Does a spellcaster have to use an action each turn to maintain a concentration?

@JeremyECrawford Does a spellcaster have to use an action each turn to maintain a concentration spell?

— cawoodpublishing (@cawoodpublish) March 21, 2016

Concentrating on a spell doesn't use your action. #DnD https://t.co/R7wOF9Zc6i

— Jeremy Crawford (@JeremyECrawford) March 21, 2016