Reinforced concrete (RC) structures are widely used in engineering due to their physical, chemical and mechanical characteristics that guarantee good durability. However, one of the main mechanisms of degradation of these structures is associated with the corrosion of the reinforcement, which often occurs due to carbonation of the concrete and/or the presence of chloride ions. To avoid or mitigate the corrosive process of the reinforcements, one of the most used techniques is the cathodic protection (CP). To design new CP systems or verify existing ones, numerical computational simulations based on the boundary element method (BEM) are used. This work aims to analyze CP systems in RC beams using BEM and experimental input data: resistivity and cathodic polarization curves. The latter are obtained experimentally and represent the relation between the applied current and the electrochemical potential generated on the metal surface. For that, three different environmental conditions were taken into account: after curing (100 days), immersed in distilled water and immersed in seawater. The cementitious materials used were pastes and concretes, without addition of rice husk ash (RHA, reference samples), and with addition of 20% of RHA. The resistivity values decreased after curing in distilled water and in seawater, as expected. The simulations show that the efficiency of the cathodic protection system depends on the impressed current intensity and the geometric arrangement of the anodes.

Impact Echo (IE) simulations with heterogeneous concrete models have been very rare in the past. However, they could prove to be a valuable tool for enhancing physical understanding and improving data evaluation through artificial intelligence for future IE testing. Such improvements would result in more accurate condition assessments in industrial applications, such as for the inspection of nuclear power plant containment structures, among others. This study presents and discusses parameters influencing the outcome of IE simulations using the elastodynamic finite integration technique (EFIT). These parameters include the effective wave speed in concrete, which depends on the degree of heterogeneity. Additionally, the study explores wave scattering in the Rayleigh limit, identified as a primary noise source during actual IE measurements and discusses approximations for the source function, which ensure stability of the simulations. Lastly, the damping properties of the simulated concrete are discussed, recognizing the challenges in simulating elastic wave damping in low-frequency regimes. Following the discussion of these influencing parameters, the study presents results from 2D and 3D IE simulations of a test specimen, comparing them to real inspection data. Generally, results from 3D simulations exhibit a good agreement with measurement data in various aspects, whereas applications for 2D simulations are more limited yet also valuable.

Setting and hardening of ultra-high-performance concrete (UHPC) and ultra-high fiber reinforced concrete (UHPFRC) have been monitored with electrical conductivity in laboratory experiments with an equipment suitable for in-field remote sensing. Key parameters permitting to identify key stages during cement hydration could be determined. The electrical conductivity mildly changed during the fluid state, remaining at relatively high levels. During setting and early hardening, a sharp transition was observed toward much lower conductivity values. In the late-hardening further conductivity reduction occurred. The contribution of graphene has been investigated in those identified stages, showing both in UHPC and UHPFRC an effect to accelerate the fluid to solid transition and to mitigate the conductivity reduction in the late hardening stage. The role of fibers has also been investigated.

In recent decades, non-destructive testing (NDT) has become an indispensable component of condition assessment in various industries such as civil infrastructure, automotive, nuclear, and other safety-related sectors. Each NDT method possesses unique strengths and weaknesses, prompting increased interest in combining these methods for comprehensive assessments. However, the full potential of NDT data remains underutilized due to a lack of standardization in estimating NDT reliability. Often, the capabilities of NDT systems for specific inspection tasks are unknown, hindering advancements in NDE 4.0, where knowledge about the reliability of non-destructive tests is crucial. For example, such information is very valuable when labeling data for machine learning purposes to define whether a measurement can be considered sound or defect. This paper underscores the pressing need for international standardization in the reliability assessment of NDT and presents the German approach. This standard outlines procedures for NDT evaluation, including (i) defining the application, (ii) developing and producing test specimens, (iii) statistically evaluating test results (iv) considering human factors, and more. By doing so, the standard ensures the comparability of reliability assessments and enhances their overall acceptance. This study specifically delves into the discussion of reliability evaluation using a model-based approach for ultrasonic inspection of concrete structures, both with and without reinforcement, and under different defect conditions. In this case, honeycombs are chosen as the investigated defect type. Furthermore, an initial case study applies a Probability of Detection (POD) analysis for ultrasonic testing (UT) data obtained from a concrete specimen with artificial defects. This study represents a pioneering effort for UT in the context of concrete structures.

For the quantification of mineralogical components in cementitious materials using XRD, the external standard method, where the standard material is measured separately from the samples, has several advantages in avoiding artifacts arising from internally mixing the standard material. This method has been applied to the quantification of cement clinker and its hydration process, but rarely to its carbonation progress. In this study, we examined its applicability to carbonated cement pastes. By determining the H₂O and CO₂ amount contained in each sample, the mass attenuation coefficient was calculated, which enabled quantification using the external standard method. Four different standard materials were examined, among which α-corundum was regarded as the most crystalline, and hence, most suitable. Comparing the obtained quantitative amounts of portlandite and calcium carbonate with those in the TG results and the calcium aluminate phases with those in ²⁷Al NMR results, we demonstrated that the external standard method can accurately quantify the crystalline amount. Additionally, it was shown that the choice of the crystal structure of vaterite for Rietveld refinement has a significant influence on the quantification in Rietveld refinement.