FILLS FOR WHITE MARBLE: PROPERTIES OF SEVEN FILLERS AND TWO THERMOSETTING RESINS
ELEONORA E. NAGY
Isotropic fillers with hollow structures in Sikadur epoxy (with resin/filler w/v concentration from 1% to 30%) provided the most promising results for matching whitish translucent calcareous stones. The glass sphere fillers (Microspheres and Eccospheres) tested here appeared the whitest, with a texture and translucency resembling white marble or limestone. They exhibited the desired lower strength and more deformation (deformed sooner and longer) in the plastic region than the natural stone control specimens, and showed acceptable water sensitivity and color difference in a wet-dry cycle in relation to the original stone. These samples are also easily reversible by mechanical means (due to their lower compressive strengths and greater strain at break than the fresh and decayed natural stones). Parallel tests with contaminated (Microspheres) and purified versions (Eccospheres) of hollow sphere glass microballon fillers produced virtually identical results. This suggests that in choosing hollow sphere fillers, contamination of the product (or broken balloon fragments in it) is of no consequence. Marble dust and Globe-o-sil fillers showed results only slightly less promising than those of the hollow sphere fillers.
Calcium carbonate, mica, and Cab-o-sil fillers do not appear to be appropriate choices for fills of white translucent calcareous stones. Their significant difference in color and texture from a natural stone and their lack of translucency proves them to be inappropriate for matching fills for white marble. Composites of these fillers tend to produce greater compressive strengths than the stone, rendering these fills irreversible and more likely to cause damage to original stone.
This study did not investigate problems such as aging of thermosetting resins, yellowing (Down 1986), thermal expansion, resistance to freeze-thaw cycles, and biodeterioration, all of which could be topics for further study.