Oh et al. (2010) — The Evolution of Strength and Crystalline Phases for Alkali-Activated Ground Blast Furnace Slag and Fly Ash-Based Geopolymers

Citation

Oh, J. E., Monteiro, P. J. M., Jun, S. S., Choi, S., & Clark, S. M. (2010). The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers. Cement and Concrete Research, 40(2), 189–196.

DOI: 10.1016/j.cemconres.2009.10.010
Atlas layer: core
Related Victor Li book chapter: Chapter 4: Matrix Fracture Toughness & Chemistry & Chapter 9: Green ECC (Slag and Fly Ash Geopolymer Systems, pp. 307–342)
Source PDF: oh-2010-the-evolution-of-strength-and-crystalline.pdf
Extracted text: full_text/oh-2010-the-evolution-of-strength-and-crystalline_full_text.md
Source note: source_notes/oh-2010-the-evolution-of-strength-and-crystalline_source_note.md

Why this paper matters

A foundational synchrotron X-ray diffraction (XRD) study from UC Berkeley and Lawrence Berkeley National Laboratory mapping the mineralogical evolution of alkali-activated slag, Class C, and Class F fly ash geopolymers, proving that hydrotalcite universally precipitates in slag/geopolymer binders and that zeolitic ABC-6 precursors (hydroxycancrinite) form the basic building units of N-A-S-H gels.

Main contribution

Utilizes synchrotron radiation at Beamline 12.2.2 (Advanced Light Source, LBNL) to track crystalline phase evolution and compressive strength growth in alkali-activated slag (AAS), Class C fly ash (FAC), and Class F fly ash (FAF) systems.
Discovers that hydrotalcite ($\text{Mg}6\text{Al}_2\text{CO}_3(\text{OH})$) forms as a stable nanocrystalline phase in both alkali-activated slag and fly ash systems, binding magnesium and carbonate ions.}\cdot 4\text{H}_2\text{O
Identifies hydroxycancrinite (a member of the ABC-6 zeolitic family) exclusively in fly ash geopolymers, demonstrating that amorphous N-A-S-H gels share disordered sub-nanometer cage structures with zeolites.
Clarifies the activator synergy: demonstrates that combining NaOH with waterglass accelerates early aluminosilicate dissolution and enhances ultimate compressive strength ($> 65\text{ MPa}$).

Evidence summary

Precursors & Activators:
GGBFS (Australia), Class C Fly Ash (FAC, $14.2\%\ \text{CaO}$), Class F Fly Ash (FAF, $4.1\%\ \text{CaO}$).
Activators: 10 M $\text{NaOH}$, sodium silicate waterglass ($M_s = 3.22$), and hybrid combinations; cured at 80 °C.
Synchrotron XRD & Phase Identification:
AAS (Slag): Forms poorly crystalline C-S-H(I) / C-A-S-H gel and hydrotalcite.
FAF (Class F): Forms amorphous 3D N-A-S-H gel, hydroxycancrinite, and hydroxysodalite (ABC-6 zeolite family).
FAC (Class C): Forms co-existing C-A-S-H and N-A-S-H hybrid networks.
Compressive Strength Kinetics:
NaOH-activated pastes achieve rapid strength gain within 24 hours ($f_c = 45\text{--}68\text{ MPa}$).
Waterglass buffered with NaOH (FAC_NW) achieves $f_c = 65.4\text{ MPa}$ at 14 days without rheology loss.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
04_material_systems/geopolymer_ecc.md
04_material_systems/green_ecc.md
02_concepts/matrix_fracture_toughness.md
02_concepts/circular_economy_materials.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (Matrix Microstructure) and Chapter 9 (Green ECC).
Provides the crystalline and molecular-scale thermodynamic foundation for geopolymer matrix engineering, explaining how activator choice ($M_s$ and alkalinity) governs the formation of amorphous C-A-S-H vs. N-A-S-H frameworks that control matrix fracture toughness ($K_m$) in green ECCs.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/geopolymer_ecc.md`	Hydrotalcite forms universally in alkali-activated slag and fly ash geopolymers, while hydroxycancrinite zeolitic units form in Class F fly ash	Synchrotron X-ray diffraction (ALS Beamline 12.2.2) and Rietveld refinement	Section 3.3 & 3.4, Fig. 3-6, Table 3	verified_from_pdf
`04_material_systems/green_ecc.md`	Hybrid NaOH and waterglass activation accelerates aluminosilicate dissolution and yields $f_c > 65\text{ MPa}$ at 80 °C	Universal testing machine compressive strength evolution over 14 days	Section 3.2, Fig. 2, Table 3	verified_from_pdf

Verification status

PDF preserved: yes (oh-2010-the-evolution-of-strength-and-crystalline.pdf)
Text extracted: yes (full_text/oh-2010-the-evolution-of-strength-and-crystalline_full_text.md)
DOI verified: yes (10.1016/j.cemconres.2009.10.010)
Metadata verified: yes (Cem. Concr. Res., Vol. 40, No. 2, pp. 189–196, 2010)
Claim-evidence matrix ready: yes

Cautions

High-modulus waterglass ($M_s = 3.22$) without NaOH causes severe workability loss and delayed strength development in calcium-rich slag and Class C fly ash systems.
Synchrotron XRD measurements at 80 °C promote crystallization; room temperature ambient geopolymers remain predominantly amorphous N-A-S-H gels.