Microwave-treated Eucalyptus globulus wood for construction applications: Enhanced impregnability, biological resistance, and preserved mechanical performance

The application of Eucalyptus globulus as a construction material is limited by its low permeability and challenging drying behavior, despite its high mechanical performance. This study evaluated the effects of low-intensity microwave (MW) treatment on a wide range of properties of E. globulus heartwood. Small clear heartwood specimens were subjected to MW treatment. The microstructure, chemical composition, preservative retention, water repellency efficiency (WRE), anti-swelling efficiency (ASE), density, biological resistance to decay fungi and termites, and mechanical properties of these materials were thoroughly analyzed. The MW treatment enhanced preservative retention by 78 %, alongside improvements in WRE and ASE, likely due to induced chemical modifications, especially the reduction in hemicelluloses, and the hornification phenomenon. Scanning electron microscopy confirmed that the MW-Treated specimens did not present significant alterations or damage to their cells or other microstructural elements. Furthermore, the strength and modulus of elasticity in bending, compression, and tension parallel to the grain and brittleness remained statistically equivalent to those of untreated specimens. Notably, the Reference group exhibited unexpectedly good biological resistance, offering new insights into the natural durability of E. globulus heartwood. Furthermore, the combined application of MW treatment and preservative impregnation was highly effective in enhancing biological durability, resulting in substantial reductions in decay and termite-induced mass loss. These results demonstrated that low-intensity MW treatment can improve key properties of E. globulus heartwood relevant to construction applications, without worsening its mechanical properties. • Microwave treatment improved E. globulus impregnability by 78 %. • Mechanical strength was preserved after microwave modification. • Biological resistance increased with MW and preservative combination. • Water repellence and anti-swelling efficiencies were significantly enhanced. • MW-treated E. globulus shows strong potential as a construction material.