Environmental (wet and dry) cycling of hydraulic lime mortars

This study investigates the impact moisture control has on the aftercare of freshly manufactured hydraulic lime mortars by wet and dry cycling. Mechanical properties were monitored by periodic compressive testing and the extent of carbonation by phenolphthalein staining of cross sections. Hydration products after 28 days of cycling were identified by microstructural analysis using scanning electron microscopy. The cycling procedure caused a dramatic increase in compressive strength development. This was attributed to an increased rate of carbonation and hydration in three different mix designs containing aggregates with different particle size distributions. The cycling process also increased the depth of carbonation significantly. It was found that finer aggregates had greater depths of carbonation, in all exposure conditions. The strength development, as a result of 28 days of cycling, was similar in the fine and mixed-particle aggregate mix designs since they were both fully carbonated, whereas the equivalent strength increase was lower for the coarse aggregate mix as the specimens weren't fully carbonated. This illustrates the importance of carbonation on strength development within hydraulic lime mortars, with a finer aggregate causing a faster strength increase.