Impact of Aggregate Type on Air Lime Mortar Properties

In recent years, the need for low energy materials has become increasingly recognised. Government targets aim to achieve a decrease in carbon emissions by 80% before 2050. With the construction industry being responsible for approximately 50% of UK carbon emissions, an increased use of low energy materials could go a long way to achieving this target. With this in mind, it is also important that materials still have adequate properties to fit their purpose. For this study, four limestone aggregates were compared with a silicate aggregate in order to assess the impact of the aggregate type on the properties of air lime mortar (CL90). The primary focus was to assess the differences in compressive strength, and investigate reasons behind the measured differences. Without exception, the mortars made with limestone aggregate have higher compressive strengths than those made with silicate sand. Phenolphthalein staining shows slight differences in carbonation levels at 28 days, which could help to explain the strength differences observed. Furthermore, SEM analysis has revealed differences at the binder/aggregate interface between limestone aggregate mortars and silicate sand mortars.