Comprehensive Study of Mortar Joint Thickness on Masonry Performance: Experimental and Numerical Approaches

Abstract This study investigates the impact of mortar joint thickness on the mechanical properties of masonry walls under compression. Specifically, it examines the behaviour of masonry specimens with varying mortar joint thicknesses—5 mm, 10 mm, and 20 mm. A combination of experimental and numerical approaches was used, including uniaxial compression tests and finite element modelling in ABAQUS. The experimental results revealed that increasing mortar joint thickness significantly reduced the compressive strength and stiffness of the masonry, with the most pronounced effects seen in the 20 mm joint thickness. Strain measurements indicated non-uniform stress distribution within the masonry specimens, with maximum deformations occurring in the central region, identified as the Representative Volume Element (RVE). The study also demonstrated the crucial role of the 9-row masonry fragment as the RVE for accurate modelling of masonry behaviour. Numerical simulations using the Concrete Damage Plasticity (CDP) model showed strong agreement with experimental results, confirming the validity of the approach for predicting masonry failure modes. The findings highlight that thinner mortar joints (5 mm) enhance masonry’s load-bearing capacity and structural integrity, whereas thicker joints (20 mm) lead to reduced performance due to increased plastic deformations and failure at lower stress levels. This research provides valuable insights for optimizing mortar joint thickness in masonry design, particularly for high-rise structures.