Use of high strength, high ductility engineered cementitious composites (ECC) to enhance the flexural performance of reinforced concrete beams

Bai

et al. 2021

This paper examines the performance of reinforced concrete girders under cyclic loading. Seven T-girders were casted and tested. All girders were loaded under different constant cyclic loading in the midspan with the load ratio of 0.14∼0.23 and frequency of 3∼4 Hz. The study shows that the longitudinal reinforcement fracture is the main cause of girder rupture. And during cyclic loading, the concrete cracks, strains, and deflections generally indicate a “three-stage” law. The measured data were small but developed quickly in the initial stage. Thereafter, the degradation gradually stabilized and continued for a long time. In the final stage, the cracks, strains, and stiffness degradation developed sharply and the girders failed quickly. The duration of the stage is very short and may be difficult to be caught. For the life estimation, the longitudinal rebar S-N curve is fitted using different collected data. The results show that the curve is in good agreement with the corresponding data, which may be an excellent candidate for the evaluation of fatigue life.

Section: Introductionmentioning

confidence: 99%

[Retracted] Fatigue Performance of Reinforced Concrete T‐Girders under Cyclic Loading

Bai

et al. 2021

“…ECC has excellent mechanical properties and ductility. e compressive strength of ECC could range from 20 to 180 MPa depending on the mix compositions [10][11][12]. Unlike the brittleness of conventional concrete and strain-softening of fiber reinforced concrete [13], ECC exhibits the metallike strain-hardening behavior after the first crack occurring, accompanied by multiple microcracks under tensile loading.…”

Section: Introductionmentioning

confidence: 99%

Flexural Performance of Emulsified‐Asphalt‐Modified ECC for Expansion Joint Use

Mao

Ma³

2021

Self Cite

The concrete transition zone plays an important role in bridge expansion joint structure, which provides a good connection between the expansion joint installation and bridge decks. However, the premature deteriorations of concrete transition zone are found to be the major diseases of expansion joint during service life. Therefore, a material with high ductility, superior durability, and low modulus/stiffness is highly desired for transition zone. Engineering cementitious composites (ECC), a kind of high-performance concrete featuring the prominent ductility and durability, are a promising material for transition zone of expansion joint. This paper introduces a specific ECC material for transition zone, which is modified by emulsified asphalt (EA-ECC), and has the high deformation ability and low modulus/stiffness. The flexural mechanical properties including flexural stress-load displacement relation, flexural secant stiffness, and elastic modulus of the EA-ECC’s matrix were investigated experimentally. The microstructures of EA-ECC were observed via scanning electron microscope (SEM) imaging. Additionally, the influence of test temperature on flexural mechanical properties of EA-ECC was also investigated. It is found that the ultimate flexural stress of EA-ECC reduces gradually with increasing EA content. Conversely, the flexural deformation capacity shows an increasing trend with EA content. Additionally, incorporating EA significantly reduces the flexural secant stiffness and elastic modulus of EA-ECCs. The research results concluded that incorporating EA in ECC can significantly improve the flexural deformation ability accompanied by relatively lower modulus, which is likely to reduce the impact load on transition zone caused by vehicle bumping and prolong the service life of the whole bridge expansion joint structure.

“…In 2002, researches on cement-based functionally graded material showed that fibers should be distributed according to the stress field characteristics of materials [18]. Based on the research of engineered cementitious composites (ECC), Qin et al put the concept of ultrahigh toughness cementitious composites (UHTCC) obtaining functionally graded composite beam by using UHTCC to replace part of the concrete, which surrounds the main longitudinal reinforcement, and studied its bending properties [19,20]. ECC is a kind of highly ductile fiber reinforced concrete; it shows a special strain-hardening behavior under tensile loadings; meanwhile, along with developing multiple microcracks on specimens, as a result, its tensile strain capacity is several hundred times of convention concrete [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Microsteel Fiber Reinforced Concrete and Its Gradient Design in the Partially Reinforced RC Beam

Fang

Luo

et al. 2020

Effects of two kinds of microsteel fibers were employed in reinforced concrete (RC) with different fiber volumes fraction. The RC beam was partially reinforced by microsteel fiber reinforced concrete (MSFRC) based on the idea of gradient design. Flexural performances were specially investigated. Results show that microsteel fiber highly strengthened and toughened the concrete matrix. With the same fiber volume content, the concrete reinforced by Type I fiber was generally better in strength compared with that of Type II, while the bending toughness was substantially improved. The bending strength of the concrete reinforced by microsteel fiber in partial section of tensile region was comparable to that in whole section. Based on the traditional strength theory, the critical MSFRC layer depth of in the partially reinforced RC beam was about 0.3 times of the beam depth, which possessed the same crack resistance ability with the beam composed of MSFRC in the whole section. Compared with that of the reference beam, the cracking load of the partially reinforced beam was enhanced by 119%, and the ratio of the cracking moment to ultimate moment improved by 91%. Moreover, the width and height of the cracks in the partially reinforced beam developed much slower than those in the reference beam, and the steady state in which all cracks emerged appeared later; meanwhile, the crack spacing in the pure bending region was smaller, and the number of cracks in the bending-shear region was less, which means that the partially reinforced beam is of excellent properties to resist cracking and bending. Finally, the calculation formula of the bearing capacity of the partially reinforced beam was proposed, which was in good agreement with experimental results.