Comparison of sawdust bio-composites based on magnesium oxysulfate cement and ordinary Portland cement

This study incorporated sawdust (SD) as a bio-aggregate into magnesium oxysulfate cement (MOSC) and ordinary Portland cement (OPC) for the preparation of composite lightweight materials. The effect of sawdust dosage on the mechanical properties, thermal properties, water absorption, and water resistance of the two bio-composites was investigated. Experimental results revealed that SD-MOSC presented lower density, higher compression strength, and excellent thermal insulation properties than SD-OPC. Thus, MOSC is more suitable as a binder for sawdust aggregates than OPC. Microstructure observation showed that 5 Mg(OH)2·MgSO4·7H2O (5·1·7) phase whiskers preferred to form at the defects of sawdust, indicating that MOSC had better compatibility with sawdust. The increase of sawdust hindered the generation of 5·1·7 phase, resulting in the strength reduction. MOSC-based sawdust bio-composites are a promising material for production of thermal insulation panels and are favorable for environmental protection.