The interface between rock-concrete under high water pressure may lead to concrete leaching, which is crucial to the safety of concrete gravity dams. However, the mechanism of concrete leaching in the micro pore-structure is not well understood. Thus, this study aims to investigate the effect of concrete leaching on the microstructure and permeability of the rock-concrete interfacial transition zone (ITZ).First, rock-concrete specimens were subjected to an accelerated leaching process using ammonium chloride. Subsequently, the micro pore-structure, calcium compound, and micro-morphology of the degraded rock-concrete interface were analyzed by nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Permeabilities of the ITZ under different dissolution times were measured by the steady-state method. The above results indicate that the cement slurry dissolves most rapidly in the ITZ, forming a dominant leakage channel. The seepage characteristics of the ITZ are primarily determined by the micro pore-structure. As the dissolution process progresses, the increase in capillary pores enhances the permeability. Finally, considering the penetration of cement slurry, a novel mathematical model of permeability evolution in ITZ was proposed. Compared with experimental results, it shows that this mathematical model can predict the deterioration of permeability in ITZ.
The current methods of electric–magnetic flux leakage structural health monitoring that use tubular coils as electro-magnetizers fail to detect concrete rebar structures without a head and a tail. This article proposes a novel electric–magnetic flux leakage structural health monitoring technique for concrete rebar using open electromagnetic coils as magnetizers. Three-dimensional finite element simulations and experiments are conducted to compare the magnetization effect, defect-detection capability, and magnetic force interaction of traditional tubular coils and the proposed open electromagnetic coils. The agreement between the simulation and experimental results confirms the reliability and validity of the proposed structural health monitoring technique for concrete rebar. Additionally, two types of magnetizer coils are designed and manufactured using optimized structures, and both limitations and solutions are discussed. Overall, the proposed open magnetizer coils show great potential for future structural health monitoring applications for concrete rebar.
This study presents an efficient approach to fabricating photothermal coatings using copper sulfide (CuS) nanoparticles for effective deicing on glass. The influence of nanoparticle shape on light absorption was economically evaluated using Finite Different Time Domain (FDTD) simulations, identifying CuS nanorods as the optimal choice in terms of light absorption and heat generation. Simulation results guided the fabrication of transparent photothermal coatings incorporating CuS nanorods and transparent acrylic resin paint. Deicing tests under 808 nm illumination demonstrated efficient active deicing potential of the developed coating covered with a 3mm-thick ice layer, raising the surface temperature from-20.0 °C to 42.5 °C within 400s. This combined simulation guidance and test validation approach introduces a cost-effective method for designing high-performance deicing coatings embedded with photothermal nanoparticles.
In order to explore the dynamic mechanical properties of concrete under biaxial compression-compression, a true triaxial instrument was used to conduct an experimental study on the dynamic mechanical properties of plain concrete under biaxial compression-compression. Eight different lateral compressive stresses (0 MPa~14 MPa) and four strain (10−5/s, 10−4/s, 10−3/s and 10−2/s) rate were considered. From this, the effects of lateral compressive stress and loading strain rate on the biaxial compression-compression properties of concrete were compared and analyzed by obtaining the failure modes, principal compressive stress-strain curves and related mechanical characteristic parameters of plain concrete under different loading conditions. The research results show that: with the increase of lateral compressive stress, the failure modes of concrete were developed from columnar failure at low lateral compressive stress to sheet-like failure at high lateral compressive stress. With the increase of lateral stress, the development trend of concrete failure mode decreased gradually under the influence of strain rate. With the increase of lateral compressive stress, the variation range of concrete principal compressive stress decreased first and then tended to be relatively stable under the influence of strain rate. With the increase of strain rate, the increase range of concrete principal compressive stress decreased under the influence of lateral compressive stress. The influence mechanism of lateral compressive stress and strain rate on biaxial compression-compression performance of concrete was analyzed. Meanwhile, based on Kupfer biaxial compression failure criterion, a biaxial compression dynamic failure criterion model considering the effect of loading strain rate on plain concrete was proposed. The research results provided an important theoretical basis for the application and development of concrete engineering.
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