Alkali-Activated / Geopolymer Ultra-Ductile Position

1. Research axis definition

This research axis positions Professor Bang Yeon Lee's lab as an early and sustained contributor to transferring ECC/SHCC strain-hardening design from ordinary Portland cement matrices into cementless alkali-activated slag (AAS), fly ash/slag geopolymer, and engineered geopolymer composite (EGC) systems.

The axis is not simply "green binder replacement." Its scientific core is:

Victor Li micromechanics
  -> PSH strength and energy criteria
    -> binder/matrix/interface adaptation in AAS and EGC
      -> distributed multiple cracking and tight crack-width control
        -> cementless / low-carbon ductile composites

2. Global literature anchor

Global anchor:

• Victor C. Li 2019 book: ECC is defined by tensile ductility and controlled multiple cracking rather than compressive strength alone.
• Foundational PSH criteria and fiber bridging logic: [[strain_hardening_criteria]], [[fiber_bridging_law]], [[interface_properties]], [[flaw_design]].
• Green ECC and EGC extension nodes: [[green_ecc]], [[geopolymer_ecc]], [[cementless_composites]], [[extreme_ductility_ecc]].

Within the global Atlas, this axis extends the ECC framework into binder systems where the matrix chemistry, setting behavior, shrinkage, pore structure, and fiber/matrix interface differ substantially from OPC ECC.

3. Lee lab representative papers

4. Key evidence and metrics

• AAS feasibility: Lee et al. 2012 reports 100% cementless AAS mortar with 2.0 vol% PVA fibers reaching 4.48% tensile strain capacity, compared with 0.020% for matrix alone.
• Cement vs AAS matrix: Choi et al. 2016 reports PE-AAS composites with tensile strain capacity up to 5.92%, and AAS-based composites showing higher tensile-to-cracking strength ratio than cement-based counterparts.
• AAS fiber-bridging verification: Choi et al. 2020 reports PE-AAS composite with 7.5% direct tensile ductility, 8.5 MPa tensile strength, and PSH indices exceeding practical thresholds.
• Fly ash EGC ultra-ductility: Nguyen et al. 2021 positions fly ash-based EGC as an ultra-ductile cement-free branch.
• Extreme AAS ductility: Luong et al. 2023 reports AAS-based composite with 22.34% tensile strain capacity in the verified source-note record.

5. What is distinctive about Lee lab contribution

The distinctive contribution is the sustained transfer of ECC micromechanics into cementless binder systems while preserving direct tensile strain-hardening. The lab's work does not only replace cement with slag or fly ash; it evaluates whether the altered matrix can still satisfy the PSH conditions through adjusted rheology, interface, fiber aspect ratio, matrix toughness, and crack-width behavior.

6. Strategic novelty claims

• Lee lab provides an early experimental bridge from classic PVA-ECC to cementless AAS-ECC/EGC.
• The lab demonstrates that alkali-activated and geopolymer matrices can be engineered as ductile composites rather than treated as brittle low-carbon binders.
• The lab's AAS/EGC line shows that high ductility can coexist with low-carbon binder design when fiber bridging and matrix cracking strength are jointly controlled.
• The lab's work provides a platform for low-carbon infrastructure materials that are not merely greener, but mechanically ductile and crack-width-controlled.

7. Manuscript intro/discussion reusable paragraphs

Intro paragraph draft:

ECC research established that tensile strain-hardening requires simultaneous control of matrix cracking resistance and fiber bridging capacity. While this principle was originally developed mainly for Portland cement-based systems, practical sustainability requires transferring the same micromechanical logic to cementless binders. Professor Lee's research line provides a source-grounded route for this transfer, beginning with alkali-activated slag strain-hardening mortar and extending to PE-reinforced AAS and fly ash/geopolymer composites with high or ultra-high tensile ductility.

Discussion paragraph draft:

The present results should be interpreted within the broader Lee lab lineage of cementless ductile composites. Across AAS and EGC systems, ductility is achieved not by binder substitution alone, but by tuning the matrix and interface so that multiple cracking remains energetically favorable. This places the current material within a Green ECC design pathway where sustainability and strain-hardening are co-optimized.

8. Proposal background reusable paragraphs

Low-carbon cementitious materials often suffer from brittleness, shrinkage, or unstable cracking, limiting their use in resilient infrastructure. A key research opportunity is to combine cementless binder chemistry with ECC micromechanics so that low-carbon binders also exhibit tensile ductility and controlled crack width. The Lee lab publication record demonstrates the feasibility of this approach across AAS and EGC systems, providing a foundation for next-generation sustainable, ductile, and damage-tolerant construction materials.

9. Open research opportunities

1. Ambient-curing one-part EGC with reliable fiber dispersion and low shrinkage.
2. Quantitative coupling between geopolymer reaction products and fiber pullout behavior.
3. Low-fiber EGC design using flaw/matrix tailoring to reduce PE fiber dependency.
4. Field-relevant durability of cementless ductile composites under chloride, carbonation, freeze-thaw, and wet-dry cycles.
5. AI/Wiki-RAG guided selection of binder chemistry, fiber type, and flaw design.

10. Linked Atlas nodes and source files

• [[green_ecc]] — 04_material_systems/green_ecc.md
• [[geopolymer_ecc]] — 04_material_systems/geopolymer_ecc.md
• [[cementless_composites]] — 04_material_systems/cementless_composites.md
• [[strain_hardening_criteria]] — 02_concepts/strain_hardening_criteria.md
• [[fiber_bridging_law]] — 02_concepts/fiber_bridging_law.md
• [[direct_tensile_test]] — 05_experiments/direct_tensile_test.md
• Lab source index: 00_sources/by_lee_lab_publications/metadata/by_lee_lab_publications_source_index.csv
• Lab claim matrix: 07_visualization/by_lee_lab_publications_claim_evidence_matrix.csv