Lao et al. (2023) — Seawater sea-sand Engineered Geopolymer Composites (EGC)...

Citation

Jian-Cong Lao, Bo-Tao Huang, Ling-Yu Xu, Mehran Khan, Yi Fang, Jian-Guo Dai (2023). Seawater sea-sand Engineered Geopolymer Composites (EGC) with high strength and high ductility. Cement and Concrete Composites, Vol. 138, Article 104998.

DOI: 10.1016/j.cemconcomp.2023.104998
Atlas layer: extension
Related Victor Li book chapter: Chapter 4: Special ECCs / Geopolymers; Chapter 3: Micro-mechanics
Source PDF: lao-2023-seawater-sea-sand-engineered-geopolymer-composites.pdf
Extracted text: atlas/full_text/lao-2023-seawater-sea-sand-engineered-geopolymer-composites_full_text.md
Source note: atlas/source_notes/lao-2023-seawater-sea-sand-engineered-geopolymer-composites_source_note.md

Why this paper matters

Breakthrough paper establishing world-first high-strength, high-ductility seawater sea-sand Engineered Geopolymer Composites (SS-EGC) with 2.0 vol% PE fibers under ambient curing, achieving 143.0 MPa compressive strength, 11.9 MPa tensile strength, 6.9–8.1% tensile strain capacity, and ultra-tight 59.4 μm crack widths with superior sustainability over cement-based ECC.

Main contribution

Developed 100% cement-free SS-EGC using unwashed sea-sand and raw seawater with FA/GGBS precursors and borax retarder.
Achieved $143.0\text{ MPa}$ compressive strength and $11.9\text{ MPa}$ tensile strength in GGBS-dominated mixes (F2S8–S) and $8.1\%$ strain capacity in FA-dominated mixes (F8S2–S).
Discovered through TGA and nanoindentation that seawater ions promote hydrotalcite nanocrystals, increasing ultra-high-density phases and optimizing fiber/matrix frictional bond.

Evidence summary

Compressive strength: F2S8–S reached $143.0\text{ MPa}$ (only -1.5% vs freshwater counterpart); F8S2–S reached $84.5\text{ MPa}$ (Table 4, page 7, Fig. 6).
Direct tensile properties:
F2S8–S (UHS SS-EGC): $\sigma_{tu} = 11.9\text{ MPa}$, $\varepsilon_{tu} = 6.9\%$, $w_{avg} = 59.4\ \mu\text{m}$, $s_w = 15.7\ \mu\text{m}$.
F8S2–S (HD SS-EGC): $\sigma_{tu} = 9.0\text{ MPa}$, $\varepsilon_{tu} = 8.1\%$, $w_{avg} = 62.4\ \mu\text{m}$.
Comparison: Surpasses cement-based SS-ECC ($7.1\text{ MPa}$ tensile strength, $86.0\ \mu\text{m}$ crack width) by +67% higher tensile capacity (Table 4).
Sustainability: Substantially reduces embodied carbon to $0.278\text{ t }CO_2/\text{m}^3$ vs $0.803\text{ t }CO_2/\text{m}^3$ in cement SS-ECC.

Linked Atlas nodes

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

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/green_ecc.md`	Seawater sea-sand EGC (SS-EGC) achieves over 140 MPa compressive strength, 11.9 MPa tensile strength, and 6.9–8.1% strain capacity with 2.0 vol% PE fibers under ambient curing.	Direct tensile and compressive testing on ambient-cured SS-EGC verified 143.0 MPa compressive strength and 11.9 MPa tensile strength.	Pages 1, 7, Section 4.1 & Abstract, Table 4, Figs. 6, 13	verified_from_pdf
`04_material_systems/high_strength_ecc.md`	Seawater ions promote hydrotalcite nanocrystals in alkali-activated slag, increasing the ultra-high-density phase and refining crack width to 59.4 μm.	Nanoindentation deconvolution and TGA verified hydrotalcite formation and crack width narrowing to 59.4 μm.	Pages 7, 8-9, Section 3.4 & 4.2, Table 3, Table 4, Figs. 12, 16	verified_from_pdf

Verification status

PDF preserved: yes (lao-2023-seawater-sea-sand-engineered-geopolymer-composites.pdf)
Text extracted: yes (atlas/full_text/lao-2023-seawater-sea-sand-engineered-geopolymer-composites_full_text.md)
DOI verified: yes (10.1016/j.cemconcomp.2023.104998)
Page/figure/table verified: yes
Claim-evidence matrix ready: yes

Cautions

Seawater slightly slows early geopolymerization due to magnesium precipitation into M-S-H gels.