A comprehensive assessment of sustainable mortar containing tannery sludge and wheat straw fibre

The shortage of raw materials for construction and the problems related to waste management make the use of industrial and agricultural by-products appealing, while also offering advantages in terms of lower weight and cost. Consequently, the development of environmentally friendly mortars based on tannery sludge and wheat straw fibres (WSF) can improve thermal insulation and sound absorption while maintaining adequate mechanical strength. In this context, different mortar samples were produced with an optimal sludge content and different fibre proportions (1 to 6%) in the cement binder mass. The mortars were characterised by microstructural, mechanical, thermophysical and acoustic analyses. The incorporation of low WSF content into the mud mortar significantly improved the thermomechanical behaviour of the composite. The density and thermal conductivity of the mortars measured after 28 days decreased with the fibre content increased. Adding 6 wt.% WSF reduces the dry composite’s lighter by 15% and enhances its thermal insulation capacity by about 70%. Furthermore, the samples with high straw content show an improved acoustic absorption in 500–1000 Hz audio range. The 4 wt.% WSF-cemented composite fulfils the structural specifications of lightweight concrete, where the crack-bridging mechanism contributes to mortar reinforcement by enhancing tensile and flexural responses, suppressing crack initiation and propagation, and improving fracture toughness, thereby ensuring reliable mechanical integrity.