In the present study, a simple and cost-effective method for the preparation of a superhydrophobic calcium aluminate cement (SCAC) with superstable mechanical stability is reported. Room-temperature vulcanized silicone rubber (RTV) is used as an internal hydrophobic additive in concrete. The as-prepared cement surface and all cross-sections exhibit superhydrophobicity. The mechanical stability of the superhydrophobic-cement sample was evaluated by multiple severe mechanical damages. The SCAC sample exhibits super mechanical stability against sandpaper abrasion under high pressure, long-time impinging with sand, repeated knife scratches, and electric-cutter cutting. Amazingly, the cement sample was ground into powder, which was also superhydrophobic. In addition, the SCAC sample shows improved corrosion resistance for rebar against Cl- in comparison with the superhydrophilic-cement sample. Moreover, the application of superhydrophobic cement can be extended to oil water separation using SCAC powder combined with an adhesive.