Papers by Keyword: Pull-Out Test

Abstract: This study evaluates the impact of adding metalized plastic waste (MPW) fibers to lightweight concrete that is used as a filler material in building slopes and bridge ramps. The goal is to open up new opportunities for recycling plastic waste and promote a more sustainable and productive construction industry. This study examined the mechanical behavior of lightweight concrete (LC) at 3, 28, and 90 days, both with and without MPW fiber (1%, 2%, and 3%). Compression tests, 3-point bending tests, and pull-out tests were used to measure the fibers' compressive strength, flexural strength, and maximum load-bearing capacity, respectively. According to the results, the compressive strength (CS) and elasticity modulus (MOE) decreased with increasing fiber content when MPW fiber was added. In the long term, the CS and MOE decrease for the LC containing 3% MPW fiber was 8% and 7%, respectively, lower than for the control concrete. At 90 days, the flexural strength of the LC with 1% MPW fiber was marginally higher than that of the control concrete, rising by 2.40%. After this initial rise, however, the flexural strength declined as the fiber concentration increased, eventually reaching an 8% reduction for LC with 3% MPW fiber.The optimum method for determining maximal load-bearing and comprehending the deformation mechanism is hence the fiber pull-out test. The microstructure study of the LC examined how the pull-out test affected the quality of bonding at fiber-matrix interfaces. The tensile and flexural strength of lightweight concrete are enhanced by MPW fiber's ability to bear significant pulling stress.

Abstract: DARE2C (Durable Aluminium Reinforced Environmentally-friendly Concrete Construction) project is to develop a more environmental-friendly concrete and use aluminium (Al) as reinforcement material, instead of steel. The new concrete uses supplementary cementitious materials (SCM), which provides a low alkaline environment suitable for aluminium reinforcement. Unlike steel, aluminium has a better stability in medium pH environment, which can largely improve the durability of the new Al-reinforced concrete (RC). Cover thickness can be reduced since aluminium withstands environment and carbonation does not pose a threat. The usage of lighter aluminium as reinforcement would help greatly reduce the total weight of the Al-RC structure. The objective of this work is to investigate the compatibility of different aluminium alloys in the new DARE2C concrete by gas chromatography measurement during the cement hydration. Together with the pull-out test results, the best aluminium candidate will be determined.DARE2C (Durable Aluminium Reinforced Environmentally-friendly Concrete Construction) project is to develop a more environmental-friendly concrete and use aluminium (Al) as reinforcement material, instead of steel. The new concrete uses supplementary cementitious materials (SCM), which provides a low alkaline environment suitable for aluminium reinforcement. Unlike steel, aluminium has a better stability in medium pH environment, which can largely improve the durability of the new Al-reinforced concrete (RC). Cover thickness can be reduced since aluminium withstands environment and carbonation does not pose a threat. The usage of lighter aluminium as reinforcement would help greatly reduce the total weight of the Al-RC structure. The objective of this work is to investigate the compatibility of different aluminium alloys in the new DARE2C concrete by gas chromatography measurement during the cement hydration. Together with the pull-out test results, the best aluminium candidate will be determined.

Abstract: Lately, considerable efforts have been directed towards investigating the practicality of using coarse recycled concrete aggregate as a potential substitute for natural coarse aggregate (NCA) in concrete construction. Research has shown that both the proportion of replacement and the properties of recycled aggregates play a significant role in affecting the tensile strength, compressive strength, and bonding characteristics of concrete. In certain cases, recycled aggregate concrete exhibits lesser mechanical properties when compared to concrete made with normal aggregates. The current study investigated the performance of Sika AnchorFix-1 to enhance the bond strength between steel bars and recycled aggregate concrete. The findings suggest that Sika AnchorFix-1 successfully prevented the concrete rupture in the case of concrete with recycled concrete aggregates, whereas concrete rupture could not be prevented in the case of concrete with recycled brick aggregates. Hence, a lower bond strength was obtained for specimens with recycled bricks aggregates than specimens with recycled concrete aggregates.

Abstract: Effective and reliable force transfer between steel reinforcing bars and concrete is necessary for reinforced concrete buildings to be designed as efficiently as possible. Significant reductions in load capacity and structural rigidity could be the outcome of inadequate connection between the bars and concrete. With the recent discovery of graphene, new opportunities for the development of nano-sized cementitious additives have emerged. The present study investigates the effect of graphene nanoplatelets (GnP) on the bond stress capacity of steel reinforcing bars embedded in GnP-enhanced high-performance concrete (HPC). Effects of various GnP contents and diameter and embedded length of the bar were evaluated. Bond stress-slip behaviour between the bar and concrete was examined by performing pull out tests on cylindrical samples. Findings revealed that the GnP-enhanced HPC improved the bond stress owing to the confinement and bridging effects of GnP. Addition of GnP at the concentration of 0.02 % increased the bond stress by more than 41.28, 18.9 and 53.90% for steel bars with diameters of 10, 12 and 16 mm, respectively, at the same bar embedded length. Presence of GnP reduced the initial slip of the bar owing to the improved adhesion between the bar and the surrounding concrete.

