Choi et al. (2020) — Micromechanics of Ductile Alkali-Activated Slag Composites

Citation

Jeong-Il Choi, Hyeong-Ki Kim, Bang Yeon Lee (2020). Mechanical and Fiber-Bridging Behavior of Slag-Based Composite with High Tensile Ductility. Applied Sciences, 10(12), 4300.

• DOI: 10.3390/app10124300
• Atlas layer: supporting
• Related Victor Li book chapter: Chapter 4: Micromechanics-Based Material Design (also Chapter 9 & Chapter 2)
• Source PDF: primary_data/choi-2020-mechanical-and-fiber-bridging-behavior-of.pdfIJP05420E_Micromechanics AAS_AppSci.pdf`
• Extracted text: secondary_data/full_texts/choi-2020-mechanical-and-fiber-bridging-behavior-of_full_text.mdsecondary_data/full_texts/IJP05420E_Micromechanics AAS_AppSci_full_text.md`
• Source note: secondary_data/source_notes/choi-2020-mechanical-and-fiber-bridging-behavior-of_source_note.mdsecondary_data/source_notes/IJP05420E_Micromechanics AAS_AppSci_source_note.md`

Why this paper matters

Provides the definitive experimental micromechanics and fiber-bridging validation for 100 % cement-free alkali-activated slag composites ($V_f=1.5\text{ vol. \%}$ PE), determining frictional bond $\tau_i = 1.49\text{ MPa}$, matrix fracture toughness $K_m = 0.34\text{ MPa}\cdot\text{m}^{1/2}$ ($J_{tip} = 11.3\text{ J/m}^2$), and complementary energy $J_b' = 100\text{ J/m}^2$, proving that $I_{EP} = 8.9$ and $I_{SP} = 2.5$ underpin its 7.5 % direct tensile ductility and 8.5 MPa tensile strength.

Main contribution

• Experimental Micromechanical Dataset: Measured $\tau_i = 1.49\text{ MPa}$, $G_i = 0\text{ J/m}^2$, $\beta_i = -0.06$, $K_m = 0.34\text{ MPa}\cdot\text{m}^{1/2}$, $E_m = 10.3\text{ GPa}$, and $J_{tip} = 11.3\text{ J/m}^2$.
• High-Fidelity Bridging Model: Numerically calculated $\sigma_{B,max} = 8.7\text{ MPa}$ and $J_b' = 100\text{ J/m}^2$, matching experimental tensile strength (8.5 MPa) within 2.3 % error.
• PSH Design Verification: Verified that $I_{EP} = 8.9$ (3.3x design target) and $I_{SP} = 2.5$ (2.0x target) explain the saturated multiple cracking (100 cracks, spacing 0.8 mm, width 59.8 $\mu\text{m}$) and $7.5 \pm 0.4\text{ \%}$ tensile strain capacity.

Evidence summary

• Direct Tensile Performance:
• $f_{ts} = 8.5 \pm 0.5\text{ MPa}$, $f_{1cs} = 3.4 \pm 1.1\text{ MPa}$, $\epsilon_u = 7.5 \pm 0.4\text{ \%}$, Toughness = $0.44\text{ MPa}\cdot\text{m/m}$ (Table 3 & Fig. 4, Page 5).
• Compressive Strength: $f_{cs} = 36.8 \pm 1.7\text{ MPa}$ (Table 3, Page 5).
• Crack Microstructure: 100 cracks in 80 mm gauge length, crack spacing 0.8 mm, average crack width $59.8\ \mu\text{m}$ (Table 4 & Fig. 5, Page 6).
• Micromechanical & PSH Values:
• $\tau_i = 1.49\text{ MPa}$, $\beta_i = -0.06$, $K_m = 0.34\text{ MPa}\cdot\text{m}^{1/2}$, $J_{tip} = 11.3\text{ J/m}^2$ (Table 5 & Fig. 7, Pages 7–8).
• $J_b' = 100\text{ J/m}^2$, $I_{EP} = 8.9$, $I_{SP} = 2.5$ (Table 7 & Fig. 9, Pages 9–10).

Linked Atlas nodes

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

Relationship to Victor Li book

• Primary book anchor remains Victor Li (2019), Engineered Cementitious Composites (ECC).
• Directly supports Chapter 4 (Micromechanics-Based Material Design) by confirming that Li's PSH steady-state cracking criteria and analytical bridging formulations rigorously hold for 100 % cement-free slag matrices.

Claim-evidence rows to add

Verification status

• PDF preserved: yes (in primary_data/IJP05420E_Micromechanics AAS_AppSci.pdf)
• Text extracted: yes (PyMuPDF, 12 pages)
• DOI verified: yes (10.3390/app10124300)
• Page/figure/table verified: yes (all checked in PDF text)
• Claim-evidence matrix ready: yes

Cautions

• Hydrophobic PE fibers have no chemical adhesion ($G_i=0$); the mechanism relies entirely on frictional interfacial shear stress ($\tau_i = 1.49\text{ MPa}$).