PSI - Issue 70

Janani P.K. et al. / Procedia Structural Integrity 70 (2025) 525–532

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The SEM analysis showed uniform distribution of PET- SiO₂ particles throughout the geopolymer material which created a seamlessly interconnected interface between them. The dense microstructure included minimal voids which confirmed better matrix stability and lower porosity. Durability and load-transfer performance of the material improve because PET and nano-silica work together in a harmonious manner.

Fig.7. SEM Morphology of PET- SiO₂ Composite

The modified concrete contained PET polymer as verified by spectroscopic analysis through UV-Vis absorbance testing and reflectance examination. PET-containing mixes showed a clear absorbance peak at 250 nm together with NIR reflectance increase above 2000 nm which indicated molecular interaction forces.

Fig. 8. UV-Vis : (a) Absorption and (b) Reflectance Spectra of PET- SiO₂ Geopolymer (Validation of PET polymer integration within the geopolymer matrix) 4. Discussion of Experimental Results Research shows the addition of 4g of PET- SiO₂ to geopolymer concrete results in a 20% increase in compressive strength at 28 days and enhances resistance to water absorption, chloride ion penetration, and acid attack, making it ideal for marine structures and harsh environments. SEM-EDX analysis reveals a denser microstructure, improving durability and reducing permeability. However, tensile and flexural strength are lower than that of the normal mix, as PET- SiO₂ does not provide fiber reinforcement, which is essential for withstanding tensile and flexural stresses. While PET- SiO₂ contributes to better durability and sustainability, it is unsuitable for structural components like beams and slabs, which require higher flexural resistance. Future research should explore alternative reinforcement techniques, assess long-term material behaviors such as creep and shrinkage, and validate these findings through full-scale testing.