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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. [ABSTRACT FROM AUTHOR]

Additive manufacturing in construction typically consists of ground-based platforms. Introducing aerial capabilities offers scope to create or repair structures in dangerous or elevated locations. The Aerial Additive Manufacturing (AAM) project has developed a pioneering approach using Unmanned Aerial Vehicles (UAV, 'drones') to deposit material during self-powered, autonomous, untethered flight. This study investigates high and low-density foams autonomously deposited as structural and insulation materials. Drilling resistance, mechanical, thermal and microscopy tests investigate density variation, interfacial integrity and thermal stability. Autonomous deposition is demonstrated using a flying UAV and robotic arm. Results reveal dense material at interfaces and directionally dependent cell expansion during foaming. Cured interfacial regions are vulnerable to loading parallel to interfaces but resistant to perpendicular loading. Mitigation of trajectory printing errors caused by UAV flight disturbance is demonstrated by a stabilising end effector, with trajectory errors =10 mm. AAM provides a significant development towards on-site automation in construction. [ABSTRACT FROM AUTHOR]

Aerial additive manufacturing (AAM) represents a paradigm shift in using unmanned aerial vehicles (UAVs, often called 'drones') in the construction industry, using self-powered and untethered UAVs to extrude structural cementitious material. This requires miniaturisation of the deposition system. Rheological properties and known hydration times are important material parameters. Calcium aluminate cement (CAC) systems can be advantageous over purely ordinary Portland cement (OPC) binders as they promote hydration and increase early strength. A quaternary OPC/pulverised fuel ash (PFA)/CAC/calcium sulphate (CS) system was combined with polyvinyl alcohol (PVA) fibres and pseudoplastic hydrocolloids to develop a novel AAM material for miniaturised deposition. CAC hydration is affected by environmental temperature. Intending material to be extruded in situ, mixes were tested at multiple temperatures. OPC/PFA/CAC/CS mixes with PVA fibres were successfully extruded with densities of ≈1700 kg/m 3 , yield stresses of 1.1–1.3 kPa and a compressive strength of 25 MPa. Pseudoplastic OPC/PFA/CAC/CS quaternary cementitious systems are demonstrated to be viable for AAM, provided mixes are modified with retarders as temperature increases. This study can significantly impact industry by demonstrating structural material which can be extruded using UAVs in challenging or elevated in situ construction, reducing safety risks. [ABSTRACT FROM AUTHOR]

Many culturally important historic buildings contain fibrous plaster ceilings. The collapse at London's Apollo Theatre in 2013, which injured 88 people, highlighted the importance of inspecting and restoring ceilings effectively. This study focuses on traditional and modern materials which are applied to the topsides of existing historic fibrous plaster ceiling elements during repair and maintenance. Fibrous plaster ceilings are commonly suspended from primary or secondary structural roof members using fibrous plaster wadding ties or 'wads'. The application of additional repair material requires the formation of an interface, defining the strength of the repair. Properties of this interface were evaluated through a novel methodology employing pull-off tests' of approximately 200 specimens consisting of Alpha plaster, Beta plaster, Jesmonite and Aramid gel. Notably, the effect of fibrous reinforcement, and compatibility with historic and degraded material was also investigated. This study has enabled quantification of interfacial properties and evaluated cohesive and adhesive failure modes. Importantly, the extent of redundancy within historic plaster ceiling practice has been demonstrated, with pull-off occurring from 0.5 kN to 2 kN loading, and the ductile behaviour of repair materials evaluated. Results highlight the importance of surface condition, with clean surfaces exhibiting double the tensile loading capacity compared to soiled (dirty) surfaces representative of those encountered on-site. The significance of this study lies in the quantification of repair material performances and consideration of variations in performance, methodology and in-situ environmental factors. Impact stems from the ability of practitioners to make informed decisions relating to adhesion performance when carrying out repairs. A key outcome is more effective preservation of historic elements in heritage buildings, higher levels of safety and serviceability. [ABSTRACT FROM AUTHOR]

The MgO–CO2–H2O system have a variety of important industrial applications including in catalysis, immobilisation of radionuclides and heavy metals, construction, and mineralisation and permanent storage of anthropogenic CO2. Here, we develop a computational approach to generate phase stability plots for the MgO–CO2–H2O system that do not rely on traditional experimental corrections for the solid phases. We compare the predictions made by several dispersion-corrected density-functional theory schemes, and we include the temperature-dependent Gibbs free energy through the quasi-harmonic approximation. We locate the Artinite phase (Mg2CO3(OH)2·3H2O) within the MgO–CO2–H2O phase stability plot, and we demonstrate that this widely-overlooked hydrated and carbonated phase is metastable and can be stabilised by inhibiting the formation of fully-carbonated stable phases. Similar considerations may apply more broadly to other lesser known phases. These findings provide new insight to explain conflicting results from experimental studies, and demonstrate how this phase can potentially be stabilised by optimising the synthesis conditions. [ABSTRACT FROM AUTHOR]

