From waste to high-performance cement: enhancing mechanical and microstructural characteristics with iron-rich industrial by-products

This research explores the valorization of iron-rich industrial waste as a sustainable partial substitute for OPC, aiming to reduce clinker dependence and carbon emissions while enhancing microstructural performance. Cement pastes containing 10–50% iron waste micro-powder were evaluated under water and oven-dried curing to assess mechanical, physical and morphological evolution. The results showed that low substitution levels (≤10%) enhance the filler-nucleation synergy, refining the microstructure by promoting C-S-H formation and pore refinement. In contrast, over-inclusion (≥20%) resulted in dilution and retardation effects, reducing Ca(OH)2 formation and weakening the cementitious matrix. The scanning electron microscopy (SEM) investigation confirmed the transition from dense and continuous OPC gels to porous and discontinuous structures at higher waste content. Among all studied composites, the 10% improved formulation revealed superior strength, microstructural integrity and sustainability potential. This research demonstrates an innovative pathway for the circular utilization of iron-rich waste, contributing to the development of low-carbon, high-performance binders for eco-friendly construction applications.