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Frontiers of Structural and Civil Engineering

ISSN 2095-2430

ISSN 2095-2449(Online)

CN 10-1023/X

邮发代号 80-968

2019 Impact Factor: 1.68

Frontiers of Structural and Civil Engineering  2016, Vol. 10 Issue (2): 214-223   https://doi.org/10.1007/s11709-016-0332-3
  本期目录
The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites
Souzana P. TASTANI(),Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS
Department of Civil Engineering, Democritus University of Thrace, Vas. Sofias Street, #12 Xanthi 67100, Greece
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Abstract

Stress transfer between reinforcing bars and concrete is engaged through rib translation relative to concrete, and comprises longitudinal bond stresses and radial pressure. The radial pressure is equilibrated by hoop tension undertaken by the concrete cover. Owing to concrete’s poor tensile properties in terms of strength and deformability, the equilibrium is instantly released upon radial cracking of the cover along the anchorage with commensurate abrupt loss of the bond strength. Any improvement of the matrix tensile properties is expected to favorably affect bond in terms of strength, resilience to pullout slip, residual resistance and controlled slippage.The aim of this paper is to investigate the local bond of steel bars developed in adverse tensile stress conditions in the concrete cover. In the tests, the matrix comprises a novel, strain resilient cementitious composite (SRCC) reinforced with polypropylene fibers (PP) with the synergistic action of carbon nano-tubes (CNT). Local bond is developed over a short anchorage length occurring in the constant moment region of a four-point bending short beam. Parameters of investigation were the material structure (comprising a basic control mix, reinforced with CNTs and/or PP fibers) and the age of testing. Accompanying tests used to characterize the cementitious material were also conducted. The test results illustrate that all the benefits gained due to the synergy between PP fibers and CNTs in the matrix, namely the maintenance of the multi-cracking effect with time, the increased strength and deformability as well as the highly increased material toughness, were imparted in the recorded bond response. The local bond response curves thus obtained were marked by a resilient appearance exhibiting sustained strength up to large levels of controlled bar-slip; the elasto-plastic bond response envelope was a result of the confining synergistic effect of CNTs and the PP fibers, and it occurred even without bar yielding.

Key wordscarbon nanotubes    strain resilient cementitious composite    polypropylene fibers    tensile bending    bond
收稿日期: 2015-04-17      出版日期: 2016-05-11
Corresponding Author(s): Souzana P. TASTANI   
 引用本文:   
. [J]. Frontiers of Structural and Civil Engineering, 2016, 10(2): 214-223.
Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS. The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites. Front. Struct. Civ. Eng., 2016, 10(2): 214-223.
 链接本文:  
https://academic.hep.com.cn/fsce/CN/10.1007/s11709-016-0332-3
https://academic.hep.com.cn/fsce/CN/Y2016/V10/I2/214
Fig.1  
mix design portl. cem., 42.5 fine fly ash fine sand (dagg <0.5 mm) water HRWRa) PPb) (vol.)
M1 1 2.8 1.12 1.4 (0.368)c) 0.09 1.5%
M2 1 2 1.1 1.1 (0.366)c) 0.1 2%
Tab.1  
Fig.2  
Fig.3  
Fig.4  
Fig.5  
Matrix ID – (age in days) Experimental results Tensile indices
Dy (mm) Du(mm) Du. 85% (mm) Py (kN) Pu (kN) Gf(Nt?m?1) ft,fl(MPa)
Control(70 d) 0.16 0.16 0.16 1.45 1.45 73 4.75
Control –CNT(30 d) 0.23 0.23 0.23 2.39 2.39 172 7.83
SRCC(30 d) 0.28 1.80 2.62 1.55 2.53 3275 5.10
SRCC(70 d) 0.28 0.93 1.47 2.70 2.36 1997 8.86
SRCC-CNT(30 d) 0.18 1.56 2.25 1.66 3.01 3307 5.43
SRCC-CNT(70 d) 0.27 2.21 3.01 1.66 2.84 4193 5.46
Tab.2  
Fig.6  
Fig.7  
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