Abstract
A convenient method is described to appreciate damage levels of building marble plates caused by acid rain in a relatively short exposure period. The relative lightness and arithmetical average roughness height (Ra) are determined on the surfaces of plates (thickness 5 mm, width 30 mm and length 70 mm) after exposing the sample plates for 1-9 months at both outdoor and indoor sites on a mountain top, on a mountain foot and by a highway.
The lower pH of rain water fell, the more remarkable loss of lightness appeared in a short period on the surface of outdoor samples in 1-3 month exposure tests. Physical change of the plate surface may be estimated by using the lightness change optically measured bacause the Ra is inversely correlated to the relative lightness.
In 3-9 month indoor-exposure tests, differences of the lightness were quantitatively observed, but little differences of the Ra were recognized among the different exposure sites.
Damage levels of the marble plates were 4-11 times higher at outdoor sites by rain water than those at indoor sites by air pollutants in the ambient air.
Thus, the optical method may be useful to appreciate damagelevels of marble building meterials caused by acid-rain water after exposing them for a relatively short period.
