SEATTLE – A 31/2-week-long concrete workers strike, which stalled numerous construction projects in King County, ended Friday night as union members ratified contracts with four major companies.

The companies reported the contract agreement, The Seattle Times reported. Union officials did not return calls.

The International Union of Operating Engineers Local 302 ratified contracts with the four companies that provide concrete for nearly all the building projects in King County: Redmond-based Cadman; Renton-based Stoneway Concrete; and Glacier Northwest and Salmon Bay Sand &Gravel, both of Seattle.

The employers said 100 union members, who have been on strike since July 31, accepted an offer that gives workers a pay raise of $3.95 an hour over three years and also allows them to honor strikes by other trades. Union members had rejected an offer Aug. 20 because, they contended, it would have prevented them from honoring other strikes.

“They did get the improvements in picket-line language that they were seeking,” Ed Owens, senior vice president of Glacier Northwest, told The Times. “This is good for the employees and their families as well as the customers of the four companies affected by the strike.”

Barry Meade, vice president and general manager of Cadman, said management is looking forward to employees returning.

“It will take us a day or two to gear up again, but we expect to be back in full operation on Monday,” he said.

The walkout essentially cut off the supply of concrete in the county, idling dozens of construction projects.

An estimated 1,000 carpenters, ironworkers, laborers and other tradespeople had been laid off, said Lee Newgent, assistant to the executive secretary at the Seattle/King County Building and Construction Trades Council.

Affected projects ranged from Sound Transit’s light-rail line in Seattle’s Rainier Valley to a high-rise expansion at Lincoln Square in Bellevue. The Oct. 28 opening of the Seattle Art Museum’s new Olympic Sculpture Park was pushed back because more than 500 cubic yards of concrete needed for the project could not be poured.

State transportation projects were less affected, with officials saying only four of about 50 highway projects were idled.