Development and Characterization of Eco-efficient Magnesium Oxysulfate Composites: Influence of Carbonation on Phase Formation and Material Properties

Abstract This study investigates the development of eco-efficient composites based on magnesium oxysulfate (MOS) cement reinforced with lignocellulosic fibers and subjected to accelerated carbonation. The aim is to evaluate how carbonation time influences phase formation and the physical–mechanical properties of the material. Composite samples were exposed to a CO 2 -rich atmosphere (10% CO 2 , 90% RH, 20 °C) for 24 h and 7 days. Mechanical tests, X-ray diffraction (XRD), infrared (FTIR), and Raman spectroscopy were employed to monitor phase evolution and microstructural changes. The results indicate that short-term carbonation promotes microstructural densification and increases toughness, despite a slight reduction in mechanical strength due to partial transformation of hydration products. Prolonged carbonation, however, led to a significant decline in strength parameters as the mechanically active 5-1-7 phase was consumed, replaced by hydrated magnesium carbonates such as nesquehonite and hydromagnesite. These findings underscore the critical role of carbonation in tailoring composite performance. Optimization of CO 2 curing parameters is essential to enhance durability while preserving structural integrity. The study contributes to the advancement of sustainable construction materials with lower carbon footprints and improved long-term behavior.