Wang et al. (2024) — Elucidating the Role of Recycled Concrete Aggregate in Ductile Engineered Geopolymer Composites: Effects of Recycled Concrete Aggregate Content and Size
Citation
Wang, C., Zhang, Z., Liu, X., Zhang, Y., & Ma, Z. (2024). Elucidating the role of recycled concrete aggregate in ductile engineered geopolymer composites: Effects of recycled concrete aggregate content and size. Journal of Building Engineering, 95, 110150.
- DOI:
10.1016/j.jobe.2024.110150 - Atlas layer: core
- Related Victor Li book chapter: Chapter 4: Pseudo Strain-Hardening Criteria & Chapter 7: Alternative Reinforcing Fibers (PE Fibers) & Chapter 9: Green ECC (Recycled Concrete Fine Aggregate Substitution, pp. 307–342)
- Source PDF:
wang-2024-elucidating-the-role-of-recycled-concrete.pdf - Extracted text:
full_text/wang-2024-elucidating-the-role-of-recycled-concrete_full_text.md - Source note:
source_notes/wang-2024-elucidating-the-role-of-recycled-concrete_source_note.md
Why this paper matters
A comprehensive experimental study from Yangzhou University and Shanghai University demonstrating that replacing 100 % of virgin silica sand with Recycled Concrete Fine Aggregate (RFA) in PE-EGC not only eliminates natural aggregate consumption but actually increases tensile strength (+5.7 %) and strain capacity (+8.6 % to 12.9 %) via secondary geopolymerization and micro-flaw crack initiation.
Main contribution
- Investigates the complete substitution of virgin quartz silica sand with recycled concrete fine aggregate (RFA) across replacement ratios (0 %, 25 %, 50 %, 75 %, 100 %) and particle gradations (0–0.15 mm, 0.15–0.30 mm, 0.30–0.60 mm, 0.60–1.18 mm).
- Uncovers the chemical role of attached old mortar: active alkaline hydrates in RFA undergo secondary geopolymerization in $\text{Na}_2\text{SiO}_3/\text{NaOH}$ solutions, forming dense C-(N)-A-S-H gels that refine the composite microstructure.
- Demonstrates that inherent micro-pores in RFA act as uniform Griffith-like defect sites that facilitate multi-crack initiation, increasing tensile ductility without sacrificing matrix strength.
- Proves that 100 % RFA-blended EGC achieves a compressive strength of 58.2 MPa, tensile strength of 9.4 MPa (+5.7 %), and tensile strain capacity of 7.60 % to 7.90 % (+8.6 % to +12.9 % higher than pure silica sand control).
- Identifies optimal alkaline activator modulus ($M_s = 1.5$) and PE fiber length (12 mm) for maximum mechanical synergy in 100 % recycled aggregate matrices.
Evidence summary
- Material Matrix System: Class F Fly Ash + GGBFS (60:40) + 10 % silica fume, activated by $\text{Na}_2\text{SiO}_3 + \text{NaOH}$ ($M_s = 1.2\text{--}1.8$), liquid/binder = 0.45.
- Aggregate Substitution: Recycled fine aggregate (RFA) derived from crushed 46.3 MPa concrete waste; apparent density $2343\text{ kg/m}^3$, water absorption $11.2\%$.
- Fiber Specifications: UHMWPE fibers ($V_f = 2.0\text{ vol. \%}, l_f = 12\text{ mm}, d_f = 24\ \mu\text{m}, \sigma_f = 3000\text{ MPa}, E_f = 100\text{ GPa}$).
- Mechanical Results across RFA Dosages & Sizes:
EGC-Ref(100 % Silica Sand, 0.15–0.30 mm): $f_c = 55.4\text{ MPa}$, $\sigma_u = 8.9\text{ MPa}$, $\epsilon_u = 7.00\%$.100% RFA (0.15–0.30 mm): $f_c = \mathbf{58.2\text{ MPa}}$, $\sigma_u = \mathbf{9.4\text{ MPa}}$, $\epsilon_u = \mathbf{7.60\%}$ (+8.6 % strain gain).100% RFA (0.30–0.60 mm): $f_c = 54.1\text{ MPa}$, $\sigma_u = 9.1\text{ MPa}$, $\epsilon_u = \mathbf{7.90\%}$ (+12.9 % strain gain).Silicate Modulus ($M_s = 1.5$): Delivered peak tensile strain-hardening response.
Linked Atlas nodes
02_concepts/strain_hardening_criteria.md02_concepts/flaw_design.md04_material_systems/geopolymer_ecc.md04_material_systems/green_ecc.md04_material_systems/pe_ecc.md05_experiments/direct_tensile_test.md02_concepts/circular_economy_materials.md02_concepts/life_cycle_analysis.md
Relationship to Victor Li book
- Extends Victor Li (2019) Chapter 4 (PSH Criteria & Flaw Size Distribution), Chapter 7 (PE Fibers), and Chapter 9 (Green ECC, pp. 307–342).
- Validates the micromechanical defect theory: proves that RFA aggregate porous micro-flaws lower first-cracking stress relative to fiber bridging capacity ($\sigma_0/\sigma_{fc} > 1.2$), converting aggregate waste into a beneficial pseudo strain-hardening promoter.
Claim-evidence rows to add
| Atlas node | Claim | Evidence summary | Page/Figure/Table | Status |
|---|---|---|---|---|
02_concepts/circular_economy_materials.md |
100 % replacement of silica sand with recycled fine aggregate (RFA) increases EGC tensile strength to 9.4 MPa and strain capacity to 7.6–7.9 % | Direct uniaxial dogbone tension and ASTM C39 compression tests | Section 3.1–3.4, Fig. 5-9, Table 4 | verified_from_pdf |
04_material_systems/geopolymer_ecc.md |
Residual hydrated paste in RFA undergoes secondary geopolymerization in alkaline solution, forming dense C-(N)-A-S-H bonding gels | SEM-EDS microstructural and mineralogical analysis | Section 3.5, Fig. 11 & 12 | verified_from_pdf |
Verification status
- PDF preserved: yes (
wang-2024-elucidating-the-role-of-recycled-concrete.pdf) - Text extracted: yes (
full_text/wang-2024-elucidating-the-role-of-recycled-concrete_full_text.md) - DOI verified: yes (
10.1016/j.jobe.2024.110150) - Metadata verified: yes (J. Build. Eng., Vol. 95, 110150, 2024)
- Claim-evidence matrix ready: yes
Cautions
- Coarse RFA particles ($> 0.60\text{ mm}$) increase matrix fracture toughness and water demand, slightly reducing compressive strength.
- High water absorption of RFA ($7.6\%\text{--}11.2\%$) requires pre-soaking or moisture compensation in liquid activator batching.