Synthesis of water-resistant hybrid geopolymer composites using polydimethylsiloxane and triethoxysilane

This study presents the development of a novel hydrophobic geopolymer system based on metakaolin, engineered through the direct incorporation of polydimethylsiloxane (PDMS) and triethoxysilane (TES) into the precursor mix. Aimed at overcoming the limitations of traditional internal waterproofing approaches, this method imparts hydrophobicity at the matrix level without compromising mechanical integrity. Comprehensive characterization including contact angle measurements, FT-IR, SEM, EDX, and water absorption tests revealed significant enhancements in hydrophobicity, structural density, and long-term impermeability. The PDMS modified geopolymer exhibited a superhydrophobic contact angle of 150° and a water absorption rate as low as 0.21 % after 28 days, compared to 1.55 % for the unmodified control. FT-IR and EDX analyses confirmed the successful integration of hydrophobic groups, while SEM images showed improved matrix compaction. These findings highlight the potential of PDMS and TES as a water-resistant geopolymer suitable for infrastructure applications in aggressive or moisture-prone environments.