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• Moisture and fungi degrade fibrous plaster. This is a major issue, emphasised by the Apollo theatre ceiling collapse in 2013. • Fibrous plaster samples were subjected to moisture and fungal treatments for up to 2 years and degradation was evaluated. • Submersion in water, wetting and drying and exposure to fungi over 2 years caused major reductions in mechanical properties. • Peak ratio methods used on FTIR hessian fibre spectra identified different treatments as clusters in scatter plot results. • FTIR and mechanical results can be used to determine causes of moisture or fungal degradation in fibrous plaster. Fibrous plaster degradation has been a key concern over recent years, with ceiling failures occurring suddenly in historic buildings, including the Apollo theatre in 2013. This rigorous investigation explores fibrous plaster degradation through subjecting 290 specimens to a range of moisture and fungal-related treatment conditions over periods of up to two years and analysis using mechanical flexural tests, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Deoxyribonucleic Acid (DNA) sequencing. Using FTIR peak ratios from spectra of hessian fibres and mechanical tests in conjunction, an original methodology for identifying mechanisms and severity of fibrous plaster degradation through moisture and fungal exposure was developed. Results showed defined clusters for differing moisture and fungal treatments when two peak ratios are plotted together and compared with mechanical data. Fungal exposure over two years, water submersion and wetting and drying were particularly detrimental conditions for fibrous plaster. Fungal exposure resulted in degradation of cellulose bonds in hessian fibres, with defined clusters on the extreme left of peak ratio plots correlating with a pronounced reduction in fibrous plaster mean flexural strength of 51%. Fungal species Penicillium and Chaetomium were identified on test samples. Moisture affected plaster matrices significantly with wetting/drying and water submersion treatments resulting in a 71% reduction in mean flexural strength for unreinforced plaster, reducing to 26% with hessian-reinforced fibrous plaster. Many buildings containing fibrous plaster are listed and removal of material is often minimised - the high impact of this research stems from the ability to rapidly assess the mechanical integrity of a very small quantity of harvested historic hessian fibres using FTIR. Identifying the location of weakened fibres in a ceiling is highly important for effective restoration and conservation. [ABSTRACT FROM AUTHOR]

Hessian fibre-reinforced gypsum, known as fibrous plaster, is a common material used for the manufacture of decorative features, including ceilings and walls in historic buildings, such as theatres and ballrooms, since the mid 19th century. It is still fabricated with modern materials for the decoration of new buildings in the UK, the Middle East and elsewhere. Following several recent failures of historic fibrous plaster ceilings in England, there is an urgent need to understand how these materials perform. There is no previous scientific investigation into the physical and mechanical properties of this material. As an initial experimental study, the microstructure of low and high density gypsum plaster were evaluated together with traditional hessian fabrics and modern glass fabrics, which are supplementing or replacing hessian fabrics. The chemical and physical characteristics were evaluated by X-ray diffraction, mercury intrusion porosimetry and dynamic vapour sorption. For the hessian, fibre density was measured and single filament strength measured to ascertain the effect of long-term ageing in new and historic material. Flexural tests were performed on gypsum plaster reinforced with different configurations of hessian and glass fabric reinforcements. Single filaments from historic hessian were weaker than filaments from new hessian and the larger scatter in strength was demonstrated using a Weibull distribution function. High density gypsum absorbed less moisture (0.2%) than low density gypsum (1%), as expected, but the jute fibres in the hessian absorbed more than 20% of the moisture. High density gypsum was considerably stronger than low density material, and random glass mats as reinforcement resulted in the highest flexural strengths and ability to yield to higher strains, due to enhanced interfacial bonding. This work will have high impact by providing a much needed basis for understanding the long-term degradation of fibrous plaster systems. [ABSTRACT FROM AUTHOR]

• • Novel inorganic fullerene tungsten disulfide (IF-WS 2) CEM1 nanocomposite. • • Formation of CaWO 4 interface layer between IF-WS 2 and hydration products. • • 1 wt% addition of IF-WS 2 provides highest energy adsorption capability. • • 86% improvement in flexural strength of IF-WS 2 enhanced 3D printed specimens. An original cement based material enhanced with inorganic fullerene tungsten disulfide (IF-WS 2) nanoparticles has been engineered with superb shock absorbing properties. Physical properties were attributed to the IF-WS 2 nano-hollow multiple layered onion-like structure. The effect of IF-WS 2 concentration at 0.1 wt%, 1 wt% and 5 wt% on the hydration kinetics of ordinary Portland cement (CEM1), electrical impedance, thermal stability, rheology and strength development was thoroughly evaluated. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies confirmed the formation of the new phase, calcium tungstate (CaWO 4), at the nano-particle/cement matrix interface during early hydration. 1 wt% IF-WS 2 additions enhanced the impact energy of CEM1 by 89% compared to the control. An IF-WS 2 cementitious mixture was developed for 3D printing based on the 1% WS 2 -CEM composition. The mix exhibited excellent workability and buildability enabling the creation of a layer-by-layer printed component. Intimate interlayer adhesion minimized the presence of voids leading to a high flexural strength of 6.7 MPa, which equated to an over 86% improvement compared to plain CEM1 printed components. This study showcases IF-WS 2 nanoparticles as a new ground-breaking additive enabling the production of high-performance cementitious construction materials, for use under extreme environments demanding high strength and impact resistance. [ABSTRACT FROM AUTHOR]