Hi, fellow Catalans and Spaniards! Greetings from Poland! :)
I was on a trip to Lloret de Mar and of course I couldn't forget about OSM while going to Barcelona when I noticed an unfinished section of C-32. I don't think that it's correct to tag this as highway=construction since it's obviously finished. In Poland when a road is finished, unused, but further construction is underway or will be reasonably soon, we tag that as highway=motorway and access=no, just like S1 near Żywiec (OSM way 92315741). But I did some research and it seems like C-32 won't be extended for... quite a while? If that happens, we tag those roads as highway=service, access=no and proposed:highway=motorway. Look at the N-S route in Warsaw (OSM way 124271723) or S7/S74 junction near Kielce (OSM way 235633429; note the changeset description).
We've got that tagging scheme established since there's quite a bunch of expressway construction going on in Poland for a couple of years. We tried to make this tagging scheme accurate and reflecting the general OSM tagging convention. Feel free to "import" it to the rest of Catalonia and Spain if you liked it :)