A blue light mediated photochemical process using solid graphitic carbon nitride (g-C3N4) in ambient air/isopropanol vapour is suggested to be linked to "nanophase" water inclusions and is shown to produce approx. 50 μmol H2O2 per gram of g-C3N4, which can be stored in the solid g-C3N4 for later release for applications, for example, in disinfection or anti-bacterial surfaces. [ABSTRACT FROM AUTHOR]

The impact of dewatering on lime mortars modified using brick dust was studied, as it is of particular importance in conservation applications. Dewatering takes place when freshly mixed mortars come into contact with a porous substrate, such as brick or stone, during on site construction. Since the dewatering process between the mortar and its substrate can modify the mortar properties, understanding the dewatering process enables pozzolan-modified hydrated lime mortars to be optimised for the masonry units being bonded. Evaluation of the water transport kinetics on brick dust—hydrated lime binder systems demonstrated their more water releasing behaviour. Investigations of non-dewatered and dewatered specimens in the volume ratio of 1:1:2 (lime:brick dust:sand) showed that the addition of brick dust to lime mortar increased dewatering, which in turn led to greater compressive strength, carbonation depth, decreased porosity and depth of water penetration. These properties are of great importance in the conservation of historic masonry, as mortars that are too strong or possess low permeability can accelerate degradation. This study will enable identification of the most suitable mix designs thereby increasing the durability and prolonging the life of historic masonry. [ABSTRACT FROM AUTHOR]

Additive manufacturing methods1–4 using static and mobile robots are being developed for both on-site construction5–8 and off-site prefabrication9,10. Here we introduce a method of additive manufacturing, referred to as aerial additive manufacturing (Aerial-AM), that utilizes a team of aerial robots inspired by natural builders11 such as wasps who use collective building methods12,13. We present a scalable multi-robot three-dimensional (3D) printing and path-planning framework that enables robot tasks and population size to be adapted to variations in print geometry throughout a building mission. The multi-robot manufacturing framework allows for autonomous three-dimensional printing under human supervision, real-time assessment of printed geometry and robot behavioural adaptation. To validate autonomous Aerial-AM based on the framework, we develop BuilDrones for depositing materials during flight and ScanDrones for measuring the print quality, and integrate a generic real-time model-predictive-control scheme with the Aerial-AM robots. In addition, we integrate a dynamically self-aligning delta manipulator with the BuilDrone to further improve the manufacturing accuracy to five millimetres for printing geometry with precise trajectory requirements, and develop four cementitious–polymeric composite mixtures suitable for continuous material deposition. We demonstrate proof-of-concept prints including a cylinder 2.05 metres high consisting of 72 layers of a rapid-curing insulation foam material and a cylinder 0.18 metres high consisting of 28 layers of structural pseudoplastic cementitious material, a light-trail virtual print of a dome-like geometry, and multi-robot simulations. Aerial-AM allows manufacturing in-flight and offers future possibilities for building in unbounded, at-height or hard-to-access locations.An additive manufacturing method using a team of autonomous aerial robots allows for scalable and adaptable three-dimensional printing, and is used to deposit building materials during flight. [ABSTRACT FROM AUTHOR]

Policy and technical guidance are only as good as their implementation. Often well-meaning legislation has unintended consequences, as individuals and organisations overlay their own risk perceptions and understanding to an issue. This paper illustrates how behavioural science can be applied to risk-based engineering decisions to improve decision outcomes. It is framed around an analysis of the management of earthquake prone public buildings in New Zealand. It demonstrates how the individual, social and cultural contexts can influence how risks and impacts are perceived, evaluated, and communicated. The framing of the decision, unconscious biases, cognitive limitations, trust, and other social influences are all critical factors in translation of technical policy to effective outcomes. [ABSTRACT FROM AUTHOR]

