A federal judge, overriding a prosecutor's objection that the sentence was too lenient, ordered an asphalt paving company executive yesterday to serve 60 days in a halfway house for his role in Virginia's bid-rigging scandal.

The sentence, imposed in Samuel B. Bartlett III, vice president of a Chantilly-based subsidiary of Ashland-Warren Inc., is among the lightest levied in the Justice Department's 2 1/2-year investigation into price fixing on state highway contracts.

District Judge Richard L. Williams sentenced Bartlett to a one-year prison term, but said he was suspending all but 60 days and sparing Bartlett from prison because of the 57-year-old defendant's medical condition. An official familiar with the case later said Bartlett suffers from diabetes.

Williams also ordered that Bartlett perform 300 hours of community service. Bartlett will be permitted to keep working for his company while at the halfway house.

Justice antitrust lawyer Hays Gorey Jr. asked yesterday that Bartlett receive a minimum prison sentence of 90 days. Gorey said Bartlett had agreed earlier to the 90-day prison term in a plea agreement reached in exchange for his guilty plea on a single conspiracy count.

"This is a crime committed by reasonable people who assess the risks before they go forward," Gorey told Williams. The government lawyer also noted that one of Bartlett's subordinates, Peter W. Herring, was sentenced April 29 by Williams to 60 days in prison for the same offense.

The government's plea agreement with Bartlett then was rejected by Williams because, the judge said, it did not call for community service as well as incarceration. Stripped of the plea arrangement, Bartlett could have been sentenced to a maximum of three years in prison and a $100,000 fine.

Three other paving company executives, including Herring, were sentenced immediately after they pleaded guilty during the April 29 hearing in U.S. District Court in Alexandria. Only Bartlett asked for a delay in sentencing while a presentence report was prepared by probation officials.

Besides Herring, Alexandria paving company executive Ernest Czarnecki also received a 60-day prison term. The third defendant Patrick C. Wilbourn of Leesburg, said he suffered from a severe heart ailment and was fined $100,000 but received no prison term.

Approximately 22 asphalt industry officials have been ordered incarcerated for terms ranging from 30 to 120 days since Justice began its Virginia investigation in 1979. Two were allowed to participate in work-release programs but spent 60 nights in local jails. One defendant served 50 days in a halfway house after spending 10 days in the Richmond jail.