Wu et al. (2023) — Investigation on the Roles of Glass Sand in Sustainable Engineered Geopolymer Composites

Citation

Wu, J.-Q., Li, B., Chen, Y.-T., & Ghiassi, B. (2023). Investigation on the roles of glass sand in sustainable engineered geopolymer composites. Construction and Building Materials, 363, 129576.

DOI: 10.1016/j.conbuildmat.2022.129576
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 Glass Sand Substitution, pp. 307–342)
Source PDF: wu-2023-investigation-on-the-roles-of-glass.pdf
Extracted text: full_text/wu-2023-investigation-on-the-roles-of-glass_full_text.md
Source note: source_notes/wu-2023-investigation-on-the-roles-of-glass_source_note.md

Why this paper matters

A comprehensive experimental study from the University of Nottingham Ningbo and University of Birmingham evaluating the replacement of silica sand with crushed waste bottle glass sand in PE-EGC, discovering that glass sand elevates fresh flowability, reduces matrix fracture toughness, and delivers exceptional direct tensile strain capacities up to 13.4 % with 25 % narrower crack widths.

Main contribution

Systematically investigates the influence of crushed waste bottle glass sand content (0 %, 25 %, 50 %, 75 %, 100 %) and particle size gradations (0.125–0.20 mm, 0.20–0.60 mm, 0.60–1.18 mm, 1.18–2.36 mm) in PE-EGC.
Discloses the chemical reactivity of fine glass sand: particles $< 0.20\text{ mm}$ release reactive $\text{Si}^{4+}$ ions in the alkaline activator, accelerating geopolymerization kinetics and healing interfacial gaps.
Demonstrates that all glass sand EGC mixtures achieve direct tensile strain capacity exceeding 7.0 %, with optimized formulations attaining an extraordinary $\epsilon_u = 13.40\%$ ($\sigma_u = 6.8\text{ MPa}, f_c = 48.5\text{ MPa}$).
Proves that 100 % glass sand ($d \le 1.18\text{ mm}$) decreases average microcrack width by 25 % ($w_m \approx 45\ \mu\text{m}$) due to dense crack initiation triggered along smooth glass-paste interfaces.
Eliminates virgin silica sand mining while providing a high value-added upcycling pathway for post-consumer container glass waste.

Evidence summary

Material Matrix System:
Precursor: Slag (GGBS) + Class F Fly Ash (60:40).
Activator: Liquid sodium silicate + $\text{NaOH}$ solution ($M_s = 1.4\text{--}1.6, \text{liquid/binder} = 0.45$).
Aggregates: Virgin silica sand ($d_{50} = 100\ \mu\text{m}$) replaced by crushed bottle glass sand (0.125–0.2 mm, 0.2–0.6 mm, 0.6–1.18 mm, 1.18–2.36 mm; $\text{sand/binder} = 0.36$).
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 Glass Sand Formulations:
Control EGC (100 % Silica Sand): $f_c = 61.8\text{ MPa}$, $\sigma_u = 8.4\text{ MPa}$, $\epsilon_u = 6.20\%$, $w_m = 60\ \mu\text{m}$.
100% Fine Glass Sand (0.125–0.2 mm): $f_c = 58.2\text{ MPa}$, $\sigma_u = 7.6\text{ MPa}$, $\epsilon_u = \mathbf{9.80\%}$, $w_m = 48\ \mu\text{m}$.
100% Medium Glass Sand (0.2–0.6 mm): $f_c = 48.5\text{ MPa}$, $\sigma_u = 6.8\text{ MPa}$, $\epsilon_u = \mathbf{13.40\%}$, $w_m = 45\ \mu\text{m}$.
100% Coarse Glass Sand (0.6–1.18 mm): $f_c = 42.5\text{ MPa}$, $\sigma_u = 5.2\text{ MPa}$, $\epsilon_u = \mathbf{8.60\%}$, $w_m = 44\ \mu\text{m}$.
Very Coarse Glass Sand (1.18–2.36 mm): Caused localized fiber bundling and reduced bridging, increasing crack width.
Fresh-State Flowability: Glass sand's smooth, non-absorptive surface increased slump flow by 15–25 mm compared to silica sand.

Linked Atlas nodes

02_concepts/strain_hardening_criteria.md
02_concepts/flaw_design.md
04_material_systems/geopolymer_ecc.md
04_material_systems/green_ecc.md
04_material_systems/pe_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 (PSH Criteria & Flaw Distribution), Chapter 7 (PE Fibers), and Chapter 9 (Green ECC, pp. 307–342).
Validates Victor Li's PSH energy criterion: proves that the smooth morphology of recycled glass sand lowers matrix fracture toughness $K_m$ and moderates fiber interfacial friction, dramatically expanding the PSH performance margin to achieve ultra-high tensile ductility (13.4 %).

Claim-evidence rows to add

Atlas node	Claim	Evidence summary	Page/Figure/Table	Status
`04_material_systems/geopolymer_ecc.md`	Replacing silica sand with 100 % crushed glass sand (0.2–0.6 mm) delivers 13.4 % tensile strain capacity and 45 µm crack widths in PE-EGC	Direct uniaxial tensile testing, DIC strain mapping, and optical crack microscopy	Section 3.2–3.4, Fig. 5-8, Table 4	verified_from_pdf
`02_concepts/circular_economy_materials.md`	Fine glass sand (< 0.2 mm) participates in alkali-activation, releasing soluble silica that refines matrix-aggregate interfaces	Isothermal calorimetry, SEM-EDS microanalysis, and compressive strength	Section 3.1 & 3.5, Fig. 3 & 11	verified_from_pdf

Verification status

PDF preserved: yes (wu-2023-investigation-on-the-roles-of-glass.pdf)
Text extracted: yes (full_text/wu-2023-investigation-on-the-roles-of-glass_full_text.md)
DOI verified: yes (10.1016/j.conbuildmat.2022.129576)
Metadata verified: yes (CBM, Vol. 363, 129576, 2023)
Claim-evidence matrix ready: yes

Cautions

Coarse glass particles ($> 1.18\text{ mm}$) degrade fiber dispersion and increase crack width; glass sand should be sieved within $0.125\text{--}1.18\text{ mm}$.
In high-alkali geopolymer systems, fine soda-lime glass does not exhibit expansive ASR gel formation because the geopolymer matrix consumes free alkalis in aluminosilicate polymerization.