Synthetic microfibres released during textile drying are considered an emerging source of microplastic pollution, yet this waste stream is generally discarded without treatment. This study investigates a valorisation route by incorporating waste dryer-filter microfibres into a potassium-based/metakaolin geopolymeric coating for architectural applications, with the dual objective of preventing environmental release and enhancing material performance. Geopolymer pastes containing 0.1–0.3 wt.% of synthetic microfibres were characterised in terms of physical, mechanical and microstructural behaviour. Microfibre addition produced a marked toughening effect, with flexural strength increasing from about 3 MPa for the unreinforced matrix to 7.5 MPa for the composite containing 0.3 wt.% fibres, while compressive strength decreased moderately due to the presence of a compliant fibrous phase. Microstructural observations confirmed fibre dispersion and fibre–matrix bonding, supporting crack-bridging mechanisms. Density, porosity and water absorption measurements indicated a stable geopolymer gel structure with a connected pore network. Thin-layer applications onto clay brick exhibited satisfactory workability and adhesion, confirmed by pull-off testing (~0.12 MPa) and interfacial microscopy. The results demonstrate that textile-derived microfibres can be effectively immobilised within a potassium geopolymer matrix while improving flexural performance, offering a feasible circular strategy for microfibre waste reuse in mineral coatings.
Murri et al. (Fri,) studied this question.