Nguyễn et al. (2019) — Mechanical Properties and Self-Healing Capacity of Eco-Friendly Ultra-High Ductile Fiber-Reinforced Slag-Based Composites

Citation

Nguyễn, H. H., Choi, J.-I., Kim, H.-K., & Lee, B. Y. (2019). Mechanical properties and self-healing capacity of eco-friendly ultra-high ductile fiber-reinforced slag-based composites. Composite Structures, 229, 111401.

DOI: 10.1016/j.compstruct.2019.111401
Atlas layer: core
Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 7: Alternative Reinforcing Fibers (PE Fibers) & Chapter 10: Durability and Autogenous Self-Healing (pp. 343–384)
Source PDF: nguyn-2019-mechanical-properties-and-self-healing-capacity.pdf
Extracted text: full_text/nguyn-2019-mechanical-properties-and-self-healing-capacity_full_text.md
Source note: source_notes/nguyn-2019-mechanical-properties-and-self-healing-capacity_source_note.md

Why this paper matters

A landmark study from Chonnam National University revealing the distinct autogenous self-healing chemistry of ultra-high ductile alkali-activated slag (AAS) composites across different activators: demonstrating that sodium silicate activation drives C-(N)-A-S-H gel recrystallization with high stiffness recovery (72 %), whereas calcium hydroxide activation produces calcite ($\text{CaCO}_3$) precipitation.

Main contribution

Formulates eco-friendly ultra-high ductile alkali-activated slag composites (AAS-PE) comparing three single activators: $\text{Ca(OH)}_2$, $\text{NaOH}$, and $\text{Na}_2\text{SiO}_3$ (each at 10 wt% of GGBS, $w/b = 0.30$, 1.75 vol. % PE fibers).
Evaluates mechanical strength, direct tensile stress-strain behavior, surface crack closure kinetics via digital optical microscopy, and dynamic elastic modulus recovery via resonant frequency (RF) testing.
Discovers that $\text{Na}_2\text{SiO}_3$-activated slag composite achieves the highest mechanical strength ($f_c = 64.2\text{ MPa}, \sigma_u = 12.4\text{ MPa}, \epsilon_u = 6.2\%$) and superior stiffness recovery (72 %).
Identifies the chemical healing divergence via SEM-EDS: $\text{Ca(OH)}_2$-AAS heals predominantly via calcite ($\text{CaCO}_3$) crystal formation, whereas $\text{Na}_2\text{SiO}_3$-AAS heals via secondary C-(N)-A-S-H gel condensation.

Evidence summary

Material Formulations ($w/b = 0.30, V_f = 1.75\text{ vol. \%}$):
Ca-AAS: 100 % GGBFS + 10 wt% solid $\text{Ca(OH)}_2$.
Na-AAS: 100 % GGBFS + 10 wt% $\text{NaOH}$ solution.
Si-AAS: 100 % GGBFS + 10 wt% solid $\text{Na}_2\text{SiO}_3$.
Fiber Specifications: UHMWPE fibers ($l_f = 18\text{ mm}, d_f = 12\ \mu\text{m}, \sigma_f = 2700\text{ MPa}, E_f = 88\text{ GPa}$).
Mechanical Properties:
Si-AAS: $f_c = \mathbf{64.2\text{ MPa}}$, $\sigma_u = \mathbf{12.4\text{ MPa}}$, $\epsilon_u = \mathbf{6.20\%}$.
Ca-AAS: $f_c = 48.5\text{ MPa}$, $\sigma_u = 8.8\text{ MPa}$, $\epsilon_u = \mathbf{7.50\%}$.
Na-AAS: $f_c = 32.1\text{ MPa}$, $\sigma_u = 6.5\text{ MPa}$, $\epsilon_u = 4.80\%$.
Self-Healing Quantification (28-day water immersion):
Crack Healing Threshold: Complete sealing for cracks $w_m \le 50\ \mu\text{m}$.
Resonant Frequency Recovery: Si-AAS = 72 %, Ca-AAS = 60 %, Na-AAS = 52 %.
Microstructural Nature: SEM-EDS confirms Ca-AAS cracks fill with rhombohedral calcite crystals, while Si-AAS cracks fill with dense C-(N)-A-S-H gel fibers.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
04_material_systems/geopolymer_ecc.md
04_material_systems/green_ecc.md
04_material_systems/pe_ecc.md
05_experiments/direct_tensile_test.md
05_experiments/dynamic_modal_testing.md
02_concepts/durability.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (PSH Criteria), Chapter 7 (PE Fibers), and Chapter 10 (Durability and Autogenous Self-Healing).
Expands Victor Li's self-healing framework from cement hydration to alkali-activated slag systems, demonstrating that secondary aluminosilicate polymerization provides an effective alternative autogenous healing pathway.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`02_concepts/durability.md`	Sodium silicate-activated slag PE composite achieves 72 % resonant frequency recovery via secondary C-(N)-A-S-H gel crack filling	ASTM C215 dynamic resonant frequency testing and SEM-EDS analysis	Section 3.2 & 3.3, Fig. 6-10, Table 4	verified_from_pdf
`04_material_systems/green_ecc.md`	$\text{Na}_2\text{SiO}_3$-activated slag composite achieves 64.2 MPa compressive strength and 12.4 MPa tensile strength with 6.2 % ductility	Uniaxial direct tensile dogbone testing and ASTM C109 cube compression	Section 3.1, Fig. 4 & 5, Table 3	verified_from_pdf

Verification status

PDF preserved: yes (nguyn-2019-mechanical-properties-and-self-healing-capacity.pdf)
Text extracted: yes (full_text/nguyn-2019-mechanical-properties-and-self-healing-capacity_full_text.md)
DOI verified: yes (10.1016/j.compstruct.2019.111401)
Metadata verified: yes (Comp. Struct., Vol. 229, 111401, 2019)
Claim-evidence matrix ready: yes

Cautions

NaOH solution causes rapid flash setting if not pre-dissolved and cooled, and exhibits a strength regression after 14 days.
Complete autogenous healing is restricted to crack widths below $50\ \mu\text{m}$; microcrack width control via PSH micromechanics is mandatory.