He et al. (2017) — Strain hardening ultra-high performance concrete...

Citation

Shan He, Jishen Qiu, Junxia Li, En-Hua Yang (2017). Strain hardening ultra-high performance concrete (SHUHPC) incorporating CNF-coated polyethylene fibers. Cement and Concrete Research, Vol. 98, pp. 50-60.

DOI: 10.1016/j.cemconres.2017.04.003
Atlas layer: extension
Related Victor Li book chapter: Chapter 3: Fiber/Matrix Interface; Chapter 5: Ultra-High Performance ECC
Source PDF: he-2017-strain-hardening-ultra-high-performance-concrete.pdf
Extracted text: atlas/full_text/he-2017-strain-hardening-ultra-high-performance-concrete_full_text.md
Source note: atlas/source_notes/he-2017-strain-hardening-ultra-high-performance-concrete_source_note.md

Why this paper matters

Pioneering study developing a non-destructive dip-coating method to deposit carbon nanofibers (CNFs) onto hydrophobic PE fibers via aqueous self-assembly, increasing the interfacial frictional bond by 22% and developing a >150 MPa SHUHPC with 15.0 MPa tensile strength, 2.3% tensile ductility, and 50% tighter crack widths.

Main contribution

Developed a simple aqueous hydrophobic self-assembly method to coat dense CNFs on PE fibers without fiber damage.
Proved via single-fiber pullout tests that CNFs in the ITZ bridge nano-cracks and increase frictional bond $\tau_0$ from 2.43 to 2.96 MPa.
Produced SHUHPC achieving compressive strength of 153 MPa, tensile strength of 15.0 MPa, and tensile ductility of 2.3% at 1.5 vol% fiber content.

Evidence summary

Tensile properties: Tensile strength = $15.0 \pm 0.5\text{ MPa}$, First cracking strength = $8.8 \pm 0.7\text{ MPa}$, Tensile strain capacity = $2.3 \pm 0.3\%$ (Table 4, page 54).
Compressive strength: $153 \pm 4\text{ MPa}$ at 28 days (Table 4, page 54).
Crack characteristics: Average crack width reduced from $142\ \mu\text{m}$ to $71\ \mu\text{m}$ (50% reduction); crack count increased from 16.3 to 38.3 (Table 4, page 54).
Interfacial bond: $\tau_0$ increased by 22% (from 2.43 to 2.96 MPa).
PSH performance indices: $J_b'/J_{tip} = 1.39$, $\sigma_0/\sigma_{fc} = 1.83$.

Linked Atlas nodes

02_concepts/interface_properties.md
02_concepts/strain_hardening_criteria.md
04_material_systems/green_ecc.md
05_experiments/direct_tensile_test.md

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`02_concepts/interface_properties.md`	CNF coating on PE fibers increases interfacial frictional bond by 22% in UHPC matrix without chemical fiber damage.	Single fiber pullout showed $\tau_0$ increased from 2.43 to 2.96 MPa due to nano-pore filling and nano-bridging by CNFs.	Pages 50, 54, Section 3.2, Table 4	verified_from_pdf
`02_concepts/strain_hardening_criteria.md`	CNF-SHUHPC achieves compressive strength >150 MPa, tensile strength of 15.0 MPa, and tensile ductility of 2.3% with crack widths of 71 $\mu\text{m}$.	CNF-SHUHPC reached $f_c = 153\text{ MPa}$, $\sigma_{tu} = 15.0\text{ MPa}$, and $\varepsilon_{tu} = 2.3\%$.	Page 54, Table 4, Fig. 6	verified_from_pdf

Verification status

PDF preserved: yes (he-2017-strain-hardening-ultra-high-performance-concrete.pdf)
Text extracted: yes (atlas/full_text/he-2017-strain-hardening-ultra-high-performance-concrete_full_text.md)
DOI verified: yes (10.1016/j.cemconres.2017.04.003)
Page/figure/table verified: yes
Claim-evidence matrix ready: yes

Cautions

Distinguish high-strength UHP-ECC ductility (2.3%) from low-strength extreme ductility systems (>8%).
Uniform dispersion of CNF suspension in water is required for consistent coating.