Thin in-place cast textile reinforced cementitious (TRC) composites appear a promising solution for the repair of masonry where macro-cracks put in question the structural integrity. Reinforcement is provided in the form of external patches that are attached to the masonry front side. The interaction between the existed structure and the newly placed repair patch is tracked in this study by testing small-scale traditional brick masonry- TRC composite samples on pull-off using an integrated monitoring setup: Digital Image Correlation tracks debonding and cracks formed at the intersections (masonry-composite and textile-cement internally into the composite); Acoustic Emission monitors the elastic wave activity emitted due to internal damage and by analyzing the signal characteristics the damage mode and source are evaluated. Beyond the state-of-the-art, the advanced experimental monitoring aims to provide an insight full-field view of damage progress.

Ultrasonic examination of bubbly liquid like fresh concrete supplies important information from very early age. While the traditional pulse velocity is very indicative of the setting and stiffening processes, it utilizes essentially only one point of the waveform (first threshold crossing) without supplying specific information on the microstructure. More recently, ultrasonic dispersion has been proposed as a strong upgrade to monitoring as the level of velocity dependence on the frequency is related to the degree of heterogeneity. Cavities or air bubbles suspended in the viscous matrix are strong wave scatterers. The air bubbles pose strong dispersion and attenuation in the liquid state while their influence is minimized in a stiff matrix. Although, dispersion curves are indicative of the current condition, their measurement is a delicate process that involves calculations of the phase in the FFT domain of the received signals. To establish some references, experiments are conducted in water considered ideal medium and shampoo with and without bubbles . Results indicate that initially, shampoo exhibits stronger dispersion, seen by the strong influence of frequency on the propagation velocity, while gradually as bubbles are released to the surface due to settlement (in shampoo) the dispersive trend weakens reaching towards the nearly flat dispersion curve of water.

Nowadays, the cement industry still constitutes an important pollutant industrial sector. Then, the strategies to reduce its environmental impact are a popular topic of research. One of these strategies consists of replacing partially clinker with other materials, such as volcanic powder. Here, it has been analyzed the effects at 1500 hardening days of the addition of volcanic powder on the microstructure and durability properties of mortars that incorporate 10% and 20% of this addition as clinker replacement. Reference mortars prepared with ordinary Portland cement without additions were also studied. The volcanic powder has been obtained from the last eruption of the Calbuco volcano (41 ° 20 ′ S, 72 ° 37 ′ W, 2003 m.a.s.l.). This volcano is placed in the southern Andes, between the cities of Ensenada and Puerto Montt in Chile, and its last subplinian eruption occurred on April 2015.

The mortars were kept in an optimum condition (20ºC and 100% relative humidity) until the testing age. Their microstructure has been characterized using mercury intrusion porosimetry, impedance spectroscopy, differential thermal analysis and scanning electron microscopy. As durability parameters, among others, the steady-state chloride diffusion coefficient and the absorption after immersion have been determined. According to the results obtained, mortars with volcanic powder showed similar porosities and more refined microstructure compared to reference mortars. Furthermore, the durability properties at 1500 hardening days of mortars which incorporate volcanic powder were similar or even better than those noted for reference ones without additions, with the added value of contributing to sustainability.

The present study deals with the acoustic emission (AE) monitoring of fracture behavior of repaired marble specimens. Different types of specimens were ultrasonically interrogated. Subsequently, the damage was induced to these specimens by three-point bending. The damaged specimens were repaired using a suitable epoxy agent; then, they were mechanically loaded again. Apart from the well-known correlation of pulse velocity to strength for building materials, which also holds for the materials used in this study, AE provides a unique insight into the fracture behavior of the specimens. A statistical analysis of the experimental data has been performed to investigate the correlation between AE parameters and the strength of the specimens. This work discusses the passive monitoring of fracture in repaired marble specimens and shows that AE parameters, well-known to successfully characterize cementitious materials, also provide satisfactory results in characterizing monolithic materials such as marble. It is concluded that AE monitoring during a proof loading can provide good insight information of the materials and characterize their restoration.

