Repairs to large cracks that run across the Tomb of the Unknowns at Arlington National Cemetery are finished and holding up well, cemetery officials said, but the recent work will be checked again in the spring to see how it fares this winter.

Heeding the advice of preservationists who had feared that the historic structure would be jeopardized with a botched repair, the cemetery contacted stone experts who appeared to have developed the right grout for the job.

The cracks in one of the most iconic monuments at the country’s premier military burial ground had been repaired in 1975 and 1989. But in 2007, they became visible. One was nearly 30 feet long; the other measured 16.2 feet. At the time, the cemetery announced plans to replace the 48-ton white marble monument.

Preservationists said that the tomb, the site of the changing of the guard ceremony, should be repaired to maintain its authenticity, and in April 2010, the cracks were fixed.

Last fall, however, cemetery officials noticed that the grout was flaking and, in some areas, falling out. Again prodded by National Trust for Historic Preservation, the cemetery consulted with experts. Last month, a specially designed grout was used to fill the cracks, and inspectors found the repairs to be working well, a cemetery spokeswoman said this week.

Preservationists who had criticized the cemetery for what they said was lax oversight and poor care of its historic artifacts said they are pleased with the progress. “You don’t want to get this wrong,” said Robert Nieweg, the director of the trust’s southern field office.