Images: Preserving a national treasure: Tomb of the Unknowns [Image 31 of 61]
Photo by Kerry Solan
Test mixtures are shown in marble to simulate what they will look like when dry. A formula of lime, cement and crushed marble was developed to fill cracks in the stone at the Tomb of the Unknown at Arlington National Cemetery. Norfolk District, U.S. Army Corps of Engineers has partnered with the cemetery and other agencies to preserve the tomb by repairing the cracks.