Advertisement

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
Research Article

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.

Keywords

carbon nanotubes strain resilient cementitious composite polypropylene fibers tensile bending bond 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Tastani S P, Pantazopoulou S J. Direct tension pullout bond test: experimental results. ASCE Structural Engineering, 2010, 136(6): 731–743CrossRefGoogle Scholar
  2. 2.
    Tastani S P, Pantazopoulou S J. Reinforcement and concrete bond: state determination along the development length. Journal of Structural Engineering, 2013, 139(9): 1567–1581CrossRefGoogle Scholar
  3. 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): 781–790Google Scholar
  4. 4.
    Bandelt MJ, Billington S L. Bond behavior of steel reinforcement in high-performancefiber-reinforced cementitious composite flexural members. Materials and Structures, 2016, 49(1-2): 71–86CrossRefGoogle Scholar
  5. 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, 393–400Google Scholar
  6. 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): 110–115CrossRefGoogle Scholar
  7. 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: 115–124Google Scholar
  8. 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): 897–906Google Scholar
  9. 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, 2013Google Scholar
  10. 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 Inter- national RILEM Conference on Strain Hardening Cementitious Composites, 3-5 November, 2014, Dordrecht, the NetherlandsGoogle Scholar
  11. 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): 1052–1059CrossRefGoogle Scholar
  12. 12.
    Hersam M C, Seo JWT, 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, 2011Google Scholar
  13. 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, 2002Google Scholar

Copyright information

© Higher Education Press and Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Souzana P. Tastani
    • 1
  • Maria S. Konsta-Gdoutos
    • 1
  • Stavroula J. Pantazopoulou
    • 1
  • Victor Balopoulos
    • 1
  1. 1.Department of Civil EngineeringDemocritus University of ThraceXanthiGreece

Personalised recommendations