CC BY-SA 4.0Biasi Taiano, Maximiliano2026-10-0808-10-26 12026Biasi Taiano, M. (2026). Feasibility study and design of polyhydroxybutyrate (PHB) fibers produced by fermentation for the reinforcement of cementitious composites [Master's thesis, Universidad de los Andes]. Repositorio Institucional UANDES. https://repositorio.uandes.cl/handle/123456789/70605https://repositorio.uandes.cl/handle/123456789/70605Tesis para optar al grado académico de Magíster en Ciencias de la IngenieríaFiber reinforcement can improve the durability and service performance of cementitious composites, contributing to longer-lasting structures and potentially reducing their environmental impact. However, many of the synthetic fibers currently used for this purpose are petroleum-derived, motivating the search for more sustainable alternatives. Polyhydroxybutyrate (PHB) is a biodegradable polymer produced by bacteria that has the potential to replace petroleum-based materials in a wide range of applications. This thesis establishes an experimental foundation for evaluating PHB-based fibers as a sustainable alternative to conventional reinforcement fibers in cementitious composites. The research encompasses bacterial production of PHB, polymer recovery, fiber processing, and characterization of the resulting materials. PHB was produced through fed-batch fermentation of Cupriavidus necator, achieving reproducible concentrations of approximately 14–17 g/L. A chloroform-based extraction and purification process was developed, resulting in a final PHB purity of approximately 98%. Direct extrusion of the locally produced polymer did not provide stable fiber formation due to processing and thermal stability limitations. Therefore, continuous fibers manufactured from commercial thermoplastic-grade PHB were used to complete fiber-level characterization. The resulting materials were evaluated through physicochemical, thermal, mechanical, aging, and alkaline degradation analyses. The extruded PHB fibers exhibited tensile strengths between 34 and 42 MPa and strains at failure of approximately 0.7–0.8%, indicating that their untreated mechanical properties are not yet sufficient for the intended reinforcing function. In contrast, the fibers demonstrated favorable alkaline stability, with negligible mass loss after up to 168 hours of exposure at 20 °C and maximum average mass losses of approximately 10% under accelerated exposure at 70 °C. Overall, the results support PHB as a technically viable precursor for cementitious reinforcement applications while identifying fiber processing and mechanical performance as the principal remaining challenges. The findings provide a foundation for future development of PHB fibers through stabilization, drawing, and thermal post-processing, contributing to the advancement of more sustainable reinforcement materials for cementitious composites. Keywords: Polyhydroxybutyrate (PHB), Cementitious Composites,Biodegradable Fibers.enAcceso abiertoPolyhydroxybutyrate (PHB)Cementitious CompositesBiodegradable FibersFiber ReinforcementBacterial FermentationTesisIngeniería y TecnologíaIngeniería MecánicaIngeniería Mecánica49