This study aims in examining the fracture behavior of recycled mortar specimens using acoustic emission technique. To produce the recycled mortar beams a portion of fine recycled concrete aggregates and natural sand has been used and the specimens were tested in three-point bending and compression. The ultrasonic velocity and dynamic elastic modulus of the samples were also determined. This work led to a comparison of the fracture behavior of plain and fiber-reinforced recycled mortar specimens with a baseline mortars fabricated with 100% natural sand. The results show that the use of recycled aggregates in mortars can be successfully characterized by acoustic emission parameters. This approach offers a reliable evaluation of the fracture mechanism making acoustic emission a valuable nondestructive evaluation tool in the growing sector of recycled building materials.

The mechanical properties of Textile Reinforced Cementitious (TRC) composites have been extensively investigated in recent years. This material is constituted by a fine-grained cementitious matrix and a continuous textile reinforcement, a combination that has proven to be a lightweight, durable, and sustainable alternative for reinforced concrete. TRC is capable of generating curved slender components, offering the versatility to produce complex geometries not previously possible with reinforced concrete. The mechanical behavior and durability of these materials are highly affected by manufacturing and curing conditions. Non-Destructive Techniques (NDT’s) can provide a powerful reliable tool to monitor early age TRC without affecting nor compromising its properties. Along this manuscript, in order to provide an accurate assessment on the TRC mechanical and physical changes occurring during curing, Ultrasound Wave Reflection (UWR), Ultrasound Pulse Velocity (UPV) and Millimeter Wave (MMW) spectrometry are combined in an attempt to exploit the capabilities of elastic and electromagnetic waves for material characterization and monitoring. Experimental results evidence that UPV effectively monitors the development of stiffness in the material, while MMW spectrometry is more sensitive to evaporation of water and chemical reactions involved in the hydration of cement. Additionally, the applicability and resolution of these two contact and non-contact (US and MMW Spectrometry) techniques are discussed.

Natural gas is one of the most essential elements of our daily life. People have been using it for decades in an unorganized manner. Majority of the people in Bangladesh are not aware of the critical demand of energy. The amount of natural gas storage is inadequate and it is finishing quickly. In Bangladesh, natural gas is used for many purposes. One of the most important uses of natural gas is in the households for cooking purposes. The major issue is that in domestic cooking, wastage of gas is very common. Users sometime forget to stop the cooker after they are finished cooking, which causes wastage of natural gas. Domestic users of natural gas are not very serious about gas wastage. They are also not much aware of the consequences of wastage of natural gas. It is very difficult for the gas companies to monitor gas wastage and prevent it. It is necessary to monitor and prevent the wastage of gas that is used for cooking purposes. In this paper, development of a smart Internet of Things (IoT) based system to monitor and prevent household gas wastage is proposed. An IOT based gas wastage monitoring system has been developed. The system needs to be integrated with the cooker. There are sensors integrated with the system that will determine if the cooker is being used for cooking purpose. If it is found that the cooker is not in use, there is an automated switch off technique to turn off the supply of gas. The system also includes a cloud storage feature. With the help of this cloud storage system, the use of gas per day per user can be monitored. This process will help to detect the misuse of natural gas per user at the end of the day. The system has been tested and it is working well. In the future more features will be added to the system and will further help reduce the wastage of natural gas in Bangladesh.

Multi-layer titanium nitride/titanium aluminium nitride film growth was simulated by means of kinetic Monte Carlo code NASCAM [1]. Results of the simulation were compared to experimental data [2]. Film growth was simulated for different number of bi-layers TiN/TiAlN, with the number of bi-layers equals from 5 to 100. The total thickness of the whole stack was the same for all samples. That means that the thickness of bi-layers became smaller with the increase of bi-layer numbers.

Calculation of the thermal conductivity of simulated multi-layer film was conducted in two steps. Firstly, the thermal conductivity of the single layer was calculated by using Landauer relation based on effective medium theory [3]. Secondly, the thermal conductivity of the whole stack was calculated taking into account as the termal resistance of all the single layers TiN or TiAlN as well as the thermal resistance of the interfaces between the TiN/TiAlN layers.

