In the midst of one of the biggest building booms ever in Northern Virginia and with construction jobs going begging in the peak construction season, Dave Zimmerman laid off seven carpenters at a site in Fairfax City yesterday.

It wasn't that there was no work to be done, but that Zimmerman could not get the concrete he needed before the carpenters' work could be done.

The strike by Teamsters Local 639 against Virginia Concrete Co., the state's largest concrete supplier, "is starting to hurt," said Zimmerman, project manager for Turner Construction, which is building Gatewood Plaza on Arlington Boulevard (Rte. 50).

Zimmerman said he expects that by today the strike will really begin to slow things down. His workers are supposed to pour foundations for the five-story Gatewood Plaza office building all day today, but Virginia Concrete has given him no guarantees of delivery.

The strike of about 270 Teamsters against the giant concrete company entered its fourth day yesterday, affecting 90 percent of the company's customers.

Construction superintendents at a dozen sites in Northern Virginia said yesterday they were juggling tasks to do without concrete, and members of Virginia Concrete's management were driving concrete mixers in an effort to supply as much concrete as possible to work sites. About 30 of 201 trucks were reported rolling from one of the company's 11 plants yesterday.

If the strike lasts until next week, building officials said there would be layoffs, cost overruns and delays in completion of everything from town houses to highway interchanges.

No progress was reported yesterday in settling the strike. Drivers, mechanics and maintenance workers walked out last Thursday over pay, benefits and job security issues.

The two sides have not met since May 14, and although officials of the Federal Mediation Service said they were in touch with both sides, no talks have been scheduled.

The strike produced its first violence and criminal charges yesterday in an early morning altercation involving a picketing striker and two off-duty Fairfax County police officers who had been hired as security guards by the company, with police department approval.

When the officers asked picketers to move out of the way so trucks could enter the plant, one man refused, police said, and was forcibly removed by the two officers.

James McLaughlin, 44, of Alexandria suffered two broken ribs and was charged with disorderly conduct and obstructing traffic yesterday. He refused to comment on the incident.

Police spokesman Warren R. Carmichael said that the employment of off-duty police officers by Fairfax companies was routine. However, the department revoked permission yesterday for its officers to work for Virginia Concrete "to avoid any public perception that we were in any way trying to serve as agents for the company against the union," Carmichael said.

Philip Feaster, president of Teamsters Local 639, called the incident "very nasty" and "police brutality."

Company officials did not return a reporter's telephone calls yesterday.