Open Access

To facilitate the reuse of reinforced concrete structural modules extracted from existing buildings, a comprehensive assessment of individual components is required. It is well established that factors such as material aging, environmental exposure, and variable load histories can significantly affect the load-bearing capacity of structural modules, even when their nominal material properties are identical. Furthermore, the performance of individual elements is influenced by geometric characteristics, construction details, reinforcement layout, as well as the type, location, and quantity of embedded reinforcement. An accurate evaluation of the current physical condition of a structural element necessitates a combination of visual inspection and non-destructive testing (NDT) techniques. The scope of this study includes the characterization of steel and concrete materials, as well as the overall structural performance of reinforced concrete modules with respect to their expected remaining service life. The investigated reinforced concrete beam was extracted from a structure constructed in approximately 1970. A suite of NDT methods was employed to determine the in-situ material properties, including air permeability testing, surface hardness measurements, and internal structure mapping using ground-penetrating radar. Based on the experimental results, a numerical model of the beam was developed, enabling the estimation of the maximum internal resistance of the structural member prior to the onset of failure. Finally, general monitoring procedures and assessing the condition of reinforced concrete structures are proposed.

In this work, operando 7Li solid-state nuclear magnetic resonance (ssNMR) spectroscopy was employed to monitor the lithium-ion storage undergone within a lithium-ion capacitor (LIC) formed by activated carbon (AC) cathode and hard carbon (HC) anode. The lithium source is provided by the in-situ decomposition of dilithium squarate (Li2C4O4) incorporated as sacrificial salt in the positive electrode. By selectively monitoring the evolution of lithium-ion environments during electrochemical cycling, operando 7Li ssNMR provided direct insight into the dynamics of lithium insertion and storage in the HC anode under realistic operating conditions. Two different LIC configurations were compared: a reference AC//HC system without sacrificial salt and a LIC system containing Li2C4O4 sacrificial salt in the positive electrode. The operando NMR results revealed that, during the first charge, only limited lithium insertion into HC occurred in the absence of sacrificial salt, whereas the LIC system containing sacrificial salt exhibited significantly higher capacity together with clear evidence of reversible lithium insertion/extraction processes, as demonstrated by both the electrochemical behavior and the reversible evolution of the 7Li NMR resonances associated with lithiated HC environments. In addition, further operando 7Li NMR experiments were performed on LIC systems with different sacrificial salt-to-hard carbon ratios to evaluate the extent and evolution of the pre-lithiation process in real time. These findings demonstrate the effectiveness of sacrificial salt-assisted pre-lithiation in LICs and highlight operando 7Li ssNMR as a powerful tool for directly monitoring lithium storage in full-cell energy storage Systems.

High power tandem gas metal arc welding (T-GMAW) enables increased productivity in thick plate applications by supplying two wires to a single melt pool. Besides increasing the deposition rate, T-GMAW has previously been demonstrated to offer improved energy efficiency and a reduced environmental footprint compared to single wire process variants. However, due to the complex interaction of both arc processes, achieving stable and reliable welding conditions has historically been challenging, especially at high deposition rates. Introduction of advanced process mode variants for pulsed and controlled short-circuiting transfer modes have increased the stability of the T-GMAW process and widened the field of applications. Since these new technologies are emerging and availability of publications and datasets in T-GMAW is limited – especially with modern equipment and process modes – we want to present an initial comprehensive multimodal T-GMAW dataset covering a variety of process mode combinations and deposition rates. A common multi-layer V-Groove joint design is chosen to reflect real world thick plate applications. The dataset covers high resolution time series recordings of the welding process parameters, its arc process signatures, power and material consumptions and the exact movement of the welding torch along the groove in a weaving pattern. Furthermore, detailed 3D measurements of the weld seam surface are included for each layer together with high dynamic range video recordings of the T-GMAW process. The dataset enables researchers to analyse the process in a variety of ways. Possible applications could include the calculations of heat input and process efficiency dependent on the chosen process parameters or evaluation of the process signatures in relation to the groove geometry and weaving pattern for arc sensing. The provided video recordings also allow estimations of the melt pool size and shape which are widely used as inputs for welding simulations. Researchers interested in life-cycle inventory development can compare the advanced T-GMAW process to other joining and manufacturing processes based on the included data.

Predicting the thermal runaway (TR) characteristics of lithium-ion battery (LIB) cells based on easily accessible key cell features — such as i) cell format, ii) cathode type, iii) cell capacity and/or energy, and iv) state of charge (SOC) — would be highly beneficial. Herein, 10 different commercial LIB-cell types with four cathode variations were tested at various SOCs in both single cell and propagation scenarios, totaling 170+ abuse tests. The TReffects, including onset temperature, maximum cell temperature, emitted gas volume, and maximum overpressure, are analyzed as functions of the key cell features. Two cathode-based groups emerge: (A) lithium- manganese cobalt oxide (NMC), lithium cobalt oxide (LCO) and lithium nickel cobalt aluminum oxide (NCA), and (B) lithium iron phosphate (LFP). Intriguingly, the gas volume emitted from group (A) scales linearly with the SOC-dependent cell energy (0.46 L Wh􀀀 1) regardless of the test atmosphere. TR-propagation tests show that NMC/LCO/NCA cells propagate at 70–100% SOC but typically not at 30%, with propagation classified as non-, slow-, or fast-propagating. Overall, the results indicate that TR-effects of specific LIB-cells may be predictable based on key cell features, improving mechanistic understanding and enabling the development of advanced safety measures.

This work presents analytical solutions for the impedance of a relaxation process whose time‐constant distribution follows 1) a Cauchy‐distribution or 2) a Gauss‐distribution. Both functions are commonly used as basis for the numerical reconstruction of the time‐constant distribution from experimental impedance data (i.e., the opposite way). Herein it is, however, demonstrated that neither a single Cauchy, nor a single Gauss function, can resemble common experimental features of impedance—especially the nonperpendicular traversal in the Nyquist representation, which is oftentimes seen for experimental data. While both functions will (depending on their width) qualitatively introduce a ‘depressed semi‐circle’ in the Nyquist plot, a Gaussian relaxation function leads to a perpendicular intercept with the abscissa and a Cauchy‐type relaxation function to an angle of zero degree at high and low frequencies.