Teamsters agreed yesterday to end their fractious and crippling three-week strike against Virginia Concrete Co., the area's largest concrete supplier. The strike came in the midst of a building boom in the Washington suburbs and slowed work on many construction projects in the region.

The company's 270 unionized drivers and mechanics, who struck May 16 over salary, benefits and job security, will return to Virginia Concrete's 11 plants this morning, having won wage increases of $1.10 an hour over the next three years.

They also won increases in pension contributions, but the amounts were less than union officials had sought.

Neither side declared victory in the settlement, which was approved 163 to 41 by the members of Teamsters Local 639, but both sides and the region's builders said they were satisfied.

"Our people are happy," said Local 639 President Philip Feaster.

"They gave a little and we gave a little," said company negotiator Tom Wotring. "That's how this agreement came about."

The workers are currently paid between $7.50 and $10.50 an hour. All will receive the wage increase.

The strike against the concrete giant was peaceful until this week, when the company bused 100 nonunion drivers from its parent company in Florida to begin driving concrete trucks.

The move inflamed pickets, who jeered and cursed at the workers as they rolled trucks out of three of the company's plants.

At the company's main location in Springfield, about three dozen police officers were on hand to keep order. Three strikers were arrested there.

Announcement of the settlement was welcomed by area building trades and construction officials. "We're so glad," said Robert Parker of the Washington Building Construction Trades Council, the umbrella group of area construction unions.

"I know it affected a lot of our people, I know it put a lot of our people out of work," Parker said.

Neither Parker nor Tony Ahuja of the Northern Virginia Builders Association could provide estimates on the strike's monetary damage.

"It certainly had a tremendous impact," said Wotring, the Virginia Concrete spokesman. "I'm not even sure my client knows how big, but they usually run 180 or 190 concrete trucks a day."

Feaster said the strike cost each of his members between $1,500 and $2,000 and said he believed it cost Virginia Concrete "millions." He said 90 percent of construction in the Northern Virginia area was slowed by the strike.

A major sticking point -- whether the contract would expire in May as the union wanted or in November as the company sought -- was settled with a compromise that officials said was typical of the negotiations.

The contract will expire in May 1988, typically the prime building season, but the union agreed to reopen bargaining in November 1987 to provide time to avoid a spring strike.

Workers have struck the company six times in the last 21 years, officials said.