Abstract
Different samples of calcium sulfoaluminate phase doped with iron, (Ca 4Al(6-2x)Fe2xSO16) with x = 0, 0.2 and 0.5, were synthesized at 1350°C. The hydration kinetics of the resulted phases was investigated by calorimetric and conductimetric techniques. The hydrated samples were analyzed by X-ray diffraction and scanning electron microscopy. The hydration of calcium sulfoaluminate was slightly modified by inclusion of iron in its structure. Dissolution rate of calcium sulfoaluminate phase doped with iron appeared to be slowed down such as the nucleation rate during the induction period while the percentage of reaction after 1 day was slightly increased. The analysis of hydrates indicated the formation of the same hydrates, ettringite and calcium monosulfoaluminate and the gibbsite, with or without iron replacement. Gibbsite played a major role in the kinetics of the induction period and thus the presence of iron may decrease its nucleation rate forming (A, F)H3 instead of AH3.
Highlights
The mineral phase, calcium sulfoaluminate named as Ye’elimite (C4A3S), has been known as hydraulic phase for several decades, but its potential in non expansive cementitious materials has only recently been reported
Dissolution rate of calcium sulfoaluminate phase doped with iron appeared to be slowed down such as the nucleation rate during the induction period while the percentage of reaction after 1 day was slightly increased
Gibbsite played a major role in the kinetics of the induction period and the presence of iron may decrease its nucleation rate forming (A, F)H3 instead of AH3
Summary
The mineral phase, calcium sulfoaluminate named as Ye’elimite (C4A3S), has been known as hydraulic phase for several decades, but its potential in non expansive cementitious materials has only recently been reported. In comparison to Portland cement, cements based on calcium sulfoaluminate react faster, and most of the hydration heat evolution occurs between 2 and 12 h of hydration [18].The hydration products are mainly ettringite (3CaO· Al2O3·3CaSO4·32H2O) and alumina gel (Al2O3· nH2O) but calcium monosulfoaluminate hydrate (3CaO· Al2O3·CaSO4·12H2O) can be present depending on the level of calcium sulfate addition. This last phase is formed when sulfate ions are depleted from the aqueous phase [8]. Microstructural investigations [18, 19] revealed mainly the formation of large space filling ettringite needles, together with calcium monosulfoaluminate hydrate, aluminium hydroxide and calcium silicate hydrates (coming from C2S), and leading to a dense microstructure
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