Recycling glass-polishing sludge and aluminum anodising sludge in polyurethane and cement composites: fire performance and mechanical properties

This article aims to study the mechanical strength and fire resistance of polyurethane/cement (PuCem) composites containing glass sludge and sludge from aluminum anodizing. Scanning electron microscopy (SEM) results showed that the replacement of 24.5% of the cement with sand (San), aluminum anodizing (Aas), or glass-polishing sludge (Gla) maintained the alveolar structure in the composites. Also, energy-dispersive X-ray spectroscopy and FTIR analyses showed that the cement hydration reaction forms hydrated aluminates and silicates. ANOVA–Tukey tests showed that the PuCemAas composites’ areas are significantly different from those of PuCemGla and PuCemSan, which are similar to each other. The compressive strength decreases upon replacing cement with the aggregates. The TGA thermograms were similar for the four composites and the polyurethane matrix. The specimens were declassified in the vertical and horizontal position (UL-94). Thus, the composites were an alternative for reducing the use of raw materials from non-renewable sources. Graphic abstract