Constituent and composite level characterisation of fibrous plaster in decorative suspended ceilings

Fibrous plaster (FP) is a fabric-reinforced composite of plaster of Paris (POP) and woven jute fabrics, widely used in historic UK ceilings since the late 19th century. Despite its importance, FP remains under-researched, hindering structural assessments and maintenance. Recent collapses due to tensile failures of the supporting component ‘wad’ highlight the need for comprehensive characterisation. This study investigates physical, chemical, and mechanical properties of historic FP’s constituent materials and their modern proxies using optical microscopy, micro-X-ray computed tomography ( μ -XCT), and X-ray diffraction (XRD). The analysis reveals key properties, including density, jute fibre/yarn diameters, yarn’s fibre volume ratio, chemical composition, yarn’s tensile strength, and POP’s dynamic elastic modulus. Modern POP, representative of historic POP, was further assessed for static elastic modulus using the virtual fields method (VFM) applied to digital image correlation (DIC) data, tensile strength measured by direct tensile, flexural, and Brazilian splitting tests, and compressive strength. Fabric-matrix bonding properties were accurately characterised by a innovative fabric pullout test setup, analysed with an adapted Naaman model, and a novel force-fitting method. Direct tensile tests on dogbone FP specimens investigated the composite’s tensile behaviour at the wad-scale, providing a detailed demonstration on how hessian enhances FP ductility. • First study of fibrous plaster (FP) from a Grade-II listed UK building. • FP comprehensively characterised across multiple levels using advanced techniques. • Novel fabric pullout methods with adaptive modelling to measure bond strengths. • Hessian enhances FP ductility and structural behaviour in direct tensile tests.