Experimental Investigation of Gypsum Composites Incorporating Polymeric Rubber Waste from the Vulcanization Industry

The aim of this study was to comprehensively evaluate the influence of rubber waste originating from the vulcanisation industry on the mechanical performance of gypsum composites. Three rubber fractions (0–0.6 mm, 0.3–1.5 mm and 1–4 mm) were incorporated at contents ranging from 0% to 50% of binder mass. Increasing rubber content resulted in a systematic reduction in composite density, decreasing from 1534 kg/m3 for the reference material to 1204 kg/m3, 1128 kg/m3 and 1031 kg/m3 at 50% addition for the three fractions, respectively. Flexural strength dropped from 0.296 MPa to 0.059 MPa (fine fraction) and 0.033 MPa (coarse fraction), while compressive strength decreased from 4.556 MPa to 1.542 MPa and 1.370 MPa at 25% rubber content. These results demonstrate that both particle size and quantitative share of rubber significantly affect the mechanical response of the composite. Generalised regression-based correlations were developed for flexural and compressive strength as a function of density and rubber content, providing practical descriptive models for the analysed range. The findings offer a quantitative basis for further research on the incorporation of rubber waste into gypsum-based materials and for assessing their potential use in non-structural applications.