Crystallisation and phase transformation processes during clinkering in portland cement (pc) by means of in situ and ex situ analyses

•In-situ high-temperature experiments highlighted the effects of Cl-doped cement raw meals during heating and clinkering.•Cl-doping extremely affects the polymorphism of all cement crystal phases.•Cl-doping increases the stability field of mayenite at expense of celite.•Chlorine is partly volatilised during clinkering and partly hosted in mayenite.•The simultaneous effects of more dopants can not be predicted by the simple sum of the effects of single element doping. An important challenge of cement industry is the waste reuse as a feasible substitute of natural materials, thus reducing cement manufacture footprint. A critical gap in literature is the lack of a comprehensive overview on minor element effects commonly carried from wastes. This study aimed to fill this gap investigating the effects of multiple minor element occurrence (Mg, S, Na and Cl) on Ordinary Portland Clinker mineralogy, microstructure, phase polymorphism and chemical reactions occurring during clinkering. The findings highlighted that minor elements are strongly correlated to each other in influencing clinker properties: during clinkering, all raw meals exhibited similar reaction temperatures and melting phase formation; conversely, large differences are observed on reactivity, crystal phase composition and polymorphism.