Nguyễn et al. (2023) — Activator Pretreatment Micromechanics of 18.6 % Ductile Geopolymer Composite

Citation

Huy Hoàng Nguyễn, Quang-Hiếu Lương, Phương Hoàng Nguyễn, Hyeong-Ki Kim, Youngsang Kim, Bang Yeon Lee (2023). Micromechanical and mineralogy analyses on extremely ductile engineered geopolymer composites with different activator pretreatments. Journal of Building Engineering, 80, 108093.

• DOI: 10.1016/j.jobe.2023.108093
• Atlas layer: extension
• Related Victor Li book chapter: Chapter 4: Micromechanics-Based Material Design & Chapter 9: Green ECC
• Source PDF: primary_data/nguyen-2023-micromechanical-and-mineralogy-analyses-on.pdfIJP07723E_Micromechanical and mineralogy_JBE.pdf`
• Extracted text: secondary_data/full_texts/nguyen-2023-micromechanical-and-mineralogy-analyses-on_full_text.mdsecondary_data/full_texts/IJP07723E_Micromechanical and mineralogy_JBE_full_text.md`
• Source note: secondary_data/source_notes/nguyen-2023-micromechanical-and-mineralogy-analyses-on_source_note.mdsecondary_data/source_notes/IJP07723E_Micromechanical and mineralogy_JBE_source_note.md`

Why this paper matters

Discovers an activator pretreatment conditioning mechanism in fly ash-based geopolymer composites (ED-EGC, 1.75 vol. % PE fiber). Cooling pretreatment (CP, 24 h at 23 °C) lowers matrix fracture toughness ($K_m = 0.06\text{ MPa}\cdot\text{m}^{1/2}$) and crack tip toughness ($J_{tip} = 0.62\text{ J/m}^2$) to achieve an unprecedented $18.62 \pm 1.59\text{ \%}$ direct tensile strain capacity with an energy performance index ($PSHE = 817.2$) 303 times higher than the design threshold, surpassing the ductility of structural steel rebars.

Main contribution

• Record 18.6 % Direct Tensile Strain Capacity: Cooling pretreated composite (ED-EGC-CP) achieved $\epsilon_{sc} = \mathbf{18.62 \pm 1.59\text{ \%}}$, $f_{ts} = 5.54\text{ MPa}$, and $f_c = 20.7\text{ MPa}$ ($\rho = 1.46\text{ g/cm}^3$).
• Activator Pretreatment Conditioning: Proved warming pretreatment (WP, 50 °C for 5 min) yields dense N-A-S-H with higher strength ($f_c = 31.1\text{ MPa}, f_{ts} = 8.72\text{ MPa}, \epsilon_{sc} = 10.97\text{ \%}$), while cooling pretreatment (CP, 23 °C for 24 h) prioritizes extreme ductility.
• PSH Micromechanical Validation: Single crack and notched beam tests confirmed $J_{tip} = 0.62\text{ J/m}^2$ and $J_b' = 57.52\text{ J/m}^2$, driving $PSHE = \mathbf{817.2}$ (CP) and $PSHE = \mathbf{452.4}$ (WP), with EDS identifying N-A-S-H gel as the governing reaction matrix.

Evidence summary

• Density & Compressive Strength:
• ED-EGC-WP: $\rho = 1.64\text{ g/cm}^3$, $f_c = 31.1\text{ MPa}$ (Table 1, Fig. 8, Pages 3 & 8).
• ED-EGC-CP: $\rho = 1.46\text{ g/cm}^3$, $f_c = 20.7\text{ MPa}$ (Structural lightweight).
• Direct Uniaxial Tensile Performance:
• ED-EGC-CP: $\epsilon_{sc} = \mathbf{18.62 \pm 1.59\text{ \%}}$ (18.6 %), $f_{ts} = 5.54 \pm 0.10\text{ MPa}$, $f_{cs} = 3.40\text{ MPa}$, $U_t = 0.83\text{ MPa}\cdot\text{m/m}$, 72.8 cracks ($w_c = 199.3\ \mu\text{m}, s_c = 1.07\text{ mm}$) (Table 4 & Figs. 9–11, Pages 5, 8–10).
• ED-EGC-WP: $\epsilon_{sc} = 10.97 \pm 1.31\text{ \%}$, $f_{ts} = 8.72 \pm 0.76\text{ MPa}$, $f_{cs} = 4.67\text{ MPa}$, $U_t = 0.73\text{ MPa}\cdot\text{m/m}$, 50.0 cracks ($w_c = 171.8\ \mu\text{m}, s_c = 1.57\text{ mm}$).
• Micromechanical PSH Metrics:
• Matrix properties: $K_m = 0.06\text{ MPa}\cdot\text{m}^{1/2}, J_{tip} = 0.62\text{ J/m}^2$ for CP vs $K_m = 0.11, J_{tip} = 1.25\text{ J/m}^2$ for WP (Table 6, Page 10).
• Performance Indices: $PSHE = \mathbf{817.2}$ for CP vs $\mathbf{452.4}$ for WP; $PSHS = 1.63$ vs $1.87$ (Table 7, Page 10).
• Morphology & Mineralogy:
• Pure fiber pullout failure observed under SEM/BSE (Fig. 12, Page 11).
• EDS elemental mapping and ternary phase diagram confirmed N-A-S-H gel as primary matrix product (Figs. 13–14, Pages 12–13).

Linked Atlas nodes

• 02_concepts/strain_hardening_criteria.md
• 02_concepts/flaw_design.md
• 04_material_systems/green_ecc.md
• 04_material_systems/lightweight_ecc.md
• 05_experiments/direct_tensile_test.md

Relationship to Victor Li book

• Primary book anchor remains Victor Li (2019), Engineered Cementitious Composites (ECC).
• Directly extends Chapter 4 (Micromechanics-Based Material Design) and Chapter 5 (PSH Criteria) by demonstrating that alkali activator thermal conditioning directly tailors matrix fracture toughness ($K_m = 0.06\text{ MPa}\cdot\text{m}^{1/2}$), driving $PSHE$ to 817.2 and realizing a record 18.62 % direct tensile strain capacity in a 100 % fly ash geopolymer.

Claim-evidence rows to add

Verification status

• PDF preserved: yes (in primary_data/IJP07723E_Micromechanical and mineralogy_JBE.pdf)
• Text extracted: yes (PyMuPDF, 15 pages)
• DOI verified: yes (10.1016/j.jobe.2023.108093)
• Page/figure/table verified: yes (all checked in PDF text)
• Claim-evidence matrix ready: yes

Cautions

• Cooling pretreated mixture requires high SP dosage (0.037) and 5 d initial curing before demolding.
• Compressive strength of CP is modest ($20.7\text{ MPa}$) compared to WP ($31.1\text{ MPa}$).