Installing a outswing door that’s right at grade. Door is cut into the foundation. RO is about 2.5 inches taller than door, so I’d like to raise the threshold and make use of the extra vertical space. Initially I wanted to pour a small concrete curb, but got feedback that it might be too small/short for concrete and I’d be better off with pvc or pt. 

1. If I go with pvc (likely two pieces glued together), what’s the best waterproof adhesive to  attach the pvc curb to the existing concrete?

2. The door’s threshold is flush with the door and the jamb, which isn’t what I was expecting, presumably so the door can swing all the way out and trim can be attached to the outside. Can I install some kind of trim to the threshold that will sit proud of the door opening?