The role of foreign ions in Portland cement production and properties: A state-of-the-art review on phase formation, polymorphism and hydration

Abstract

Adopting alternative raw materials and fuels has significantly increased in the last few years. This practice introduces minor constituents (or foreign ions) into cement kilns, influencing the synthesis process and subsequent clinker/cement properties. This paper examined the impact of zinc, titanium, phosphorus, fluorine, and copper on clinker/cement characteristics, focusing on phase formation, polymorphism, and hydration behavior. These constituents often serve as mineralizers or fluxes, modifying melting temperatures and viscosity of the melt in kilns and/or altering clinker mineralogy. A general trend of hydration retardation was identified in the presence of these minor constituents, with threshold incorporation levels underlined. Gaps in the current knowledge were identified, such as the effect of foreign ions in polymorphism, especially C₃A. By synthesizing current research, this work provides valuable insights for the cement industry and the academy. Moreover, it proposes research directions to further understand the effects of co-processing and minor constituents on cement production.