There are currently 70.8 million forcibly displaced people, globally. Bangladesh hosts the largest refugee camp in the world. Much effort has gone into the research, design and delivery of mass-produced shelters. Yet most refugees live in self-built shelters using simple shelter materials. This paper aims to demonstrate the benefits of using a transdisciplinary approach for holistic data collection in such shelters. A total of 1594 households were surveyed in refugee camps in Bangladesh using diverse methods—e.g. surveys, semi-structured interviews, physical measurements. It was only because of the use of various methods that the reasons behind identified issues were discovered or quantified. For example, household surveys uncovered the issue of poor ventilation, but only the semi-structured interviews exposed the reasons behind it, while physical measurements assessed the implications of this—annual particulate exposure 13 times the recommended limit. Furthermore, several methods pointed to issues with materials, but only the focus groups discussions exposed the need for gender-sensitive technical training tailored for women on the correct use of the materials. This study demonstrates that a diverse team (humanitarian staff, building physicists, and anthropologists) using several approaches to data-gathering and working in a transdisciplinary manner has much to offer the sector, and by including quantitative physical measurements allows costed improvement plans to be developed, targets to be set and general, rather than case specific, knowledge to be generated. The findings of this study have resulted in new shelter interventions by the aid sector that were rolled out in over 70,000 shelters. [ABSTRACT FROM AUTHOR]

Ground granulated blast-furnace slag (GGBS), activated with olivine (Mg2SiO4) and sodium hydroxide (NaOH), was used to stabilise a clayey soil. Mechanical and microstructural properties of the stabilised soil were assessed through uniaxial compression strength (UCS) tests, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS), after curing periods of 7, 18 and 90 days. The UCS of the GGBS-treated soil (without activation with NaOH), even at the highest slag dosage (G20S), after 90 days, showed only a slight increase (142 kPa) relatively to the original soil. When olivine was added to the GGBS-treated mixture (O20G20S), the UCS increased to 444 kPa, after 90 days. However, when NaOH was used as an activator, the UCS of the olivine–GGBS-treated soil (NO20G20S) increased to more than 6000 kPa, after 90 days. This significant strength increase was attributed to the higher reaction degree provided by the NaOH, which enabled a more effective exploitation (dissolution) of the Ca and Mg present in the slag and olivine, respectively, forming a mixture of C–S–H and M–S–H gels. [ABSTRACT FROM AUTHOR]

The development of wood treatments is of increasing industrial importance. A novel technique for improving the properties of lodgepole pine and white pine through modification of the microstructure is described. The present investigation is devoted to the synthesis and determination of in situ parameters of citric acid and glycerol based polymers for wood impregnation. This solvent free approach is environmentally friendly and achieved through an esterification condensation reaction under acidic conditions. Crude glycerol and citric acid reactants were cross-linked via a curing process at 160 °C creating a polymer with only water as the byproduct. The ester bonds and crosslinking levels were controlled using different catalysts and citric acid contents and related to the reaction time and temperature. The nature of bonding within the polymers and at the wood cell walls was determined by FT-IR analysis. The thermal properties such as glass transition temperature (Tg) were studied using TGA/DSC and the effect of citric acid content and catalyst type determined. Dimensional stability of impregnated wood samples improved above 50% for each sample with HCl and p-TSA catalysts compared to control samples. FTIR spectra were studied to show the presence of the ester linkages of the polymer in situ at the wood cell walls. Bonding between the polymer and wood macromolecules were observed by scanning electron microscopy and interpreted as evidence of chemical bonds at the wood cells. When prepared using a catalyst, the polymer was intimately incorporated into wood structure significantly improving the substrate dimensional stability. Enhanced stability makes this approach of particular interest for exterior wood products especially as a green renewable option for the wood industry. [ABSTRACT FROM AUTHOR]

This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and compositional changes were evaluated using microscopic, spectroscopic, and diffraction techniques. Results demonstrate the advantages of using olivine in the presence of NaOH and the associated increases in soil shear strength of up to 40% over 90 days. Samples subjected to carbonation for a further 7 days led to additional increases in soil strength of up to 60%. Microstructural investigations before and after carbonation attributed the strength development to the formation of Mg(OH)2, hydrated magnesium carbonates, and M─S─H, A─S─H gel phases. The impact of this work is far reaching and provides a new soil stabilization approach. Key advantages include significant improvements in soil strength with a lower carbon footprint compared with lime or cement stabilization. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4)/polyvinyl alcohol (PVA) core-shell composite nanoparticles were successfully synthesized using a coprecipitation of ferrous and ferric chloride followed by coating with PVA. The resulting nanoparticles were characterized using X-ray diffraction, Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, X-ray photo electron spectroscopy, Zeta potential measurements, UV-Vis spectroscopy, Thermogravimetric Analysis, and Vibrating Sample Magnetometry (VSM). The average particle size was 13 nm. The presence of characteristic functional groups of PVA around the core of magnetite nanoparticles was confirmed by FTIR spectroscopy while the amount of PVA (%) bound to it was estimated by TGA analysis. Zeta potential measurements made by dispersing dilute sonicated samples in a Phosphate Buffer Saline (PBS pH 7.4) confirmed that the particles were negatively charged. The stability and retention of the coating material PVA in PBS (pH7.4) over a period of time were substantiated by UV-Vis spectroscopy. Room-temperature magnetic measurements were made with a VSM which demonstrated the superparamagnetic nature of the particles with higher saturation magnetization of 56.41 emu/g. Furthermore, in vitro cytocompatibility testing of Fe3O4/PVA core-shell composite nanoparticles was carried out on human cervix cancer cells. This confirmed a 97% cell viability with no significant cytotoxicity and thereby substantiated their biocompatibility. [ABSTRACT FROM AUTHOR]

