Mechanical Performance and Stress–Strain Modelling of Coal Ash Brick Masonry Assemblages Under Flexural Loading

The increasing demand for sustainable construction materials has prompted the utilisation of industrial by‐products such as coal ash (CA) in masonry units. This study investigates the mechanical performance and stress–strain behaviour of masonry prisms (MPs) and wall assemblages constructed with CA bricks, compared with those constructed with conventional clay (CC) and fly ash (FA) bricks. Experimental evaluation was carried out using three mortar mixes with cement–sand ratios of 1:3, 1:4.5 and 1:6 to examine the influence of mortar strength on masonry response. A total of 54 MPs and 81 wall elements were tested under uniaxial compression and flexural loading. Flexural behaviour was assessed under loading conditions parallel and perpendicular to the bed layer joint (BLJ) to capture the anisotropic characteristics of masonry. The results indicate that prisms constructed with CA bricks exhibited higher compressive strength and greater deformability than those constructed with CC brick masonry. The stress–strain response remained linear up to approximately one‐third of peak stress, followed by nonlinear behaviour leading to failure. The secant modulus of elasticity was found to range from 330 to 870 times the masonry’s compressive strength, with an optimal proportionality factor identified. Regression‐based analytical models were developed to establish relationships between masonry compressive strength and the strengths of constituent materials, showing good agreement with experimental observations and Eurocode‐based formulations. Flexural strength was significantly influenced by loading orientation, with higher values observed when loading was applied perpendicular to the bed joints. Additionally, an increase in slenderness ratio led to a reduction in compressive strength of wall elements. The findings demonstrate that CA bricks provide a viable and sustainable alternative to traditional masonry units, offering improved mechanical performance and ductility while contributing to waste utilisation and environmental conservation.