during the production of Portland cement, alternative materials such as alkali-activated composites, or geopolymers, could provide a sustainable and durable approach. The most used raw materials in the production of alkali-activated geopolymer materials are ﬂy ash and furnace/steel slag. Given the fact that the industries that produce these types of wastes are constantly growing, using these materials as raw materials oﬀers the premises for producing alternative materials. As the need for steel increases globally, the waste produced by the steel processing industry will also increase. Hazardous waste from steel processing is produced in the form of a coarse, dense aggregate, called steel slag [1]. In 1999, Palomo proposed the possibility of activating puzzolanic materials such as furnace slag and ﬂy ash “using alkaline liquids, to form a binder and completely replace the use of Portland cement in the production of concrete” [2]. Geopolymer concrete, known as alkali-activated cement [3], inorganic polymer concrete [4] or geocement [5], has emerged as an innovative way of new engineering materials, entirely replacing traditional Portland cement. In order to successfully produce geopolymer Proceedings 2020, 63, 30; doi:doi:10.3390/proceedings2020063030 www.mdpi.com/journal/proceedings