Preliminary Experimental Investigation on Mechanical Properties of Historical Fibrous Plaster

Fibrous plaster (FP) is a natural fabric-reinforced composite material. It has been widely used to produce decorative suspended ceilings in high-profile historical buildings in the UK since the late 19th century. The constituent materials of FP are plaster of Paris (POP) and woven jute fabrics. Despite its prevalence, FP has been neglected in scientific research, which makes the associated structural assessments challenging. Recent collapses of several historical suspended FP ceilings highlight the need to characterise mechanical properties of FP and structural behaviours of historical FP suspended ceilings. However, the lack of research on historical FP’s constituent materials is a significant challenge, making material characterisation research necessary. This paper characterises physical and mechanical properties of historical and new POP and jute fabrics. Specimens were prepared from historical FP suspended ceilings of the Institution of Civil Engineers (ICE) building in London while commonly used modern repair materials were used for the new specimens. For POP, compression tests and impulse excitation of vibration (IEV) tests were performed to characterise mechanical properties. For jute fabrics, single yarn tensile tests were performed to characterise mechanical properties. Optical microscope, micro-X-ray computed tomography (µ-XCT), and moisture analyser were used to obtain physical properties including diameters of single fibres and yarns, fibre volume ratio of yarns, and the water content of yarns, respectively. By comparing the results from historical specimens with those obtained from new specimens, modern constituent materials that can be used for further investigations of FP are identified.