Abstract
This work shows how additive-controlledcrystallizationmay be leveraged as an alternative route toward more sustainable productionof hydraulic binders. Bassanite (calcium sulfate hemihydrate) is one of themost extensivelyused inorganic binders in construction applications. Current industrialprocesses for the large-scale production of the mineral rely almostexclusively on the thermal dehydration of ...
Abstract
This work shows how additive-controlledcrystallizationmay be leveraged as an alternative route toward more sustainable productionof hydraulic binders. Bassanite (calcium sulfate hemihydrate) is one of themost extensivelyused inorganic binders in construction applications. Current industrialprocesses for the large-scale production of the mineral rely almostexclusively on the thermal dehydration of gypsum (calcium sulfatedihydrate), which consumes considerable amounts of energy. Here, weshow that phase-pure bassanite can be obtained in high quantitiesby spontaneous precipitation from supersaturated solutions at moderatetemperatures, where gypsum usually forms as a predominant solid phase.Key to control over phase selection is the presence of specific additivesduring crystallization, which carry functional groups for bindingonto calcium sulfate surfaces as well as additional moieties thatwithdraw water in the local microenvironment. Some of the investigatedadditives allowed bassanite to be recovered in large amounts at temperaturesas low as 40 degrees C and added concentrations of only 0.1 M or evenless. The concepts described in this work pave the way toward alternativeapproaches, enabling a less energy-intensive and thus more sustainableproduction of bassanite for use in construction and other appliedsystems.
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