Novel Electromagnetic Sensors Embedded in Reinforced Concrete Beams for Crack Detection

This paper investigates the possibility of applying novel microwave sensors for crack detection in reinforced concrete structures. Initially, a microstrip patch antenna with a Split Ring Resonator (SRR) structure was designed, simulated and fabricated. To evaluate the sensor’s performance, a series of structural tests were carried out and the sensor responses were monitored. Four reinforced concrete (RC) beam specimens, designed according to the European Standards, were tested under 3-point bending. The load was applied incrementally to the beams and the static responses were monitored via the use of a load cell, displacement transducers and crack width gauges (Demec studs). In parallel, signal readings from the microwave sensors, which were employed prior to casting of the concrete, located at the neutral axis at the mid-span of the beam, were recorded at various load increments. The microwave measurements were analysed and compared with those from crack width gauges. A strong linear relationship between the crack propagation and the electromagnetic signal across the full captured spectrum was found, demonstrating the technique’s capability and its potential for further research offering a reliable, low cost option for structural health monitoring (SHM)

Properties of tungsten mine waste geopolymeric binder

Tungsten mine waste mud (TMWM) geopolymeric binder is a new cementitious material with a very high early age strength. It is obtained from dehydroxylated mine waste powder mix with minor quantities of calcium hydroxide and activated with NaOH and water-glass solutions. Tests on properties of TMWM binders such as workability, setting time, unrestrained shrinkage, water absorption and static modulus of elasticity were carried out and the results are reported in this paper. This is followed by comparisons with literature related data and a discussion about it. The results showed that current devices use to assess OPC fresh properties are not recommended to evaluate TMWM binders. It has also been found that traditional procedures used to evaluate unrestrained shrinkage may be responsible for misleading results when using those new binders. Water absorption data shows that TMWM has a very compacted structure. Results concerning the static modulus of elasticity are similar to the ones obtained by other authors. However the hypothesis related to modulus of elasticity decrease due to the use of high Al/Si alkali activated mixtures was not confirmed

The Theory of Critical Distances to predict static and dynamic strength of notched plain concrete under mixed-mode I/II loading

The Theory of Critical Distances (TCD) is a powerful design tool capable of estimating the strength of notched/cracked materials by post-processing the linear-elastic stress fields ahead of the relevant stress raisers. The purpose of this paper is to reformulate the TCD to make it suitable for predicting the static/dynamic strength of notched unreinforced concrete subjected to Mixed-Mode I/II loading. The accuracy and reliability of the new extension of the TCD were checked using a large number of experimental results generated by testing plain concrete containing different geometrical features and tested under different loading rates and loading multiaxility. The predictions based on the proposed approach were seen to be within an error interval of ±30%. This level of accuracy is acceptable because it is within the scattering level of the experimental results used to calibrate the approach. These findings are promising and proving that this new reformulation of the TCD can be used to design notched plain concrete by modelling concrete as a linear-elastic, homogeneous, and isotropic material

Self-consistent modelling of hot plasmas within non-extensive Tsallis' thermostatistics

A study of the effects of non-extensivity on the modelling of atomic physics in hot dense plasmas is proposed within Tsallis' statistics. The electronic structure of the plasma is calculated through an average-atom model based on the minimization of the non-extensive free energy.Comment: submitted to "Eur. Phys. J. D

An experimental study of cathodic protection for chloride contaminated reinforced concrete

Cathodic protection (CP) is being increasingly used on reinforced concrete structures to protect steel reinforcing bars from corrosion in aggressive conditions. Due to the complexity of environmental conditions, the design specifications in national and international standards are still open to discussion to achieve both sufficient and efficient protection for reinforced concrete structures in engineering practices. This paper reports an experimental research to investigate the influence of chloride content on concrete resistivity, rebar corrosion rate and the performance of CP operation using different current densities. It aims to understand the correlation between the chloride content and concrete resistivity together with the CP current requirement, and to investigate the precision of the CP design criteria in standards

Mesoscopic simulations of laser-plasma interaction

We present millimeter-scale numerical studies we have performed about laser-plasma interaction. We have developed for that purpose a specific software, which we call $H\!\rho\alpha$ (Héra) and that we use for studying filamentation, Brillouin and Raman instabilities. We assume the paraxial wave propagation and bitemperature quasi-neutral fluid approximations. A brief description of the main models within $H\!\rho\alpha$, as well as some computation results, will be presented