Autoclaved Aerated Concrete Masonry: A Critical Review of Structural, Seismic, Hygrothermal, and Durability Performance

Autoclaved aerated concrete (AAC) masonry offers low self-weight and favorable thermal insulation, but its porous, relatively brittle matrix creates challenges for structural reliability and environmental durability. This study presents a targeted narrative critical review of experimental and numerical research on AAC manufacturing, pore structure, block–mortar interaction, seismic and blast behavior, hygrothermal performance, durability, and sustainability. Findings are critically compared in relation to material density, joint configuration, loading history, and moisture exposure, with emphasis on mechanisms connecting material-scale characteristics to wall-scale response. The synthesis indicates that stronger mortar adhesion can redirect cracking from joints into AAC units, while prior in-plane seismic damage can diminish subsequent out-of-plane resistance through cracking and loss of boundary restraint. Moisture accumulation increases thermal conductivity and can weaken masonry bonds, whereas freeze–thaw deterioration depends strongly on saturation and material properties. Strengthening benefits vary with reinforcement, anchorage, and test configuration and cannot be treated as universal improvement factors. Likewise, potential operational and structural environmental savings must be weighed against autoclaving energy and maintenance demands. The review identifies priorities for matched-condition testing, coupled hygrothermal–mechanical assessment, sequential seismic evaluation, and assembly-specific performance-based design guidance.