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 calcium oxide. Calcium hydroxide mixed with selected additives before and after slaking 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. Results suggest that the microstructure of portlandite altered by the presence of carbohydrates and sulfonates show 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 calcium hydroxide to specific applications in both, the conservation and the construction industry. Similarly, these results show that it is possible to enhance the characteristics of lime for other applications such as the synthesis of precipitated calcium carbonate and the design of CO2 sorbents, all of which have an important role in helping reduce the global anthropogenic CO2 emissions.