Investigation on in-situ geopolymer coatings: A comparative analysis of lycopodium powder and polydimethylsiloxane as functional additives

Abstract

Geopolymer-based inorganic coatings provide an effective alternative to conventional chemical-based solutions. However, the coatings are not universally applicable, especially in critical applications such as underwater. This research aims to investigate and enhance geopolymer-based coating through specific utilization of functional additives such as reduced graphene oxide (rGO), lycopodium powder (LCP), and polydimethylsiloxane (PDMS) for underwater applications. These additives were incorporated in limited dosages (<3 wt.% of binder), and their potential is further assessed in improving the coating material in terms of the resulting water resistance, mechanical properties, and durability against NaCl, MgSO4, HNO3, and H2SO4 attacks. The introduction of rGO facilitated a 35% increase in the 28-day compressive strength and 33.83% in the scratch hardness, whereas (rGO + LCP) improved the water contact angle by 125%. Additionally, the developed coatings were further analyzed using an optical microscope and x-ray diffractometer to understand their bonding potential with steel or cementitious substrates and phase formation. Life cycle cost analysis was also conducted to evaluate the economic viability of the geopolymer coatings, revealing a potential cost reduction of approximately 16%-42% with the sourcing of locally available materials.