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Concrete structures exposed to marine environments are most prone to high degradation through chloride-induced corrosion and, therefore, require modern materials with superior hydrophobicity and corrosion resistance. This paper focuses on the optimisation of a Symbio-Pozzolanic Composite Hydrophobic Powder to improve the overall mechanical performance and durability of the cementitious matrix. Using Response Surface Methodology with a Central Composite Design, 30 formulations were prepared and tested with major ingredients Class F Fly Ash, Silica Fume, Metakaolin, and Zinc Stearate. The optimised mix attained the age of 56 days with a C of 46.19 MPa and an outstandingly low corrosion rate of 0.000241 mm per year, which reflects superior resistance to chloride and durability. Water contact angle measurements showed a high value of 146.5°, confirming effective hydrophobicity due to the synergistic interaction between Zinc Stearate and supplementary cementitious materials. Microstructural analyses revealed a denser matrix characterised by increased calcium-silicate-hydrate and calcium-alumino-silicate-hydrate phases, reduced porosity and the formation of hydrophobic surface layers. The results of this research reveal that SPCHP, particularly Mix M4, can be an alternative material that is durable in marine environments. The material contains mechanical strength together with hydrophobic and anti-corrosive properties to prolong service life while minimising the costs of maintaining concrete infrastructures exposed to severe environmental conditions. The research provides insights into SPCHP performance in relation to the further development of sustainable and durable concrete technologies.
Gnanaraj et al. (Mon,) studied this question.