Improvement of Hydrophobic Surface and Mechanical Properties of Beta‐Hemihydrate Desulfurization Gypsum by Graphene Modification

Abstract Beta‐hemihydrate desulfurization gypsum (β‐HDG) is considered one of the green and low‐carbon building materials, which is widely used in the fields of construction materials and decoration. Nevertheless, its inherent deficiency in water resistance and other drawbacks significantly limit its application scope. In this study, the gypsum‐based materials with surfaces that exhibit hydrophobic properties were prepared. The surface contact angle was analyzed to examine the surface hydrophobic characteristics. The compressive strength, flexural strength, ratio of compressive strength to flexural strength, water absorption rate, and softening coefficient of hardened specimens were measured to assess the mechanical properties. Furthermore, the pore structure and microstructure of hardened specimens were characterized to evaluate the impact of hydrophobically modified reduced graphene oxide (H@rGO). Furthermore, when the content of H@rGO was 0.15 wt%, the thermal conductivity of specimen was 0.55 W/m•K with optimal mechanical properties; the surface hydrophobicity of the hardened sample was significantly improved, with the surface contact angle, water drop penetration time, and softening coefficient reaching 113.898°, 567s, and 0.77, respectively. This enhancement was accompanied by a reduction in pore size and total porosity in the hardened samples, thereby contributing to the improved softening coefficient and mechanical properties of gypsum‐based composites. Because of lower energy consumption in H@rGO process and extensive utilization of industrial solid waste, the preparation process of incorporating H@rGO into β‐HDG exhibits superior cost‐effectiveness.