Effects of Organic Additives on Portlandite Microstructure during CaO Hydration

This study evaluates the effect of various organic additives on the microstructure of portlandite crystals during the hydration of CaO. Calcium hydroxide mixed with selected additives was prepared and characterised in terms of crystal size and habit, platelets abundance, and particle size distribution using various techniques such as XRD, SEM and Particle Size Analysis. The results suggest that the microstructure of portlandite is altered by the presence of carbohydrates and sulfonates, showing higher platelets abundance, smaller crystallite size, and higher specific surface area. The presence of hydroxyl-rich carbohydrates induces more marked effects compared to sulfonates. These results show that it is possible to tailor the properties of lime to specific applications in both, the conservation and the construction industry. Furthermore, the results show that it is possible to enable the development of materials specifically dedicated to other applications such as the synthesis of precipitated calcium carbonate and the design of CO2 sorbents, all of which will have the added value of reducing the global anthropogenic CO2 emissions.