Exploratory evaluation of the physical-mechanical, microstructural, and eco-efficiency behavior of concretes reinforced with natural Ichu fibers from the Bolivian Altiplano

The present study experimentally evaluated the physical, mechanical, microstructural, and environmental behavior of concretes reinforced with natural Ichu fibers from the Bolivian Altiplano, with the aim of analyzing their potential as a technically viable and environmentally sustainable alternative for regional construction applications. Mixtures containing 0%, 0.5%, 1.0%, 1.5%, and 3.0% fiber by volume were studied, using fibers with a nominal length of 25 mm. Fiber characterization included morphological analysis through stereoscopy and SEM, FTIR spectroscopy, and tensile testing. Likewise, fresh-state properties, physical properties, and mechanical strengths under compression, indirect tensile, and flexural loading were evaluated using water-cured concrete specimens tested at 7 and 28 days. The results showed a progressive reduction in workability as the fiber content increased. The mixture containing 0.5% fiber presented moderate increases in compressive strength (11.9%), indirect tensile strength (4.3%), and flexural strength (5.3%) at 28 days compared to the reference mixture; however, these variations were not statistically significant. Higher fiber contents generated progressive losses in mechanical performance, increased voids, and higher water absorption, associated with the weakening of the interfacial transition zone observed by SEM. The environmental analysis showed a theoretical reduction in CO₂ emissions as the fiber content increased; however, the eco-efficiency indicator revealed that only the mixture with 0.5% fiber presented a favorable balance between emission reduction and mechanical performance. The obtained results establish an experimental baseline for future research aimed at the optimization and treatment of natural Ichu fibers in cementitious matrices.