Physicomechanical Properties of Recycled Gypsum Composites with Polyvinyl Acetate Emulsion and Treated Short Green Coconut Fibers

The reintegration of waste into the production chain represents a sustainable method of reducing environmental impact while promoting economic growth. This also aligns with social and environmental demands. In this study, composites were produced from commercial and recycled gypsum, polyvinyl acetate (PVA) emulsions, and chemically treated short green coconut fibers, and characterized by physical and mechanical analyses. The addition of PVA improved paste workability, extended setting time, and reduced porosity, while fiber pretreatment enhanced adhesion and tensile performance. XRD, FTIR, and TGA-DTA confirmed modifications in crystallinity, bonding, and thermal stability due to the combined action of PVA and fibers. Compared with the recycled gypsum reference (RG), the optimized composite (R50C50P5F10) exhibited a 69.1% reduction in sorptivity (from 5440 × 10−4 to 1680 × 10−4 kg/m2·s0.5), a 27.9% increase in flexural tensile strength (from 2.65 to 3.39 MPa), and a 15.1% increase in compressive strength (from 6.18 to 7.12 MPa). Surface hardness values remained statistically equivalent to RG but complied with normative requirements, maintaining all formulations within the moderate hardness category (55–80 Shore C). The results demonstrate the technical feasibility of incorporating recycled gypsum and agro-industrial fibers into gypsum composites, providing a sustainable route for developing more durable construction materials.