Determination of carbonation profiles in non-hydraulic lime mortars using thermogravimetric analysis

The carbonation profile of material taken at various depths in a lime mortar specimen has been determined at different times from manufacture using a novel, high-speed thermogravimetric analysis (TGA) method. While conventional phenolphthalein staining suggests a sharp boundary between carbonated and non-carbonated regions, the new TGA technique shows that up to 15% (w/w) of portlandite remains uncarbonated at the exterior of the mortar and that the extent of carbonation declines linearly over up to 15 mm into the interior. The technique demonstrates the possibility of identifying the presence of Liesegang patterns by measuring variations in the concentration of Ca(OH)2 through the depth profile.