Alite-yeʹelimite cement: Synthesis and mineralogical analysis

Alite-yeʹelimite cement is an alternative cement that combines desirable characteristics of calcium sulfoaluminate cements and Portland cement in that it shows improved strength development at early age while retaining high portlandite contents. The key problem in the clinkering process is to produce the alite-yeʹelimite phase assemblage so that both phases can co-exist. In this study, a new synthesis method is proposed to achieve the coexistence of alite and yeʹelimite consisting of a secondary heat treatment step at 1250 °C after regular Portland clinker firing at 1450 °C. Quantitative X-ray powder diffraction and electron microscopy were used to analyze the phase composition of clinker before and after the secondary heat treatment. The results show that yeʹelimite develops during secondary heat treatment of calcium sulphate enriched clinker by reaction of C3A and sulphate phases. Additional ferrite is formed as result of rejection of Fe originally in solid solution with C3A during yeʹelimite formation.