Kwon et al. (2018) — Tensile Strain-Hardening Behaviors and Crack Patterns of Slag-Based Fiber-Reinforced Composites

Citation

Kwon, S.-J., Choi, J.-I., Nguyễn, H. H., & Lee, B. Y. (2018). Tensile strain-hardening behaviors and crack patterns of slag-based fiber-reinforced composites. Computers and Concrete, 21(3), 231–237.

DOI: 10.12989/cac.2018.21.3.231
Atlas layer: core
Related Victor Li book chapter: Chapter 7: Alternative Reinforcing Fibers (PP, PE, and PBO Fibers) & Chapter 9: Green ECC (Alkali-Activated Slag Systems)
Source PDF: kwon-2018-tensile-strain-hardening-behaviors-and-crack.pdf
Extracted text: full_text/kwon-2018-tensile-strain-hardening-behaviors-and-crack_full_text.md
Source note: source_notes/kwon-2018-tensile-strain-hardening-behaviors-and-crack_source_note.md

Why this paper matters

Provides a direct tri-fiber benchmark (PP vs. PE vs. PBO at 1.75 vol. %) in cementless alkali-activated slag across water-to-binder ratios (0.35, 0.45, 0.55), proving that PE fibers deliver the highest tensile ductility (up to 7.2 %), while PBO fibers achieve the highest tensile strength (up to 12.4 MPa) and tightest crack widths ($< 35\ \mu\text{m}$).

Main contribution

Formulates 9 cementless composite mixtures using GGBFS and solid $\text{Ca(OH)}_2$ activator across three synthetic fiber types: Polypropylene (PP), Polyethylene (PE), and Polyparaphenylene-benzobisethiazole (PBO) at $V_f = 1.75\text{ vol. \%}$.
Evaluates the effect of water-to-binder ratio ($w/b = 0.35, 0.45, 0.55$) on compressive strength, uniaxial tensile stress-strain relationships, and digital microscopic crack patterns.
Demonstrates that PE-AAS composites deliver superior tensile strain capacity ($\epsilon_u = 4.8\%\text{ to }7.2\%$) due to slip-hardening pullout behavior and high complementary energy ($J_b'$).
Demonstrates that PBO-AAS composites produce the highest ultimate tensile strength ($\sigma_u = 8.5\text{--}12.4\text{ MPa}$) and tightest saturated crack widths ($w_m < 35\ \mu\text{m}$) due to extreme fiber elastic modulus ($E_f = 270\text{ GPa}$) and tensile strength ($\sigma_f = 5800\text{ MPa}$).

Evidence summary

Binder System: 100 % GGBFS activated with solid $\text{Ca(OH)}_2$ (10 wt% of slag); $w/b = 0.35, 0.45, 0.55$.
Fiber Properties ($V_f = 1.75\text{ vol. \%}, l_f = 12\text{ mm}$):
PP: $d_f = 18\ \mu\text{m}, \sigma_f = 700\text{ MPa}, E_f = 7.5\text{ GPa}$.
PE: $d_f = 12\ \mu\text{m}, \sigma_f = 2700\text{ MPa}, E_f = 88\text{ GPa}$.
PBO: $d_f = 13\ \mu\text{m}, \sigma_f = 5800\text{ MPa}, E_f = 270\text{ GPa}$.
Mechanical Properties (28-day water cured):
Compressive strength: 45.2 MPa ($w/b = 0.35$) $\rightarrow$ 16.5 MPa ($w/b = 0.55$).
PE Series: $\sigma_u = 6.5\text{--}8.8\text{ MPa}$, $\epsilon_u = 4.8\%\text{--}7.2\%$, crack width $w_m \approx 50\text{--}70\ \mu\text{m}$.
PBO Series: $\sigma_u = 8.5\text{--}12.4\text{ MPa}$, $\epsilon_u = 1.8\%\text{--}3.2\%$, crack width $w_m \approx 20\text{--}35\ \mu\text{m}$.
PP Series: $\sigma_u = 2.8\text{--}3.9\text{ MPa}$, $\epsilon_u = 0.8\%\text{--}1.9\%$, crack width $w_m \approx 120\text{--}180\ \mu\text{m}$.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
04_material_systems/green_ecc.md
04_material_systems/pe_ecc.md
04_material_systems/pp_ecc.md
05_experiments/direct_tensile_test.md
02_concepts/circular_economy_materials.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 7 (Alternative Reinforcing Fibers, pp. 175–204) and Chapter 9 (Green ECC).
Validates the micromechanical fiber tailoring spectrum in cementless alkali-activated slag: shows that low-modulus PP fibers struggle to satisfy the energy criterion, high-modulus PE fibers optimize tensile ductility ($\epsilon_u > 7\%$), and ultra-high-modulus PBO fibers maximize composite tensile strength ($\sigma_u > 12\text{ MPa}$) and crack control.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/pe_ecc.md`	PE fiber reinforcement in AAS composite delivers direct tensile ductility up to 7.2 % and tensile strength of 8.8 MPa	JSCE direct uniaxial tensile testing across $w/b = 0.35\text{--}0.55$	Section 3.2, Fig. 5-7, Table 4	verified_from_pdf
`04_material_systems/pp_ecc.md`	PBO fibers achieve tensile strength up to 12.4 MPa and crack widths $< 35\ \mu\text{m}$ in AAS, outperforming PP and PE fibers in strength	Comparative tensile stress-strain and microscopic crack width measurements	Section 3.2 & 3.3, Fig. 5-8, Table 4	verified_from_pdf

Verification status

PDF preserved: yes (kwon-2018-tensile-strain-hardening-behaviors-and-crack.pdf)
Text extracted: yes (full_text/kwon-2018-tensile-strain-hardening-behaviors-and-crack_full_text.md)
DOI verified: yes (10.12989/cac.2018.21.3.231)
Metadata verified: yes (Comput. Concr., Vol. 21, No. 3, pp. 231–237, 2018)
Claim-evidence matrix ready: yes

Cautions

PP fibers exhibit limited strain-hardening and wide crack widths ($> 120\ \mu\text{m}$) due to low elastic modulus ($7.5\text{ GPa}$) and weak mechanical bond in AAS paste.
PBO fibers have extremely high costs, making them primarily suited for high-value structural retrofits where high tensile strength ($\sigma_u > 12\text{ MPa}$) is required.