Development of hydrophobicity in geopolymer composites-Progress and perspectives

The long-term durability of geopolymer concrete is one of the main problems that needs to be overcome before it can be universally acknowledged as a viable alternative to conventional concrete. The main cause of the durability issue is the migration and transport of water in the hydrophilic porous structure of geopolymer materials. To increase the long-term durability of geopolymer concrete, hydrophobic modification of geopolymers has recently garnered the interest of the researchers, and there is a lack of comprehensive summarization of the literature on hydrophobic geopolymer concrete composites, their preparation strategies, characterization methods, and properties, which has been the inspiration behind this literature review. This paper discusses the recent developments in the field of hydrophobic modification of geopolymer concrete, the different modification approaches, surface classification based on wettability, materials used, and the properties affected due to hydrophobic alternation. Properties studied include Water Contact Angle (WCA), surface energy, physical, mechanical, durability, and microstructural properties of the modified composites. Based on the literature reviewed, a pilot study was also carried out using an organosilane-based material to induce hydrophobicity in geopolymer concrete. Integral hydrophobic modification yielded a WCA of 66.083whereas surface modification yielded a WCA as high as 106.038, which indicates successful modification of a hydrophilic surface to a hydrophobic one. Although the work on hydrophobic geopolymer concrete is limited, this paper is anticipated to serve as a roadmap for future investigations into the creation, processing, and characterization of hydrophobic geopolymer concrete.