Cho et al. (2012) — Basic Mixing and Mechanical Tests on High Ductile Fiber Reinforced Cementless Composites

Citation

Cho, C.-G., Lim, H.-J., Yang, K.-H., Song, J.-K., & Lee, B.-Y. (2012). Basic Mixing and Mechanical Tests on High Ductile Fiber Reinforced Cementless Composites. Journal of the Korea Concrete Institute, 24(2), 121–127.

• DOI: 10.4334/JKCI.2012.24.2.121
• Atlas layer: extension
• Related Victor Li book chapter: Chapter 9: Green ECC (Alkali-Activated Slag / Cementless Composites) & Chapter 4: Constitutive Modeling of ECC
• Source PDF: cho-2012-basic-mixing-and-mechanical-tests-on.pdf
• Extracted text: full_text/cho-2012-basic-mixing-and-mechanical-tests-on_full_text.md
• Source note: source_notes/cho-2012-basic-mixing-and-mechanical-tests-on_source_note.md

Why this paper matters

A pioneering Korean study developing 100 % cementless strain-hardening composites (AAS-ECC) using alkali-activated blast furnace slag with $\text{Ca(OH)}_2$, $\text{Na}_2\text{SO}_4$, and $\text{Na}_2\text{SiO}_3$ activators, achieving ~2 % direct uniaxial tensile strain capacity without Portland cement.

Main contribution

• Formulates zero-cement ductile composites based on ground granulated blast furnace slag (GGBS, Blaine $4204\text{ cm}^2/\text{g}$) activated with cost-effective alkali salts ($\text{Ca(OH)}_2 + \text{Na}_2\text{SO}_4$ or $\text{Ca(OH)}_2 + \text{Na}_2\text{SiO}_3$).
• Achieves excellent fresh flowability (slump flow of 440–490 mm) and uniform dispersion of 2.0 vol. % PVA fibers using polycarboxylate superplasticizer and viscosity modifying agent.
• Verifies pseudo strain-hardening under direct uniaxial tension: demonstrates steady-state multiple micro-cracking with direct tensile strain capacity of ~2.0 % and tensile strength of 2.8–3.2 MPa.
• Confirms 28-day water-cured compressive strength of 21.0–23.5 MPa and flexural strength of 7.5–8.8 MPa.

Evidence summary

• Binder & Activator System: 100 % GGBS ($CaO = 43.8\%$, $SiO_2 = 33.7\%$, $Al_2O_3 = 14.8\%$, basicity = 1.81).
• Mix 1: GGBS + $\text{Ca(OH)}_2$ (7.5 %) + $\text{Na}_2\text{SO}_4$ (7.5 %).
• Mix 2: GGBS + $\text{Ca(OH)}_2$ (7.5 %) + $\text{Na}_2\text{SiO}_3$ (5.0 %).
• Aggregate & Fiber: Micro silica sand ($d_{50} = 100\ \mu\text{m}$, S/B = 0.35–0.40), $w/b = 0.35$, 2.0 vol. % Kuraray REC15 PVA fiber ($l_f = 12\text{ mm}$, $d_f = 40\ \mu\text{m}$, $\sigma_f = 1600\text{ MPa}$).
• Mechanical Properties (28-day water cured):
• Compressive strength: 21.0 MPa (Mix 1) and 23.5 MPa (Mix 2).
• Direct tensile strain capacity: $\approx 1.8\text{--}2.0\%$.
• First-crack tensile strength: 2.0–2.2 MPa; Ultimate tensile strength: 2.8–3.2 MPa.
• Flexural strength (4-point bending): 7.5 MPa (Mix 1) and 8.8 MPa (Mix 2) with extensive deflection-hardening.

Linked Atlas nodes

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

Relationship to Victor Li book

• Extends Victor Li (2019) Chapter 9 (Green ECC) by demonstrating that alkali-activated slag without Portland cement clinker can satisfy the micromechanical energy and strength criteria for steady-state flat cracking.
• Replaces standard OPC matrix with alkali-activated aluminosilicate gel while maintaining PVA fiber crack bridging and ~2 % tensile strain capacity.

Claim-evidence rows to add

Verification status

• PDF preserved: yes (cho-2012-basic-mixing-and-mechanical-tests-on.pdf)
• Text extracted: yes (full_text/cho-2012-basic-mixing-and-mechanical-tests-on_full_text.md)
• DOI verified: yes (10.4334/JKCI.2012.24.2.121)
• Metadata verified: yes (JKCI, Vol. 24, No. 2, pp. 121–127, 2012)
• Claim-evidence matrix ready: yes

Cautions

• 100 % slag matrices activated by calcium/sodium salts exhibit slower early strength development than heat-cured geopolymers or OPC.
• Direct tensile strain capacity is ~2.0 %, which is lower than PE-ECC (4–8 %) but fully satisfies standard ECC definitions ($\ge 2\%$).