Abstract: The paper verifies anti-corrosion barrier protective properties of PE/PAK (polyethylene/polyacrylate), PE/PPE (polyethylene/polyproplylene) and PAD (polyamide) coatings of specific thickness on the surface of conventional ribbed bar B500B. Using pull-out test, the bond strength of such system was compared with bond strength of normal strength concrete (C30/37). Results of these tests show that key properties of coated systems are comparable to the previously tested epoxy coatings in case of their use in technical practice (protection of conventional rebar). In conclusion, their effective protective effect corresponds to minimal thickness higher than 300 μm but simultaneously lower the bond strength between the ribbed rebar and concrete. Keywords: corrosion of steel in concrete, organic coatings, bond strength, pull-out test, porosity

Abstract: This study presents a simple one-dimensional analytical model describing the pull-out process of an elastic fibre embedded in a cement matrix, which captures the ductile behaviour of Fibre Reinforced Concrete (FRC) elements.The shear stress arising at the frictional interface between fibre and matrix during the pull-out is assumed to increase with the slippage distance, as a consequence of the growing abrasion of the fibre surface.The equilibrium conditions between the external axial load and the interfacial shear stress are imposed with reference to the undeformed configuration.The model is validated through comparison with both experimental data obtained by testing partially recycled polymeric fibres embedded in a cement matrix, and several datasets available in the literature comprising polypropylene fibres with and without silica coatings.The proposed model can properly describe the response of synthetic fibres that exhibit considerable axial elongation and slip-hardening interface behaviour.However, it may also predict the non-linear relation between the tensile load and the fibre displacement for different kinds of fibre, by setting adequately the constitutive parameters.

Abstract: There has been considerable attention drawn to the application of textile reinforced mortar (TRM) composites for strengthening existing masonry and concrete structures. These composites are made from textile fibers embedded in an inorganic matrix and act as externally bonded reinforcement (EBR). Therefore, a careful observation must be made of the bond of the mortar to the substrate and the bond of the mortar to the textile. Despite numerous studies of the bond behavior of TRM composites conducted in recent years, no constitutive bond behavior law under cyclic loading has been determined. In most available studies, the most common method of testing TRM-to-substrate bonds is the single-lap shear test. Contrary to that, the bond performance of fibers to mortar has received little attention and has been the subject of this study. This paper describes a laboratory study investigating the textile's interfacial bond behavior to the mortar fiber under cyclic loading. It was shown that cycling can cause a loss in strength, which varies with the number of cycles.

Abstract: The reinforcing steel embedded in concrete is generally protected against corrosion by the high alkalinity (pH = 12.5 to 13.5) of the concrete pore solution. The structural degradation of concrete structures due to reinforcement’s corrosion has an impact on the safety, serviceability and durability of the structure. The corrosion of reinforcements in the construction of a transport infrastructure (especially bridges), parking areas, etc., is primarily initiated by chlorides from de-icing salts. Glass fiber reinforcement polymer (GFRP) bars are suitable alternatives to steel bars in reinforced concrete applications. The bond between concrete and reinforcement is one of the basic requirements for the composite action of both materials. The transfer of forces between the steel reinforcement and the concrete is provided by the following mechanisms: adhesion, friction and mechanical interlocking. The bond between GFRP reinforcement and concrete is different and it is ensured by friction and mechanical interlocking of the rebar surface. The chemical bond does not originate between GFRP reinforcement and the surrounding concrete, so adhesion does not contribute to transfer of the bond forces. Some few test methods are used to determine the bond between GFRP reinforcement and concrete. The pull-out tests were used to determine the bond behavior between GFRP rebars and concrete. This paper describes the preparation, process, results and evaluation of the pull-out tests.

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: High strength steel bars are widely used for the strengthening of masonry buildings, in particular to improve the connection between different structural elements, such as orthogonal walls and multi-leaf walls. A particular type of steel connector is the twisted bar, which due to its particular shape works as a self-threading screw, anchoring to the support material without any binder. The effectiveness of such technique mainly relies on the bond between the bar and the substrate, where adhesion, mechanical interlocking and friction play an important role. In this paper, a preliminary experimental study on pull-out behavior of twisted steel connectors inserted in brick units of different materials that can be commonly found in existing masonry buildings in Italy and in Europe is presented. Additionally, mechanical characterization of the materials is conducted to understand the influence of the compression strength and elastic modulus on the adhesion between the connector and the substrate. Preliminary results show that the pull-out response strongly depends on the mechanical properties of the substrate material.