New strategy for closing the plastic loop: Lightweight concrete by the waste of recycled synthetic fibers

Abstract

Environmental protection related to the mismanagement of plastic waste and rational consumption of natural raw materials is an essential goal of the building materials industry and the production of structural lightweight concrete. Plastic waste is not a degradable polymer and increases severe environmental burdens each moment due to its significant quantity. In addition, the recycling of plastic materials is lower than that of other materials. It is usually described as an inefficient and complex process. The textile industry offers an eco-green, effective part of the recycling loop of plastics. Therefore, many textile mills consider recycled plastics as synthetic fiber raw material, particularly for household applications. Unfortunately, such a process results again in another waste known as popcorn. This study aims to introduce an end-of-life management option for the waste of synthetic textile fibers manufactured from recycled plastic materials in construction. Furthermore, the study presents a novel approach to develop an eco-green lightweight structural concrete by incorporating a unique type of lightweight aggregate (popcorn aggregate) as a 100% environmentally friendly product. To achieve that, fourteen mixes of fine and coarse popcorn aggregate contents (25%, 50%, and 100%) are considered to replace the fine and coarse natural aggregate by volume. In addition, the workability, compressive, splitting tensile, flexural strength, microstructure analysis, and Energy Dispersive X-ray Spectrometry are assessed. The results revealed that the higher the substitution ratio of ordinary aggregates by popcorn aggregates, the higher the slump value. Meanwhile, the unit weight of hardened concrete exhibited a tangible decrease at a 100% replacement ratio of fine and coarse natural aggregates; a 56% reduction achieved a dry density of 1059 kg/m³. Moreover, the compressive strength results indicated a decrease of 32% for mixing 25% fine e popcorn aggregate with 100% coarse popcorn aggregate, resulting in a compressive strength of 45 MPa. Fine ally, no evidence of chemical interactions between the popcorn aggregate and the cementitious element during hydration is found.