Papers by Keyword: Bond Strength

Abstract: Information on deformation of coatings at different loading levels during peeling is given. It is shown that the deformations of the organosilicon coating appear already at the initial stages of loading, and the obtained data correlate with the data on acoustic emission. For a polyvinyl acetate coating at low loading levels, equal to 0.3-0.4 R, the release of acoustic signal energy is not observed. The absence of signals with a large amplitude at loading levels up to 0.7-0.8 R indicates the development of plastic deformations in the contact zone of the coating with the substrate. It was found that early localization of bond breaking in the contact zone, leading to the formation of a fracture focus, occurs in organosilicon coatings KO-168. For PVAC coatings, an abrupt growth of cracks is characteristic, which is preceded by its slow growth. The pseudoplastic mechanism of destruction of PVAC coatings has been established. The influence of the nature of the substrate on the change in the nature of the peeling of the coatings is considered.

Abstract: Thermal Barrier Coating are highly advanced material systems usually applied to metallic surfaces, such as gas turbine or aero-engine parts, operating at elevated temperatures. They have ceramic and metallic multilayers which have been widely used in the aeroturbine engines to increase the life of metallic components and turbine efficiency. Many different types of coatings are used to protect variety of engineering materials from wear, corrosion and erosion. Of all these, TBC’s play a vital role in providing thermal insulation and protect the material from high temperature environment. In this paper Lanthanum Zirconate (La₂Zr₂O₇) is used as a coating material which is phase-stable to its melting point, Lanthanum Zirconate is a promising material which exhibit lower thermal conductivity and higher thermal stability compared to other TBC system. High quality Lanthanum Zirconate based TBC is developed by plasma spray technique on superalloys. In the present investigation porosity, microstructure, hardness and bond strength of the developed TBC’s were characterized and significant parameters of plasma spray process were identified.

Abstract: This article studies the effect of chromate (CrO₄^2-) addition to concrete mix on the corrosion behavior of hot-dip galvanized reinforcement and primarily on the bond strength of this reinforcement with concrete. According to the original literature, the addition of chromates should prevent corrosion of the coating in fresh concrete with the evolution of hydrogen. The results show that this is indeed the case, but the need for a greater amount of added chromates also reduces the mechanical properties of the concrete. This ultimately affects the bond strength of the hot-dip galvanized reinforcement with concrete. Due to legislation, it is totally unacceptable to add any amount of chromates to the concrete mix (Cr^VI - toxic substance).

Abstract: At present, fiber reinforced composite materials (FRP) are widely used in the reinforcement of concrete structures. The bonding interface between FRP plates and concrete is the key part of the strengthening of concrete structures with FRP plates. The bonding performance directly determines the success or failure of structural reinforcement. Based on the self-developed test device, the development of FRP and concrete in direct shear debonding test specimens, with the aid of advanced digital image correlation DIC technology, accurate measurement of specimen strain distribution on the surface of the FRP plate, and the FRP plate surface strain along the plate long distribution rule and the bond strength of the specimens was well researched, it reveals that the stripping of FRP and concrete interface failure process, and provides technical guidance for the treatment of FRP-concrete bond interface in practical projects.

Abstract: The mechanical properties of masonry structural members strengthened by FRP (Fiber Reinforced Polymer) are affected by the bond strength of the reinforcement interface, in addition to the strength of the material FRP itself. This project is aimed at the new technology of Sprayed Fiber Reinforced Polymer Composites (SFRP), which is currently attracting attention. The bond strength between SFRP layer and masonry surface under high-humidity condition during strengthening construction and dry-wet cycle conditions after reinforcement were studied by experimental method. Different masonry substrates and different reinforcement methods were set as the test parameters. It is concluded that, compared with the currently used GFRP (Glass Fiber Reinforced Polymer) sheets reinforcement method, the SFRP reinforcement method has an significant improvement in the bond strength and the durability.

Abstract: In the case of exposure of reinforced concrete structure to accidental fire, an assessment of its residual capacity is needed. Bond strength of concrete was observed under elevated temperatures (150°, 250°, 350° and 500°C) in this study. Cylindrical specimens were prepared for pull-out tests to find out the bond behavior and to observe the mechanical properties of concrete. All the specimens were 100 mm diameter and 200 mm height. The pull-out specimens contain a 10 mm steel bar at its center. The specimens were tested at 52 days age following a 28 days water curing. Samples were preheated for 3 hours at 100°C temperature and then put into the furnace for 1 hour at the target temperature. Samples were tested before preheating as controlled specimens. In case of mechanical properties and the bond strength of concrete, there were no remarkable changes due to elevated temperature up to 150°C. However, the mechanical properties and bond strength were decreased gradually after 150°C temperature. Maximum reduction of bond strength observed was 52.13% and 49.8% at 500°C for testing within 1 hour and after 24 hours of heating respectively when compared to the controlled specimens. Bond strength was found to reduce at a greater rate than compressive strength due to the elevated temperature.

Abstract: This study investigates the bond strength of tension lap splice of self-compacted concrete (SCC) beam with various confining reinforcement. Four beam specimens were cast with SCC for test, in which three kinds of confined conditions were selected. Results indicate that the spiral steel at the tension lap splice presents similar confined effect as that of the transverse stirrups with same pitch. The beam reinforced with moderate stirrups in addition to the spiral steel may increase the confining effect. SCC beam should arrange proper amount of stirrups at the region of tension lap splice to preserve the flexural ductility of the beam.

Abstract: The article presents the results of the market research of dry mixtures produced in the Russian Federation. The established that glue dry construction mixes are in great demand. Information on the main produced glue dry mixes presented in the Russian market presented. The formulation of tile glue containing amorphous aluminosilicates as a modifying additive developed. The established that the synthesized aluminosilicates have a high activity equal to 350 mg/g. It has been established that samples of cement-based tile adhesive are characterized by high adhesion strength, which is more than R_kog = 1.4 MPa and R_adg> 1.1 MPa. In the article carried out the estimation of technical and economic indicators of production of the adhesive dry mixes. The shown that the developed formulation of glue dry mixes is economically efficiency.

Abstract: This paper investigates the bond strength of tension lap splice in the ordinary concrete (OC)beam and self-compacted concrete (SCC) beam. A total of six beam specimens were cast for thebending test. Results indicate that the SCC beam and OC beam present similar bond strength at thelap splice of tension bar. Current code for the tension lap splice is available for the SCC beam. Bothof the SCC and OC beams with transverse stirrups could have ductile flexural behavior in the regionof tension lap splicer. Only minor spalling between reinforcing steel and concrete was found underservice loading, such that the corrosion resistance of the tension lap splice in the SCC and OC beamscould be preserved.

Abstract: This paper discusses the structure and regularities of formation of compounds during explosive welding plate steel-aluminum composite. The influence of thickness of the welded element on the structure and the shear deformation of the metal in the heat-affected zone under different conditions of explosive loading was investigated.