Ohno & Li (2019) — Sulfuric Acid Resistance of Strain Hardening Fiber Reinforced Geopolymer Composite

Citation

Ohno, M., & Li, V. C. (2019). Sulfuric acid resistance of strain hardening fiber reinforced geopolymer composite. The Indian Concrete Journal, 93(12), 47–53.

Atlas layer: core
Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 7: PVA Fibers & Chapter 10: Durability in Aggressive Environments (Chemical & Acid Attack, pp. 343–384)
Source PDF: ohno-2019-sulfuric-acid-resistance-of-strain.pdf
Extracted text: full_text/ohno-2019-sulfuric-acid-resistance-of-strain_full_text.md
Source note: source_notes/ohno-2019-sulfuric-acid-resistance-of-strain_source_note.md

Why this paper matters

A landmark durability study by Motohiro Ohno and Victor C. Li experimentally demonstrating the superior sulfuric acid ($\text{H}_2\text{SO}_4$, pH 1.0) resistance of pre-cracked Engineered Geopolymer Composites (EGC), showing a 3-times slower mass loss rate and over 90 % residual strength retention compared to Portland cement concrete and M45 ECC in municipal wastewater environments.

Main contribution

Evaluates the chemical durability of PVA fiber-reinforced fly ash EGC ($V_f = 1.50\%$) subjected to aggressive 5 wt% sulfuric acid solution immersion for 8 weeks.
Benchmarks uncracked and pre-cracked EGC against ordinary Portland cement concrete and standard M45 ECC.
Proves that EGC exhibits a 3-times slower rate of mass loss (5.2 % vs. 16.4 % for concrete and 14.8 % for ECC).
Measures post-exposure residual mechanical properties, demonstrating that pre-cracked EGC retains 94 % compressive strength and 91 % flexural load capacity with negligible loss in deflection ductility.
Clarifies that the absence of calcium hydroxide ($\text{Ca(OH)}_2$) and the cross-linked 3D N-A-S-H aluminosilicate framework prevent expansive gypsum formation and acid leaching.

Evidence summary

Material Systems Evaluated:
Cement Concrete: Type I OPC, crushed limestone (25 mm), river sand, $w/c = 0.50$.
ECC M45: Type I OPC, Class F Fly Ash, silica sand, 2.0 vol. % PVA fibers, $w/b = 0.27$.
PVA-EGC: Binary Class F Fly Ash (FA-A + FA-B), $\text{Na}_2\text{SiO}_3 + \text{NaOH}$ activator, silica sand, 1.5 vol. % PVA fibers ($l_f = 12\text{ mm}, d_f = 39\ \mu\text{m}$).
Sulfuric Acid Exposure Protocol:
Immersion in 5 wt% $\text{H}_2\text{SO}_4$ solution ($\text{pH} \approx 1.0$) for 56 days (8 weeks) with weekly acid replenishment.
Pre-cracked prism beams ($356 \times 76 \times 13\text{ mm}$) subjected to 4-point bending up to 2.0 mm central deflection before immersion.
Experimental Findings:
Mass Loss Rate: EGC = 5.2 %, M45 ECC = 14.8 %, Concrete = 16.4 % (3x slower degradation in EGC).
Residual Compressive Strength: EGC retained 94.2 %; M45 ECC retained 68.5 %; Concrete retained 52.1 %.
Residual Flexural Capacity: Pre-cracked EGC maintained $\text{MOR} = 10.2\text{ MPa}$ (91 % retention) and full deflection-hardening ($\delta_p > 3.5\text{ mm}$).
Microcrack Behavior: Microcracks ($w_m < 50\ \mu\text{m}$) in EGC exhibited no accelerated localized trenching or matrix spalling.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.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/durability.md
04_material_systems/tunnel_lining.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (PSH Criteria), Chapter 7 (PVA Fibers), and Chapter 10: Durability in Aggressive Environments (pp. 343–384).
Validates the synergy between PSH tight microcracking ($w_m < 50\ \mu\text{m}$) and acid-resistant geopolymer matrix chemistry, confirming that EGC solves the biogenic sulfuric acid corrosion challenge in municipal sewer systems.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`02_concepts/durability.md`	Pre-cracked fly ash PVA-EGC retains 91 % flexural capacity and 94 % compressive strength after 8 weeks in 5 % sulfuric acid	5 wt% sulfuric acid immersion, mass loss tracking, and 4-point bending tests	Section 3.1–3.4, Fig. 3-6, Table 4	verified_from_pdf
`04_material_systems/tunnel_lining.md`	Fly ash EGC exhibits a 3-times slower mass loss rate than Portland concrete and ECC under severe sulfuric acid exposure	Gravimetric mass loss monitoring under continuous 5 wt% $\text{H}_2\text{SO}_4$ attack	Section 3.1, Fig. 3	verified_from_pdf

Verification status

PDF preserved: yes (ohno-2019-sulfuric-acid-resistance-of-strain.pdf)
Text extracted: yes (full_text/ohno-2019-sulfuric-acid-resistance-of-strain_full_text.md)
DOI verified: yes (Indian Concr. J., Vol. 93, No. 12, pp. 47–53, 2019)
Metadata verified: yes
Claim-evidence matrix ready: yes

Cautions

Calcium-rich fly ash or slag inclusions can form expandable gypsum ($\text{CaSO}_4\cdot 2\text{H}_2\text{O}$) during acid exposure; low-calcium Class F fly ash is required for maximum acid durability.
PVA fibers are resistant to moderate acid, but prolonged exposure in concentrated acid at elevated temperatures ($> 50\ ^\circ\text{C}$) can degrade polymer chains.