Citation: Bahij, S.; Omary, S.; Steiner, V.; Feugeas, F.; Ibrahimkhil, M.H. Effect of Non-Woven Polyethylene Terephthalate (PET) Tissue on Fresh and Hardened Properties of Concrete. Materials 2022, 15, 8766. https:// doi.org/10.3390/ma15248766 Academic Editors: Yeou-Fong Li, Bing-Jean Lee, Chih-Hong Huang and Walter Chen Received: 13 October 2022 Accepted: 6 December 2022 Published: 8 December 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/). materials Article Effect of Non-Woven Polyethylene Terephthalate (PET) Tissue on Fresh and Hardened Properties of Concrete Sifatullah Bahij 1,2, *, Safiullah Omary 1 , Vincent Steiner 1 , Françoise Feugeas 1 and Mohammad Hashim Ibrahimkhil 3 1 ICube, UMR CNRS 7357, INSA-Strasbourg, 24 Bld de la Victoire, University of Strasbourg, 67084 Strasbourg, France 2 Department of Civil and Industrial Construction, Kabul Polytechnic University, Kabul 1010, Afghanistan 3 Department of Building Construction Management, Kabul Polytechnic University, Kabul 1010, Afghanistan * Correspondence: sifatullah.bahij@insa-strasbourg.fr Abstract: This study will investigate the effect of non-woven PET plastic tissue on the fresh, physical, mechanical, acoustic, thermal, and microstructural behaviors of concrete. Including reference speci- mens, non-woven fabrics were considered in two ways: (a) as a layer with four various configurations of 1-layer, 2-sides, 3-sides, and full wrapping (4-sides) to strengthen specimens, and (b) as (10 × 10) mm cut pieces with three different incorporated percentages of 0.25%, 0.50%, and 0.75%. Based on the experimental results, mechanical properties (compressive, split tensile, and flexural strengths) were remarkably improved by applying non-woven sheets as a layer. For instance, the cylindrical compressive and split tensile strengths were improved by 13.40% and 15.12% for the strengthened specimens compared to the reference specimens, respectively. Moreover, control specimens were damaged to many fragments after mechanical testing, but the samples strengthened by such fabrics or containing cut pieces were maintained and not separated into many small parts. The acoustic behavior and thermal conductivity declined by 9.83% and 19.67% with the attachment of tissue on one side and 2-sides, respectively. Acoustic behaviors decreased by 10.0%, 17.60%, and 26.30% and thermal conductivity decreased by 6.60%, 12.10%, and 15.50%, with the incorporation of 0.25%, 0.50%, and 0.75% of cut pieces, respectively. Finally, it was discovered that non-woven tissue is advised to enhance particular properties of concrete. Keywords: plastic wastes; non-woven tissue; fresh and physical properties; mechanical behaviors; ultrasonic pulse velocity; thermal conductivity 1. Introduction In recent decades, plastic consumption has been vastly increased because of rapid urbanization and economic growth. The recycled amount is still comparatively lower and results in an increase of plastic wastes. These wastes cause many environmental problems because of the absence of enough space for landfilling and their low biodegradability [1–6]. A total of 348 million tons of plastic were produced worldwide in 2017, while 61.8 million tons of that total were produced in Europe. In 2018, this sum was enlarged to 359 million tons worldwide and to 64.4 million tons in Europe. In addition, in the same year, 32.5% of plastic wastes were recycled, 42.6% were used in energy recovery, and about a quarter (24.9%) were dumped in landfills worldwide. It is also estimated that the production of plastic will become double by 2035 and quadruple by 2050 [7–10]. Therefore, for better sustainable waste management, it is necessary to recycle and reuse plastic wastes that result in saving natural resources, decreasing pollution of the environment, and reducing embodied energy [11]. In general, plastics are classified into two groups based on their ingredients and mix proportions: (1) Thermoplastics can melt when heated and harden when cooled. Based Materials 2022, 15, 8766. https://doi.org/10.3390/ma15248766 https://www.mdpi.com/journal/materials