Boston ? Six men who worked for the Big Dig’s largest concrete supplier were arrested Thursday on federal charges accusing them of falsifying records to hide the inferior quality of concrete delivered to the massive highway project.

The six, all current or former employees of Aggregate Industries, face a variety of charges including making false statements, mail fraud and conspiracy to defraud the government between 1996 and August 2005.

The indictment charges the men with recycling concrete that was too old or already rejected by inspectors, and in some cases double-billing for the loads. The company was paid $105 million for 135,000 truckloads of concrete, and at least 5,000 truckloads did not meet specifications, according to the indictment.

The Big Dig, formally called the Central Artery and Third Harbor Tunnel project, buried Interstate 93 in tunnels beneath downtown and connected the Massachusetts Turnpike to Logan Airport with a third tunnel beneath Boston Harbor.