I looked it up  Takes 51 Senators for a quorum, so if all Republicans show up, they can do business without a single Dem in the place.    If all the Dems show up, they can try a filibuster, but they changed to rules on that to a simple majority.  IIR - after the time expires it goes to a vote and they can't block it.  https://www.reference.com/government-politics/quorum-house-senate-357b697fdb606355