Li & Li 2012/2013 - Rheology, Fiber Dispersion, and Robust Properties of ECC

Citation

Li, M., Li, V.C. (2013). Rheology, fiber dispersion, and robust properties of Engineered Cementitious Composites. Materials and Structures, 46(3), 405-420 (RILEM). DOI: 10.1617/s11527-012-9909-z. (Accepted 12 July 2012; online 2012.)

Source paths

• PDF: 00_sources/foundational_papers/originals/li-2012-rheology-fiber-dispersion-and-robust.pdf
• Extracted full text: 00_sources/foundational_papers/extracted_text/li-2012-rheology-fiber-dispersion-and-robust.md
• Source note: 00_sources/foundational_papers/source_notes/li-2012-rheology-fiber-dispersion-and-robust.md

Why the paper matters for the Atlas

• First systematic, quantitative correlation on PVA-ECC between fresh mortar plastic viscosity, PVA fiber dispersion coefficient α, and hardened tensile strain capacity — the primary literature anchor for processing_rheology and fiber_dispersion.
• Provides a practical, transferable QC tool (Marsh cone flow time, optimal 24-33 s for the specified fiber and mixer) directly usable in Professor Lee's lab-scale ECC/EGC processing.
• Gives the micromechanics-based mechanistic bridge from dispersion to strain capacity: low α → lower σ_0 at weakest section → reduced J_b' and increased c_mc → fewer flaws activated → less multiple cracking.

Direct evidence extracted from source text

• Marsh cone flow time and rotational-viscometer plastic viscosity are linearly correlated with R = 0.95 across seven mixes.
• Optimal Marsh cone flow time 24-33 s (Hobart 12 L force-based mixer, REC15 PVA at 2 vol%, mix given in Table 2) gives dispersion coefficient α ≈ 0.7-0.85 and tensile strain capacity ~3 % with much reduced scatter.
• Below the window (Marsh cone ≤ 12-17 s): softening or unstable strain-hardening; above the window (Marsh cone 39 s / 0.04 % VMA): dispersion still high but larger entrapped air pores lower first-crack and ultimate tensile strength.
• WHITE ECC case study: adding 0.05 % VMA lifts Marsh cone from 12 s to 28 s, α from ~0.53 to ~0.8, average strain capacity from ~2 % to ~3 %; further VMA to 0.10 % (Marsh cone 38 s) still improves consistency but lowers UTS.
• Fiber dispersion measured by fluorescence imaging (Nikon TE300, Hamamatsu CCD) on 5 mm slice at the failure section, 76.2 × 12.7 mm cross section reconstructed at 23,005 × 4,186 px from 21 × 5 tiles, α = exp(-w(x)) on 5 × 21 unit cells.

Atlas node links

• Concept: 02_concepts/processing_rheology.md (primary), 02_concepts/strain_hardening_criteria.md, 02_concepts/flaw_design.md, 02_concepts/fiber_bridging_law.md.
• Experiment: 02_concepts/fiber_dispersion.md, 05_experiments/direct_tensile_test.md.
• Related paper cards: li_wang_2006_microstructure_variability.md, zhou_etal_2012_mixing_sequence_fiber_distribution.md, kanda_li_2006_practical_design_criteria_psh.md.

Graph implications

• Adds/strengthens candidate edges:
• processing_rheology → fiber_dispersion (quantitative — via plastic viscosity / Marsh cone)
• fiber_dispersion → strain_hardening_criteria (α determines σ_0 at weakest section → J_b')
• fiber_dispersion → direct_tensile_test (tensile strain capacity and scatter tied to α)
• Provides evidence to promote processing_rheology → fiber_dispersion and fiber_dispersion → fiber_bridging_law from candidate toward confirmed.

Status

PDF received; text extracted; source-note created; detailed evidence pending (per-specimen strain-capacity row assignments in Table 3 and exact figure numbering — to verify against the original layout).