Interface between steel rebar and concrete, studied by electromechanical pull-out testing

A finite element study carried out using LS DYNA and aimed to simulate the monotonic pull-out test of deformed steel rebar embedded in concrete is presented in this paper. Three models of the interface between deformed steel rebar and well-confined concrete, i.e. perfect bond model and two bond-slip models are observed and compared. Bond stress-slip response and rebar stress-slip response obtained numerically are validated with experimental data and empirical equations available from the literature. The full bond model overestimates the response, providing higher rebar stress. In the bond-slip models, good agreement is observed between numerical and experimental bond stress and rebar Stress–slip responses. The empirical equation of bond-slip proposed by Murcia-Delso and Shing (2014) is found to overestimate the peak bond stress.

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Experimental Investigation of Adhesive Bonding for Post‐installed Rebars into Concrete at High Temperatures

IABSE Congress, New York, New York 2019: The Evolving Metropolis ◽

10.2749/newyork.2019.1169 ◽

2019 ◽

Author(s):

Thanyawat Pothisiri ◽

Pitcha Jongvivatsakul ◽

Vanichapoom Nantavong

Keyword(s):

Experimental Investigation ◽

High Temperatures ◽

Mechanical Behaviour ◽

Epoxy Resins ◽

Adhesive Bonding ◽

Elevated Temperatures ◽

Adhesive Bond ◽

Steel Rebar ◽

Pull Out ◽

Embedment Length

<p>The use of post‐installed rebars into existing reinforced concrete structures bonded with epoxy resins was constantly increasing due to the advantage of equivalent or even higher bearing capacities at service temperature, compared with conventional cast‐in‐place rebars. Previous studies have examined the effects of different parameters on the mechanical properties of bonded post‐installed rebars at normal temperature. These studies showed that, for rebar diameter equal to 10 mm, the load bearing capacity increases linearly with the embedment length up to 75 mm. However, upon exposure to high temperatures, the glass transition of epoxy resins may occur and affect the mechanical behaviour of the adhesive bond. Studying the mechanical behaviour of an adhesive anchor at high temperatures is therefore necessary. An experimental investigation is conducted herein to examine the characteristics of the adhesive bonding stress between steel rebar and concrete interface at elevated temperatures using a series of pull‐out tests with varying rebar diameters and embedment lengths.</p>

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Workability of Ribbed Bar with Nano-Ceramic Coating

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.838-841.84 ◽

2013 ◽

Vol 838-841 ◽

pp. 84-90

Author(s):

Chiou Wang Jia-Jiunn ◽

Shang Long Li ◽

Jiong Li ◽

Ying Liu ◽

Guang Xin Xu ◽

...

Keyword(s):

Corrosion Test ◽

Ceramic Coating ◽

Significant Loss ◽

Bending Test ◽

Coating Process ◽

Coated Steel ◽

Chemical Test ◽

Steel Rebar ◽

Pull Out ◽

New Material

A nanoceramic composite is proposed to coat steel rebar used in reinforced concrete with the purpose of protecting it from corroding. This is a new material in the civil engineering field. For this reason several tests have been performed over coated steel rebar with the nanoceramic composite in order to know its viability and its properties. A bending test showed that the coating is stiff, and therefore not flexible enough to bend it as a stirrup. For this reason if a bended rebar were needed, it should be bent before coating it. While the pull-out test concluded, there is no significant loss of bond strength due to the contact of the coating with the concrete. The chemical test indicated that the coating cannot bear strong alkali and acid environments, but resisted without problems under saline environments with neutral pH. Finally a cathodic disbondment test and a corrosion test were performed. These tests showed problems with the coating process because the behavior of during the execution of the test differed from the expected.

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An experimental study of damage characteristics at bond of RC after microwave heating

Journal of the Croatian Association of Civil Engineers ◽

10.14256/jce.2925.2020 ◽

2021 ◽

Vol 73 (02) ◽

pp. 107-117

Keyword(s):

Thermal Damage ◽

Interfacial Bond ◽

Bond Slip ◽

Damage Characteristics ◽

Steel Rebar ◽

Pull Out ◽

Irradiation Power ◽

Splitting Failure ◽

Microwave Irradiations ◽

Characteristic Points

With an increase in urban construction waste, and in order to find an effective method of microwave-assisted mechanical RC regeneration, thermal damage characteristics of the interfacial bond between steel rebar and concrete after different microwave irradiations are analysed in this paper. The results show that, with an increase in microwave power, the overall failure mode of the specimen changes from splitting failure to pull-out failure. Bond slip curves and the corresponding fitting equations were obtained at various levels of microwave irradiation. By analysing characteristic points of the curve, 3500W was determined as a reasonable irradiation power.

