11/15/2023 0 Comments Rebar scatter gun ammoThese results predict that a rebar-concrete interface could be distinguished from a rebar-air interface with only 1 second of heating. ![]() Theoretical results are also presented of the predicted temperature versus time curves expected for rebar inside concrete with and without air defects at the rebar-concrete interface. Microwave thermoreflectance measurements made in a 5 second measurement time are compared with conventional thermographic measurements of the temperature distribution at the concrete surface which require a 10 minute measurement time. Results will be presented for a series of test specimens produced by deliberately corroding rebar inside concrete in the laboratory. ![]() This is in contrast to infrared thermographic approaches which monitor the surface temperature of the concrete and are dependent on waiting for considerable lengths of time for heat flow from the rebar to the concrete surface. The rebar inside the concrete is heated with an induction heater and then the surface temperature of the rebar inside the concrete is probed using a microwave reflectance method. BenĪ microwave-based approach under development for detecting corrosion of rebar is described. Microwave thermoreflectometry for detection of rebar corrosion These properties indicate promising applications with 3D rebar GFs in devices requiring stable mechanical and electrochemical properties. After 500 cycles of testing at a high current density of 6.50 mA cm -2, the LIC shows 78% energy density retention. ![]() The 3D rebar GF also shows stable performance as a highly porous electrode in lithium ion capacitors (LICs) with an energy density of 32 Wh kg -1. Both the mechanical and finite element models are validated with the available test data sets and are superior to existing models in prediction of average bond strength (3150Ã- the foam's weight with no irreversible height change, and shows only a âˆ❂5% irreversible height change after loading >8500Ã- the foam's weight. To understand the fracture process associated with bond failure, a probabilistic meso-scale model of concrete is proposed and its sensitivity to interface and confinement strengths are investigated. This mechanics-based model can take into account the combined effect of concrete splitting and interface shear-off failures, resulting in average bond strengths for all practical scenarios. In this study, a unified bond model is proposed and developed based on an analogy to the indentation problem around the rib front of deformed rebar. Their accuracy highly depended upon the test data sets selected in analysis and calibration. Two distinct groups of bond models were traditionally developed based on the dominant effects of concrete splitting and near-interface shear-off failures. The validity of the proposed method was demonstrated by both experimental tests and numerical analysis.Ī unified bond theory, probabilistic meso-scale modeling, and experimental validation of deformed steel rebar in normal strength concreteīond between deformed rebar and concrete is affected by rebar deformation pattern, concrete properties, concrete confinement, and rebar-concrete interfacial properties. A transition part was added between the free segment of the rebar and the tube, which could eliminate the stress concentration effectively and thus yield more accurate values for the properties of FRP rebar. An improved testing method is developed in this paper to avoid this issue. So the test results would be regarded as invalid. The changing abruptly of the section induced stress concentration. ![]() Numerical simulations of the stress field at bar ends in such tests by ANSYS revealed that such unexpected failure modes were caused by the test setup. However, most of specimens were failed at the ends where the section changed abruptly. In these tests, the ends of each rebar specimen were embedded in steel tube filled with expansive cement, and the rebar was loaded by gripping the tubes with the conventional fixture during the tensile tests. We have conducted a series of tests to measure tensile strength and modulus of elasticity of fiber reinforced polymer (FRP) rebar. An improved method for testing tension properties of fiber-reinforced polymer rebar
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