- Author
-
Clifton, J. R.
- Title
- Preliminary Performance Criteria for Stone Treatments for the United States Capitol.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Report
-
NBSIR 87-3542
October 1987
42 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
renovating; reconditioning; limestone; performance; criteria; treatment; paints; weathering
- Identifiers
- United States Capitol
- Abstract
- The West Central Front of the United States Capitol is being restored, including cleaning and repainting the sandstone, and replacing badly deteriorated sandstone with Indiana limestone. Application of stone treatments was proposed as a way of extending the lives of the sandstone and paint. However, without adequate selection criteria there was no certainty of effective performance by stone treatments. The purpose of the study was to develop performance criteria to assist in the selection of stone treatments. Based on an analysis of expected deterioration processes, it is concluded that deterioration of the sandstone was most likely associated with water penetration into the exposed outer surface. Therefore, if a treatment is to be used, it should protect the outer surface of the sandstone from rain penetration. In addition, the treatment should penetrate and consolidate any deteriorated stone. Also, treatment should not cause premature failure of the paint. Based on these requirements, four preliminary performance criteria were developed, but have not been verified by long-term studies. Of five stone treatments evaluated, one met the four criteria. It is recommended that treatment be used on areas of deteriorated sandstone needing consolidation and on stone in areas subjected to the most severe weathering locations.