Innovative barnacle-inspired organic–inorganic hybrid magnesium oxychloride cement composites with exceptional mechanical strength and water resistance

In response to the growing demand for energy conservation, emission reduction, and carbon neutrality in the building industry, the development of high-strength, low-carbon, and environmentally friendly magnesium oxychloride cement (MOC) as a replacement for traditional Portland cement is of great significance. However, MOC possesses inherent limitations, such as low strength and poor water resistance, which restrict its application in construction and wood adhesives. To overcome these challenges, we developed a biomimetic organic–inorganic hybrid cement material (MOC-TA-AS), inspired by the adhesion mechanism of marine barnacles. Tannic acid (TA) and acorn powder (AS) were incorporated as organic components to provide additional active sites for Mg²⁺ ions in MOC, forming a stable double-chelate network. The MOC-TA-AS composite showed significant improvements over MOC-based materials, including a 14% increase in compressive strength (109.79 MPa after 28 days of curing) and a 57.8% improvement in water resistance coefficient compared to the control. After water immersion, the content of the 5-phase increased by 72.8% (MOC-AS/1.5-TA/0.8), while the Mg(OH)₂ content decreased by 25.8%. These improvements are attributed to the weak acidity and catechol structure of tannic acid, which promote the formation of a gel-like 5-phase structure. Additionally, the large dendritic starch structure of acorn powder, in conjunction with tannic acid, helped create a chelating network. The protective coating provided by TA and AS to the 5-phase products, along with their chelation with Mg²⁺ ions, was also investigated. This research provides an effective approach to enhancing MOC cement materials and offers a feasible strategy for developing high-performance, eco-friendly building materials for practical applications.