Simulation results were compared to the experimental data and to the results of the calculation by means of the equation given above and it was found the perfect agreement between all the data.

[1] https://www.unamur.be/sciences/physique/ur/larn/logiciels/nascam

[2] M.K. Samani et al, Thermal conductivity of titanium nitride/titanium aluminum nitride multilayer coatings deposited by lateral rotating cathode arc, Thin Solid Films 578 (2015) 133–138).

[3] R. Landauer, The electrical resistance of binary metallic mixtures, J. Appl. Phys. 23, 779-784, 1952

Transparent conducting oxides (TCO) present a large range of applications such as optoelectronic devices, especially transparent front-side contact for photovoltaic cells. In this last case, aluminium doped zinc oxide (ZnO:Al or AZO) can be a good alternative to indium doped tin oxide (ITO). However, the electrical and optical properties of such coatings highly depend on the structuration of the substrate. The present study focuses on nano-scale characterizations of AZO thin film deposited on micro-scale patterns.

The first step consists of nano-scale modelling of AZO deposition by reactive magnetron sputtering [1] on mono-crystalline silicone substrates thanks to a kinetic Monte Carlo model [2]. For these simulations, metallic (Zn, Al), reactive (O) and neutral (Ar) fluxes can be defined individually, with their own angular and energy distributions. Moreover, in order to mimic large samples, the periodic-supercell method [3] is used. Then, electrical and optical characterizations of the coating can be performed. Electrical properties (effective electrical conductivity) are computed by the mean of a finite-element code solving the Maxwell-Faraday equation (hypothesis: near absence of varying magnetic field). Optical properties (effective optical index) are evaluated by using effective medium models (Maxwell-Garnett and/or Bruggeman). During all the process, a special attention is given to the substrate shape.

The second step is based on a micro-scale modelling of a full multi-layered structured c-Si thin film solar cell. The optical characterization (optical efficiency and short circuit current density) is done by RCWA (rigorous coupled wave approximation) [4] allowing to predict complex optical phenomena like scattering or light trapping. The major novelty of such study is the introduction in the RCWA simulation of the effective refractive indices of AZO depending on the position on the substrate (flat or tilted section of the pattern). This optical model is introduced in a full optimization process done by genetic algorithm [5] in order to find the solar cell structural parameters providing the best short circuit current density.

References:
1. K. Ellmer et al., Surf. Coat. Technol., 93 (1) (1997), pp. 21-26
2. R. Tonneau et al., J. Phys. D. Appl. Phys. 51 (2018) 195202
3. A. Zunger et al., Phys. Rev. Lett. 65, 353 (1990)
4. J. Müller and al., Opt Express 2015 Jun 1;23(11):A657-70
5. A. Mayer et al., Proceedings of SPIE, vol. 10671, p.1067127 (2018)

Aim The rise of temperature during polymerization might affect tooth pulp with potential pulpar damage. This study aims to investigate dentinal temperature increase during light activation of bulk fill materials using different restoration techniques.

Materials and methods Extracted premolars received standardized MOD preparations. K-type single-use thermocouples were used to measure temperature profiles. Thermocouples were placed in a standardized hole created within each premolar 1 mm below the cavity floor. Each specimen was heated at 35°C through the ThermBlock system (FALC), and this temperature was kept constant during the test. The EMS Swiss Master Light lamp 1000 mW/cm² operating for 20 s was used for the polymerization process. Data were subjected to statistical analysis (one-way anova).

Results Flowable composites show higher temperature rise(p<0.05) than packable composites. Peak temperatures higher than 42°C were measured for the incremental layering technique using flowable composites.

Conclusions Use of bulk-fill technique shows safe temperature values in association with light curing modality of 1000 mW/cm2 for 20 s. Otherwise, for the incremental layering technique, potentially dangerous temperature peaks have been measured for flowable composites.