Perforate the vinyl shower sheets using a wallpaper-perforating tool. Push the perforating surface into the vinyl and pull the tool downward to make small tears in the vinyl, so your adhesive remover can get through to the glue. If any portions of the vinyl shower sheet become loose during this process, pull them off the wall and dispose of them in a garbage bag.
Wear rubber gloves and protective eye wear to protect yourself from chemical adhesive removers and cleaners.
Lay a plastic drop cloth on the floor to prevent the adhesive remover from affecting your floor surface.
Paint citrus-based adhesive remover over the remaining vinyl shower sheets and exposed adhesive using a paintbrush. Allow the paste to sit for the time recommended on the package. As it sits on the adhesive, it softens the hardened glue so it can be removed.
Peel off remaining vinyl shower sheet in pieces and place it in the trash bag. Scrape softened adhesive off with a scraper to remove as much as possible. Apply more adhesive remover to any remaining adhesive and then scrape it off once it has softened.
Mix 1 gallon hot water with 1/4 cup trisodium phosphate. With gloved hands, dip a clean cloth in the cleansing solution and wash your concrete walls. Rinse with cloths dampened in water and allow the concrete to dry fully.