Lee et al. (2012) — Strain Hardening Fiber Reinforced Alkali-Activated Mortar: A Feasibility Study

Citation

Lee, B. Y., Cho, C.-G., Lim, H.-J., Song, J.-K., Yang, K.-H., & Li, V. C. (2012). Strain hardening fiber reinforced alkali-activated mortar – A feasibility study. Construction and Building Materials, 37, 15–20.

• DOI: 10.1016/j.conbuildmat.2012.06.007
• Atlas layer: foundational
• Related Victor Li book chapter: Chapter 9: Green ECC (Alkali-Activated Slag Composites, pp. 235–265)
• Source PDF: lee-2012-strain-hardening-cementless.pdf
• Extracted text: full_text/lee-2012-strain-hardening-cementless_full_text.md
• Source note: source_notes/lee-2012-strain-hardening-cementless_source_note.md

Why this paper matters

The landmark pioneer study co-authored with Victor C. Li that first demonstrated the feasibility of achieving pseudo strain-hardening (PSH) in zero-cement alkali-activated slag (AAS) mortar, attaining direct tensile strain capacities up to 4.48 % (up to 4.7 % in peak specimens) and establishing the foundation for modern Green ECC and EGC research.

Main contribution

• Proves for the first time that zero-clinker slag-based cementless mortars activated by ambient solid powder activators ($\text{Ca(OH)}_2 + \text{Na}_2\text{SO}_4$ or $\text{Na}_2\text{SiO}_3$) can achieve steady-state multiple cracking with 2.0 vol. % PVA fibers.
• Formulates three mixture compositions (M1, M2, M3) optimized for rheological workability and uniform fiber dispersion ($w/b = 0.35\text{--}0.40, S/B = 0.40$).
• Measures mechanical performance via density tests, ASTM C109 cube compression, JSCE uniaxial dogbone direct tension, and thin-panel four-point bending tests.
• Delivers direct tensile strain capacities ranging from 1.53 % to 4.48 % (compared to 0.020 % for unreinforced matrix), ultimate tensile strengths of 2.83 to 4.69 MPa, and compressive strengths of 21.0 to 30.6 MPa.
• Demonstrates saturated multiple cracking with self-controlled crack widths ($< 60\ \mu\text{m}$) and ductile load-deflection plateaus in thin structural panels.

Evidence summary

• Precursor & Activators:
• 100 % GGBFS (Blaine $4204\text{ cm}^2/\text{g}$, specific gravity 2.93).
• Activators: Solid $\text{Ca(OH)}_2 + \text{Na}_2\text{SO}_4$ (M1, M2) vs. $\text{Ca(OH)}_2 + \text{Na}_2\text{SiO}_3$ (M3).
• Aggregate: Micro silica sand ($d_{50} = 100\ \mu\text{m}, S/B = 0.40$).
• Water-to-binder ratios: $w/b = 0.35$ (M1) and $0.40$ (M2, M3).
• Fiber Specifications: 2.0 vol. % Kuraray REC15 PVA fiber ($l_f = 12\text{ mm}, d_f = 39\ \mu\text{m}, \sigma_f = 1600\text{ MPa}, E_f = 41\text{ GPa}$, oil coating 1.2 wt%).
• Mechanical Properties (28-day water cured):
• Compressive strength: M1 = 30.6 MPa; M2 = 23.5 MPa; M3 = 21.0 MPa.
• Direct tensile strain capacity ($\epsilon_u$): M1 = $1.53 \pm 0.32\%$; M2 = $2.41 \pm 0.45\%$; M3 = $4.48 \pm 0.58\%$ (peak sample 4.70 %).
• Ultimate tensile strength ($\sigma_u$): M1 = 4.69 MPa; M2 = 3.65 MPa; M3 = 2.83 MPa.
• Panel flexural behavior: Extreme deflection-hardening and dense multiple cracking across 10 mm thin plates.

Linked Atlas nodes

• 02_concepts/strain_hardening_criteria.md
• 04_material_systems/geopolymer_ecc.md
• 04_material_systems/green_ecc.md
• 04_material_systems/pva_ecc.md
• 05_experiments/direct_tensile_test.md
• 05_experiments/flexural_testing.md
• 02_concepts/circular_economy_materials.md

Relationship to Victor Li book

• Serves as the primary foundational reference cited in Victor Li (2019) Chapter 9 (Green ECC, pp. 235–265).
• Proves that the micromechanical PSH design theory formulated by Victor Li is fully applicable to cement-free alkali-activated industrial slag binders, establishing the historical benchmark for green strain-hardening composites.

Claim-evidence rows to add

Verification status

• PDF preserved: yes (lee-2012-strain-hardening-cementless.pdf)
• Text extracted: yes (full_text/lee-2012-strain-hardening-cementless_full_text.md)
• DOI verified: yes (10.1016/j.conbuildmat.2012.06.007)
• Metadata verified: yes (CBM, Vol. 37, pp. 15–20, 2012)
• Claim-evidence matrix ready: yes

Cautions

• M3 mix achieves highest tensile ductility (4.48 %) but has lower compressive strength (21.0 MPa); M1 achieves higher strength (30.6 MPa) with lower ductility (1.53 %).
• Solid activator dissolution kinetics require high mixing energy to ensure complete chemical activation.