Hydration and hardening processes of Portland cements obtained from clinkers mineralized with fluoride and oxides

The hydration and hardening processes of Portland cements prepared from clinkers mineralized with sodium fluoride and/or oxides (SnO2 or CuO) was studied. Type I cements (CEM I) were prepared by grinding with gypsum (5%) of clinkers obtained by the burning of an industrial raw mix with different mineralizers: sodium fluoride, oxides (CuO and SnO2) or mixtures of sodium fluoride and oxide (NaF + CuO or NaF + SnO2). The influence of foreign ions on the clinker morphology was assessed by scanning electronic microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The hydration processes of modified cements were examined by X-ray diffraction analysis (XRD) and thermal analysis techniques (TG and DTA). The main properties of the cements, i.e., flexural and compressive strengths, setting time, and soundness were also determined. A good correlation between the chemically bound water or portlandite content in pastes hydrated 2–28 days and compressive strength developed by mortars was observed. The influence of mineralizers on the kinetic of hydration processes and main properties of cements is different—0.5% NaF and 0.5% SnO2 and their mixture increase the rate of cement hydration and hardening processes, opposite to 0.5% CuO that reduce the rate.