Li, Wang & Wu (2001) — Tensile Strain-Hardening of PVA-ECC

Citation

Li, Victor C., Wang, Shuxin, & Wu, Cynthia (2001). Tensile strain-hardening behavior of polyvinyl alcohol engineered cementitious composite (PVA-ECC). ACI Materials Journal, 98(6), 483-492.

DOI: 10.14359/10849
Atlas layer: supporting
Related Victor Li book chapter: Chapter 3 (Fiber/Matrix Interface), Chapter 4 (Materials Design), Chapter 7 (PVA-ECC Material System)
Source PDF: li-2001-tensile-strain-hardening-behavior-of-polyvinyl.pdf
Extracted text: atlas/full_text/li-2001-tensile-strain-hardening-behavior-of-polyvinyl_full_text.md
Source note: atlas/source_notes/li-2001-tensile-strain-hardening-behavior-of-polyvinyl_source_note.md

Why this paper matters

This paper is the seminal breakthrough study that created practical, cost-effective PVA-ECC. By discovering that a 0.8 wt% oil coating successfully tailors the hydrophilic PVA fiber surface (reducing chemical bond $G_d$ from 5.0 to 2.0 $\text{J/m}^2$), it unlocked $>4\%$ tensile ductility and tight crack widths ($<100\ \mu\text{m}$) at a low fiber volume fraction of $2.0\text{--}2.5\%$, paving the way for worldwide commercial adoption of ECC.

Main contribution

Fiber Surface Tailoring Technology: Engineered an oiling surface coating (0.8 wt%) on Kuraray REC PVA fibers to suppress excessive chemical bonding and avoid catastrophic fiber rupture.
Complementary Bridging Energy Escalation: Demonstrated a 33-fold increase in complementary bridging energy ($J_b'$ from 0.5 to $16.5\text{ J/m}^2$), providing a robust margin over matrix toughness $J_{tip}$ ($3.2\text{--}4.7\text{ J/m}^2$).
High Ductility & Saturated Multiple Cracking: Achieved tensile strain capacity of $4.59 \pm 0.36\%$ (peak 5.2%), tensile strength $4.5\text{--}5.0\text{ MPa}$, and crack spacing down to $1.8\text{ mm}$ at $V_f = 2.0\text{--}2.5\%$.
Crack Width Stabilization: Proved that crack openings self-stabilize below $100\ \mu\text{m}$ (typically $\approx 60\ \mu\text{m}$) throughout the strain-hardening phase.

Evidence summary

Interfacial bond tuning: 0.8% oiling reduces $G_d$ to $2.0\text{ J/m}^2$ and $\tau_0$ to $2.0\text{ MPa}$, boosting $J_b'$ to $16.5\text{ J/m}^2$ (Page 490, Table 4).
Direct tensile curves: Demonstrates clear pseudo strain hardening with $\varepsilon_{cu} > 4\%$ across mixtures with 0.8% oiled fibers (Pages 487-488, Table 3, Fig. 7).
Crack width evolution: Videomicroscopy reveals crack width stabilizing at $\approx 60\ \mu\text{m}$ (Page 489, Fig. 8).
SEM fracture morphology: Shows long fiber pull-out ($\sim 2\text{ mm}$) for 0.8% oiled PVA vs clean fiber rupture ($<0.2\text{ mm}$) for uncoated PVA (Page 491, Fig. 12).

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
02_concepts/interface_properties.md
02_concepts/fiber_bridging_law.md
05_experiments/direct_tensile_test.md
05_experiments/crack_width_distribution.md

Relationship to Victor Li book

Primary foundation for Chapters 3, 4, and 7 of the 2019 book, establishing the micromechanical basis for the standard M45 PVA-ECC mixture.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`02_concepts/interface_properties.md`	0.8 wt% oil coating reduces chemical bond $G_d$ from 5.0 to 2.0 $\text{J/m}^2$ and $\tau_0$ from 3.5 to 2.0 MPa in PVA fibers, suppressing rupture.	Single fiber pullout and interfacial characterization.	Pages 489-491, Table 4, Figs. 11, 12	verified_from_pdf
`02_concepts/strain_hardening_criteria.md`	Surface oiling elevates $J_b'$ to 16.5 $\text{J/m}^2$, vastly exceeding $J_{tip}$ (3.2-4.7 $\text{J/m}^2$) and satisfying steady-state cracking.	Comparison of $J_b'$ and $J_{tip}$ across oiled and uncoated PVA composites.	Page 490, Table 4, Fig. 11	verified_from_pdf
`05_experiments/direct_tensile_test.md`	PVA-ECC with 2.0-2.5 vol% tailored fibers exhibits tensile strain capacity $>4\%$ (up to 5.2%) and tensile strength 4.5-5.0 MPa.	Uniaxial direct tension tests on dogbone coupons.	Pages 487-488, Table 3, Figs. 5-7	verified_from_pdf
`05_experiments/crack_width_distribution.md`	PVA-ECC crack widths self-stabilize below 100 $\mu$m (typically $\approx 60\ \mu$m) under increasing tensile deformation.	In situ videomicroscopy measurement during tensile straining.	Pages 487, 489, Table 3, Fig. 8	verified_from_pdf

Verification status

PDF preserved: yes (li-2001-tensile-strain-hardening-behavior-of-polyvinyl.pdf)
Text extracted: yes (atlas/full_text/li-2001-tensile-strain-hardening-behavior-of-polyvinyl_full_text.md)
DOI verified: yes (10.14359/10849)
Page/figure/table verified: yes (Pages 483-492, Tables 1-4, Figs. 1-12 verified from PDF)
Claim-evidence matrix ready: yes

Cautions

Sand particle size must be strictly controlled ($d_{50} \le 110\ \mu\text{m}$) to prevent excessive matrix fracture toughness.