Utilization of Superhydrophobic Phosphogypsum in Mortar to Ameliorate Water Repellency and Mechanical Strength

Phosphogypsum (PG) is a byproduct of the phosphate fertilizer industry that can be used in cement mortar. However, PG mortar is known to have high water absorption. This paper proposes a new method to address this issue by using superhydrophobic phosphogypsum (SPG). PG was modified using stearic acid and sodium metasilicate. The hydrophobic mortar (H-mortar) was obtained by replacing a portion of the cement with SPG powder. The optimum water contact angle of the H-mortar was measured at 108.3°. Results from the experiment show that the water absorption of H-mortar was 19% lower than that of the reference mortar (Ref-M). Furthermore, the mechanical strength of H-mortar increased compared to Ref-M, as observed through strength testing. The study also investigated the impact of SPG addition rate on mortar corrosion resistance, and found that the addition of SPG reduces water migration and enhances resistance to chloride ion corrosion. The proposed method has the potential to utilize PG waste while improving mortar strength and corrosion resistance, making it suitable for use in marine mortar structures.