This paper describes a novel methodology for the real-time study of solid-gas phase photocatalytic reactions in situ. A novel reaction chamber has been designed and developed to facilitate the investigation of photoactive materials under different gas compositions. UV irradiation in the wavelength of ranges 376-387 and 381-392 nm was provided using specially designed high efficiency light emitting diode arrays. The experiments used air containing 190 ppm NO2 in a moist environment with a relative humidity of 0.1%. Photocatalytic samples consisting of pressed pellets of rutile and anatase crystalline forms of TiO2 were monitored over a period of 150 min. An ultra-high vacuum right angled bleed valve allowed a controlled flow of gas from the main reaction chamber at atmospheric pressure to a residual gas analyser operating at a vacuum of 10−5 mbar. The apparatus and methodology have been demonstrated to provide high sensitivity (ppb). The rate of degradation of NO2 attributed to reaction at the TiO2 surface was sensitive to both crystal structures (anatase or rutile) and wavelength of irradiation. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ocean surface pH levels are predicted to fall by 0.3–0.4 pH units by the end of the century and are likely to coincide with an increase in sea surface temperature of 2–4°C. The combined effect of ocean acidification and warming on the functional properties of bivalve shells is largely unknown and of growing concern as the shell provides protection from mechanical and environmental challenges. We examined the effects of near-future pH (ambient pH –0.4 pH units) and warming (ambient temperature +4°C) on the shells of the commercially important bivalve, Mytilus edulis when fed for a limited period (4–6 h day−1). After six months exposure, warming, but not acidification, significantly reduced shell strength determined as reductions in the maximum load endured by the shells. However, acidification resulted in a reduction in shell flex before failure. Reductions in shell strength with warming could not be explained by alterations in morphology, or shell composition but were accompanied by reductions in shell surface area, and by a fall in whole-body condition index. It appears that warming has an indirect effect on shell strength by re-allocating energy from shell formation to support temperature-related increases in maintenance costs, especially as food supply was limited and the mussels were probably relying on internal energy reserves. The maintenance of shell strength despite seawater acidification suggests that biomineralisation processes are unaffected by the associated changes in CaCO3 saturation levels. We conclude that under near-future climate change conditions, ocean warming will pose a greater risk to shell integrity in M. edulis than ocean acidification when food availability is limited. [ABSTRACT FROM AUTHOR]

Radiocarbon dating was first applied to historic lime mortars during the 1960s. However, despite the relative simplicity of the technique in principle, a number of subsequent studies have highlighted important aspects that should be considered. One of the most significant of these challenges arises from sample contamination by carbonaceous substances such as incompletely burnt limestone and aggregates of fossil origin containing "dead" 14C. More recent studies have shown that in the majority of old lime-based mixtures the contamination problem can be avoided through selection of pure lime lumps. These particular types of lumps are believed to originate from areas where the lime is incompletely mixed with the aggregate. It has been demonstrated that even a single lime lump can provide sufficient material for a 14C date of the mortar from which the lump was taken (Pesce et al. 2009). This paper describes the practical challenges associated with location, extraction, and preparation of 4 lime lumps extracted from 2 new sites for 14C dating. These include distinguishing the lime lumps from other lumps present in the matrix and the removal of material surrounding the lime lump. The coherence of 14C dating with other archaeological information on the chronology of historic sites is highlighted through case studies. [ABSTRACT FROM AUTHOR]

