Valorization of tuff waste in geopolymer composites for sustainable restoration of architectural heritage

The preservation and maintenance of historical structures should be carried out with sustainable materials that ensure not only the durability of interventions but also compatibility with original substrates, both in terms of materials and aesthetics. This study investigates the valorization of industrial waste accumulated in Armenian tuff mines as raw materials for the production of geocomposite materials, offering a sustainable alternative to traditional binders. The results show that water absorption (10.16–15.50%) and open porosity (15.89–31.24%) were significantly lower than those of natural stones. Mechanically, the compressive strength reached 14.03–15.90 MPa (A-series) and 14.24–15.13 MPa (H-series), while the flexural strength increased to 4.41–5.64 MPa and 3.82–4.06 MPa, exceeding that of natural tuffs. Softening coefficients (0.76–0.84) indicate high water resistance and structural stability. The findings suggest that such materials represent an environmentally effective and technically compatible solution for the sustainable conservation of historical architecture.