Microstructure development of calcium carbonate cement through polymorphic transformations

This study presents the mechanical properties and polymorphic transformation of pastes made with calcium carbonate cement, where vaterite was the main component. Both laboratory (compression tests, XRD, & SEM) and synchrotron-based techniques (transmission X-ray microscopy and microtomography) were used in the characterization of the pastes. Mechanical properties were developed by controlling the polymorphic transformation of vaterite. When converting to aragonite, calcium carbonate cement exhibited three times greater strength development compared to its conversion to calcite at a water-to-cement ratio of 0.4, which resulted in 42 % porosity. During the conversion to aragonite, the calcium carbonate cement paste develops an interpenetrating matrix of aragonite needles that enhance strength development through interlocking at a low paste bulk density of 1.6 g/cm 3 . Together the environmental and mechanical properties of calcium carbonate cement suggest its potential as a greener building material compared to traditional Portland cement.