The investigation of calcium carbonate formation using micro-Raman spectroscopy

Calcium carbonate (CaCO3) has got significant importance in nature and in several industrial processes. In its different mineral modifications, calcium carbonate is highly abundant in the earth crust, occurring as calcite, aragonite and vaterite (anhydrous crystalline polymorphs) or ikaite (calcium carbonate hexahydrate), calcium carbonate monohydrate, (hydrated crystal forms) and amorphous calcium carbonate (ACC). The CaCO3 can be formed during the process of biomineralization or synthetically with using gas diffusion method or mixing supersaturated solutions containing calcium cations and carbonate anions. The so-called carbonation reaction, plays a crucial role in hardening of lime mortars, a class of binders of relevance in culture heritage conservation. During this process, the CaCO3 is formed from Ca(OH)2 that uptake atmospheric CO2 in aqueous medium. This contribution is focused on the investigation with micro-Raman spectroscopy of CaCO3 modifications appeared during the synthesis from supersaturated aqueous calcium chloride and potassium carbonate solutions, under different reaction conditions [1], as well as during the carbonation reaction [2,3].