Sustainable fly ash-based geopolymer composites with 3D-printed reinforcements: Experimental investigation and performance analysis
Date
2025
Authors
Pourdolat Safari Tutkaboni, Navid
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Abstract
The demand for sustainable and high-performance construction materials has driven research into geopolymers as an eco-friendly alternative to cement concrete. This thesis explores the development of fly ash-based geopolymer composites reinforced with bio-inspired 3D-printed polymer structures to enhance their mechanical performance and sustainability. Given the high carbon footprint and cost of commercial sodium silicate (CSS) activators, this study evaluates the feasibility of a silica fume-derived sodium silicate alternative (SSA) in improving geopolymer performance while reducing environmental impact. Additionally, triply periodic minimal surface (TPMS) polymer reinforcements, fabricated via Fused Deposition Modeling (FDM), are investigated to mitigate the brittleness of geopolymers and enhance flexural strength, energy absorption, and ductility.
A two-phase experimental approach was adopted. Phase I optimized a two-part geopolymer mix design using SSA and sodium hydroxide (NaOH) as the alkaline activator. Fresh and hardened properties, including setting time, workability, compressive strength, and tensile and flexural performance, were assessed. Results showed that SSA-based geopolymers outperformed CSS-based counterparts, with the AS0.7-65 mix achieving the highest compressive strength while curing at a lower temperature (65 °C). Microstructural analyses (SEM, EDX, ATR-FTIR) confirmed a denser, more homogeneous matrix with fewer unreacted fly ash particles. Sustainability and cost assessments indicated that SSA-based systems are approximately 30% more cost-effective and contribute to a 2% reduction in carbon dioxide emissions.
Phase II investigated 3D-printed TPMS reinforcements embedded within the geopolymer matrix. Reinforced samples exhibited a substantial increase in energy absorption and a shift from brittle to ductile failure, with the G1-R2 configuration (a coarse lattice with higher volume fraction) exhibiting the greatest improvement in energy absorption (x10-20 more than others) and ductility (5.35 mm maximum deflection). This research advances the integration of geopolymer technology and additive manufacturing, demonstrating the potential of 3D printing for reinforced geopolymers. The findings support the development of high-performance, eco-friendly construction materials that align with global sustainability goals. Future research should focus on ambient curing, multi-material 3D printing with recycled polymers, and large-scale applications, further optimizing the mechanical performance and environmental impact of SSA-based geopolymer composites. By combining geopolymer chemistry, digital fabrication, and sustainable design, this study presents a scalable and cost-effective solution for next-generation construction materials.
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Keywords
Geopolymer, Fly Ash, Silica Fume, Sustainability, Microstructure