Lương et al. (2021) — Effects of Crumb Rubber Particles on Mechanical Properties and Sustainability of Ultra-High-Ductile Slag-Based Composites

Citation

Lương, Q.-H., Nguyễn, H. H., Choi, J.-I., Kim, H.-K., & Lee, B. Y. (2021). Effects of crumb rubber particles on mechanical properties and sustainability of ultra-high-ductile slag-based composites. Construction and Building Materials, 272, 121959.

DOI: 10.1016/j.conbuildmat.2020.121959
Atlas layer: core
Related Victor Li book chapter: Chapter 4: Matrix Flaw Size Tailoring (Artificial Flaw Concepts) & Chapter 7: PE Fibers & Chapter 9: Green ECC (Alkali-Activated Slag & Recycled Crumb Rubber)
Source PDF: long-2021-effects-of-crumb-rubber-particles-on.pdf
Extracted text: full_text/long-2021-effects-of-crumb-rubber-particles-on_full_text.md
Source note: source_notes/long-2021-effects-of-crumb-rubber-particles-on_source_note.md

Why this paper matters

A landmark study from Chonnam National University demonstrating that incorporating 5 % recycled tyre crumb rubber as tailored artificial micro-flaws in alkali-activated slag composites elevates direct tensile ductility to an extraordinary 10.7 % with ultra-dense multiple cracking (crack spacing 0.70 mm), while silica fume hybridization restores compressive strength to 53.6 MPa.

Main contribution

Develops ultra-high-ductile cementless composites combining GGBFS, solid $\text{Ca(OH)}_2$ activator, recycled tyre crumb rubber (CR, $d = 0.6\text{ mm}$ at 5 % and 10 % binder replacement), and 1.75 vol. % PE fibers.
Discovers that 5 % CR addition acts as uniform artificial micro-flaw nucleation sites, triggering saturated multiple cracking and boosting direct tensile strain capacity to 10.7 % (average crack spacing 0.70 mm, $> 100$ cracks in gauge section).
Introduces 5 wt% Silica Fume (SF) to compensate for rubber-induced strength loss, achieving $f_c = 53.6\text{ MPa}$, $\sigma_u = 10.42\text{ MPa}$, and $\epsilon_u = 8.5\%$.
Analyzes microstructural SEM morphology, proving that rubber particles prevent localized stress concentrations and promote distributed fiber bridging.
Evaluates sustainability via Material Sustainability Indicators (MSI), confirming $> 70\%$ lower carbon footprint and $> 50\%$ lower embodied energy than cement-based UHD-ECC.

Evidence summary

Material Formulation: 100 % GGBFS activated with solid powder $\text{Ca(OH)}_2$ (10 wt% of slag), $w/b = 0.30$.
Inclusions: Crumb rubber (CR, $d = 0.60\text{ mm}$) at 0 %, 5 %, 10 % binder replacement; Silica Fume (SF) at 5 wt%.
Fiber Specifications: 1.75 vol. % UHMWPE fibers ($l_f = 18\text{ mm}, d_f = 12\ \mu\text{m}, \sigma_f = 2700\text{ MPa}, E_f = 88\text{ GPa}$).
Mechanical Properties (28-day water cured):
Control (0 % CR): $f_c = 48.5\text{ MPa}$, $\sigma_u = 8.85\text{ MPa}$, $\epsilon_u = 7.50\%$, crack spacing $s = 1.30\text{ mm}$.
CR5 (5 % CR): $f_c = 38.2\text{ MPa}$, $\sigma_u = 7.33\text{ MPa}$, $\epsilon_u = \mathbf{10.70\%}$, crack spacing $s = \mathbf{0.70\text{ mm}}$.
CR10 (10 % CR): $f_c = 28.4\text{ MPa}$, $\sigma_u = 5.65\text{ MPa}$, $\epsilon_u = 7.85\%$, crack spacing $s = 0.95\text{ mm}$.
CR5-SF5 (5 % CR + 5 % SF): $f_c = \mathbf{53.6\text{ MPa}}$, $\sigma_u = \mathbf{10.42\text{ MPa}}$, $\epsilon_u = \mathbf{8.50\%}$, crack spacing $s = 0.75\text{ mm}$.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
02_concepts/fiber_bridging_law.md
04_material_systems/geopolymer_ecc.md
04_material_systems/green_ecc.md
04_material_systems/pe_ecc.md
04_material_systems/rubberized_ecc.md
05_experiments/direct_tensile_test.md
02_concepts/circular_economy_materials.md

Relationship to Victor Li book

Extends Victor Li (2019) Chapter 4 (Matrix Flaw Size Tailoring, pp. 77–114), Chapter 7 (PE Fibers), and Chapter 9 (Green ECC).
Validates Victor Li & Wang's artificial flaw seeding concept in a cement-free matrix: shows that compliant rubber inclusions generate a tightly spaced flaw spectrum that activates saturated multiple cracking across the entire gauge length, expanding tensile strain capacity past 10 %.

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/rubberized_ecc.md`	Incorporating 5 % crumb rubber as tailored flaws in PE-AAS composite achieves direct tensile strain capacity of 10.7 %	Uniaxial direct tensile tests and digital crack spacing measurements	Section 3.1 & 3.2, Fig. 4-7, Table 2	verified_from_pdf
`04_material_systems/geopolymer_ecc.md`	Hybridizing 5 % crumb rubber with 5 % silica fume restores compressive strength to 53.6 MPa and achieves $\sigma_u = 10.42\text{ MPa}$ and $\epsilon_u = 8.5\%$	ASTM compression and JSCE dogbone direct tensile testing	Section 3.1 & 3.2, Fig. 4-8, Table 2	verified_from_pdf

Verification status

PDF preserved: yes (long-2021-effects-of-crumb-rubber-particles-on.pdf)
Text extracted: yes (full_text/long-2021-effects-of-crumb-rubber-particles-on_full_text.md)
DOI verified: yes (10.1016/j.conbuildmat.2020.121959)
Metadata verified: yes (CBM, Vol. 272, 121959, 2021)
Claim-evidence matrix ready: yes

Cautions

Crumb rubber content $> 10\%$ causes excessive drops in compressive strength ($< 28\text{ MPa}$) and reduces fiber-matrix bond stiffness.
Silica fume hybridization is recommended to maintain compressive strength $> 50\text{ MPa}$ while retaining high tensile ductility ($> 8\%$).