Lao et al. (2023) — Strain-hardening alkali-activated fly ash/slag composites with ultra-high...

Citation

Jian-Cong Lao, Bo-Tao Huang, Yi Fang, Ling-Yu Xu, Jian-Guo Dai, Surendra P. Shah (2023). Strain-hardening alkali-activated fly ash/slag composites with ultra-high compressive strength and ultra-high tensile ductility. Cement and Concrete Research, Vol. 165, Article 107075.

DOI: 10.1016/j.cemconres.2022.107075
Atlas layer: breakthrough
Related Victor Li book chapter: Chapter 3: Micro-mechanics; Chapter 4: Ultra-High Strength ECC / Geopolymers
Source PDF: lao-2023-strain-hardening-alkali-activated-fly-ash-slag-composites.pdf
Extracted text: atlas/full_text/lao-2023-strain-hardening-alkali-activated-fly-ash-slag-composites_full_text.md
Source note: atlas/source_notes/lao-2023-strain-hardening-alkali-activated-fly-ash-slag-composites_source_note.md

Why this paper matters

Landmark breakthrough in sustainable cementitious composites achieving an unprecedented combination of ultra-high compressive strength (up to 180.7 MPa) and ultra-high tensile ductility (8.1–9.9%) with peak tensile strength of 15.9 MPa in 100% cement-free alkali-activated composites (SH-AAFSC), discovering that fiber bridging scales linearly with matrix elastic modulus.

Main contribution

Overcame the universal strength-ductility trade-off in geopolymers, reaching $180.7\text{ MPa}$ compressive strength with $9.1\%$ ductility and $15.9\text{ MPa}$ tensile strength in F2S8–0.22, and $9.9\%$ ductility in F2S8–0.27.
Applied modified Andreasen & Andersen continuous particle packing to ternary precursors (FA + GGBS + 5% SF) with $w/p = 0.22\text{--}0.27$.
Discovered and validated that peak fiber-bridging capacity ($\sigma_0$) is directly proportional to the nanoindentation-derived matrix elastic modulus ($E_m$).

Evidence summary

Compressive strength: Spans $94.4\text{ to }180.7\text{ MPa}$; F2S8–0.22 achieved $180.7 \pm 3.5\text{ MPa}$, close to zero-porosity theoretical limit (Table 4, page 9, Fig. 3).
Direct tensile properties:
F2S8–0.22: $\sigma_{tc} = 8.9\text{ MPa}$, $\sigma_{tu} = 15.9 \pm 1.0\text{ MPa}$, $\varepsilon_{tu} = 9.1 \pm 0.3\%$, $w = 109.0\ \mu\text{m}$.
F2S8–0.27: $\sigma_{tc} = 5.9\text{ MPa}$, $\sigma_{tu} = 12.0 \pm 0.6\text{ MPa}$, $\varepsilon_{tu} = 9.9 \pm 0.5\%$, $w = 122.5\ \mu\text{m}$.
F8S2–0.22: $\sigma_{tu} = 14.5\text{ MPa}$, $\varepsilon_{tu} = 8.8\%$; F8S2–0.27: $\sigma_{tu} = 11.2\text{ MPa}$, $\varepsilon_{tu} = 9.5\%$ (Table 4, page 9, Figs. 13, 14).
Microstructural & nanomechanical evidence: BSE-EDS, TGA, and 242-point grid nanoindentation proved that GGBS increases C(N)ASH $Ca/Si$ ratio and matrix modulus, which linearly amplifies fiber bridging clamping.

Linked Atlas nodes

04_material_systems/high_strength_ecc.md
02_concepts/extreme_ductility_ecc.md
02_concepts/strain_hardening_criteria.md
05_experiments/direct_tensile_test.md

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/high_strength_ecc.md`	SH-AAFSC achieves 180.7 MPa compressive strength, 15.9 MPa tensile strength, and 9.1–9.9% tensile ductility with 2.0 vol% PE fibers under heat curing.	ASTM C109 compression and JSCE direct tension tests verified 180.7 MPa compressive strength and 15.9 MPa tensile strength.	Pages 1, 9, Section 3.1 & 4.1, Table 4, Figs. 3, 13	verified_from_pdf
`02_concepts/strain_hardening_criteria.md`	Fiber bridging capacity in ultra-high-strength geopolymers scales linearly with the average matrix elastic modulus obtained from nanoindentation.	Multi-scale single-crack tests and grid nanoindentation verified linear dependency between bridging stress and matrix modulus.	Pages 1, 12, Section 5.1 & Abstract, Fig. 18, Eq. 4	verified_from_pdf

Verification status

PDF preserved: yes (lao-2023-strain-hardening-alkali-activated-fly-ash-slag-composites.pdf)
Text extracted: yes (atlas/full_text/lao-2023-strain-hardening-alkali-activated-fly-ash-slag-composites_full_text.md)
DOI verified: yes (10.1016/j.cemconres.2022.107075)
Page/figure/table verified: yes
Claim-evidence matrix ready: yes

Cautions

Attained using 72 h heat curing at 80 °C; ambient-cured formulations achieve ~143 MPa (Lao et al. 2023 CCC).