Impact of high-magnesium limestone combined with ion doping on the mineralogical characteristics and properties of cement clinker

The scarcity of high-grade raw materials in conventional cement manufacturing has necessitated the utilization of alternative sources, such as low-grade minerals and industrial by products. This study systematically investigates the production of portland cement (PC) clinker and calcium sulfoaluminate cement (CSA) clinker through incorporation of high-magnesium limestone (HMLS) and industrial wastes (iron ore tailings, fly ash, etc.). Ion doping techniques were applied to optimize clinker performance, aiming to establish a sustainable pathway for low-value feedstock utilization. Some experiments were carried out, such as burnability, mineralogical composition, hydration heat, chemical shrinkage, hydration products, and compressive strength. For PC clinker synthesis, blending 25 wt% HMLS1 with 2.5 wt% IOT achieved clinker meeting industrial standards (MgO < 5 wt%). Fluorine and sulfur additives further suppressed MgO crystallization while enhancing clinker performance. Notably, IOT1 demonstrated superior compatibility with HMLS1 compared to IOT2, with calcium fluoride proving critical in facilitating calcination when paired with IOT2. In CSA clinker production, formulations containing 30 wt% HMLS2 and 1 wt% FA yielded qualified clinker. Additional incorporation broax (0.5 % of raw meal mass) effectively mitigates MgO-induced hydration instability by promoting ye'elimite (C₄A₃$) crystallization and stabilizing dicalcium silicate (C₂S), thereby increasing compressive strength by 30 % compared to undoped controls in 7 days. Phase evolution analysis revealed borax-mediated transitions from C₄A₃$-C to C₄A₃$-O and β-C₂S to α-C₂S. These findings offer technical insights for eco-efficient cement production.