The effect of coadsorption with deoxycholic acid (DCA) on the performance of dye-sensitized solar cell based on perylene monoimide derivative (PCA) as sensitizer and liquid electrolyte had been investigated. The current-voltage characteristics under illumination and incident photon to current efficiency (IPCE) spectra of the DSSCs showed that the coadsorption of DCA with the PCA dye results in a significant improvement in short circuit photocurrent and slight increase in the open circuit photovoltage, which lead to an overall power conversion efficiency. The enhancement of short circuit current was attributed to the increased electron injection efficiency from the excited state of PCA into the conduction band of TiO2 and charge collection efficiency. The current-voltage characteristics in dark indicates a positive shift in the conduction which also supports the enhancement in the photocurrent. The coadsorption with DCA suppressed charge recombination as indicated from the electrochemical impedance spectra and thus improved the open circuit photovoltage. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of dewatering on the strength and microstructure of mortars manufactured from Portland cement, hydrated calcium lime (CL90), and natural hydraulic limes of classification 2, 3.5, and 5 with binder/aggregate/water ratios of 1:2:0.78. Dewatering was achieved by placing the mortars on a high porosity brick. Dewatered and nondewatered specimens were exposed to an atmosphere containing 400 ppm carbon dioxide with a relative humidity of 65%, at 20°C for periods of 14, 28, and 56 days. Following hardening for these periods, compressive strengths were compared with evaluate the mechanical performance. The structural morphology of the samples was determined using scanning electron microscopy and chemical composition by Raman spectroscopy. Results showed CL90 mortars are unaffected by dewatering. However, dewatering resulted in an increase in the compressive strength for the hydraulic limes and cement mortars tested. [ABSTRACT FROM AUTHOR]

Abstract: Ammonia and methanol both bind to the water oxidising complex of photosystem II during its turnover, possibly at sites where water binds during the normal water oxidation process. We have investigated the interaction between these two water analogues at the S2 state of the water oxidising cycle using electron magnetic resonance techniques. We find evidence that ammonia displaces methanol from its binding site. [Copyright &y& Elsevier]

Lead zirconium titanate (PZT) has recently emerged as a low-cost material for non-destructive monitoring for civil structures. Despite the numerous studies employing PZT transducers for structural health monitoring, no studies have assessed the effects of both damage and repair on the electromechanical impedance response in cementitious materials. To this end, this study was conducted to assess the effects of the damage and repair of mortar samples on the electromechanical response of a surface-mounted PZT transducer. When damage was introduced to the specimen in stages, the resonance frequencies of the admittance signature were shifted to lower frequencies as the damage increased, and an increase in the peak amplitude was detected, indicating an increase in the damping and a reduction in the material stiffness properties. Also, increasing the damage in the material has been shown to decrease the sensitivity of the PZT to further damage. During the repair process, a noticeable difference between the after-damage and the after-repair admittance signatures was noted. The root-mean-square deviation (RMSD) showed a decreasing trend during the repair process, when compared to the before repair RMSD response which indicated a partial recovery for the material properties by decreasing the damping property in the material. [ABSTRACT FROM AUTHOR]

Protecting stone buildings from weathering and decay is a major challenge in the conservation of built heritage. Most of the stone consolidants currently available are well suited to silicate stones, but are less compatible with limestone. In this paper we present for the first time the results over a 4-year period of various consolidation treatments carried out using nanolime on 6 of the most representative and significant stones used in historic buildings in the United Kingdom. Tests investigated the influence of stone type, environmental conditions and pre-treatments on the effectiveness of the consolidation treatment. A comprehensive and rigorous testing programme was carried out to evaluate the short (12 weeks) and longer-term (4 years) effects. Stone samples were characterised before and after treatment using light and electron microscopy, sorptivity tests and a novel methodology employing drilling resistance to interrogate the near surface effects. Results show that for some of the stones, such as Clunch and Bath Stone, the positive effect of the treatment with nanolime is noticeable after 4 years since application. However, results for other stones such as Portland and magnesian limestone showed that the initial beneficial effect of the treatment is reduced after 4 years. Nanolime treatment of Ham Stone produced an unnoticeable effect on the continuous natural reduction of the drilling resistance of the specimen over time. The results presented are of immense value to conservators as they provide essential guidance on the most appropriate repair approach. Impact to the conservation industry will be to avoid the use of nanolime on stones where there is no perceivable benefit, reducing the risk of adverse effects, including potential damage to buildings. In additional costs will be saved which might otherwise have been spent on ineffective treatments. [ABSTRACT FROM AUTHOR]

The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-Ti4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (λ) 376–387 nm and 381–392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350–400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings. [ABSTRACT FROM AUTHOR]