Valorization of Recycled Textile Fibers from Moroccan Industrial Waste for Cementitious Composites: A Multi-Level Experimental Investigation

Abstract

The valorization of industrial textile waste as reinforcement in cementitious materials offers a promising approach for reducing polymer waste while improving the performance of cement-based composites. This study investigates recycled polypropylene (PP) fibers recovered from Moroccan pre-consumer textile waste for application in mortar and concrete. Thirteen fiber types were initially screened based on their geometrical and morphological characteristics, and four representative fibers were selected for detailed characterization and experimental evaluation. Fiber-reinforced mortars were first investigated to assess the influence of fiber type and dosage, followed by concrete-scale evaluation through mechanical, shrinkage, transport-related, and microstructural tests. The results showed that fiber characteristics and dosage influenced composite performance, with the magnitude and direction of the mechanical response depending on the fiber formulation. Statistical analysis confirmed that compressive strength was significantly affected by fiber type, dosage, and their interaction, whereas no statistically significant effect was detected for flexural strength at the 95% confidence level. The F8 mixture containing 0.10% fibers exhibited the highest compressive strength among the investigated concrete formulations, reaching 28.75 MPa compared with 26.25 MPa for the reference concrete. Flexural strength showed numerical increases of up to 8.2% for selected formulations, although these differences were not statistically significant. Early-age shrinkage was reduced by up to 75% compared with the reference mixtures, representing the most pronounced effect observed in the study. Increasing fiber content reduced workability and promoted fiber agglomeration, highlighting the importance of controlled dosage and dispersion. Among the investigated dosage levels, 0.10% by mass of cement was selected for subsequent durability and microstructural investigations because it provided a favorable overall balance among the evaluated properties for the selected formulations; this dosage should not be interpreted as a universal optimum. The F8 formulation exhibited favorable transport-related properties after 90 days of water curing, while SEM observations indicated a generally homogeneous fiber distribution within the investigated regions. Overall, the results demonstrate the potential of heterogeneous recycled PP textile fibers as reinforcement for cementitious composites under the investigated conditions and provide a systematic multi-scale experimental workflow for their screening and evaluation.