Browsing by Author "Ball, Richard J."

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Analysis of mosaic mortars from the Roman, Byzantine and Early Islamic periods sourced from Gerasa’s Northwest Quarter
(SPRINGER OPEN, 2024) Ball, Richard J.; Ansell, Martin P.; Su-Cadirci, Tuğçe Büşra; Baki, Vahiddin Alperen; Fletcher, Philip J.; Lichtenberger, Achim; Raja, Rubina; Wootton, Will; 0000-0001-6617-0924; AGÜ, Mimarlık Fakültesi, Mimarlık Bölümü; Su-Cadirci, Tuğçe Büşra
This study analyses and compares around 650 years of mosaic mortar production spanning the Roman, late Roman and Umayyad periods, at Gerasa/Jerash in Jordan, offering a better understanding of composition, structural features, and manufacturing processes. It assesses the value of optical and electron microscopy examination of morphological and textural features, pore structure using MIP, and composition studies using EDX, XRD, FTIR, TGA, and Raman spectroscopy. The study indicated high density lime adhesive was used compared to other mortars. Wood was used as a fuel when producing the lime and natural fibres were incorporated when manufacturing mortars. Aggregates were primarily calcitic with a small proportion of silica-based aggregates. Key outcomes of the study conclude that early Roman mortars were of highest quality, which was demonstrated through the careful selection of materials including different stone for lime and tesserae, and differences between layers. Late Roman mortars used the same slaked lime plus fibres and charcoal. Mortars dating from the Umayyad period also had the same higher lime content than late Roman, but higher porosity with fibres and charcoal. In general, the mortars showed slight differences in content and aggregate; different stone for lime and tesserae. The research attests to underlying traditions as well as changes in mortar mixes and methods according to context and time. The resulting data is contextualized within local and regional approaches.
Piezoresistivity and piezopermittivity of cement-based sensors under quasi-static stress and changing moisture
(Elsevier Ltd, 2024) Zhang, Jiacheng; Heath, Andrew; Ball, Richard J.; Chen, Binling; Tan, Linzhen; Li, Guisheng; Pan, Jingbang; Su-Cadirci, Tugce Busra; Paine, Kevin; 0000-0001-6617-0924; AGÜ, Mimarlık Fakültesi, Mimarlık Bölümü; Su-Cadirci, Tugce Busra
Integrated cement-based sensors offer an economic alternative to extrinsic sensors for health monitoring applications in concrete structures due to their high strength to cost ratio, geometrical versatility, low shrinkage, and natural compatibility. Nonetheless, their performance under in-service conditions were in lack of investigations. While the piezoresistivity (change in resistance with stress) has been commonly used for mechanical sensing, the piezopermittivity (change in capacitive reactance with stress) is rarely characterized. Exploiting the high relative permittivity and electrical conductivity of carbon fibre reinforced cement-based sensors, this study investigates the piezoresistivity and piezopermittivity under changing stress and moisture using electrochemical impedance spectroscopy (EIS). Two types of sensors were evaluated: one containing 0.5 vol% of carbon fibres whose electrical conductivity was ionically dominant, and another with electronically dominant (1.2 vol% of carbon fibres) conductivity. Results highlighted that the piezopermittivity is “moisture content-dominant” whilst the piezoresistivity is “fibre content-dominant”. As the moisture content decreased, the sensitivity of piezopermittivity for both sensor types decreased, while the sensitivity of piezoresistivity decreased for the ionically dominant sensor but increased for the electronically dominant sensor. The piezoresistivity of the electronically dominant sensor was less sensitive than piezopermittivity at a water saturation of 80%. Conversely, the piezoresistivity of the ionically dominant sensor was more sensitive than piezopermittivity at the tested water saturations ≤ 80%. For the first time, this study presents the combined effects of moisture and fibre content on the pressure sensitive response of cement-based sensors through a dual-phase (i.e., piezoresistivity and piezopermittivity) EIS interpretation technique, providing valuable information to benefit further behaviour prediction and single-effect recognition in the field scenario where the sensors are subject to simultaneous environmental effects causing moisture variations such as temperature and humidity variations, freeze-thawing, and so on.