pH and Temperature-Dependent Dissolution Kinetics of Commercial Lightly-Burned Magnesia: Bridging Methodological Gaps for Cement Applications

Performance variability in MgO-based cements stems partly from poorly characterized dissolution kinetics of commercial lightly burned magnesia (LBM). Existing studies focus on high-purity materials under acidic conditions, but LBM dissolves also in alkaline condition where Mg(OH)2 precipitation prevents reliable sampling at high pH. We validated pH monitoring against ICP-AES for tracking initial LBM dissolution kinetics across pH 2.0-11.0 and temperatures 25-85°C. Commercial LBM (32 m2/g, 7.5 wt% CaO) exhibited rates one to two orders of magnitude higher than synthetic magnesia (10−8 to 10−12 mol/cm2·s). X-ray diffraction, electron microscopy with energy-dispersive spectroscopy, and BET analysis revealed enhanced reactivity from poor crystallinity, multiphase composition, and high surface area with textural porosity. Temperature effects peaked at 75°C before declining due to Mg(OH)2 passivation. The validated method provides practical guidance for MBC quality control and performance optimization.