Ohno & Li (2014) — A Feasibility Study of Strain Hardening Fiber Reinforced Fly Ash-Based Geopolymer Composites
Citation
Ohno, M., & Li, V. C. (2014). A feasibility study of strain hardening fiber reinforced fly ash-based geopolymer composites. Construction and Building Materials, 57, 163–168.
- DOI:
10.1016/j.conbuildmat.2014.02.005 - Atlas layer: core
- Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 7: Polyvinyl Alcohol (PVA) Fibers & Chapter 9: Green ECC (Engineered Geopolymer Composites, pp. 307–342)
- Source PDF:
ohno-2014-a-feasibility-study-of-strain.pdf - Extracted text:
full_text/ohno-2014-a-feasibility-study-of-strain_full_text.md - Source note:
source_notes/ohno-2014-a-feasibility-study-of-strain_source_note.md
Why this paper matters
The historic genesis paper by Victor C. Li and Motohiro Ohno establishing the foundational proof-of-concept for Engineered Geopolymer Composites (EGC), demonstrating that micromechanics-based design enables 100 % fly ash geopolymer binders to achieve robust pseudo strain-hardening with $> 4.3\%$ direct tensile ductility and tight microcrack widths ($w_m = 45\ \mu\text{m}$) via DIC full-field measurement.
Main contribution
- Establishes the feasibility of pseudo strain-hardening (PSH) in zero-cement, Class F fly ash geopolymer matrices reinforced with 2.0 vol. % oiled PVA fibers.
- Solves setting time control in fly ash geopolymers by blending two distinct Class F fly ashes (0.8:0.2 ratio) to achieve optimal hardening kinetics and fiber dispersion.
- Demonstrates that thermal curing (60 °C for 24 h) promotes geopolymerization, yielding an ultimate tensile strain capacity of 4.30 % with $f_c = 27.6\text{ MPa}$ and $\sigma_u = 3.60\text{ MPa}$.
- Utilizes Digital Image Correlation (DIC) to track full-field crack initiation and opening, proving that saturated steady-state microcracking maintains average crack widths below $45\ \mu\text{m}$ (maximum $117\ \mu\text{m}$) even at 4.5 % strain.
Evidence summary
- Binder Formulation: Binary Class F Fly Ash (Fly Ash A: $1.3\%\ \text{CaO}$; Fly Ash B: $12.9\%\ \text{CaO}$ in 0.8:0.2 ratio), activated by $\text{Na}2\text{SiO}_3$ solution ($8.9\%\ \text{Na}_2\text{O}, 28.7\%\ \text{SiO}_2$) + $\text{NaOH}$ pellets + silica sand ($d, S/B = 0.30$), $w/b = 0.32$.} = 110\ \mu\text{m
- Fiber Specifications: PVA fibers (Kuraray K-II REC15, 2.0 vol. %, $l_f = 12\text{ mm}, d_f = 39\ \mu\text{m}, \sigma_f = 1600\text{ MPa}, E_f = 42.8\text{ GPa}$, 1.2 wt% oil coating).
- Curing Regimes:
RT Curing: Ambient room temperature ($23\ ^\circ\text{C}$).Heat Curing: 60 °C for 24 hours in sealed containers followed by ambient air storage.- Mechanical & Cracking Performance:
- Compressive strength: $f_c = 27.6\text{ MPa}$ (60 °C heat cured) vs. $13.5\text{ MPa}$ (room temperature cured).
- First cracking strength: $\sigma_{fc} = 2.10\text{ MPa}$.
- Ultimate tensile strength: $\sigma_u = \mathbf{3.60\text{ MPa}}$.
- Direct tensile strain capacity: $\epsilon_u = \mathbf{4.30\%}$ (with individual specimens reaching $> 4.8\%$).
- DIC Crack Pattern: Over 30 multiple microcracks across the 80 mm gauge length; average crack width $w_m = \mathbf{45\ \mu\text{m}}$ at $\epsilon = 4.5\%$.
Linked Atlas nodes
02_concepts/strain_hardening_criteria.md04_material_systems/geopolymer_ecc.md04_material_systems/green_ecc.md04_material_systems/pva_ecc.md05_experiments/direct_tensile_test.md05_experiments/digital_image_correlation.md02_concepts/life_cycle_analysis.md
Relationship to Victor Li book
- Serves as the primary reference for Victor Li (2019) Chapter 9: Green ECC (Section on Fly Ash Geopolymer ECC, pp. 307–342).
- The historical milestone paper that transitioned ECC micromechanics from Portland cement hydration to alkali-activated aluminosilicate geopolymerization.
Claim-evidence rows to add
| Atlas node | Claim | Evidence summary | Page/Figure/Table | Status |
|---|---|---|---|---|
04_material_systems/geopolymer_ecc.md |
Fly ash-based PVA-EGC achieves $> 4.3\%$ direct tensile ductility and 27.6 MPa compressive strength under 60 °C curing | Dogbone uniaxial tensile testing and cube compression tests | Section 3.1 & 3.2, Fig. 3 & 4, Table 4 | verified_from_pdf |
05_experiments/digital_image_correlation.md |
DIC analysis confirms fly ash PVA-EGC maintains average microcrack widths below $45\ \mu\text{m}$ at 4.5 % tensile strain | Digital Image Correlation full-field strain and crack opening displacement mapping | Section 3.3, Fig. 5-8 | verified_from_pdf |
Verification status
- PDF preserved: yes (
ohno-2014-a-feasibility-study-of-strain.pdf) - Text extracted: yes (
full_text/ohno-2014-a-feasibility-study-of-strain_full_text.md) - DOI verified: yes (
10.1016/j.conbuildmat.2014.02.005) - Metadata verified: yes (CBM, Vol. 57, pp. 163–168, 2014)
- Claim-evidence matrix ready: yes
Cautions
- Mono-source Class F fly ashes may suffer from either delayed hardening (low CaO) or flash setting (high CaO); binary fly ash blending is recommended.
- Heat curing (60 °C for 24 h) is necessary for this specific alkali activator formulation to achieve mature geopolymerization within 28 days.