Citation: Attia, M.M.; Abdelsalam, B.A.; Amin, M.; Agwa, I.S.; Abdelmagied, M.F. Metal-Nails Waste and Steel Slag Aggregate as Alternative and Eco-Friendly Radiation Shielding Composites. Buildings 2022, 12, 1120. https:// doi.org/10.3390/buildings12081120 Academic Editor: Haoxin Li Received: 17 June 2022 Accepted: 25 July 2022 Published: 29 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 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/). buildings Article Metal-Nails Waste and Steel Slag Aggregate as Alternative and Eco-Friendly Radiation Shielding Composites Mohammed M. Attia 1, *, Bassam Abdelsalam Abdelsalam 1 , Mohamed Amin 1 , Ibrahim Saad Agwa 1,2 and Mohammad Farouk Abdelmagied 3 1 Civil and Architectural Constructions Department, Faculty of Technology and Education, Suez University, Suez 43713, Suez, Egypt; bassam.abdelsalam@suezuniv.edu.eg (B.A.A.); h_scc@yahoo.com (M.A.); ibrahim.agwa@suezuniv.edu.eg (I.S.A.) 2 Civil Engineering Department, El-Arish High Institute for Engineering and Technology, El-Arish 45511, North Sinai, Egypt 3 Civil Engineering Department, Benha Faculty of Engineering, Benha University, Benha 13511, Qalyubiyya, Egypt; dr.mohamed.farouk@bhit.bu.edu.eg * Correspondence: mohammed.mahmoudattia@suezuni.edu.eg Abstract: Metal waste recycling has become a global requirement owing to its environmental benefits and powerful economic activity. Metal nail waste (MNW) is a byproduct of metal nail manufacture. MNW has an equal size, contains a high ratio of iron, and has a high specific gravity comparable to normal aggregate. We present MNW recycling as a partial replacement for fine aggregates and electric arc furnace steel slag (EAFSS) as coarse aggregates to produce sustainable heavyweight concrete (HWC). Our main research aim was to study the radiation shielding and mechanical properties of sustainable HWC by partially replacing MNW with 10, 20, 30, and 40% sand. EAFSS is a coarse aggregate for 60% of the total volume. Fresh and hardened properties of HWC are presented. Furthermore, we analysed the internal structure of HWC mixes using a scanning electron microscope. Our results showed the positive effects of MNW on the unit weight of concrete. The density of HWC mixes ranges between 2650 and 3170 kg/m 3 . In addition, MNW contributes to increasing the compressive strength of concrete mixes with their use of up to 30%. Therefore, the MNW ratios improved the failure behaviour of HWC mixes. The improved linear attenuation coefficient of HWC mixes was due to using MNW ratios and higher densities than the reference mix. Keywords: electric arc furnace steel slag; heavyweight concrete; mechanical properties; metal nails waste; radiation shielding; sustainable concrete 1. Introduction Concrete is the most commonly used material in the construction industry because of its availability, durability, and low cost [1–3]. The EN 206-1 specification indicates that concrete is considered heavyweight concrete HWC with a dry specific gravity >2600 kg/m 3 [4–7]. The most common aggregates to produce HWC are limonite, hematite, magnetite, ilmenite, and barite [8,9]. HWC is widely used for radiation protection in industrial, medicinal, and research applications [10], leading to the consumption of raw natural heavyweight aggregates [4,5]. However, the availability of natural heavyweight aggregates is decreasing due to high demand, leading to an increased need for alternative sources [11]. Although the HWC is more suitable for radiation shielding, the production of HWC is expensive. Waste materials such as recycled aggregates of lead waste, copper slag, steel slag, etc., present good radiation shielding and reduce costs [12,13]. According to the United Nations’ World Commission on Environment and Develop- ment, sustainability means “meeting the needs of the present without compromising the ability of the future generations to meet their own needs” [14]. Therefore, managing mate- rials sustainably necessitates paying attention to a product’s whole life cycle, from the time Buildings 2022, 12, 1120. https://doi.org/10.3390/buildings12081120 https://www.mdpi.com/journal/buildings