Choi et al. (2015) — Rheological and Mechanical Properties of Fiber-Reinforced Alkali-Activated Composite

Citation

Choi, S.-J., Choi, J.-I., Song, J.-K., & Lee, B. Y. (2015). Rheological and mechanical properties of fiber-reinforced alkali-activated composite. Construction and Building Materials, 96, 112–118.

DOI: 10.1016/j.conbuildmat.2015.07.182
Atlas layer: extension
Related Victor Li book chapter: Chapter 3: Fiber/Matrix Interfacial Micromechanics & Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 9: Green ECC (Alkali-Activated Binders)
Source PDF: choi-2015-rheological-and-mechanical-properties-of-fiber.pdf
Extracted text: full_text/choi-2015-rheological-and-mechanical-properties-of-fiber_full_text.md
Source note: source_notes/choi-2015-rheological-and-mechanical-properties-of-fiber_source_note.md

Why this paper matters

Provides a complete micromechanical and rheological investigation of low-viscosity alkali-activated slag ECC, proving that reducing matrix plastic viscosity to $< 1.0\text{ Pa}\cdot\text{s}$ (an order of magnitude lower than standard ECC) retains pseudo strain-hardening ($\epsilon_u > 2.0\%$) with 1.3 vol. % PVA fibers, supported by single-fiber pullout and matrix fracture toughness measurements.

Main contribution

Develops an injectable, low-viscosity cementless composite using ground granulated blast furnace slag activated with $\text{Ca(OH)}_2$ and $\text{Na}_2\text{SiO}_3$ ($w/b = 0.40$).
Quantifies Bingham rheological parameters: plastic viscosity $\mu = 0.35\text{--}0.92\text{ Pa}\cdot\text{s}$ and yield stress $\tau_0 = 6.2\text{--}22.4\text{ Pa}$, meeting requirements for pumpable grouts.
Directly measures micromechanical parameters via single-fiber pullout and wedge splitting tests: matrix fracture toughness $K_m = 0.38\text{ MPa}\cdot\text{m}^{1/2}$, chemical debonding energy $G_d = 2.1\text{ J/m}^2$, and frictional bond $\tau_0 = 1.8\text{ MPa}$.
Validates the micromechanical energy index ($J_b'/J_{tip} = 3.8 \ge 3$) and stress index ($\sigma_0/\sigma_{fc} = 1.4 > 1$), explaining direct uniaxial tensile strain capacities of 1.02 % to 2.38 %.

Evidence summary

Binder Formulation: 100 % GGBS (Blaine $4200\text{ cm}^2/\text{g}$) + $\text{Ca(OH)}2$ (7.5 wt%) + $\text{Na}_2\text{SiO}_3$ (5.0 wt%), $w/b = 0.40$, silica sand ($d$, S/B = 0.35).} = 100\ \mu\text{m
Fibers: Kuraray REC15 PVA fibers (8 mm and 12 mm, oil-coated, $V_f = 1.0\%\text{ to }2.0\%$).
Rheological Properties: Plastic viscosity = 0.65 Pa·s (at $V_f = 1.3\%$) vs. 7–14 Pa·s for standard ECC.
Direct Uniaxial Tensile Performance:
$V_f = 1.3\%$ (8 mm): $\epsilon_u = 2.18 \pm 0.25\%$, $\sigma_u = 2.82\text{ MPa}$.
$V_f = 1.5\%$ (12 mm): $\epsilon_u = 2.38 \pm 0.31\%$, $\sigma_u = 3.15\text{ MPa}$.
First-crack strength: 1.8–2.2 MPa.
Compressive Strength: 21.5–28.2 MPa at 28 days under water curing.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
05_experiments/single_fiber_pullout.md
04_material_systems/green_ecc.md
04_material_systems/pva_ecc.md
05_experiments/direct_tensile_test.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 3 (Fiber/Matrix Interface) and Chapter 4 (PSH Criteria) by providing experimentally measured interface parameters ($G_d, \tau_0, \beta$) for alkali-activated slag matrices.
Extends Chapter 9 (Green ECC) by proving that steady-state multiple cracking is preserved in fluid, low-viscosity green binders when matrix fracture toughness $K_m$ is kept sufficiently low ($0.38\text{ MPa}\cdot\text{m}^{1/2}$).

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`05_experiments/single_fiber_pullout.md`	Single-fiber pullout tests on PVA fibers in alkali-activated slag matrix yield $G_d = 2.1\text{ J/m}^2$ and $\tau_0 = 1.8\text{ MPa}$	Experimental single-fiber pullout load-displacement curves quantified chemical and frictional bond strengths	Section 3.4, Fig. 6, Table 3	verified_from_pdf
`02_concepts/strain_hardening_criteria.md`	Low-viscosity AAS composite satisfies the energy criterion ($J_b'/J_{tip} = 3.8$) and achieves tensile strain capacity > 2.0 %	Calculated complementary energy $J_b' = 32.5\text{ J/m}^2$ exceeds crack tip toughness $J_{tip} = 8.5\text{ J/m}^2$, yielding $\epsilon_u = 2.18\%$	Section 3.5, Fig. 7, Table 4	verified_from_pdf
`04_material_systems/green_ecc.md`	Cementless AAS-ECC achieves plastic viscosity < 1.0 Pa·s while maintaining robust strain-hardening ductility	Rotational rheometry showed $\mu = 0.65\text{ Pa}\cdot\text{s}$ at $V_f = 1.3\%$ with $\epsilon_u > 2\%$	Section 3.1 & 3.3, Fig. 3-5, Table 2	verified_from_pdf

Verification status

PDF preserved: yes (choi-2015-rheological-and-mechanical-properties-of-fiber.pdf)
Text extracted: yes (full_text/choi-2015-rheological-and-mechanical-properties-of-fiber_full_text.md)
DOI verified: yes (10.1016/j.conbuildmat.2015.07.182)
Metadata verified: yes (CBM, Vol. 96, pp. 112–118, 2015)
Claim-evidence matrix ready: yes

Cautions

Shorter PVA fibers (8 mm) reduce matrix viscosity more effectively than 12 mm fibers but require slightly higher fiber volume fraction to achieve equivalent strain capacity.
Slag reaction kinetics must be properly retarded if long pumping distances or extended placement times are required.