- Author
-
Knab, L. I.
|
Clifton, J. R.
|
Waters, N.
- Title
- Evaluation of a Surface Treatment to Improve the Erosion Resistance of Coquina Stone at Castillo de San Marcos.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Report
-
NISTIR 90-4277,
March 1990,
40 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
abrasion resistance
|
Castillo de San Marcos
|
consolidant
|
coquina stone
|
erosion resistance
|
moisture
|
preservation
|
stone surface treatment
|
temperature
|
water repellent
- Abstract
- A surface treatment, which was intended to improve the erosion resistance of coquina stone at the Castillo de San Marcos, was evaluated. The commercially-available stone surface treatment was claimed to contain both consolidating and water-repellent agents. Limited, short-term tests intended to simulate two types of erosion and to identify any severe degradation problems were conducted. Erosion of sawn surfaces caused by (i) mechanical abrasion from strokes with a steel brush, and (ii) a thin stream of water flow were investigated in the laboratory in different stone orientations. The erosion resistance, based on mass loss, of the treated stone was compared with that of the untreated stone. The results showed that, for some test conditions, the erosion resistance of the stone was significantly improved by the treatment. For the other test conditions, however, the erosion resistance of the treated and untreated specimens was not significantly different. Hot-cold cycling, freeze-thaw cycling, and ultraviolet light-intermittent moisture exposure tests were conducted and no degradation was observed. In some cases, a slight darkening was discernible on the surface of treated stone with sawn surface. It was recommended that the surface treatment be applied to several trial areas at the Castillo de San Marcos, where erosion due to water flow or mechanical abrasion or both are occurring. The areas should be periodically observed and the erosion documented quantitatively, if possible, over an extended time period.