Basic magnesium sulfate cement (BMSC) is a non-conventional binder with advantages such as fire resistance, lightweight properties, and low alkalinity, widely used in lightweight panels. However, the effects of cellulosic fiber incorporation on the hydration mechanisms and mechanical performance of BMSC remains insufficiently explored. This study evaluates the effects of incorporating different dosages of bleached eucalyptus fibers (EB) on the physical, mechanical, and microstructural properties of BMSC composites. Additionally, it examines their influence on hydration reactions and phase formation to determine optimal compositions for construction applications. The composites were analyzed using mechanical tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and DIC. Results indicate that the 5-1-7 phase enhances mechanical strength through a space-filling effect, while fiber incorporation increases porosity and alters phase distribution. Higher fiber contents led to increased porosity and a reduction in compressive strength, whereas flexural strength and energy absorption were improved due to fiber-bridging effects. These findings highlight the potential of optimizing fiber dosage to balance strength and toughness in BMSC composites for construction applications.

Fiber-reinforced cementitious composites have become increasingly important in the development of durable and sustainable construction materials, particularly following the replacement of asbestos-based reinforcements. However, the long-term performance of these composites is strongly influenced by the characteristics of the fiber–matrix interface, where moisture transport, interfacial degradation, and stress transfer mechanisms govern durability and mechanical behavior. Consequently, considerable efforts have been devoted to developing surface engineering strategies capable of improving fiber–matrix compatibility and enhancing composite performance. This review examines recent advances in surface modification and interfacial engineering approaches applied to fiber-reinforced cementitious composites. The discussion covers fiber–matrix bonding mechanisms and the main modification strategies, including alkali treatments, hornification, silane coupling agents, polymeric and hydrophobic coatings, nanomaterial-assisted modifications, and carbonation-induced surface engineering. The effects of these approaches on interfacial properties, durability, dimensional stability, and mechanical performance are critically assessed. The literature indicates that treatments combining surface chemistry modification, moisture control, and mineral-based densification provide more consistent improvements in durability than single-mechanism approaches. Future developments are expected to focus on scalable treatment methods, low-carbon cementitious systems, and advanced materials design strategies, enabling the development of next-generation fiber cement composites with enhanced durability, sustainability, and long-term performance.