Kan et al. (2020) — Development and Characterization of Fly Ash Based PVA Fiber Reinforced Engineered Geopolymer Composites Incorporating Metakaolin

Citation

Kan, L.-L., Wang, W.-S., Liu, W.-D., & Wu, M. (2020). Development and characterization of fly ash based PVA fiber reinforced Engineered Geopolymer Composites incorporating metakaolin. Cement and Concrete Composites, 108, 103521.

DOI: 10.1016/j.cemconcomp.2020.103521
Atlas layer: core
Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 5: Multiple Cracking & Chapter 9: Green ECC (Fly Ash/Metakaolin Geopolymers)
Source PDF: kan-2020-development-and-characterization-of.pdf
Extracted text: full_text/kan-2020-development-and-characterization-of_full_text.md
Source note: source_notes/kan-2020-development-and-characterization-of_source_note.md

Why this paper matters

Applies the Taguchi orthogonal optimization method to micromechanically tailor Fly Ash/Metakaolin PVA-EGC, achieving early-age tensile ductility up to 6.8 % (3-day) and 5.2 % (28-day) with saturated microcracking ($w_m \approx 25\ \mu\text{m}$) and proving rigorous satisfaction of both the PSH strength and energy criteria in zero-cement geopolymer matrices.

Main contribution

Utilizes the Taguchi orthogonal experimental method to optimize four key mixture parameters: Metakaolin content, liquid-to-solid ratio ($L/S$), alkaline activator modulus ($M_s$), and sand-to-binder ratio ($S/B$) in PVA-reinforced geopolymer composites.
Achieves high tensile ductility across early and mature ages: 6.8 % at 3 days, 6.4 % at 7 days, and 5.2 % at 28 days ($\sigma_u = 4.25\text{ MPa}$, $f_c = 41.2\text{ MPa}$).
Produces ultra-tight saturated micro-cracking: average crack width is restricted to only ~25 $\mu\text{m}$ with crack spacings of 2–5 mm.
Verifies micromechanical PSH criteria through single-crack tensile tests and notched beam fracture toughness tests ($K_m$), confirming $J_b'/J_{tip} \ge 3.0$ and $\sigma_0/\sigma_{fc} \ge 1.25$.
Confirms via XRD, FT-IR, and SEM that the matrix is dominated by 3D amorphous N-A-S-H aluminosilicate network gel.

Evidence summary

Material Matrix: Class F Fly Ash + Metakaolin (5–15 wt% substitution) activated by liquid sodium silicate ($\text{Na}_2\text{SiO}_3 + \text{NaOH}$, $M_s = 1.2\text{--}1.5$).
Aggregate: Micro-silica sand ($S/B = 0.30\text{--}0.36$).
Fiber Specifications: 2.0 vol. % Kuraray REC15 PVA fiber ($l_f = 12\text{ mm}, d_f = 39\ \mu\text{m}, \sigma_f = 1600\text{ MPa}, E_f = 42\text{ GPa}$).
Mechanical Properties:
Compressive strength: 38.5 to 44.2 MPa (28-day).
Uniaxial direct tensile strain capacity ($\epsilon_u$): 6.8 % (3d), 6.4 % (7d), 5.2 % (28d).
Ultimate tensile strength ($\sigma_u$): 3.8 to 4.5 MPa.
Saturated crack width: average $w_m \approx 25\ \mu\text{m}$.
Micromechanical PSH Metrics:
Matrix fracture toughness: $K_m = 0.35\text{--}0.48\text{ MPa}\cdot\text{m}^{1/2}$.
Crack tip toughness: $J_{tip} = 0.008\text{--}0.015\text{ kJ/m}^2$.
Complementary energy: $J_b' = 0.045\text{--}0.072\text{ kJ/m}^2$.
Energy margin: $J_b'/J_{tip} = 3.2\text{--}6.8 \ge 3.0$.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
02_concepts/fiber_bridging_law.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
02_concepts/matrix_fracture_toughness.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (PSH Criteria) and Chapter 9 (Green ECC).
Demonstrates how the micromechanical design framework established by Victor Li is fully transferable to multi-precursor geopolymer systems (FA + Metakaolin), allowing systematic optimization of interfacial chemical/frictional bonds to produce ultra-tight crack widths ($25\ \mu\text{m}$).

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/geopolymer_ecc.md`	Optimal MFA-EGC achieves direct tensile ductility of 6.8 % (3d) and 5.2 % (28d) with average crack width of 25 µm	Uniaxial tensile testing on JSCE dogbone specimens across ages (3, 7, 28 days)	Section 3.1 & 3.2, Fig. 5-7, Table 4	verified_from_pdf
`02_concepts/strain_hardening_criteria.md`	MFA-EGC satisfies PSH criteria with $J_b'/J_{tip} \ge 3.0$ and $\sigma_0/\sigma_{fc} \ge 1.25$	Single-crack tensile test and pre-notched three-point bending fracture toughness tests	Section 3.3, Fig. 8-10, Table 5	verified_from_pdf

Verification status

PDF preserved: yes (kan-2020-development-and-characterization-of.pdf)
Text extracted: yes (full_text/kan-2020-development-and-characterization-of_full_text.md)
DOI verified: yes (10.1016/j.cemconcomp.2020.103521)
Metadata verified: yes (Cement and Concrete Composites, Vol. 108, 103521, 2020)
Claim-evidence matrix ready: yes

Cautions

Metakaolin dosages exceeding 15 wt% increase matrix fracture toughness ($K_m$) excessively, degrading the energy margin $J_b'/J_{tip}$ and reducing tensile ductility.
Liquid sodium silicate activators require strict dosage control to avoid rapid setting and rheology loss during casting.