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Fracture patterns and mechanical properties of GFRP bars as internal reinforcement in concrete structures

Challenge Journal of Concrete Research Letters ◽

10.20528/cjcrl.2020.03.003 ◽

2020 ◽

Vol 11 (3) ◽

pp. 69

Author(s):

Mehmet Canbaz ◽

Uğur Albayrak

Keyword(s):

Mechanical Properties ◽

Concrete Structures ◽

Concrete Block ◽

Glass Fiber Reinforced Plastic ◽

Gfrp Bars ◽

Steel Rebar ◽

Pull Out ◽

Steel Bars ◽

Bonding Properties ◽

Modulus Of Resilience

Glass Fiber Reinforced Plastic (GFRP) composites as rolled bars can be used as steel rebar to prevent oxidation or rust which is one of the main reasons concrete structures deteriorate when exposed to chlorides and other harmful chemicals. GFRP is successful alternative for reinforcement with high tensile strength- low strain, corrosion resistance and congenital electromagnetic neutrality in terms of longer service life. The main goal of the study is to investigate the mechanical and bonding properties of GFRP bars and equivalent steel reinforcing bars then compare them. GFRP and steel rebar are embedded in concrete block with three different levels. Mechanical properties of GFRP and steel bars in terms of strength and strains are determined. On the other hand; modulus of elasticity of GFRP and steel bars, modulus of toughness and modulus of resilience were calculated using stress-strain curves, as a result of the experiments. Pull-out tests are conducted on each GFRP and rebar samples which are embedded in concrete for each embedment level and ultimate adherence strengths are determined in terms of bar diameter–development length ratio. Yield strength, strain and modulus of elasticities of GFRP samples are compared to steel rebar. According to the test results reported in this study, GFRP bars are used safely instead of steel bars in terms of mechanical properties.

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The influence of heat treatment on the fiber/matrix interface in a SiC-reinforced glassceramic

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105771 ◽

1988 ◽

Vol 46 ◽

pp. 742-743

Author(s):

E. Bischoff ◽

O. Sbaizero

Keyword(s):

Heat Treatment ◽

Aluminum Silicate ◽

Lithium Aluminum ◽

Interfacial Region ◽

Specimen Preparation ◽

Crack Wake ◽

Pull Out ◽

Annealed Material ◽

Ultrasonic Drilling ◽

Fiber Matrix Interface

Fiber or whisker reinforced ceramics show improved toughness and strength. Bridging by intact fibers in the crack wake and fiber pull-out after failure contribute to the additional toughness. These processes are strongly influenced by the sliding and debonding resistance of the interfacial region. The present study examines the interface in a laminated 0/90 composite consisting of SiC (Nicalon) fibers in a lithium-aluminum-silicate (LAS) glass-ceramic matrix. The material shows systematic changes in sliding resistance upon heat treatment.As-processed samples were annealed in air at 800 °C for 2, 4, 8, 16 and 100 h, and for comparison, in helium at 800 °C for 4 h. TEM specimen preparation of as processed and annealed material was performed with special care by cutting along directions having the fibers normal and parallel to the section plane, ultrasonic drilling, dimpling to 100 pm and final ionthinning. The specimen were lightly coated with Carbon and examined in an analytical TEM operated at 200 kV.

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Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154755 ◽

1989 ◽

Vol 47 ◽

pp. 556-557

Author(s):

K.L. More ◽

R.A. Lowden

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Chemical Vapor ◽

Chemical Vapor Infiltration ◽

Frictional Stress ◽

Fiber Reinforced ◽

Pull Out ◽

Carbon Coated ◽

Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

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Advances in ultramicrotomy for physical sciences applications

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149386 ◽

1993 ◽

Vol 51 ◽

pp. 710-711

Author(s):

G. McMahon ◽

T. Malis

Keyword(s):

Particle Surface ◽

Zeolite Catalysts ◽

Physical Sciences ◽

Pull Out ◽

Large Particles ◽

Novel Applications ◽

Metal Wires ◽

Frequent Problem ◽

Specific Orientation ◽

Diamond Knife

As with all techniques which are relatively new and therefore underutilized, diamond knife sectioning in the physical sciences continues to see both developments of the technique and novel applications.Technique Developments Development of specific orientation/embedding procedures for small pieces of awkward shape is exemplified by the work of Bradley et al on large, rather fragile particles of nuclear waste glass. At the same time, the frequent problem of pullout with large particles can be reduced by roughening of the particle surface, and a proven methodology using a commercial coupling agent developed for glasses has been utilized with good results on large zeolite catalysts. The same principle (using acid etches) should work for ceramic fibres or metal wires which may only partially pull out but result in unacceptably thick sections. Researchers from the life sciences continue to develop aspects of embedding media which may be applicable to certain cases in the physical sciences.

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