The etymological root of the word has little bearing on that word’s meaning in modern usage, tho I’ve never heard the term “viaduct bridge” to mean “designed to look like an aquaduct” before. As far as I’m aware they’re both just pillar bridges, one specifically for carrying water…

A viaduct is a bridge that consists of a series of arches, piers or columns supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct overpass across a wide valley, road, river, or other low-lying terrain features and obstacles.