Crystal development during carbonation of lime-based mortars in different environmental conditions

Abstract This study examines crystal development during the carbonation of lime mortars according to the additives used and curing conditions. Two types of samples were prepared, one with sand and the other one additionally including Roman ceramics. These mortars were cured: 1) by spraying with a carbonation accelerator product under laboratory conditions; 2) in a climate chamber under 20 °C, 60% relative humidity, and 1600 ppm CO 2 ; and 3) under laboratory conditions as controls. Polarized light microscopy, SEM-EDS and XRD were used at 28, 90, 120 and 180 days to monitor the carbonation process. Observations indicate the development of different CaCO 3 polymorphs, which appeared as metastable phases. The early nucleation of a well-defined calcite phase as the most stable CaCO 3 polymorph was only identified in the chamber-cured samples. Differences in the pore network were observed depending on the composition and morphology of the mortar components and the environmental curing conditions.