Zhu et al. (2026) — Serpentine-induced synergistic enhancement of tensile strength and ductility in...

Citation

Ji-Xiang Zhu, Si-Zhe Xue, Ling-Yu Xu, Ji-Rong Lan, Bo-Tao Huang, Jian-Guo Dai (2026). Serpentine-induced synergistic enhancement of tensile strength and ductility in high-strength Engineered/Strain-Hardening Cementitious Composites (ECC/SHCC). Cement and Concrete Composites, Vol. 168, Article 106505.

DOI: 10.1016/j.cemconcomp.2026.106505
Atlas layer: extension
Related Victor Li book chapter: Chapter 4: Special ECCs / Ultra-High Strength & Sustainable Aggregates; Chapter 2: Micromechanics and Materials Design
Source PDF: zhu-2026-serpentine-induced-synergistic-enhancement-of-tensile.pdf
Extracted text: atlas/full_text/zhu-2026-serpentine-induced-synergistic-enhancement-of-tensile_full_text.md
Source note: atlas/source_notes/zhu-2026-serpentine-induced-synergistic-enhancement-of-tensile_source_note.md

Why this paper matters

Completely substitutes natural silica sand with serpentine ore mining waste aggregates (SOA: 0–4.75 mm) in high-strength ECC (83.5–91.8 MPa compressive strength), overcoming the strength-ductility trade-off by simultaneously boosting ultimate tensile strength by 27.0% (to 11.3–13.3 MPa) and tensile ductility by 35.1% (to 5.0%) through Mg²⁺ interfacial densification and coarse SOA active flaw tailoring.

Main contribution

First exploration of low-grade serpentine ore mining waste ($Mg_3Si_2O_5(OH)_4$) as full aggregate replacement in HS-ECC ($w/b = 0.25$, $s/b = 0.3$, $2.0\text{ vol\%}$ PE fibers).
Overcame the classic strength-ductility trade-off in high-strength ECC, demonstrating simultaneous enhancement in tensile strength ($11.3\text{ MPa}$, +27.0%) and tensile ductility ($5.0\%$, +35.1%) in mix S4.75 ($0\text{--}4.75\text{ mm}$ SOA).
Discovered that $Mg^{2+}$ ion dissolution densifies the SOA/matrix ITZ ($9\ \mu\text{m}$ width, $111.3\text{ HV}$ microhardness) and enhances PE fiber interfacial friction.
Proved via 2D/3D XCT that coarse SOA particles introduce active defects (Weibull $\lambda = 0.60$) that trigger saturated multi-cracking (25 cracks, average width $158.8\ \mu\text{m}$).
Reduced embodied carbon by 49.0% and material cost by 51.8% per overall performance index ($f_c f_t \varepsilon_t / w$).

Evidence summary

Mechanical properties:
S4.75 ($0\text{--}4.75\text{ mm}$ SOA): $f_c = 91.8\pm 1.2\text{ MPa}$, $\sigma_t = 11.3\pm 0.1\text{ MPa}$, $\varepsilon_t = 5.0\pm 0.5\%$, crack width $158.8\pm 21.3\ \mu\text{m}$, 25 cracks.
S2.36 ($0\text{--}2.36\text{ mm}$ SOA): $f_c = 86.6\pm 0.8\text{ MPa}$, $\sigma_t = 13.3\pm 0.6\text{ MPa}$, $\varepsilon_t = 4.1\pm 0.2\%$, crack width $194.3\ \mu\text{m}$, 17 cracks.
S1.18 ($0\text{--}1.18\text{ mm}$ SOA): $f_c = 83.5\pm 2.0\text{ MPa}$, $\sigma_t = 11.5\pm 0.6\text{ MPa}$, $\varepsilon_t = 3.5\pm 0.4\%$, crack width $198.2\ \mu\text{m}$, 14 cracks.
F0.30 (Control FSS): $f_c = 101.1\pm 3.5\text{ MPa}$, $\sigma_t = 8.9\pm 0.2\text{ MPa}$, $\varepsilon_t = 3.7\pm 0.1\%$, crack width $180.7\ \mu\text{m}$, 16 cracks (Table 5, Fig. 2).
Microhardness & ITZ: SOA ITZ reached $111.3\text{ HV}$ compared to $74.5\text{ HV}$ in bulk paste and $53.7\text{ HV}$ in FSS paste; BSE-EDS confirmed $9\ \mu\text{m}$ wide Mg-rich reaction zone (Table 7, Fig. 3).
XCT Flaw Analysis: Weibull distribution modeling confirmed larger active flaw sizes in S4.75 ($\lambda = 0.60$) reducing crack spacing $x_d$ (Table 8, Fig. 4).

Linked Atlas nodes

04_material_systems/high_strength_ecc.md
04_material_systems/green_ecc.md
02_concepts/strain_hardening_criteria.md
02_concepts/flaw_design.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`	Full replacement of silica sand with 0–4.75 mm serpentine ore aggregates (S4.75) in high-strength ECC achieves 91.8 MPa compressive strength, 11.3 MPa tensile strength, and 5.0% tensile ductility (a 27.0% strength and 35.1% ductility increase over silica sand control).	Cube compression and JSCE dumbbell tensile testing confirmed 91.8 MPa compressive and 11.3 MPa tensile strength with 5.0% ductility.	Pages 1, 4, 8, Section 3.2, 4 & Abstract, Table 5, Fig. 2A, 2B	verified_from_pdf
`02_concepts/flaw_design.md`	The strength-ductility trade-off in HS-ECC is resolved by dual mechanisms: Mg²⁺ ion diffusion from SOA densifies the ITZ (111.3 HV) and increases PE fiber friction (raising tensile strength to 11.3–13.3 MPa), while coarse 4.75 mm SOA acts as active flaws (Weibull λ = 0.60) to promote saturated multi-cracking (25 cracks, 5.0% strain).	Vickers microhardness, BSE-EDS elemental mapping, and XCT Weibull flaw modeling verified coupled chemical and physical mechanisms.	Pages 6, 7, 8, Section 3.5, 3.7, 3.8, 3.9, Tables 7, 8, Figs. 3, 4, 5	verified_from_pdf

Verification status

PDF preserved: yes (zhu-2026-serpentine-induced-synergistic-enhancement-of-tensile.pdf)
Text extracted: yes (atlas/full_text/zhu-2026-serpentine-induced-synergistic-enhancement-of-tensile_full_text.md)
DOI verified: yes (10.1016/j.cemconcomp.2026.106505)
Page/figure/table verified: yes
Claim-evidence matrix ready: yes

Cautions

SOA has a high water absorption ($10.9\%\text{--}17.7\%$), requiring careful water adjustment.