Kan et al. (2025a) — Engineered Geopolymer Composites for Concrete Repair: Durability Behavior and Mechanistic Investigation Under Sulfate Wet-Dry Cycles

Citation

Kan, L., Chen, B., & Gan, Y. (2025). Engineered geopolymer composites for concrete repair: Durability behavior and mechanistic investigation under sulfate wet-dry cycles. Journal of Building Engineering, 114, 114323.

DOI: 10.1016/j.jobe.2025.114323
Atlas layer: core
Related Victor Li book chapter: Chapter 10: Long-Term Durability (Sulfate Resistance) & Chapter 11: Infrastructure Repair and Structural Retrofitting
Source PDF: kan-2025-engineered-geopolymer-composites-for-concrete.pdf
Extracted text: full_text/kan-2025-engineered-geopolymer-composites-for-concrete_full_text.md
Source note: source_notes/kan-2025-engineered-geopolymer-composites-for-concrete_source_note.md

Why this paper matters

Pioneers the evaluation of high-ductility PE-reinforced Engineered Geopolymer Composites (PE-EGC, $\epsilon_u \approx 8.0\%$) as an overlay repair material for high-strength concrete under severe 10 % $\text{Na}_2\text{SO}_4$ wet-dry cycles (up to 175 cycles), establishing that coexisting N-A-S-H/C-A-S-H interfacial gels limit bond strength reduction to $< 19\%$ while completely eliminating delamination spalling.

Main contribution

Develops a high-ductility ternary EGC (GGBS:FA:SF = 44:44:11) reinforced with 1.50 vol. % PE fibers, attaining an ultimate tensile strain capacity of ~8.0 %, tensile strength of 5.49 MPa, and compressive strength of 60.58 MPa.
Tests EGC-repaired high-strength concrete (HSC, $f_c = 61.4\text{ MPa}$) composite specimens under up to 175 harsh wet-dry cycles in 10 wt% sodium sulfate solution.
Evaluates direct tensile pull-off bond strength (initial 2.33 MPa) and slant shear bond strength (initial 31.8 MPa) with Digital Image Correlation (DIC) strain mapping.
Uncovers the two-stage sulfate degradation mechanism: initial pore densification (+4.7 % shear strength at 50 cycles due to continuous geopolymerization), followed by gradual decalcification and ettringite micro-cracking causing an 18.4 % pull-off and 19.6 % slant shear strength decline at 175 cycles.
Confirms via SEM-EDS and FT-IR that dense N-A-S-H/C-A-S-H hybrid gels at the interface maintain chemical bond integrity far superior to Portland cement repair materials.

Evidence summary

Material Matrix: GGBS (529 kg/m³) + Fly Ash (529 kg/m³) + Silica Fume (132 kg/m³) activated with liquid $\text{Na}_2\text{SiO}_3 + \text{NaOH}$, river sand ($S/B = 0.44$), $w/b = 0.32$.
Fiber Reinforcement: 1.50 vol. % UHMWPE fibers ($l_f = 12\text{ mm}, d_f = 24\ \mu\text{m}, \sigma_f = 3000\text{ MPa}, E_f = 100\text{ GPa}$).
Mechanical Properties:
Compressive strength: 60.58 MPa (EGC) vs. 61.43 MPa (substrate HSC).
Direct tensile strain capacity ($\epsilon_u$): $8.0\%\text{ with }66\text{ saturated microcracks}$.
Ultimate tensile strength ($\sigma_u$): 5.49 MPa; Average crack width: $96\ \mu\text{m}$.
Interfacial Bond & Sulfate Durability (175 Wet-Dry Cycles):
Water control: Tensile bond strength dropped only 5.6 % (from 2.33 to 2.20 MPa).
10 % $\text{Na}_2\text{SO}_4$ solution: Tensile bond strength dropped 18.4 % (to 1.90 MPa); Slant shear strength dropped 19.6 % (from 31.8 to 25.6 MPa).
DIC strain mapping confirmed ductile shear stress redistribution along the grooved interface without brittle debonding.

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/slant_shear_test.md
02_concepts/circular_economy_materials.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 10 (Long-Term Durability under Chemical Attack) and Chapter 11 (Infrastructure Repair and Retrofit, pp. 307–335).
Proves that replacing cement-based repair overlays with zero-clinker PE-EGC eliminates interfacial shear distress caused by substrate-overlay shrinkage mismatch and prevents sulfate-induced delamination spalling.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/geopolymer_ecc.md`	Ternary GGBS-FA-SF geopolymer composite with 1.5 vol. % PE fibers achieves tensile ductility of ~8.0 % and compressive strength $> 60\text{ MPa}$	Uniaxial tensile dogbone testing and ASTM C109 cube compression testing	Section 2.1 & 3.1, Fig. 3-5, Table 1	verified_from_pdf
`05_experiments/slant_shear_test.md`	EGC-repaired concrete maintains high slant shear bond strength ($> 25\text{ MPa}$) after 175 aggressive sulfate wet-dry cycles	ASTM C882 slant shear testing and direct pull-off bond testing under 10 % $\text{Na}_2\text{SO}_4$ WD exposure	Section 3.3 & 3.4, Fig. 8-12, Table 4	verified_from_pdf

Verification status

PDF preserved: yes (kan-2025-engineered-geopolymer-composites-for-concrete.pdf)
Text extracted: yes (full_text/kan-2025-engineered-geopolymer-composites-for-concrete_full_text.md)
DOI verified: yes (10.1016/j.jobe.2025.114323)
Metadata verified: yes (J. Build. Eng., Vol. 114, 114323, 2025)
Claim-evidence matrix ready: yes

Cautions

Beyond 125 sulfate wet-dry cycles, secondary ettringite expansion and matrix decalcification initiate microcracking at the substrate transition zone; long-term durability designs must account for ~20 % bond strength reduction.
Requires mechanical interface grooving to maximize physical shear interlock between new EGC and aged concrete.