About 70 janitors went on strike Tuesday at the Fort Belvoir military installation, saying that they are not being paid for some work they perform and that their hours have been drastically cut.

The workers started picketing outside the Army post along Route 1 about 7 a.m. as military personnel and others employed there were beginning to arrive for the day.

“We want them to recognize us as workers,” said Carlos Umana, 78, who said he isn’t paid for work done outside his normal cleaning duties at office buildings and other facilities on the 7,800-acre main post.

The janitors are striking for the second time in the two years that they’ve worked for an Atlanta-based company, Brown & Pipkins. The company, which does business as Ascential, has a federal contract to maintain facilities at Fort Belvoir. Last year, shortly after a one-day strike, the company reached a settlement with the U.S. Labor Department to provide workers with about $300,000 in back pay and benefits.

Jaime Contreras, vice president of Service Employees International Union’s 32BJ local chapter, said a 12-month union contract with Brown & Pipkins is set to expire Friday. “It’s been a nightmare,” Contreras said about negotiations. “It’s hard to understand how employers like this get this very nice contract funded by taxpayer money when they treat workers like this.”

Diedre Brown, the Brown & Pipkins chief executive, said the company is working to resolve the dispute.

So far, the company has agreed to give workers a 4 percent wage increase, a 21 percent increase in benefits and a personal day in addition to their paid federal holidays, Brown said.

A major sticking point involves union demands that the company pay extra to workers who transfer equipment between facilities at Fort Belvoir, Brown said. The union is also asking for a change in the way grievances are filed.

“We have been extending the olive branch to make a deal with this union,” Brown said. “I think we have come a long way.” Brown also said the company had not been told about the strike until after work hours Monday.

About 51,000 people work at Fort Belvoir’s main post and three affiliated military installations. Belvoir’s importance to the regional economy makes good labor relations there more significant, said Rep. James P. Moran (D-Va.), whose congressional district includes the post.

“It is critical that all of Fort Belvoir’s operations, including the service work that keeps the base clean and safe each day, operate without interruption and are held to the highest standards,” Moran wrote this week to Fort Belvoir’s garrison commander, Col. Michelle D. Mitchell, in a letter urging a speedy resolution.

Jacqueline Leeker, chief of community relations at Fort Belvoir, declined to comment directly on the dispute. Leeker said the dispute is “a matter between the contractor and its employees, and we hope that it’s resolved and the impact on our services is minimal.”