Fly Ash-Based Structural Energy Storage for Sustainable and Resilient Buildings: Materials, Durability and Life-Cycle Perspectives

Coal fly ash has emerged as a promising resource for developing multifunctional construction materials with integrated energy-storage capabilities. This structured narrative review examines fly ash-containing cementitious and geopolymer systems, fly ash-derived electroactive materials, and cenosphere-supported phase-change composites, with particular attention to their storage mechanisms, mechanical performance, durability, and potential building applications. By distinguishing electrode-level measurements from assembled-device performance and material-scale evidence from building-level functionality, the review identifies opportunities and limitations in integrating electrochemical and thermal storage into construction materials. Reported studies demonstrate laboratory-scale charge-storage functionality and measurable thermal-regulation effects, whereas long-term structural reliability, functional retention, safety, and building-scale operation remain insufficiently validated. An illustrative fixed-input screening compares a fly-ash-containing case with a no-fly-ash reference under an equal-mass cement-substitution assumption. Under the assigned material proxy coefficients, replacing 16 kg of OPC with 16 kg of fly ash reduces the A0 material-carbon proxy by 14.528 kg CO2-eq (23.38%); this conditional result does not establish equivalent strength, storage service, or service life. The review therefore identifies feedstock characterization, coupled mechanical-storage durability, device packaging, and service-specific assessment as priorities for translating fly ash-based storage concepts from materials to building components.