## 1 Introduction  
The development of self-compacting concrete (SCC) by Okamura facilitates better constructability and confers benefits to the production and placement of concrete, especially in structural components with denser reinforcements [1]. Combining the benefits of SCC with eco-friendly geopolymer concrete-made industrial waste products such as fly ash and slag as binder materials contributes to a sustainable construction technique offering significant environmental benefits [2, 3]. The similarity in properties provided by the eco-friendly sustainable concrete such as geopolymer concrete compared to ordinary concrete has received greater attention from researchers [4]. Thus geopolymer concrete is considered a viable alternative to conventional cement concrete, offering environmental benefits and decreased carbon emissions [3, 4]. The geopolymer concrete is generally composed of aluminosilicate-rich binders sourced from industrial combustion by-products (fly ash and slag), along with a highly alkaline activator such as sodium hydroxide sodium metasilicate and potassium hydroxide [3, 5, 6, 7]. In recent decades, extensive research on geopolymer concrete shows that blended geopolymer concrete containing one or more binder materials, such as slag, fly ash, and micro fly ash, aids in developing cementitious mortar under ambient conditions [8, 9, 10]. This type of blended concrete reduces the need for additional heat treatment, which was initially required for metakaolin-based or fly-based geopolymer concretes [7; 11]. Along with the inherent environmental benefits, the geopolymer concrete offers higher mechanical strengths, fire resistance, and resistance to chemical attacks. These properties make them a suitable candidate for harsh weather applications, including in marine and saline environments where concrete structures are exposed to unstable weather or water [2; 3; 12; 13]. Various studies have shown that heat treatment will improve the early age strengths of geopolymer concrete. Heat exposure beyond 60 \({}^{\circ}\)C may create a porous and non-uniform matrix of geopolymer concrete [4; 14; 15]. Many studies have focused on applying geopolymer concrete in hazardous environments, including elevated temperatures, freeze-thaw exposure, sulphate attack, and acid exposure; however, no specific publications have reported the behaviour of SCGC in marine/tidal conditions [16; 17; 18; 19]. The marine environments often lead to corrosion attacks in steel-reinforced concrete structures and are severely influenced by the tidal conditions, temperature, and moisture variations, along with abrasion attacks [16; 20]. The simulation of these factors proves to be complicated and is equally warranted for promoting the use and development of suitable mixes of geopolymer concrete in the marine environment. Earlier studies on geopolymer with liquid-based activator and high sodium concentrations under 3-year exposure in seawater caused a strength gain in geopolymer concrete [17; 21]. Furthermore, research on artificial reefs for marine biodiversity protection adopted the use of geopolymer binders due to reduced carbon emissions and better performance in marine climate [22; 23]. The activator compositions in geopolymer concrete can reduce the level of chloride ingress in geopolymer concrete, unlike the conventional OPC [17; 18; 24]. Sodium hydroxide, sodium silicates, and similar sodium-based high alkaline reagents are the most used activators in geopolymer concrete, which has been found to reduce the chloride binding capacity [16; 17; 25]. In addition to the role of activator composition, the curing conditions of the geopolymer concrete has also been assessed for the performance in marine environments against degradation by various researchers. An ultrasonic pulse velocity and surface resistivity in geopolymer concrete cured in saline water recorded higher resistance to salt ingress due to a denser internal geopolymer matrix [26].