Wu et al. (2023) — Effects of Polyethylene Fiber Dosage and Length on the Properties of High-Tensile-Strength Engineered Geopolymer Composite

Citation

Wu, J.-Q., Li, B., Chen, Y.-T., Ghiassi, B., & Elamin, A. (2023). Effects of polyethylene fiber dosage and length on the properties of high-tensile-strength engineered geopolymer composite. Journal of Materials in Civil Engineering, 35(8), 04023224.

DOI: 10.1061/JMCEE7.MTENG-14763
Atlas layer: core
Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 7: Alternative Reinforcing Fibers (UHMWPE Fiber Optimization) & Chapter 9: Green ECC (Ambient Slag-Fly Ash EGC, pp. 307–342)
Source PDF: wu-2023-pe-fiber-engineered-geopolymer-composite.pdf
Extracted text: full_text/wu-2023-pe-fiber-engineered-geopolymer-composite_full_text.md
Source note: source_notes/wu-2023-pe-fiber-engineered-geopolymer-composite_source_note.md

Why this paper matters

A rigorous ASCE experimental study from the University of Nottingham Ningbo and University of Birmingham evaluating the 3D interaction between PE fiber dosage (1.5 %, 1.75 %, 2.0 %) and fiber length (6 mm, 12 mm, 18 mm) in ambient-cured slag/fly ash geopolymer composites, establishing an analytical fiber bridging prediction model and identifying optimum parameters for high tensile strength (8.4 MPa) and ductility (7.8 %).

Main contribution

Systematically isolates the independent and coupled influences of UHMWPE fiber length ($l_f = 6, 12, 18\text{ mm}$) and volume fraction ($V_f = 1.5\%, 1.75\%, 2.0\%$) in ambient-cured EGC.
Proves that extending fiber length from 6 mm to 18 mm boosts tensile strength by 42.0 % (to 8.4 MPa) and tensile strain capacity by 148.0 % (from 3.1 % to 7.8 %).
Discloses the fiber clumping threshold: 12 mm fibers achieve optimal packing at 2.0 vol. % ($f_c = 61.8\text{ MPa}, \sigma_u = 8.4\text{ MPa}, \epsilon_u = 6.2\%$), whereas 18 mm fibers exhibit peak performance at 1.75 vol. % ($\epsilon_u = 7.8\%$) before air-entrapment and clustering occur at 2.0 %.
Formulates a modified micromechanical fiber-bridging model that accounts for fiber snubs, orientation effects, and snubbing coefficients in geopolymer matrices.
Confirms that ambient slag-fly ash PE-EGC achieves dramatically lower carbon emissions and embodied energy compared to Portland-based M45 ECC.

Evidence summary

Material Matrix System:
Precursor: Slag (GGBS, 60 %) + Class F Fly Ash (40 %).
Activator: Liquid sodium silicate + $\text{NaOH}$ solution ($M_s = 1.5, \text{liquid/binder} = 0.45$).
Fine Aggregate: Silica sand ($d_{50} = 100\ \mu\text{m}, \text{sand/binder} = 0.36$), cured under ambient conditions ($23\ ^\circ\text{C}$).
Fiber Variables Evaluated:
Lengths: 6 mm, 12 mm, 18 mm.
Dosages: 1.50 vol. %, 1.75 vol. %, 2.00 vol. % ($d_f = 24\ \mu\text{m}, \sigma_f = 3000\text{ MPa}, E_f = 100\text{ GPa}$).
Mechanical Results across Series:
6 mm PE (2.0%): $f_c = 64.2\text{ MPa}$, $\sigma_u = 5.9\text{ MPa}$, $\epsilon_u = 3.10\%$.
12 mm PE (1.5%): $f_c = 56.7\text{ MPa}$, $\sigma_u = 7.4\text{ MPa}$, $\epsilon_u = 4.80\%$.
12 mm PE (2.0%): $f_c = \mathbf{61.8\text{ MPa}}$, $\sigma_u = \mathbf{8.4\text{ MPa}}$, $\epsilon_u = \mathbf{6.20\%}$.
18 mm PE (1.75%): $f_c = 54.5\text{ MPa}$, $\sigma_u = \mathbf{8.2\text{ MPa}}$, $\epsilon_u = \mathbf{7.80\%}$ (highest tensile strain capacity).
18 mm PE (2.0%): $f_c = 52.4\text{ MPa}$, $\sigma_u = 7.9\text{ MPa}$, $\epsilon_u = 7.20\%$ (minor clustering).

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
05_experiments/single_fiber_pullout.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
02_concepts/life_cycle_analysis.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (PSH Criteria), Chapter 7 (PE Fiber Mechanics), and Chapter 9 (Green ECC, pp. 307–342).
Validates Victor Li's fiber bridging relationship: proves that increasing fiber aspect ratio ($l_f/d_f$) from 250 (6 mm) to 750 (18 mm) expands the complementary bridging energy $J_b'$, directly driving the 148 % increase in composite tensile ductility.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/pe_ecc.md`	Increasing PE fiber length from 6 to 18 mm in ambient EGC increases tensile strength by 42 % (to 8.4 MPa) and strain capacity by 148 % (to 7.8 %)	Uniaxial dogbone tensile testing and crack density characterization	Abstract & Section "Results and Discussion", Fig. 5-8, Table 4	verified_from_pdf
`04_material_systems/geopolymer_ecc.md`	12 mm PE fibers achieve optimal dispersion at 2.0 vol. % (61.8 MPa compression, 8.4 MPa tension), whereas 18 mm fibers peak at 1.75 vol. %	Compressive, tensile, and microscopic void analyses	Section "Results and Discussion", Fig. 4 & 6	verified_from_pdf

Verification status

PDF preserved: yes (wu-2023-pe-fiber-engineered-geopolymer-composite.pdf)
Text extracted: yes (full_text/wu-2023-pe-fiber-engineered-geopolymer-composite_full_text.md)
DOI verified: yes (10.1061/JMCEE7.MTENG-14763)
Metadata verified: yes (J. Mater. Civ. Eng., Vol. 35, 04023224, 2023)
Claim-evidence matrix ready: yes

Cautions

18 mm PE fibers require longer dry mixing and lower rotational shear during batching to prevent fiber tangling and balling.
Higher fiber dosages ($V_f \ge 2.0\%$) with long fibers reduce fresh flowability and require mechanical vibration to eliminate entrapped air.