Monitoring early hydration of calcium sulfoaluminate clinker

Initial hydration and setting were continuously monitored in calcium sulfoaluminate clinker (KCSA) mixed with water or 2 M NaOH isothermal conduction calorimetry, ultrasonic pulse velocity (UPV) measurement, the Vicat apparatus, (in- ex-situ) X-ray diffraction. P-wave acceleration (ap) proved highly useful to detect very rapid initial reactions, not generally perceptible other techniques. Setting water-hydrated KCSA pastes was mediated by ettringite formation. Flash due aluminate hydrate precipitation observed NaOH-hydrated clinker. Ye’elemite reacted most intensely at later times both pastes, inducing AFt AH3 formation of smaller proportions hydrates that densified matrix.