Study on the shear properties of masonry pagoda mortar and its influencing factors

Mortar stands as one of the fundamental components in masonry construction, significantly enriching the global cultural heritage, particularly evident in ancient masonry structures. In this paper, the improvements of shear strength of mortar were studied, based on the original formulation material of sticky-rice lime mortar. The study considered the effect of different aggregates and additives on the shear strength of mortar, the shear tests and scanning electron microscopy were employed to analyze the shear strength index and microscopic shear basis of the mortar. The results showed that 2 wt. % Na-SiO2 significantly enhanced the shear strength of the mortar. Furthermore, the adhesion and frictional resistance between fiber and lime played a crucial role in enhancing the mortar's shear resistance. Incorporating a 0.5 wt. % fiber additive not only effectively improved the mortar's brittleness but also acted as a deterrent to crack formation. Compared to pure lime mortar, the mixture of sand and clay aggregate exhibited a larger capacity at the same volume. This mortar also showcased better plasticity and ductility, making it more suitable for structures with significant shear deformation. These analytical findings provide valuable insights for modifying mortars in the restoration of historical buildings.