Lightweight mortars containing expanded polystyrene and paper sludge ash

•A beneficial reuse application for two industrial wastes, EPS and PSA, is reported.•Lightweight cement mortars containing PSA and EPS have low density and low thermal conductivity.•Ground EPS resulted in lower thermal conductivity than powdered EPS.•Mortars containing EPS and PSA meet the EU standards for rendering, masonry and plastering.

The objective of this research was to develop lightweight cement mortars with good thermal-insulation properties by incorporating expanded polystyrene (EPS) and paper sludge ash (PSA), both of which are problematic waste materials. The mortars formed had low thermal conductivity and low bulk density compared to control samples. Ground EPS produced lower thermal conductivity samples than powdered EPS. Resource efficient mortars containing up to 20% PSA, and 60% of EPS are considered suitable for use in rendering and plastering applications.