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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2016, Vol. 10 Issue (2) : 214-223
The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites
Department of Civil Engineering, Democritus University of Thrace, Vas. Sofias Street, #12 Xanthi 67100, Greece
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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.

Keywords carbon nanotubes      strain resilient cementitious composite      polypropylene fibers      tensile bending      bond     
Corresponding Author(s): Souzana P. TASTANI   
Online First Date: 05 April 2016    Issue Date: 11 May 2016
 Cite this article:   
Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU, et al. The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites[J]. Front. Struct. Civ. Eng., 2016, 10(2): 214-223.
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Souzana P. TASTANI
Fig.1  Bond shear stresses fb along an elementary segment and radial stresses sn sustained by hoop media stresses shoop.
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  Mix designation
Fig.2  Comparative representation of the tested mixtures M1 and M2 regarding (a) the fresh state and (b) the cracking pattern of the associated 3-point bending samples
Fig.3  Average load- deflection histories of the 3-point bending prims of M1 and M2 mixtures
Fig.4  Control and control with CNTs matrices: (a) average load – mid deflection envelopes of the 3-point bending tests on prims and (b) associated fractured surfaces
Fig.5  SRCC and SRCC-CNT matrices: (a-b) average load—mid deflection responses of the 3-point bending tests on prisms, (c) comparative representation of the average envelopes of both matrices at both ages and (d) the associated failure patterns at both ages. (Within brackets is the testing age in days)
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  Experimental average values for applied force and mid deflection at milestones (apparent first cracking-subscript y, peak-subscript u and ultimate-subscript u.85%) and analytical estimations of tensile indices (apparent flexural toughness Gf and modulus of Rupture ft,fl as per [13])
Fig.6  (a,b) Geometry and (c) detailing of the 4-point bending short beam for investigation of local bond in the constant moment region. (d) Setup and instrumentation of the specimens
Fig.7  (a) Average load—mid deflection responses of the bond tests. (b) Cracking pattern near failure on the lateral face of all bond tests. (c) Splitting cracking of the bottom cover along the bonded length occurred in every case
1 Tastani S P, Pantazopoulou S J. Direct tension pullout bond test: experimental results. ASCE Structural Engineering, 2010, 136(6): 731–743
2 Tastani S P, Pantazopoulou S J. Reinforcement and concrete bond: state determination along the development length. Journal of Structural Engineering, 2013, 139(9): 1567–1581
3 Fischer G, Li V C. Effect of matrix ductility on deformation behavior of steel-reinforced ECC flexural membersunder reversed cyclic loading conditions. ACI Structural Journal, 2002, 99(6): 781–790
4 Bandelt M J, Billington S L. Bond behavior of steel reinforcement in high-performancefiber-reinforced cementitious composite flexural members. Materials and Structures, 2016, 49(1-2): 71–86
5 Bandelt M J, Billington S L. Monotonic and cyclic bond-slip behavior of ductile high-performance fiber-reinforced cement-based composites. In: Proceedings of the 3rd International. RILEM Conference on Strain Hardening Cementitious Composites, Dordrecht Netherlands, November 3‒5, 2014, 393–400
6 Konsta-Gdoutos M S, Metaxa Z S, Shah S P. Multi-scale mechanical and fracture characteristics and early-age strain capacity of high performance carbon nanotube/cement nanocomposites. Elsevier Cement & Concrete Composites, 2010, 32(2): 110–115
7 Metaxa Z S, Konsta-Gdoutos M S, Shah S P. Mechanical properties and nanostructure of cement-based materials reinforced with carbon nanofibers and polyvinyl alcohol (PVA) microfibers. Advances in the Material Science of Concrete, 2010, 270: 115–124
8 Chao S H, Naaman A E, Parra-Montesinos G J. Bond behavior of reinforcing bars in tensile strain-hardening fiber-reinforced cement composites. ACI Structural Journal, 2009, 106(6): 897–906
9 Georgiou A V, Pantazopoulou S J, Petrou M F. Experimental analysis of fiber reinforced cementitious composites with increased toughness. In: Proceedings of the 10th HSTAM International Congress on Mechanics, Chania, Greece, 25–27 May, 2013
10 Georgiou A V, Pantazopoulou S J. Bond, crack-width estimation, crack spacing and effective material stiffness in strain hardening cementitious composites. In: Proceedings ofthe SHCC3-3rd International RILEM Conference on Strain Hardening Cementitious Composites, 3‒5 November, 2014, Dordrecht, the Netherlands
11 Konsta-Gdoutos M S, Metaxa Z S, Shah S P. Highly dispersed carbon nanotube reinforced cement based materials. Elsevier Cement and Concrete Research, 2010, 40(7): 1052–1059
12 Hersam M C, Seo J W T, Shah S P, Konsta-Gdoutos M S, Metaxa Z S. Highly Concentrated Nano-Reinforcement Suspensions for Cementitious Materials and Method of Reinforcing Such Materials. US Patent, 2011
13 ASTM C293-94. Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Center-Point Loading). ASTM International, West Conshohocken, PA, USA, 2002
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