Comprehensive study on mechanical properties of lime-based pastes with additions of metakaolin and brick dust

In order to understand the behavior of lime-based mortars, and to identify the influence of pozzolans, it is important to investigate the microstructure and properties of lime-based pastes without any aggregates. In our work, nine different sets of pastes with additions of metakaolin and brick dust were studied. The chemical composition and microstructure were investigated by means of TGA, SEM–BSE microscopy and EDX analysis. The mechanical strength and fracture properties were determined from destructive tests, while the evolution of the Young's modulus was monitored using the resonance method. The study revealed that metakaolin exhibits much stronger pozzolanic activity than brick dust, and that the mechanical properties of pastes are not necessarily enhanced by the addition of pozzolans. However, the shrinkage reduction should result in the elimination of cracking around aggregates in mortars. These information contribute to better understanding of lime-based mortars and are essential for their proper modeling and design.