Valorization of Waste Medium-Density Fiberboard in Multifunctional Lightweight Cement Mortar: Effects of Cement-Slurry and Paraffin Pretreatments on Mechanical, Thermal, and Acoustic Performance

The growing generation of waste medium-density fiberboard (MDF) from construction, renovation, and furniture-related activities creates environmental concerns associated with disposal, landfilling, and inefficient material recovery. This study investigates the valorization of waste MDF as a functional lightweight aggregate in cement mortar and evaluates whether pretreatment can mitigate its high water absorption while retaining beneficial thermal and acoustic characteristics. Waste MDF was used in three conditions: untreated MDF, Portland cement slurry-treated MDF (MDFC), and paraffin wax-treated MDF (MDFP), at addition levels of 10–50% by cement weight. The untreated MDF exhibited a water absorption of 245%, which was substantially reduced to 60% and 15% after cement-slurry and paraffin pretreatments, respectively. Increasing MDF content generally reduced mortar flowability, density, compressive strength, and flexural strength, while enhancing thermal insulation and sound absorption. Among the investigated treatments, MDFC produced the highest density and mechanical performance because the cementitious coating improved particle grading, packing efficiency, and compatibility with the cement matrix. In contrast, MDFP provided the greatest reduction in MDF particle water absorption but exhibited comparatively lower mechanical performance because of weak interfacial bonding and particle agglomeration. Untreated MDF mortar achieved the lowest thermal conductivity, decreasing to approximately 1.76 W/m·K at the highest addition level, and exhibited the highest sound absorption coefficient and noise reduction coefficient. The results demonstrate that waste MDF can be valorized in non-structural cementitious materials, providing a potential pathway for reducing MDF disposal while producing lightweight, thermally insulating, and acoustically functional building materials.