Tens of thousands of construction workers across Quebec walked off the job Wednesday, shutting down major construction sites including the Turcot Interchange, the Champlain Bridge, and other large-scale projects.

However Labour Minister Dominique Vien hinted the strike will not be alowed to last for long.

Protests began early Wednesday near the Champlain Bridge and in other locations.

Their contract ended on April 30, and they say negotiations over the past few weeks have not been in their favour.

In all, 175,000 members of five unions have joined what they call the Union Alliance: FTQ-Construction, CSN-Construction, CSD-Construction, the Quebec Construction Union (SQC), and the Quebec council of construction workers (CPQMCI).

Michel Trepanier, spokesperson for the Alliance, said employers were not willing to work with mediators to come to an agreement.

The unions say the workers are paid an average of $33.50 per hour, but the union says they only work about 1,000 hours a year.

The Quebec Construction Association, which represents employers, says that the average employee earns more than $50,000 per year.

Spokesperson François-William Simard said employers want more flexibility from empolyees, inculding an eight-hour shift that can start as early at 5:30 a.m. or run as late as 7 p.m.

"We have to wonder why they wanted to go on strike today, because in the last few hours we were really close to an agreement, and the salaries was the only thing that was left," said Simard.

"We are really disappointed because we really believe we can get an agreement."

Under the terms of the expired contract, employees can earn overtime while working an eight-hour shift if they start early or finish late.

"We want to make sure that everyone comes back safe and works decent hours," said one ironworker.

"We work at heights, we are working under pressure, and the systems we are working on could be dangerous, but we make it safe."

For their part, the unions want to be permitted to negotiate clauses that would allow them to be paid retroactively for any salary increases, and they want measures in place against strike breakers, often referred to as anti-scab legislation.

Employees said one clause in particular is irksome: being forced to work on Saturdays if they take a sick day.

Over the past few weeks, both sides have said their counterparts are not negotiating in good faith.

This is the second strike in four years, and the provincial government is not going to tolerate a long strike.

Labour Minister Dominique Vien said back-to-work legislation is being drafted and will be imposed if necessary.

"I had hoped that negotiations would work, but they have not," said Vien on Wednesday, adding that she was going to meet with both sides beginning at 1:30 p.m.

"They have all agreed to meet with me, and that is why I am on my way right now to Montreal."

Vien said that legislation would likely be tabled very soon.

"Back-to-work legislation will be imposed whenever the premier calls for it. I will be ready," said Vien.

The Federation of Chambers of Commerce (FCCQ) issued a statement Wednesday calling for an immediate end to the stirke, saying the last strike in 2013, which lasted ten days, resulted in an one percent drop in Quebec's economy.

Vien said the strike will cost the provincial economy $45 million per day.