Matrix Modification of Dual-Function Inorganic Composites for Integrated Seismic and Energy Retrofitting of Masonry: A Review

The European building stock is subject to two simultaneous demands: the decarbonisation targets set by the climate agenda and the persistent threat of seismic hazard. A large fraction of this stock consists of unreinforced masonry (URM) that is both structurally vulnerable and energy-inefficient, yet structural and energy upgrades have historically been implemented as separate, uncoordinated interventions. Post-earthquake surveys indicate that energy-only retrofits are themselves susceptible to seismic loss, motivating integrated solutions based on multifunctional materials. Inorganic-matrix composites have emerged as a promising externally bonded solution, combining seismic strengthening with the fire resistance and, particularly for lime-based matrices, the vapour permeability that organic fibre-reinforced polymers lack. This review addresses modification of the inorganic matrix as a route to a single dual-function composite, in contrast to reviews organised around reinforcement type. Based on a structured search of Scopus and Web of Science, the literature is organised by matrix-modification strategy, including mineral and lightweight aggregates, geopolymer and alkali-activated binders, and bio-based aggregates and natural-fibre systems. The reported thermal conductivity, compressive strength and testing scale of each family are synthesised and compared, together with the number of specimens underlying the reported mechanical gains. A pervasive thermo-mechanical trade-off emerges as the governing design constraint: modifications that lower thermal conductivity also tend to reduce compressive strength, stiffness and frequently bond capacity. By mapping the literature onto a thermal-versus-seismic test matrix, the review reveals that the dual-function cell, representing studies that combine thermal characterisation with seismic testing of the same modified system at masonry-element scale (wallet, wall or frame), remains nearly empty, with only three studies identified. The vapour permeability of dense alkali-activated matrices, accelerated ageing, economic feasibility and the context-dependence of environmental benefits are also critically discussed. Addressing this gap will require performance-based mix design, interface engineering, standardised durability protocols, life-cycle costing, and full-scale experimental and numerical validation across a range of climatic and seismic regions.