Composition effects on microstructure and mechanical performance of lightweight cementitious mortars incorporating recycled glass powder

The construction sector must reduce its environmental footprint by adopting circular, low-carbon materials that preserve mechanical performance. This study develops lightweight aerated mortars incorporating recycled waste glass powder (RWGP, 0–50 wt%) and hydrogen peroxide (H 2 O 2 , 0–7.5 wt%) as a chemical foaming agent. Sixteen formulations were produced through a factorial design and evaluated for bulk density, porosity, and compressive strength, supported by XRD, TGA, and X-ray micro-computed tomography. The interwoven mechanisms of RWGP-driven pozzolanic densification and H 2 O 2 -induced pore formation were quantified as RWGP promotes portlandite consumption and secondary C–S–H formation, while controlled aeration generated a uniform pore network. The mortars exhibited densities from approximately 2080 to 1820 kg/m 3 and compressive strengths between 16 and 62 MPa, with statistical analysis confirming strong density–solid fraction and strength–porosity correlations. M7.5-50 reduced the roof areal load by ∼12% relative to conventional mortar while remaining compliant with the Eurocodes, demonstrating the potential of the mortars for multifunctional roof-layer applications.