Development and performance assessment of low-carbon perlite–silica fume mortar for sustainable buildings applications

The development of lightweight cementitious composites incorporating supplementary cementitious materials is essential for reducing the environmental impact of construction while improving thermal efficiency in urban building envelopes. This study investigates silica-fume-modified expanded-perlite (EP) mortars as lightweight cementitious composites by examining the combined effects of perlite moisture condition, binary aggregate particle-size gradation, and curing regime. Dry perlite (DP) and saturated surface-dry (SSD) perlite were used in six binary combinations of 0.8, 2.0, 3.15, and 4.0 mm particles and subjected either to 28 days of air curing or to 7 days at 100 °C followed by 21 days of air curing. Density, compressive strength, displacement, water absorption, porosity, and thermal conductivity were measured, while elastic modulus was calculated using an empirical lightweight-concrete relationship. XRD, TGA, and SEM were used to interpret hydration-related phase and microstructural changes. Coarser expanded-perlite aggregate gradations increased water absorption and porosity, whereas oven curing generally reduced density and thermal conductivity. Thermal conductivity decreased from 0.323–0.432 to 0.206–0.241 W/m K in SSD mixtures and from 0.351–0.460 to 0.213–0.290 W/m K in DP mixtures. Under the dry perlite oven-curing condition, the 2.0/4.0 mm gradation achieved the highest compressive strength of 17.4 MPa at 1116 kg/m 3 . These findings demonstrate that optimized expanded-perlite grading, silica-fume refinement, moisture conditioning, and controlled curing can produce lightweight cementitious mortars with balanced compressive strength, density, and thermal-insulation performance for sustainable building-envelope and easy-wall applications.