A fast-setting and eco-friendly superhydrophobic high belite sulphoaluminate cement mortar

High belite sulphoaluminate cement (HBSC) has shown great potential as new lower CO2 footprint cementitious material. It makes sense to improve the hydrophobic property of HBSC to obtain high durability performance. In this paper, nontoxic short carbon chain lauric acid (LA) is used to match the early strength characteristic of HBSC to prepare fast-setting and eco-friendly LA-modified HBSC mortar (M-HBSCM). Sands modified with LA provide low surface energy for an integral hydrophobic effect. M-HBSCM exhibits superhydrophobicity even after hammering to expose the fractured internal structure, with a contact angle of 153.2°. And it shows outstanding self-cleaning property against contaminants such as sand and wet mud and a reduction in water absorption to around 23% of the ordinary HBSCM (O-HBSCM). The fabricated M-HBSCM has fast-setting property with an initial setting time of 29 min and a final setting time of 36 min. The abrasion test displays that the scratched area remains well superhydrophobic with high mechanical robustness when the droplets roll off on the inclined surface. Field-emission scanning electron microscope (FESEM) indicates that M-HBSCM contains more pores and coarser hydration products. The system of calcium alumina and pores exhibits a distinct hierarchical structure, providing the multilevel roughness required for the superhydrophobic surface. Fourier transform infrared (FTIR) spectrometer indicates that low surface energy functional groups have been successfully grafted onto M-HBSCM. The superhydrophobic concrete has good mechanical robustness, corrosion resistance, and fast-setting property, which can meet the demands of grouting reinforcement projects, the repair of various concrete structures, corrosion protection of marine structures and other projects.