Micro-Raman spectroscopy investigation of the carbonation reaction in a lime paste produced with a traditional technology

Micro-Raman spectroscopy has been used to follow the carbonation reaction up to 16 weeks in lime paste produced with a traditional technology and cured under controlled conditions. The transformation of calcium hydroxide into calcium carbonate was visualised using Raman Imaging. Calcite was the only crystalline CaCO3 polymorph detected under the conditions of the experiment. Three sharp zones of pure portlandite (Ca(OH)2), partially carbonated portlandite and calcite (CaCO3), could be distinguished. Amorphous calcium carbonate was determined within the carbonation front. The carbonation rate was found to be higher between first and second week of ageing. After this time, the rate was continuously decreasing until full carbonation was achieved. Results have been compared with those obtained from quantitative phase analysis with X-rays powder diffraction. The proposed approach allows for a highly accurate description of the carbonation process in traditional lime-based systems. In general, it can be applied to assess the effectiveness of treatments with inorganic agents promoting carbonation, and aimed at the conservation of cultural heritage objects. Copyright © 2016 John Wiley & Sons, Ltd.