Around 2,500 workers at the Olympic Park, a huge area that will host more than a dozen events, are seeking higher pay and more benefits.
"We don't know how long we'll be on strike," Antonio Figueiredo Souza, president of the construction workers union Sintraconst-Rio, told Reuters.
"We are not going back until we get an offer. So far that hasn't happened and so it looks like this will end up in the Labour Courts."
The strike began on April 3 and is the latest in a series of problems affecting the preparations for the 2016 games, the first ever to be held in South America.
Brazil's preparations are way behind schedule, and work at some venues has not even started. With just over two years to go before the Games begin organisers are still to say how much the extravaganza will cost and which sphere of government will pay for the different jobs that need to be done.
The IOC last week announced Rio needs more oversight and said it will send officials to the city on a more frequent basis. The IOC's executive director Gilbert Felli is to return to the city later this week.
Brazil is also hosting soccer's World Cup in June and July, and preparations for that event are similarly problematic. Three stadiums are yet to be finished with the opening match less than two months away.
- Sports & Recreation